Forecast for Sunday, May 1, 2011

High pressure is currently anchored from Canada into the Eastern United States this evening. It will move eastward on Sunday and allow for a flow off of the ocean, meaning the moisture content of the air will begin to increase and it will remain cool. A cold front will move into the region from the west late on Monday and become nearly stationary on Tuesday. The front will slowly drift off the coastline on Wednesday, but it appears quite possible that a wave of low pressure develops along the front and moves northward. This signals a potential for a coastal low pressure system.

Tonight, with the loss of daytime heating, daytime cloudiness should diminish quickly. Mostly clear skies are expected and as a result of the high pressure area, temperatures should drop decently in areas that can radiate easily. Therefore, mid and upper forties will be the general rule of thumb in the suburban areas with lower fifties in the urbanized areas.

On Sunday, a few clouds are expected during the daytime hours with the increasing easterly flow, especially along the coastline. The cold front out to our west will likely approach the Ohio valley and Tennessee Valley on Sunday Night. Sunday Night should feature more clouds than stars. Highs will likely top out in the mid and upper sixties.

On Monday, the cold front makes the closest approach late in the day. Afternoon and evening isolated showers and possibly some isolated thunderstorms could occur. With highs in the mid and upper sixties, it does not currently appear as the most unstable setup. However, if some of the model guidance is warmer on Monday…there could end up being more instability…but this solution would likely mean a drier Monday. With the front drifting eastward and over the region on Tuesday, additional showers and thunderstorms will either be ongoing or will develop with afternoon daytime heating. Tuesday will be a relatively cool day with highs in the middle sixties.

With the cold frontal passage on Tuesday Night or Wednesday Morning, even cooler air will follow. This will be reinforced with the development of a coastal low along the nearly stationary front when it is offshore on Wednesday. Further impacting the temperature will be the extensive clouds and rain. The rain could be heavy at times, but the longer range modeling has backed off on the intensity of the low. Since it is spring, I will allow for some elevated thunderstorms development. It could also be breezy on Wednesday and later forecasts will likely take a closer look at any potential gusty winds or coastal impacts, if any. The next chance for showers is on Friday Night into Saturday.

You will hear more about a review of April 2011 here in a few days, but this is the first April in two years where we did not have a heatwave. We did not hit 90 degrees this month.

A Fine, Thin Line Of Lightning

This picture is really cool and comes by way of Tim Nessler, who captured a photo of a tree after it was hit by lightning during yesterday's storms on the campus of Philadelphia Biblical University in Bucks County.

Lightning doesn't necessarily slice a tree in two, topple trees over, but it does leave its mark as the intense heat generated by lightning will help sear the bark off of a tree in the path of where the lightning travels.   The trees you see on the left managed to survive quite well compared to many other examples of trees that get zapped by Mother Nature.   Trees are more frequent targets for getting struck by lightning, in part due to their height, but in some cases certain types of trees have a higher electrical discharge (pine needles for instance) than others and makes them a more inviting target.  Trees aren't a good spot to be hanging out near during a thunderstorm, especially if you are on a golf course.  


Between 1998 and 2008, Pennsylvania had 13 lightning related deaths, tying it for 10th on the list of most fatalities among the states.   Florida, which is the most lightning prone place in the US, had 74 deaths in that time period while Texas had 28.


More:  Lightning Safety Tips (NWS) | Tree Struck By Lightning (youtube)

April 30th and May 1st, 2011 Forecast

The weekend ahead will not be like the days that just passed us by.   No humidity, no heat, and outside of this evening's shower activity in spots there doesn't seem to be much of a threat in precipitation except a slight shot (and it's a stretch) of a late day shower on Sunday to our south and west.  There's not much that can be said about Saturday's weather other than it's going to simply be awesome.  Expect a sunny, beautiful day to close out April with temperatures that generally hit 70 or the low 70's everywhere except the immediate Shore.    Get out, enjoy it, as it's going to be nice.  

Sunday will have more clouds around as a warm front approaches and, as stated, there's a slight chance for a shower but I don't think it's gonna happen.   Temperatures will be similar -- in the low 70's -- but a few more clouds will abound.   Lows tonight will be in the 40's, on Saturday night they will be in the 40's away from the city and around 50 in Philadelphia.

While the calendar may be transitioning to May, next week's weather may not be so May-like at times.  We have a chance for some midweek chilled rain that could move through.  While helpful for allergy sufferers, it may not be the nicest of days next Wednesday.  It's something that we'll talk about later this weekend.

Passing Afternoon Showers, Maybe Thunder Rumbles

The slow march of yesterday's cold front is complete as it is finally off the coast and cooler, less humid air is in place. Temperatures this morning are in the 40's and 50's around town to start, a good 15-20 degrees cooler than yesterday morning, with highs today poised to top out in the mid and upper 60's with a stiff west breeze at 12-22 mph.

An atmospheric trough will work east through the state today -- it's in Western PA this morning -- and bring a chance of showers and perhaps a thunderstorm to the region this afternoon.   Higher resolution radar modeling suggests the threat for shower activity is highest after 4 PM this afternoon, with the NAM suggesting anytime after 2 PM.   We're not talking about tornadic storms or supercells but there could be a few showers to dodge on the drive home as the atmosphere gets agitated by the trough, the stronger April sunshine, and cooler air aloft.

Today's shower activity should also be scattered, not widespread, and better chances for showers exist north of the city than south.

More:  Current Weather Page

Severe Weather Reports for 4/28/2011

Tornado Damage in York County from earlier this morning.


Tornado Damage in York County from earlier this morning.

The severe weather today in our area was plentiful in our region (although nothing like the severe devistation in the Gulf States). Several thunderstorms did prompt tornado warnings across North-Central and Northeastern New Jersey, portions of the Lehigh Valley, and in South-Central Pennsylvania. There were numerous severe thunderstorm warnings issued throughout New Jersey.

In York County (we have a few readers there), the State College National Weather Service Forecast Office has confirmed an EF1 tornado. It occurred at Roundtop Mountain Resort in Fortney Township, Pennsylvania. This touchdown occurred around 5:55 a.m. today. It was 100 yards in width. Details on the max wind speed and length are listed as "to be determined". An EF1 tornado produces wind speeds of 86 to 110 MPH.

In Hunterdon County (New Jersey), a funnel cloud was reported in Alexandria Township. In Morris County, a funnel cloud was reported in Chester Township. In Passaic County, an impressive three funnel clouds were spotted at one time in Wayne Township. There were trees and power lines knocked down in Hunterdon and Morris Counties, including in Alexandria Township. WNBC in New York is reporting possible tornado damage in Denville Township. Jersey Central Power and Light’s online outage map did show several thousand in that area without power at one point in these areas. Of course, we will keep you updated if there is a report of an actual tornado touchdown in this area.

Update: Anthony Gigi told NJ.Com the following:  "The reports that we are getting are more consistent with a severe thunderstorm rather than a tornado. We’re not seeing hundreds of trees down or roofs ripped off of homes."

Elsewhere, a tree fell down on a bus this morning in Berks County near South Heidelberg Township. In Mertztown large tree limbs were downed. In Jackson, Monroe County in Pennsylvania there was trees that were felled onto houses. Stroud Township also reported trees down. Wires were knocked down in Springfield Township in Bucks County. In Cumru Township in Berks County, trees were reported to be down. Hail was reported in Hunterdon County at White Horse Station which isn’t surprising to hear about when you have tornado characteristic thunderstorms. Trees and wires were taken down in Somerset County near North Plainfield Township.

More:   Storm Damage Reports (NWS)

April 29th, 2011 Forecast

The end of our summery pattern means less humidity...although that came with a price in the form of some nasty thunderstorms in the Mid Atlantic.   For those of us who are humidity intolerant, the front that's crossing the region today did not mean a return to 40's and 50's with chilly winds off of the Atlantic but it will mean a return to more typical late April weather as temperatures tomorrow will be in the 65-70ish range through the region, with dewpoints that are much more typical of late Spring and not late Summer.  

The return of normalcy in our weather is accompanied tonight with some possible patchy fog after midnight as the leftovers of today's rainfall hangs in the atmosphere.  Fog doesn't look to be widespread and should generally be confined to areas that received the most rains to our north and west.   Any fog that develops will quickly dissipate on Friday, however, with a decent west breeze at 12-22 mph developing in the morning and scouring out the atmosphere.  

A shower or two can't be ruled out in the afternoon, mainly north of the city, as a weak disturbance pivots through the Northeast in the wake of today's low pressure center.  These showers will be light and probably not an issue around Philly at all.

Weekend Sneak Peek:   Simply.  Awesome.  Weather.   Saturday starts cool with temperatures in the 40's but they will quickly warm into the 60's and 70's across the region with plenty of sunshine and a nice breeze at 10-15 mph.   Sunday will be milder, with some possible high clouds in the later afternoon as the wind trajectory shifts to the south ahead of another storm system, with highs generally in the 70's away from the Shore.   The next storm chances will be on Monday in the region with another cold front coming in.

April 28, 2011 Severe Weather Coverage

2:38 radar update:



2:28: PHI issues Severe Thunderstorm Warning for Burlington, Monmouth, Ocean [NJ] till 3:30 PM EDT

2:03 Update: PHI issues Severe Thunderstorm Warning for Atlantic, Burlington, Camden, Gloucester [NJ] till 3:00 PM EDT

1:53 Radar Map:



1:28 p.m. UPDATE: Thunderstorms weakened a bit about an hour ago but are starting to hit the juicy air over Delaware and South Jersey. Due to the initial weakening trend, they have become less linear and more cellular/clustered. This likely enhances the tornadic threat and hail threat, but it will continue the downdraft potential. The latest radar trends showing 50-60 DBZ increases. Clearly, areas from the Delaware River and points east will be impacted for the next two to three hours.





12:29 p.m.: Look at the two mesoscale analysis maps I have posted just recently updated.





12:20 p.m. Update: Several dangerous thunderstorms continue to ride along the slow moving front with numerous severe t-storm warnings from Northeastern NJ down through areas just west of Philadelphia...and also NE MD and N DE.

11:03 a.m.: Tornado Warning for Northampton, Hunterdon, Warren, and Bucks Counties!

10:32 a.m.: Tornado Warning number three continues for Lancaster County---very strong rotation noted on doppler radar at times!

9:53 AM Update:  A Severe Thunderstorm Watch is out for the region until 4 PM (see below).   Lancaster County area has been in and out of tornado warnings for the last hour or two while Berks, Lehigh, and Lancaster area remains under severe t-storm warnings.   Sunshine is out in parts of NJ and DE...could provide more fuel for storms.

Isolated tornadoes, despite this only being a severe t-storm watch, remain very possible....hence the warnings we have already had today.

Update, 9:40 AM:   Wanted to point out the main action that will impact our region will be coming out of Maryland over the next hour or two as most of the storms in Lancaster County at present will slide to the north of the city.   The line itself is moving east slowly while the individual thunderstorms on the line are moving northeast, which means that storms farther south will be the ones that ultimately impact us as the line gradually shifts east throughout the rest of the morning.   One particular part of the line in Maryland has had a bit of a history of damaging winds and showing signs of tornadic rotation within it.  That cell is circled on the radar map above.  This cell will be working into Northern Maryland, then into Lancaster and Chester Counties over the next hour or two, perhaps into far upper Montgomery County if it can maintain itself.  At minimum, damaging winds may be the result of that line of storms later on.

9:19 a.m.: Severe T-Storm Warning continues for Lehigh, Berks, and Lancaster Counties until 10:00 a.m.

9:04 a.m. Update: Tornado Warning has been allowed to expire for Lancaster County. A severe thunderstorm warning is in effect for Lancaster and Berks Counties.




9:00 a.m.:

A tornado warning was recently issued until 9:15 a.m. for Lancaster County. Get inside an interior closet or basement if you live near Strasburg or New Holland.

A horrific outbreak....

Just an awful, awful tornado outbreak Wednesday and Wednesday night. The death toll is staggeringly high, and those numbers will likely continue to climb today as search and rescue operations continue. My prayers remain with all of those effected....and that number is great.

No time for a video this morning due to on-air duties....but I will post a few videos from the tornado outbreak yesterday....





Tuscaloosa tornado caught on tape wreaking havoc

Thursday's Severe Weather Primer

Track today's storms on our current weather page

Update, 7 AM:   Storms have developed on the southern flank of the Central PA line and are sweeping towards the Philly region at this hour.  Storm line extends from near Allentown south into extreme Northern Delaware and is moving northeast at 70 mph.   This storm line has the potential to drop winds to over 60 mph due to its fast forward motion and the dynamic wind energy aloft and has resulted in severe thunderstorm warnings being issued for the northern and western suburbs.   This warning is out until 8 AM.   Rest of our initial post is below.


Today is shaping up as a rather active weather day on paper as the warmth and summery weather come to a halt thanks to a cold front's eastward march into the region. A line of rather nasty thunderstorms is setting up to our west, with severe thunderstorm warnings all along the line from Scranton down into Maryland, with the line slowly lifting northeast as the front is back in Western PA, slowly pressing east.  This line will take a couple of hours to approach, and several hours to cross the region.   Given the current timing and pace on radar, thunderstorms should work into the city towards mid morning and then clear the city during the mid or perhaps later afternoon.   The thunderstorms you see on radar in Central Pennsylvania will not be the ones that hit us -- our activity is back in Virginia since these storms are lifting northeast.   The Central PA storms will work through the Poconos over the next few hours, with the Virginia and Maryland activity moving in later on this morning.

With a line of nasty thunderstorms to the west and the atmosphere rather tropical, there is a threat for severe weather and the region is under a slight risk for severe thunderstorms through the day -- mainly with the Central Pennsylvania line this morning and then with the activity in Virginia as that approaches Philly later this morning and around midday.    Thunderstorms have the potential to produce damaging winds, isolated tornadoes, and heavy rains.   Flash flooding is a threat, mainly north of the city due to the damp soil conditions north of town, but the usual suspect streams and roadways that flood at a drop of a hat around here could have some issues later on if storms are strong enough.

A severe thunderstorm watch is out until 10 AM for the Philadelphia region and points west, north, and south.     It wouldn't surprise me to see the watch reissued later on this morning, perhaps as a tornado watch depending on how nasty the Virginia and Maryland activity get over the next several hours (they are under a tornado watch until 8 AM).

Thundery Day Turns To Thundery Night

11:57 p.m.: Severe Thunderstorm Watch now posted for Lancaster County and most of Central Pennsylvania.

11:30 p.m. Update: The Storm Prediction Center is suggesting in the latest mesoscale discussion a new weather watch...perhaps a tornado watch as they mention "all severe weather threats" will be possible in the early morning hours in Eastern and Central Pennsylvania. ~Doug



Update, 8:45 PM: Severe thunderstorm watch now issued for East PA and DE. Watch is out until 4AM. Higher threat for severe thunderstorms will be to the north and west of Philly but there is some chance for some storms to approach severe limits later tonight.

Update, 7:45 PM:   The tornado watch is still out until 10 PM in Central Pennsylvania, with Flash Flood Watches for Thursday for the Lehigh Valley, Poconos, and North Jersey for tomorrow's storms.   Radar up above is showing the activity lining up across Central Pennsylvania, with more activity down near Baltimore lifting northeast towards the Philly area.  If they hold together, they should move through the region around 10 PM or so.   As Doug pointed out below, we could see a tornado watch for Eastern PA, Maryland, and perhaps Delaware later on tonight as the storms down by Baltimore do have a history of some damaging winds and rotation within one of the storm cells.


7:00 p.m. Update: The Storm Prediction Center is considering a tornado watch later this evening as tornadic t-storms in Maryland and Central Pennsylvania may tend to move eastward in time...they may survive as eventual forcing gets closer along with increasing shear.



5:00 p.m. Update: Severe thunderstorm warning in effect until 515 Southwestern New Jersey. It did include parts of Delaware.


4:04 p.m. Update: Local National Weather Service says that there has been an injury this afternoon as a woman was struck by a tree in Camden County. The incident happened around 3 p.m.



3:30 p.m. Update: A flash flood watch has been issued for Thursday for the following counties: Mercer, Middlesex, Hunterdon, Carbon, Monroe, Northampton, and Lehigh Counties. Points to the immediate north of these counties are also under a flash flood watch.



3:13 p.m. Update: Lancaster County has now been put under a tornado watch which includes all of Central Pennsylvania. Earlier, a tornado watch was issued for Baltimore and Washington.



3:06 p.m. Update: According to the National Weather Service, a severe t-storm has been reported.



A severe thunderstorm warning has been issued for the Philadelphia Metro until 3:15, issued about 20 minutes ago.

Damaging winds up to 60 MPH are possible with this storm.

It will be near Philadelphia by 3:00 p.m.

Additional pop-up thunderstorms will develop this aftn and I will be updating this thread.

April 28th, 2011 Forecast

Severe weather is definitely possible in the region over the next 24 hours as our first fling of summer comes to a thundery end.  After multiple days of mid 80 degree temperatures and now humidity that's more typical of August, reality returns...thankfully this reality won't be too terribly cold as temperatures behind the upcoming front will be typical for late April (mid and upper 60's on Friday).

Thunderstorms are possible this evening and overnight, generally west of the city.   Any storms that fire up and move through have the potential of bringing heavy rain and gusty winds to any one location.   It will be a warm and humid night with breezes from the south and southwest picking up to 10-16 mph overnight.   It would not surprise me if low temperatures in the city across parts of the Philly region did not drop below 70 either as clouds will help keep temperatures up overnight.

Right now, the front is poised to cross the city during the 2-5 PM timeframe, accompanied by a several hour period of heavy rain and thunder that could bring an inch or more of rain to the region.  Severe thunderstorms (damaging wind) is also possible in advance of the frontal boundary passage.  Temperatures should warm into the mid 70's around Philly before the rain and thunder hit, cooling off to around 70 before the front and then sliding back late in the afternoon after the front crosses the region.   Winds will gust to 30 mph ahead of the front, possibly to 50 mph or higher in the strongest of storms.

We'll have a more thorough update on the thunderstorm threat for Thursday in the morning.

Wow....

It was amazing to watch the line of storms rip through Mississippi and Alabama early this morning. An incredibly intense line of storms roared through that region, and just an amazing amount of wind (and some embedded tornado) damage occurred. Some of the images coming in from that area are incredible. Over 250,000 people are without power in Alabama alone...definitely not good news with another round of severe weather on the way.

But that was only round one....the second round, and the round that will pose a very significant tornado risk, will develop in MS and AL later today, and those potentially tornadic storms will try to lift into southeastern TN and northwestern GA by this evening.

A rare 'high' risk of severe weather remain in effect for that area, and in that 'high' risk area, some dangerous, long-track tornadoes are possible.

For the Carolinas, I expect scattered storms to fire off later today and extend into this evening. I do not have a lot of confidence in what the coverage of storms will be today, but any storms that do form could grow severe. A number of the severe weather parameters you look for will be in place this afternoon and evening, and while the biggest threat today will be off to our west, we will need to watch all storms closely.

Eventually, later tonight, a potent line of storms will move into the Carolinas and exit the I-85 corridor by mid-morning tomorrow. Damaging winds and some embedded tornadoes will be possible within that line.

Here is where I will state that once again, every home needs to have a NOAA weather radio. There could very well be warnings required overnight, and you need to have some way of getting awakened if warnings are necessary.

Not As Warm, Still Humid, Maybe Some Thunder

 A warm, summery morning in the Delaware Valley as the sunny influences of Bermuda High pressure have waned somewhat and we're merely in a broad, tropical southwest flow ahead of a rather nasty storm system that is poised to move through tomorrow.   Today's weather starts murky, humid, and warm and finishes that way as well, with temperatures approaching 80 away from the ocean, only getting to around 60 at the immediate Shore, as skies stay mostly cloudy and occasionally have some sunny breaks.

Some showers are showing up on radar across coastal sections of the region, with last night's thunderstorms to the west and north now out of the picture.  The showers along and offshore will move northeast but with the heating of the day we should see a scattering of storms pop to our west and lift northeast.   Yesterday's thunder threat was generally west of I-81 although a few storms last night managed to get   into Allentown and Reading.   Today's threat is generally higher west of I-95, although those coastal showers could be a bit more numerous later this morning as a weak disturbance slides up the coast 150 miles east of the NJ coastline.   Storms will be prone to popping up after 3 or 4 PM but may end up being more numerous after sunset as storms farther southwest work their way towards us.

Areas to the west of Philly are under a slight risk for severe weather -- with the highest risk areas confined to the Tennessee Valley and Mid South as a high risk is out down there.  Any thunderstorms that do develop this afternoon may have a better chance of producing heavier rains than severe wind gusts due to the amount of moisture in the atmosphere, although those gusty winds in the storms cannot be ruled out.   Storm chances continue into the night, especially in Western Pennsylvania as the front and storm system begin to make progress towards the east, with the front crossing the region on Thursday afternoon.   Thursday will probably be our area's best overall chance at heavy rain and severe weather.

We'll talk about Thursday's event in more detail this evening.

More:   Current Weather Page

Big severe weather event continuing today...

Here is today's edition of the video...it is all about the severe weather event continuing to unfold and press toward the Carolinas.

Short Term Severe Threat for North and West Counties

11:35 p.m. UPDATE: Severe T-Storm Warning out for Berks and Carbon Counties...through 1230 a.m.






The Storm Prediction Center has issued a mesoscale discussion regarding several strong to severe thunderstorms brushing or soon to be brush our northwestern counties. There appears to be a wind damage threat for the next two hours and perhaps a brief rotating thunderstorm.

Thunder Chances Before Thursday's Main Event

The current severe weather event across the central portions of the country is rather amazing -- the damage in St. Louis to their airport last Friday, the run of storms through Arkansas yesterday, and over 15" of rain in some portions of the Ozarks from the current pattern has been remarkable to watch unfold. This storm system is finally easing east and will work towards us for Thursday. However, it will be close enough to us tomorrow to increase the odds of thunder around the region.

A slight risk of severe weather was placed out for the region for Wednesday for areas west of Philadelphia, with the highest concentration of severe thunderstorms in the Ohio Valley down into the Mid South, including Nashville, Louisville, and parts of Alabama.   Our severe risk is more for Wednesday night if the storms move quickly enough, with the main focus area for severe weather on Thursday positioned squarely over the top of us as the front closes and crosses the region.

Despite the worst of storms being to our west tomorrow, there will be an added risk for showers and thunderstorms as the atmosphere is increasingly unstable the mid level cap that was over us on Monday and most of Tuesday weakens as high pressure's grip over the region weakens somewhat.   The strong southwest flow at the lower levels and mid levels of the atmosphere will help tug tropical moisture that is east of Florida and Georgia northward into the region on Wednesday.  This will increase the thunder risk and probably lower our daytime temperatures by several degrees.  While it will still be warm, the additional clouds will keep us from getting into the 80's like we have the past three days.   Some showers and storms will develop and move through the region over the course of the day, some of which may produce heavy rainfall due to the quasi-tropical airmass that will be in place.

Storms will be scattered in nature and move through from southwest to northeast during the day and ahead of Thursday's main event, which continues to show signs of being a rather potent event whether it be a wind threat or heavy rain threat...both of which are definitely possible as a squall line may develop along the cold front Thursday afternoon.

Hopefully you have been able to enjoy most of the past three days -- while the weather hasn't been 100% perfect all of the time the past few, it's been the best weather we've had in a while.  Unfortunately, things will head downhill from here...especially on Thursday.

April 27th, 2011 Forecast

Tonight: Outside of an isolated evening storm, look for mostly cloudy skies. Patchy fog will develop after midnight. It will be a warm night with lows only dropping down near 67 degrees in Center City. Winds will be out of the south at 10 to 15 mph. The chance of rain is only about 20 percent. The sunset tonight is at 7:50 PM.

Wednesday: A mix of hazy sun and clouds. Continued breezy and warm with a high around 80 degrees. Winds will be out of the south at 10 to 20 mph with gusts near 30 mph.

Thursday: Showers and T-storms. Breezy with gusts around 35 mph. Look for some hazy sun, too. The high will be near 76 degrees. The chance of rain is about 70 percent.

Friday: Cooler and less humid with a few clouds. Expect the high to be around 67 degrees.

Wednesday Planner

7 AM 67 degrees, Hazy Sun & Clouds

Noon 75 degrees, Breezy, G 30 mph

5 PM High around 80 degrees, Warm

Sunrise 6:07 AM

Sunset 7:51 PM

Day 1 'high' risk...

The SPC has indeed pulled the trigger on an upgrade to a 'high' risk for parts of southern AR, northeast TX, and southeastern OK. The discussion and video in the posts below are still valid....

Violent severe weather outbreak continues the next couple of days...

For the Carolinas, look for scattered showers and storms to fire today and wane this evening. A few storms could be severe with damaging winds and some hail. However, our severe weather threat today is nothing like the threat to our west.

After a significant severe weather outbreak yesterday, Arkansas and many surrounding areas are in for another violent round of severe weather later today and tonight. A broad 'moderate' risk of severe weather is out for that area, and it is possible that an upgrade to 'high' could occur in later outlooks today.

Then the threat shifts eastward tomorrow. Frankly speaking, the synoptic (large) scale setup is about as bad as it gets for the Tennessee Valley. All of the necessary parameters for severe weather are there in spades. However, with severe weather, small scale features are always the determining factor between a major and a minor event, and that won't be evident until tomorrow. However, all of the larger scale features you look for to favor a severe weather outbreak are there.

In short, northern MS, northern AL, TN, KY, northeast GA, and into the mountains of the Carolinas could have a major severe weather event tomorrow.

Below is the Significant Tornado Parameter valid tomorrow afternoon, which combines several different severe weather indices, and is normally a good way to diagnose tornado potential on the modeling. Keep in mind, this is only model output. These are very significant values for the Tennessee Valley.

The storms will wind up spreading east of the mountains by Wednesday night and early Thursday morning. Although the storms will likely be in a weakening phase, severe weather is quite possible in the Piedmont regions with this system.

We will of course watch all of this very carefully.

Be sure and scroll to the post below this one to see today's edition of the video....tons of stuff in there.

Scattered storms today...

Once again this morning, tons to talk about in the video. Give it a look. Two more extremely active severe weather days across the southern US....I talk about that, and what it means for the Carolinas, in the video.

Skipping Spring

Crazy to think that just 72 hours ago we were in the 40's in many locations and "enjoying" a chilled east wind as we entered last weekend.   Such is Spring in the Delaware Valley -- and the flip of a switch, northward advance of a warm front, and southwest winds have brought us from early March to late June in just the span of 48 hours.

Today's high of 85 in Philadelphia is the highest of the year and our first back-to-back foray into the 80's since late last September (the 24th-25th).   Temperatures topped 80 almost everywhere away from the water and the Poconos today and even Mount Pocono's 74 degree high was 16 degrees above average for today.

Other area highs included 86 in Pottstown, 83 in Dover, and 81 in Doylestown.

Ending Early Summer

After a multi-day run of 80+ degree weather around these parts, all good things must come to an end for a time. A stronger cold front will finally move into the region on Thursday after weaker boundaries failed to push into the Bermuda High in the Atlantic. This stronger storm system will not only end the 80 degree warmth but also bring a potentially nasty round of thunderstorms to the region -- if the timing is right.

Computer modeling consensus suggests the front passes through the region around midday Thursday -- the Euro and NAM computer models are latest and suggest a Thursday PM timeframe (more optimal for bad storms) while the GFS suggests a morning timeframe.   Storms that develop could bring strong gusty winds but given the setup of the storm system (shifting winds aloft) some tornadoes can't be ruled out.   Plenty can change given we're three days out but the setup, on paper, looks good for at least some severe weather around the region on Thursday.   We'll update the potential as we get closer but it looks like summer's first foray in the region could end with a few pops and bangs.

Before that, however, there is a chance for some thunderstorms on Wednesday as the humid airmass that's moving north could pull some tropical moisture into the region from a disturbance that's down in the Bahamas at present.   The tropical disturbance won't become a tropical storm or anything of the sort but it could enhance some thunderstorms in parts of the region on Wednesday afternoon.

April 26th, 2011 Forecast

Tuesday is shaping up as the "best" day of the warm stretch as the warm front fully lifts north of the area and we get just enough drying to allow for temperatures to take off.   Thunderstorm chances should generally be confined to Central Pennsylvania on west and while we can't fully rule out a thunderstorm sneaking into the Philly area, tomorrow looks to be the "least" thundery and rainy day of the stretch as the Bermuda High exerts just enough muscle to keep thunderstorms away from most of the region.

Evening thunderstorms are possible tonight, however, as the warm front trudges north and those thunder chances are highest to the west and northwest of the city.   Some patchy fog can't be ruled out in the northern and western burbs later on tonight.   Temperatures won't drop much again -- only into the upper 50's north and 60's elsewhere.   Tuesday may be close to Easter Sunday in terms of temperatures -- 80's in many locations away from the Shore, with the Shore in the 60's, as southwesterly winds at 12-18 mph enforce the warmth for a couple of days.

First Daytime Thunder:   It's been a rare sight this Spring...the thunderstorm, but Reilly Sharp sent us this photograph composite (that's why the picture is a bit choppy on the northeast corner) of one of three thunderstorms that tracked through Bucks County on Easter Sunday.   Spring may be fully sprung with our current warmup and thanks Reilly for capturing something that we have not seen around here during the day (the March thundersleet notwithstanding) for the most part this year.