April Fools' Storm A Day Away

We're a bit less than 24 hours away from the April Fools' Storm's arrival in the region, with a soggy start and for those north & west of the city, a snowy ending as the storm intensifies tomorrow night and early Friday, leading to a transition from rain to snow for higher elevations north of the city.   The potential does exist for significant accumulations in the Poconos, the higher elevations of the Lehigh Valley, and North Jersey -- Winter Storm Watches are out for those areas.  

For the city, the "best" chances for snow will come at the end of the event on Friday morning as the heaviest precipitation is pulling away and colder air pulls in aloft.  We might get a brief mix in the city and the immediate burbs.   Computer guidance is suggesting that snow should accumulate to the north of the city -- after starting as rain -- as the storm intensifies and cold air ingests into the storm's western flank.  However, not everyone on the western flank will see snow.  Elevation helps -- if you're in the Poconos you'll probably get a good bit of snow.  Likewise, those in the upper parts of Bucks and Chester Counties should get some accumulations as well.   However, valleys and the urban core of I-95 will likely stay mostly rain.

Timing-wise, any transition of rain to snow should take place in the late evening or overnight hours on Thursday -- after rain starts up on the front end tomorrow afternoon or early evening.   Snow accumulation could be fast/furious over the higher elevations -- perhaps two inches per hour in the Poconos.   How quickly that snow fires up is dependent on how quickly the storm intensifies.   A slower intensification means less snow overall.   We'll have an accumulation forecast for the storm out tomorrow afternoon.

As far as Philadelphia is concerned, this should be a mainly rain event and should be over early Friday morning...perhaps during the morning commute.  Assuming no unforeseen accumulations of snow overnight tomorrow, the game may be delayed out of the gate but it looks like the Phillies have a decent shot of playing on Friday.   As always, stay tuned.

It May Be Spring, But...

 The calendar and meteorology both say it's "Spring" by definition -- in fact in a meteorological sense it's been Spring for over 20 days.   However, Mother Nature and Old Man Winter don't care to agree with such silly wishes of warmth from most of the masses and wants to send a plethora of precipitation types into the region tomorrow.    Radar is already showing the first fingers of the storm system extending into West Virginia, with the main show of this storm back in Minnesota and Wisconsin.   Moisture that's streaming out east-southeast of the main low is in association with a frontal boundary that's slipping south along the East Coast and will play a huge factor in the storm's track, our temperature, and what ultimately falls from the sky.

This will not be an easy forecast -- the dreaded "nowcast" applies to this storm as temperatures at the surface will arguably make or break your precipitation type and one's forecast.   However, with temperatures poised to be colder to the north that at least some accumulating snow is likely from Montgomery and Bucks County on north, particularly the upper parts of the county.   I'm not so convinced that applies to the city...yet...but I do think it's pretty likely that the city does get some wet snowflakes mixing in.   It all comes down to timing and temperature with this event.   More on that in a minute.

Winter Storm Watches are out for the Lehigh Valley and Berks County on north -- the watches in the Poconos definitely make sense given the profile in temperatures is going to be cold enough for mostly frozen precipitation up there although one can't rule out some rain mixing in from time to time during the day on Wednesday up north.  The Lehigh Valley and Berks, in my opinion, are the "battle zone" where a colder solution such as the one the NAM is painting gives warning snowfall since little or no mixing at the surface occurs.  However, it is the only model painting that as the Euro and GFS both paint a mixed bag event where morning snow mixes and then changes to rain during the day as temperatures warm sufficiently above freezing in most locations.    The surface warming above freezing is the difference between a couple of inches of front-end snow and a six inch snowfall in the Lehigh Valley and even the upper parts of Bucks and Montco.

Farther south, the temperature profile battle as not as huge a deal but the NAM's depiction on temperatures would suggest some snow down into the immediate city on the front end before temperatures moderate enough aloft to turn the city back to rain, whereas the GFS and Euro are more of a mix to rain scenario.

The other concern is how this system wraps up on Wednesday night.  The NAM is suggesting a changeover back to snow in the suburbs, Philly, and even parts of South Jersey but again, it's the only model showing this changeover as the GFS and Euro both wrap precipitation up in the region before temperatures begin to cool off.   It's something to keep an eye on at this point.

Even if it doesn't snow at all in the city, the temperatures won't be all that high and the rain will be rather chilly.  

We'll have a snowfall forecast out this evening for the storm system and we'll update the storm as it moves through during Wednesday.