1:16 p.m. marked the official start of the calendar Summer. Enjoy the extended daylight for the next few days with some of the longest days of 2011 ahead before we begin to lose.
The main weather feature we will be following for the next 36 hours will be a slow moving warm frontal boundary that will meander through our forecast region. This is an extremely difficult forecast and the latest computer model guidance is not providing any cleat answers as to the progress of this front. The models are all over the place. This has major implications as to temperatures, dew points, and placement of precipitation.
If the warm front remains right over our region…and cloud cover remains persistent…temperatures could be held in the lower eighties at best…and we would just see some scattered showers and thunderstorms with the main threat heavy rainfall. Extreme southwestern sections of the area would be the exception and the place to watch for thunderstorm’s reaching severe criteria.
If the warm front lifts through at least the southern two-thirds of the region…we would see some sunshine break through the clouds…temperatures spike into the middle and upper eighties with even a few 90 degree readings…and we would be in the favorable quadrant for severe thunderstorms if indeed a wave develops and portions of our region lie immediately south the front within the warm sector.
At this point…it does not appear that the warm front’s movement is so aggressive that the entire area enters the core of the warm sector and thunderstorms remain mainly to our north.
Since late this weekend, the Storm Prediction Center has kept us in a slight risk for severe thunderstorms. With the uncertainty, they have removed our region from the risk…but have kept “see text” probabilities. Depending on the cloudiness…they very well may need to bring back the risk designation for Wednesday as some downbursts and hail could develop in the strongest thunderstorms. Near the warm front can also be a favorable area for the development of rotation. Needless to say, we will be keeping an eye on any developments tomorrow as it will be a day of near-term decisions and now-casting.
On Thursday, the warm front should move to our north. This should allow the region to enter the core of the warm sector. The mostly cloudy skies should clear and the region should be partly sunny with a buildup of cumulus clouds as afternoon heating takes place. With an approaching cold front from the west and hot and humid conditions…thunderstorms…scattered in nature…will be a possibility. The best chance will likely be near the focus…so north and west of Philadelphia. The entire region has been placed under a slight risk designation of severe weather in the Day 3 Convective Outlook that issued by the Storm Prediction Center. Bay and sea breezes...if they can move inland...would help serve as a possible focus.
The cold front will swing through on Friday. Showers and thunderstorms will be likely as a result. Depending on the timing of the front and amount of destabilization ahead of the front…additional strong to severe thunderstorms would be possible. A lingering opportunity for thunderstorms could occur on Saturday…especially if any upper-level features pass through behind the front.
Sunday and Monday are the driest days of the next seven with high pressure in control and more northerly wind component lowering the humidity substantially….
Flash flooding is also a possible threat Wednesday and Thursday…maybe into Friday.
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