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05/03/2011

LINE OF HEAVY SHOWERS FOR FAR WESTERN SUBURBS

A cold front is marching through the Susquehanna River Valley of eastern PA still to the west of The Tri-State area. The large swath of rain from the Deep South northeast along and just to the west of the Appalachains is found mostly behind the cold front this evening.

Out ahead of this front, temperatures warmed up nicely across central and eastern PA into far western New Jersey this afternoon to around 80 as dewpoints climbed through the 50s to close to 60 degrees by day's end, as well. Closer to the Atlantic across the remainder of The Tri-State area, the atmosphere has remained much more stable in the lower layers thanks to a southeast wind off the cooler waters. Temperatures made it to the mid 70s in NYC with 60s across Long Island. Sufficient instability led to a rapid development of thunderstorms over central PA this afternoon with a severe thunderstorm watch for much of central and eastern PA west of The Tri-State area which expired at 10 p.m.

Strong storms over Western NJ and the Catskills are bringing gusty winds and heavy downpours but there are no warnings out on these storms presently. The storms lose alot if not all of their punch as they push east across the Tri-State area reaching the more stable low level air mass. So, for the most part, most locations will have a nice evening, but we will have to keep a close eye on the radar for a storm sneaking into western areas this evening.

Otherwise, we will have to wait until later tonight for a better chance for a couple of showers (perhaps a rumble of thunder) for the remainder of the tri-state areas as the front slowly nears from the west. The best chance for wet weather appears to hold off until after midnight as more impressive upward motion and moisture convergence will set up during the second half of the night into the early morning hours of Wednesday. Showers late tonight will likely evolve into a steadier period of rain heading into Wednesday morning. Rain at times will be with us through the morning hours as the upper-level trough nearing from the west takes on more of a neutral tilt -- beginning to cutoff from the main flow later in the day. Best moisture and convergence shifts out to sea by the afternoon, but we will still have to contend with the trough axis nearing from the west which will keep the chance for a couple of showers through the afternoon.  That being said, there could also be some brightening of the sky late in the afternoon. Rainfall tonight through the end of the day tomorrow should not be all that impressive, generally around 0.25 of an inch along the I-95 corridor, locally 0.50 of inch, especially west.

Upper-level low will be overhead tomorrow night with lingering clouds, perhaps a shower. This feature will sit and spin over New England Thursday. With low heights, chilly air aloft and the fact that's it's early May, any sunshine to start off Thursday will likely result in plenty of self-destruct stratocu clouds during the midday and afternoon hours. We cannot rule out an instability shower, although the best chance of that appears to be to our north.

A fairly fast west to east flow will be set up across the northern third of the  nation later this week and into the weekend, so timing individual shortwave troughs and disturbances embedded in the flow will be the main challenge. One of this features will near from the west Friday and will likely end up diving east-southeast across the mid-Altantic around the base of the upper-level low which should still be spinning over northern New England. This will allow for more in the way of cloud cover along with an increased chance for showers. We may be able to squeak in a dry day Saturday before the next disturbance brings more showers into the area for Mothers Day.

Posted by Lee Goldberg on May 3, 2011 | Permalink

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