Technical Discussion

Synopsis...

Large dome of high pressure to dominate weather today and tomorrow.  Cold front sweeps through early Thursday followed by intense 500mb trough for Thurs/Fri/Sat as it digs into E-US promoting the chance of scattered snow showers across NW and NC zones.  Cold beginning to the weekend before moderation occurs Sunday and next week.

Short Term (Tues-Wed Night)...

Extremely cold night last night with BFD reaching 18, ABE reaching 23 and UNV getting to 27.  First widespread freeze of the season has ended growing season almost everywhere across the state if it wasn't over already.  Today will be chilly as well although not as breezy as yesterday.  Despite the brilliant sunshine, low 500mb heights and thicknesses less than 540dm will make it a chilly day.  Highs will struggle to make it out of the 40s in many locations with 50s SE.  Another good night for radiating tonight although airmass will begin to moderate as high begins to slide eastward.  We'll be on the return flow side of the high so expect chilly low temps tonight although probably a few degrees warmer than last night in most locations.  A few more high clouds expected tomorrow as cirrus from approaching cold front as well as cut off low to south overspread the region.  As the air mass modifies tomorrow, expect warmer temperatures than today.  50s for most locations with 40s in the cool spots.  A cold front will move begin to move into the state on Wed night, allowing clouds to work their way into western zones by midnight.  This will allow for less radiating and therefore warmer temperatures on Wed. night.  Front will be moisture starved for the most part as it does NOT look like it will interact much with the tropical moisture in the South associated with the cut off low.  This should be monitored however as more moisture could impact the forecast.  At this point, we're calling for just scattered rain (and a few snow) showers Wed night as front slides through the entire state by mid morning on Thurs.

Long Term (Thurs-Sat)...

500mb trough behind cold front digs sharply into northeastern quadrant of country Thursday allowing sfc low to spin up off the DE/VA coast.  At this point, it looks like it will be too far east to affect much of the forecast area.  A shift to the west must be monitored though as that could a bit of rain for Thursday for NE/SE/CR.  See RJ's discussion on Monday evening for a good break down of possible scenarios.  What does look fairly certain is that the low moves to our NE on Thursday night and Friday, bringing in northwesterly winds and colder temperatures.  500mb trough will keep temps well below normal on Friday and Saturday with scattered rain and snow showers (orographic and lake effect) across NW/NC/LH zones.  Temperatures will have a very hard time making it to 45 on Saturday so expect a chilly football game!  Flow is progressive though and trough will move out during the day on Sunday leading to nicer and warmer weather by next week with Indian Summer a possibility as highs may reach into the 60s.

-Dan DePodwin