Technical Discussion

Synopsis...

Warm front passage tonight, cold front passage tomorrow night and a chilly Tuesday.  Moderating trend with seasonable temps to close out the work week with a few chance of showers.

Near Term (thru tonight)...

Warm front precip moving into W zones at this hour but dew point depressions of ~20 degrees are making it hard for initial precip to reach the ground.  Expect rain showers overnight across the entire state as warm front lifts northward into New York.  LI's go slightly negative towards dawn and some thunder has been reported over Michigan this afternoon so would not rule out a rumble overnight although we did not mention this in the forecast due to the low probability.  As for temps, went above MOS tonight, especially in western zones where post warm frontal advection will begin earlier, leading to steady or rising temps overnight.  Overall a mild night in store for much of the state...very spring-like.

Short Term (Monday-Monday Night)...

Warm front will clear the entire state by morning tomorrow and allow the Commonwealth to break into the warm sector during the day.  Biggest question mark in temps tomorrow is how far north can the very mild (70s) air reach.  It seems that North Central will (as usual) have the hardest time seeing the very mild air although the strong WAA may help them reach into the 60s.  Across the southern half of the region, MOS is generally in the low 70s and we nudged temps slightly higher due to pre frontal conditions.  Would not be surprised to see some locale in S central PA reach 80 tomorrow.  Very warm air currently to the south and west (100 in parts of Texas this afternoon).  In addition, current MOS error in the warm sector across the mid west is 5-10 degrees.  Although it probably won't be that extreme, temps should be on the warm side tomorrow.

FROPA tomorrow night and timing is still a bit questionable.  WRF and GFS are in agreement of a ~7pm passage across the west, ~11pm across the central mountains, and after midnight across eastern zones.  Fly in the ointment will be who sees a thunderstorm tomorrow evening as the front first moves into PA.  Obviously western zones have the best chance at a rumble and possibly a gusty t-storm.  SPC has entire state in "See Text" and we'll have to monitor how this changes tomorrow.  Although severe threat looks minimal, LI's around -2 or -3 along with decent shear parameters could lead to some strong winds tomorrow evening across the western half of the state.  Front should begin to wash out as it moves farther east, along with a diminishing threat of thunderstorms.  Temps will crash into the 40s behind the front as winds back NW.  One thing to note would be the possibility of high temps tomorrow occurring after dark in some places immediately prior to FROPA.

Long Term (Tues-Thurs)...

Cold advection day on Tuesday will be quite a shock with temps in the low 40s with brisk NW winds.  Cold air aloft associated with trailing 500mb trough will promote instability and scattered showers (similar to Saturday).  A more organized disturbance will enter the region on Wednesday with more light rain showers and more widespread than Tuesday's precipitation.  By Thursday, weak high pressure takes control allowing for pleasant conditions and moderating temperatures.  Looking towards the future, the +NAO and -PNA argue for a more mild pattern in the next few weeks which will be a nice change from the previous two weeks.


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