High pressure has move offshore and a cold front with an occluded low pressure center will blast through overnight leading to freezing rain becoming rain during the morning hours. Behind the front, lake-effect snows will occur in northwest PA. The upper-level low will pass over the northeast Monday night into Tuesday. With high pressure to the southwest, a westerly wind under mostly cloudy skies and cooler conditions will be the norm until Wednesday evening. A nor'easter should bring snows to parts of the state during the overnight hours into Thursday morning. A clipper rolls in on Saturday and the cold air continues to dominate during the week.
Models Used: 18Z & 00Z NAM, Hi-Res NAM, and GFS, 12Z ECMWF & UKMET
Short Term:
The freezing rain will change to rain for all locations by 14Z (9 AM), ending shortly thereafter.
The vertical motion from PVA aloft, cold air aloft (-10°C at 850 mb), and west-northwesterly winds in the boundary layer will combine to form lake effect snows over the northwestern parts of the Commonwealth. The winds will turn more west-southwesterly by about 3-to-7 degrees per hour, ending the snows from south to north during the early morning hours Tuesday.
Long-Range:
The models are not handling the timing, location, and precipitation of the nor'easter's passage very well. We went with the consensus between the 00Z NAM, GFS, and 21Z ARW while the HPC is going with a GFS-ECENS (Euro Ensembles*) blend.
The clipper is still too far out, but the models are showing it to affect areas just along and north of the Turnpike.
-Jaron Breen
Addendum:
ReplyDelete*The European Ensembles are available on WSI, but I could not find good QPF guidance.
-Jaron