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FXUS61 KPBZ 061534

Area Forecast Discussion
National Weather Service Pittsburgh PA
1034 AM EST Fri Dec 6 2019

Light rain showers and drizzle will be possible today ahead of an
advancing cold front. High pressure is expected to bring dry and 
quiet weather this weekend.


1030am update...Added sprinkle/drizzle wording areawide this morning
as moisture increases ahead of the advancing shortwave trough, but
struggles to overcome drier air near the sfc. Otherwise, the forecast
remains on track.

Previous Discussion...
Increasing moisture will increase chances for drizzle and light rain
showers through this afternoon ahead of a passing shortwave trough.
Dry air near the sfc will initially limit areas that see precip 
reaching the ground, but continued top-down moistening and 
additional lift with the arrival of the sfc cold front will allow for
more developed rain showers. Timing of the sfc cold front plus
upslope flow means light accumulating precip will favor areas south
of I-70 and along the eastern ridges.

Passage of the shortwave trough and cold front will create a brief
period of NW-erly flow, that combined with cooler air, could create
light wintry mix showers north of I-80 and at elevations above
2,000ft. Otherwise, building sfc high pressure will bring dry
conditions to the region overnight.


Near-neutral temperature advection will maintain below average 
temperature given quasi-zonal flow aloft through Saturday. Clouds
will gradually clear late Saturday afternoon, once drier advances
into the region.

A pattern shift is then anticipated Sunday as a Hudson Bay low 
deepens, returning swly flow and warm advection aloft. Above average 
temperature is expected Sunday, with surface high pressure 


Stratiform rain chances increase Monday as a series of shortwaves 
impact the region on the van of the deepening Hudson Bay low and 
associated central Plains trough. Deep moisture transport is expected
given strong jet support, with PWAT values in exceedance of the
climatological 90th percentile. This should support widespread rain 
Monday into Tuesday.

Long term model blends agree on the arrival of an arctic front by 
Tuesday / Wednesday, changing rain over to snow given cold advection
in nwly flow behind the frontal passage. Wednesday high temperature 
should top out 15 to 20 degrees below average. Some moderation, 
albeit limited, is expected Thursday as flow aloft becomes quasi- 


Low-level wind shear likely this morning ahead of an approaching 
cold front with frontal passage over the course of the afternoon.
Scattered showers will be possible but given limited moisture should
not bring widespread restrictions other than an MVFR cigs. 

More restrictions are likely early next week with the next



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