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FXUS61 KPBZ 080852

Area Forecast Discussion
National Weather Service Pittsburgh PA
352 AM EST Sun Dec 8 2019

High pressure will maintain dry weather today. Rain returns late 
tonight and Monday with approaching low pressure.


Weak warm advection today as 850 flow veers to the SW and surface 
winds veer to the S-SE. Moisture will increase with the warmer air, 
and clouds will move in from the southwest throughout the day.


Warm air advection ramps up tonight as the zonal flow aloft is 
replaced by a southwest flow. Shortwave trough will swing through 
Ohio late tonight, behind a passing upper level jet. Large mid-level 
moisture plume will accompany the energy, deepening atmospheric 
moisture and increasing rain chances. Lower levels will take a bit 
longer to saturate, so widespread showers look to hold off until just
before dawn. 

Strengthening upper level jet, in the southwest flow aloft, will 
continue to supply moisture and lift on Monday. Widespread, soaking 
rain, is a good bet on Monday. Rain rates look to increase Monday 
morning with the passage of a low-level jet and the aforementioned 
shortwave trough. Main swath of more significant rain will swing 
northeastward Monday afternoon trailing the upper level energy. 

Even with the clouds and rain, impressive warm air advection will
promote well above normal temperatures. 

Models have lowered rainfall amounts, when compared to runs at this 
time yesterday. Generally it looks like 1 to 1.5 inches across the
region by Tuesday morning, with a large chunk of that falling on 
Monday. There is still some disagreement of where the axis of 
heaviest rain will fall, this is likely due to differences in the 
placement of the jet axis. Given the time frame of precipitation 
accumulation, and the lack of convection, any possible water 
issues would be isolated. 

Main cold front finally passes through the area late Monday night.
Widespread rain showers will continue until the front clears the
region around dawn on Tuesday. Showers will be light as upper level
support decreases and the deep moisture shifts southeastward.

Strong cold air advection on Tuesday as the surface front shifts to
the Mid-Atlantic region. The main moisture plume will get hung up
south and east of Pittsburgh on Tuesday as the system fights against
an impressive SE CONUS ridge. With the cold air pushing southeastward,
light snow will develop within this plume of moisture Tuesday 

Tuesday will feature falling temperatures throughout the day.


Area of snow will drift southeastward Tuesday night, exiting the
southeast ridges after midnight. Much colder air will remain in 
place through most of the week. A slow moderation is expected Friday
and Saturday. The overall pattern looks dry until Saturday.


Crossing high pressure will maintain VFR early this morning, but 
return flow after sunrise will result in stratus development with
high MVFR cigs possible at most sites by this afternoon. Rain and
related vis/cig restrictions are expected at the very end of the
period (PIT) or after (elsewhere) with a crossing shortwave.

Restrictions are likely to persist thru Wed with the advn and passage
of a strong cdfnt.



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