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000 
FXUS61 KPBZ 100206
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
906 PM EST Mon Dec 9 2019

.SYNOPSIS...
Rain is expected through part of Tuesday with a crossing cold front.
Snow chances return Tuesday afternoon and night, mainly east of 
Pittsburgh.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Areas of rain should continue to cross the region tonight with the 
approach and passage of a cold front. Maintained likely to
categorical pops with jet/upper support in place. Low temperatures 
should be reached late tonight/early Tuesday morning after the 
passage of the front, though most locations will remain in the 50s
for much of the night. 

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Colder air will spread across the region on Tue morning, although 
the coldest air will not invade until Wed, when the upper-level jet 
core migrates ewd. By Tue afternoon, however, the initial 
continental cold front will be through, likely supporting a non-
diurnal trend in temperature (steady to falling thru the day) as a
result of strong cold air advection.

Moisture will stall in the region Tue/Tue night as the primary upper
trough lingers to the west. As the cold air overtakes the remaining 
moisture plume, rain will mix with and change to snow by late Tue 
afternoon anywhere that an impinging dry slot does not limit 
precipitation development.

Models are finally in good agreement that most of this moisture, and
resultant snow, will set up south and east of PIT, or north of I-80.
These areas would be the focus for any accumulations, particularly 
at higher elevation where snow ratios will be higher.

The true cold, dry air will invade the region on Wed as the ern-
CONUS trough/jet exit ewd and high pressure builds. Although air 
will be sharply colder on Wed, the dry air should aid in evaporating 
sfc moisture, thus precluding a flash freeze impact.

Thereafter, mid-level flow across the CONUS then will begin to 
flatten. Temperature will be below seasonal average, but the sun 
should make an appearance late in the week.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Cold air will remain in place through Thu, exiting ewd on Fri. 
Temperature will moderate into the weekend as quasi-zonal flow
supports the development of light sly wind. The overall pattern 
looks dry until Sat, when a shortwave trough is expected to approach
the Ohio Valley.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Cig restrictions, LLWS potential,  and scattered showers will 
continue until the passage of a cold front in the morning.

Rain will diminish in the morning after FROPA. The exception is 
areas south and east of KPIT which will still be east of the dry slot
and broad lift remains in place. Precipitation in this area will 
changeover to snow during the aftn. Increased mixing in the wake in
the front will keep winds gusty through the day. Expect VFR at all
ports Wednesday morning.

.Outlook... 
Restrictions are likely with the next low pressure system this 
weekend.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

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