Area Forecast Discussion
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599
FXUS61 KPBZ 181639
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1139 AM EST Tue Dec 18 2018

.SYNOPSIS...
High pressure will support dry weather through Wednesday. Low
pressure is then projected to return rain to the region for the
latter half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
1145 AM Update: GOES 16 0.64 micron imagery continues to show
cloud cover erode across the region. 12z PBZ sounding showed a
rather strong inversion around 850mb, above the cloud deck. Dry
air mixing into the layer has helped erode these clouds, making
for a rather beautiful (albeit cold) day across the Allegheny
Plateau. The previous forecast remains on track.

Previous Discussion...
With the sunrise update, just some minor tweaks were made to
hourly temperatures and dewpoints.

Stratocumulus clouds will continue to blanket much of the
region as cold northwest flow upslopes off the lakes. Coverage
will diminish over the course of the day under increasing
subsidence with building high pressure. Northwesterly flow will
stunt temperature recovery during the day...but locations south
and west of PGH where cloud cover should decrease earliest
could see values get to near/slightly below normal. Temperatures
will drop to slightly below normal overnight with minimal cloud
coverage and light winds allowing for stronger radiational
cooling.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
Dry conditions continue on Wednesday with temperatures
increasing to the mid/upper 40s as longwave troughing over the
Plains continues to transition east and winds aloft become
southwesterly. Rain chances will then begin to increase Thursday
as the aforementioned trough deepens...begins to take on a
negative tilt...and results in surface low press developing over
the gulf states that is progged to track NNE along the
Appalachians.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Rain is likely by Thursday night with periods of more moderate
rain overnight into Friday as the sfc low continues to
strengthen and deep sly/swly moisture fetch is established.
Latest model runs show reasonable continuity with previous runs
in regards to the storm track which keeps the most substantial
precipitation east of the forecast area...and have one inch
forecast on average through Friday afternoon based off ensemble
means and analogs...which also falls close to latest WPC
guidance. This will change in the coming days as more guidance
becomes available and confidence increases in track.

In the system`s wake, precipitation may change briefly to snow
on Sat. If this transpires, any accumulation is not expected to
be of substance.

After the warm second half of the work week, temperatures will
fall back into the 30s for the weekend and have limited diurnal
range with persistent cloud cover and gusty winds.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Eastward sliding high pressure will eventually evacuate the
general MVFR stratocu to the east this morning and early
afternoon, allowing for clear skies at all ports by late in the
day.

Outlook...
Restrictions are likely in rain for the latter half of the week
with the approach and passage of deep low pressure.

&&

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

&&

$$



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