Area Forecast Discussion
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225
FXUS61 KPBZ 182108
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
408 PM EST Sat Nov 18 2017

.SYNOPSIS...
A strong cold front will cross tonight bringing strong winds
and a changeover to snow showers by early Sunday morning.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Bulk of heaviest rain will continue to shift northward, with a
bit off a lull expected until the front approaches tonight. We
should still see temperatures rapidly warm in advance of the
front, which may offer up just enough instability for a rumble
of thunder so we will keep this in the forecast through the
early eve. Will maintain the flood watch as is for now, until
precip with the front crosses. Boundary is rather progressive
so overall concerns for flooding are minimal at this point.

Still expecting a period of strong winds with the front as it
crosses and behind with as lapse rates steepen. While pressure
rises are rather impressive, this will be just along the frontal
boundary, which may lead to the need for a special weather
statement, but not long enough to hoist an advisory as none of
the other model guidance, bufkit soundings etc, suggest
widespread and prolonged advisory-level conditions. Will leave
the current wind advisory for the terrain as is, as conditions
will linger there.

Changeover to snow is expected overnight as cold air returns to
the region. Warm and saturated ground will limit accumulation
at first, with rather low snow ratios but this should improve as
the core of the coldest air approaches later Sunday.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Northwesterly flow will continue scattered snow showers and
keep temperatures in the 30s through the day. Highest PoPs
remain the snow belt north of I-80 and in the mountains of
PA/WV/MD where lake enhancement/upslope is anticipated. Still
thinking 2-4 is reasonable, though some higher amounts may be
possible. Best window for accumulating snow in the terrain looks
to be as the second shortwave dives through the trough tomorrow
afternoon, deepening the saturation layer through the snow
growth zone, but this only lasts for a short period of time.
With this in mind, have opted not to issue a winter weather
advisory at this time.

Snow showers will continue through Sunday night with the passage
of this second shortwave and northwest flow. Building ridge of
high pressure and backing flow should end chances for showers by
Monday morning, with dry conditions expected through Tuesday.
Some warming is is expected under an upper ridge, which should
get us closer to seasonal values by Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Minimal change was needed in the extended. The majority of the
week will be dry with seasonal temperatures outside of a weak
wave progged to pass to the north midweek. Have kept slight
chances in for locations north of I80 on Wednesday. Next system
is progged for late in the period, with broad troughing in
place. Model guidance differs, so opted to stay near a blend of
guidance.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
Any improvement above MVFR will be brief this evening as the
warm sector of low pressure digging toward the Southern Great
Lakes traverses the area. Expect redeterioration to IFR with
rain and then snow as the systems cold front crosses in the
predawn of Sunday.

The strong pressure gradient of this system will continue to
support llvl wind shear and gusts of 30 to 40 kts with the
frontal passage tonight.

MVFR stratocu will linger in the cold flow behind the front on
Sunday, in addition to local IFR in snow showers, especially at
FKL and DUJ.

.Outlook...
The next chance for restrictions is expected with a late Tuesday
cold front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Wind Advisory from 7 PM this evening to 10 AM EST Sunday for
     MDZ001.
OH...Flood Watch until midnight EST tonight for OHZ039>041-048>050.
PA...Flood Watch until 3 AM EST Sunday for PAZ007>009-013>016-
     020>023-029-073-074.
     Wind Advisory from 7 PM this evening to 10 AM EST Sunday for
     PAZ074-076.
WV...Flood Watch until midnight EST tonight for WVZ001-002.
     Wind Advisory from 7 PM this evening to 10 AM EST Sunday for
     WVZ510>514.

&&

$$



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