Area Forecast Discussion
Issued by NWS State College, PA

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004
FXUS61 KCTP 221300
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
800 AM EST Mon Jan 22 2018

.SYNOPSIS...
A warm front over the Interstate 80 corridor this morning will
lift slowly north today. This weather feature will bring
occasional light rain or drizzle and areas of fog this morning,
with just some lingering isolated to scattered showers for this
afternoon.

A potent area of low pressure moving across the Great Lakes
will push a trailing cold front through the Commonwealth on
Tuesday. Temperatures will rise well above normal today and
stay there through early Tuesday, before falling back to near or
slightly below normal Wednesday and Thursday. A rebound to
above normal temperatures will occur again by next weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Surface warm front extended near the RT22/322 corridor in
south-central PA early this morning with weak isentropic lift
from the southwest producing widespread low stratus to its north
and east, and a dual-multi layer of stratocu and alto cu in the
warm sector across the southern tier of PA.

Expect occasional light rain, drizzle through much of this
morning, before some improvement with just some isolated-sctd
showers leftover this afternoon as the warm front lifts across
the northern mtns and eventually into New York State by late
today.

The weak low-level isentropic...and orographic lift over the
mtns and interface of the shallow cool air and warmer moist air
aloft will yield areas of dense fog through about 14-15Z today
across the higher terrain - AOA 1800 ft MSL.

Temps will remain relatively mild for late January and mainly
in the upper 30s to lower 40s. A few pockets of cooler air
around 35F will persist across the Middle Susq Valley early
today. Blended model guidance points toward a very mild
afternoon with temps ranging from the mid-upper 40s across the
NE to the balmy upper 50s over the southern tier counties. These
highs will depart from normal by 13-15F across the NE and by
nearly 30 degrees over the Laurel Highlands.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Mild weather will continue overnight. A few showers early on
will rapidly expand in coverage from SW to NE across the region
for the second half of the night as deepening uvvel develop
with the approach of the left exit region of a 130 kt upper jet
lifting NE from the tenn Valley. The rain could fall heavy at
times for brief periods just ahead of an approaching cold front.

Cold front crosses central PA Tuesday morning with weak
secondary low forming in the lee of the Appalachians supporting
a period of enhanced rainfall over the eastern 1/2 of PA on the
order of 0.50-0.75" (as front occludes into early Tuesday
afternoon). A rather potent, SW 50kt LLJ could also generate a
rumble of thunder. River ice concerns are addressed in the
hydrology section.

Gusty WSW winds, possibly as high as 40 to 45 mph occur in the
wake of the cold front Tuesday afternoon and evening.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The progressive pattern will keep the mid/late week cool-down
rather brief before temperatures moderate/trend warmer into the
upcoming weekend.

Gusty westerly winds with top values between 35 and 45 mph will
continue Tuesday night, before gradually decreasing through the
day Wednesday.

Occasional snow showers are likely downwind of Lake Erie
Tuesday night and Wed but should only amount to light accums of
a coating to 2 inches in most places.

Dry wx under high pressure Thu- Fri with chilly starts to the
day (especially in the east) with moderating temperatures
heading into the weekend as the next (weaker) low pressure
system lifts across the Great Lakes bringing chances for rain on
Sat increasing into Sunday.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
Moist flow, along with calm winds and will continue to have VLIFR
cigs across the northern mountains (KBFD) while progressively
higher cigs are expected further south. Trapped low level
moisture along with calm winds has allowed fog/mist to develop
overnight. These reduced vsbys, along reduced cigs at UNV and
IPT will continue through the morning. Light precipitation
south of the front continues with light showers at times at MDT
and LNS with scattered showers moving in from the west. While
IPT and SEG are LIFR, areas across southeast Pa (KMDT/KLNS) at
13Z, are MVFR. The latest model soundings and MOS guidance
support the idea of a possible period of the MVFR cigs/vsbys
continuing through mid morning. Expect predominantly MVFR cigs
at KJST and AOO through the day, where a southerly flow results
in drying/downsloping off of adjacent higher terrain.

Warm front is progged to lift through western Pa on today, resulting
in a return to VFR conditions along the spine of the
Alleghenies, including KJST and AOO. Elsewhere, modest
improvement will come slowly across the eastern half of Pa on
the cold side of the front. Cigs and vsbys should decrease again
tonight with more widespread showers possible out ahead of a
cold front tonight into tomorrow morning. Along with this front
will be a LLJ which will bring a LLWS problem that will become
a concern Monday evening into Tuesday morning.

Outlook...

Tue...AM rain/low cigs poss, then windy with PM shsn poss w mtns.

Wed...AM shsn possible w mtns.

Thu-Fri...No sig wx expected.

&&

.HYDROLOGY...
Marietta gage /MRTP1/ pretty much steady right now, although ice
effects continue. The Flood Watch for this area lasts into
Monday afternoon. Due to the mild temperatures, there is a
potential for ice movement, but also deterioration/thinning with
time. All locations along rivers and streams that have
significant ice buildup should monitor water levels closely for
the next several days.

The anticipated rainfall totals of 0.5 to 0.8 inches over the
next 48 hrs is much less than we had a few days ago, and the ice
is less pervasive/extensive due to our relatively mild temps
(versus the period leading up to our previous significant
rainfall).

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 1 PM EST this afternoon for PAZ065-066.

&&

$$
SYNOPSIS...Lambert/Evanego
NEAR TERM...Lambert/Evanego
SHORT TERM...Lambert/Evanego
LONG TERM...Lambert/RXR
AVIATION...Fitzgerald/Ceru
HYDROLOGY...



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