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000 
FXUS61 KCTP 221609
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1109 AM EST Mon Jan 22 2018

.SYNOPSIS...
A warm front over the Interstate 80 corridor this morning will
lift slowly north today. 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 8 PM THIS EVENING/...
Still awaiting WFROPA here in Happy Valley. Right now, it's 
still Murky Valley, but visby is coming up. Expect to see the 
wind do an about face soon. Batch of showers sliding through 
the central mountains will take a few more hours to clear out of
the NE. However, a decent break of 10-12 hrs should occur until
more significant precip returns (from the west). Temp fcst 
still looking solid for a decent rise as the lower clouds are
almost gone from the south. 

Prev...
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 /8 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 /16Z MONDAY THROUGH FRIDAY/...
JST is now VFR and upstream obs indicate that it should continue
to be VFR for many hours. AOO, MDT and LNS all have VFR CIG, but
light fog. Rest of the srn airfields should be up to VFR VISBY,
soon. 

Prev...
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 through Tuesday afternoon for PAZ065-066.

&&

$$
SYNOPSIS...Dangelo/Lambert
NEAR TERM...Dangelo/Lambert

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