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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 170422
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1122 PM EST Sat Feb 16 2019

.SYNOPSIS...
A weak disturbance will move across the region later Sunday and
Sunday night. A stronger storm will approach for the middle of 
next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Most of the CWA has clear to scattered skies with the higher
elevations of the west and north still under a shallow blanket 
of stratocu.

The low clouds will continue to slowly shrink in coverage
leaving a mainly fair overnight. 

Dewpoints currently in the 15-20 deg range signal a seasonably 
cool night with lows expected to range from the 10-15 across 
the Northern Mountains to the lower 20s in the Southern 
Valleys.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
*Light snow accumulation (north) and mainly a light wintry mix 
 expected (south) later Sunday afternoon and Sunday night

SE Colorado low (994 MB) this afternoon will race east overnight
and weaken as it jumps the shallow cold air over the Southern 
and Central Plains states.  

Limited deep-layer moisture (PWAT gradually climbing to between
0.5-0.75 inch by Sunday afternoon), but moderately strong jet
forcing beneath its thermally indirect left exit region will
lead to some bands of enhanced 850-700 mb FGEN (mainly across
the northern half of PA) to bring a widespread light snowfall
later Sunday afternoon through Sunday night. Thermal profiles
with an elevated (few to svrl deg C above zero) layer near the
850 mb level will lead to transition of some light snow to a 
light wintry mix across the southern half of the state. 

Snow accums range from around one inch near and just south of
Interstate 80 and across the Laurel Highlands, to between 2 and
3 inches over the Northern Mtns of PA. Throughout the Southern 
Valleys of the state, the later afternoon onset of the precip
and lighter intensity (further away from the best deep-layer 
forcing across Nrn PA) will mean snow/sleet accums of generally
a coating with a thin glaze of icing possible Sunday night as
the thicker/seeder feeder clouds move off to the east and
shallow/warmer clouds take their place. 

Max temps Sunday will reach the upper 20s across the north, and
32-35F before the onset of the mid/late afternoon precip in the
south.  
 
Intermittent light snow or areas of light freezing rain will 
likely continue Sunday night across the northern mtns, where 
mean 925-850 mb temps will stay several deg C below zero.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
330 pm update... The weak low pressure wave zipping across the
mid-Atlantic Sunday night will move offshore Monday. Any
lingering light wintry mix early Monday will taper off to light
rain or snow showers.

Monday night and Tuesday, expansive surface high pressure will
expand from central/eastern Canada into the northeastern 
states, with dry and seasonably chilly weather.

Current indications still are that another wintry mix event will
affect the Commonwealth from later Tuesday night through
Wednesday, with a snow to sleet/freezing rain to perhaps rain
transition anticipated. Stay tuned for the latest forecasts, as
specific details become clearer over time. 

Overall, our weather should dry out Thursday and Friday, as the
previous system lifts away to our northeast. Cyclonic W-NW flow
could bring some light rain or snow showers, but they look
inconsequential at this early juncture. 

Current model consensus points to a deepening storm system 
lifting northward through the Great Lakes/upper Midwestern 
states. Such a storm track would be likely to ultimately bring 
rain and milder temperatures. However, an initial wintry mix 
still appears possible prior to that. Once again, uncertainty is
high this far out, so stay tuned for later details.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Late evening satellite imagery showing clear skies across much 
of central Pa. However, MVFR stratocu remains trapped beneath 
inversion across the northwest part of the state. High pressure
will build into the area tonight, resulting in a diminishing 
breeze and likely causing the lingering stratocu to break up 
over northwest Pa. 

Excellent flying conditions are expected Sunday morning.
However, expect deteriorating conditions during the afternoon
and evening, as an approaching storm spreads a light wintry mix
and lowering cigs across the region. Latest model output 
supports widespread IFR conditions by late Sunday evening. 

Outlook...

Mon...AM low cigs possible. 

Tue...No sig wx expected.

Wed...Wintry mix possible. 

Thu...AM wintry mix/low cigs possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Dangelo/Lambert
LONG TERM...Jurewicz
AVIATION...Fitzgerald