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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 162047
AFDCTP

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

.SYNOPSIS...
A ridge of high pressure over the Midwestern States will build
east into our region and provide us with dry weather and 
seasonably cold temperatures this afternoon. A weak system 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/...
Shallow stratocu and flurries have retreated wwd as anticipated
this afternoon and will stay confined near and to the west of RT
219 over the NW Mtns of PA through early tonight with a mean NNW
flow in the shallow blyr.

Elsewhere, skies will be mainly clear. The current 6-10kt
sustained NW wind (with gusts into the mid and upper teens for
the next few hours across our NE zones) will gradually veer
around through the north early tonight, before becoming light 
easterly twd daybreak.

Sfc dewpoints currently in the 15-20F range signal a seasonably
cool night as they dip several deg F with a light/dry North-NE
llvl flow. Min temps will range from the 10-15F range across the
Northern Mtns 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 /21Z SATURDAY THROUGH THURSDAY/...
Low-end VFR and MVFR bkn-ovc ceilings will stay intact through 
the first half of tonight across many areas west of RT 219, 
while VFR with SKC to few strato cu persists elsewhere.

RAP and NAM soundings indicate that vertical mixing up through 
the 2500-3000 ft AGL level this afternoon will yield a mean 
wind from 320-340 degrees at 8-10kt with minimal wind gusts
across the west, and gusts in the mid to upper teens over the
eastern half of the state.

Sfc winds will veer about 20 degrees to 350 degrees after 00Z 
Sunday and both sustained winds and gusts will relax to the 6
kts or less.

Excellent flying conditions expected Sunday morning under a 
light north to east wind and VFR conditions with just some mid- 
level clouds AOA 10KFT AGL drifting in from the west.

BKN-OVC VFR ceiling advances east across the region early 
Sunday afternoon, followed quickly by the leading edge of snow 
and mixed precipitation (with MVFR-IFR conditions) beginning 
early Sunday afternoon (west) and late in the afternoon (east).

Outlook...

Mon...MVFR cigs northwest 1/2.

Tue...No sig wx expected.

Wed...MVFR/IFR in snow/wintry mix.

Thu...areas of MVFR and a light wintry mix possible in the 
morning then some improvement to mainly VFR in the afternoon 
and night as a ridge of high pressure noses in from the west.

&&

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

&&

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