Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 231120
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
720 AM EDT Tue May 23 2017

.SYNOPSIS...
Rain should pass to the southeast of the area later today and
tonight. The most likely period for rain in Central PA will be
Wednesday night into Thursday. The weather pattern will be
unsettled into the holiday weekend with a few opportunities for
rain through Memorial Day. Seasonal temperatures will trend
a bit cooler with rain expected late-week, with a modest
rebound likely into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Dense fog has dissipated over the LSV as of 10z. Beautiful
sunrise locally with a pink and purple hues illuminating layer
of bkn-ovc cirrus. Perusal of later arriving HIRES data
including HRRR suggesting perhaps a slightly better chance for
rain to reach/crossover the Mason-Dixon line around 00z and have
adjusted POPs accordingly. Overall, expect most of the area
to remain dry through tonight with greatest risk for light pcpn
south of PA Turnpike closest to MD border. Broad SW flow in
advance of deep trough/closed low dropping south from MN to MO
will provide steady stream of high clouds which may end up
shaving a few degrees off of max temps.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The deep closed low evolves slowly east from the Mid MS Valley
across the Central Appalachians Wed-Thu with complex surface
low occlusion over the OH Valley and secondary development from
the Mid Atlantic Piedmont to the New England coast by 26/12z.
Despite differences in QPF, the models generally agree with
the most likely period of rain from Wed ngt-Thu. Total rain
amounts for the 24hr period ending 00z Fri are 0.50-1" and
derived from a multi-model/WPC blend. Rain should turn more
showery Thu ngt into Friday under cyclonic flow aloft. Temps
trend cooler with expected clouds and rain.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Cool cyclonic flow on backside of departing cyclone will
maintain risk for showers on Friday. A lower-amplitude mid
level flow pattern will develop into the weekend with some
ridging likely at 500mb. Uncertainty regarding location and
timing of shortwave impulses rounding the ridge and effect of
prior upstream convection leaves plenty of question marks for
Saturday - but there is some agreement in area of max POPs over
S OH/into WV and SW PA. NBM/ECE blend yielded the highest POPs
for Sunday across Central PA associated with cold front moving
south/eastward across the Great Lakes/Appalachians. A severe
risk may accompany the cold front but still to early for
details. The large scale pattern evolves into a broadly cyclonic
regime into early next week around an upper low between the
Great Lakes and Hudson Bay. This should keep the pattern
unsettled with another round of showers/Tstorms possible next
Tuesday.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
The dense fog is gone now. Still a little fog left.

12Z TAFS adjusted for this.

Any fog across eastern PA will burn off just after sunrise.
Most of the day will feature just some high clouds. Perhaps some
light rain late, but mainly south of the TAF sites, based on
the airmass in place and guidance keeping most of the area dry.

Wed morning may feature more fog and low clouds, given that
fcst lows are at or below fcst dewpoints, cross over
temperatures. Another factor will be that the high clouds could
cut down on the cooling late Tuesday and early Wed. Thus for
now, just added some fog late.

.OUTLOOK...

Wed...Evening rain/low cigs possible, esp JST/AOO.

Thu...Rain/low cigs likely.

Fri...Showers/MVFR cigs NW. VFR SE.

Sat...No sig wx expected.

&&

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

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Fitzgerald/Martin


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