Tuesday, May 23, 2017, 12:42 PM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 231500
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1100 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/...
Updated the forecast with latest blend and some of the HRRR.
Used GOES-16 and HRRR to modify the clouds. There will be cirrus
near us all day. But in northern and central areas the cirrus
will be thin at times so times clouds and sun. There is some
partial clearing in western PA.

To the south the clouds are thicker and will thicken as the day
goes on. KLWX shows rain mainly south of the DC area at this
time. Our blends and the HRRR all want to bring up some light
rain to and just across the PA/MD border late this afternoon and
evening. Tried to keep POPS in chance range along border a few
hours either side of about 8 PM. 

As the wave moves away overnight any light rain chances slide to
our east. 

Should be areas of patchy fog.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Any fog should burn off in morning Wednesday. Another relatively
nice day between QPF events. The approaching lumbering cut-off
low is far wetter than the wave that should have missed most of
our region on Tuesday. But chance rain should slowly increase
late in the day Wednesday in the west and slowly spread east
overnight. 

Most guidance indicates the potential for a 0.5 to 1.0 inch
event focused mainly over central PA. The first part of Thursday
looks to be quite wet. 

Previous:
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 /15Z TUESDAY THROUGH SATURDAY/...

Minor adjustments to the TAFS this morning. VFR will dominate 
today as the only weather issue of note is the high clouds
passing across the region. There could be some patchy light rain 
this evening from KTHV-KCXY-KLNS but it should be very light.

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...Grumm
SHORT TERM...Grumm/Steinbugl
LONG TERM...Steinbugl
AVIATION...Grumm/Martin

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