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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 182327

Area Forecast Discussion
National Weather Service State College PA
727 PM EDT Tue Jun 18 2019

An unsettled and stormy weather pattern will continue this week
thanks to the close proximity of a slowly meandering stationary
front. There will be multiple rounds of heavy downpours with 
the potential for flooding, along with a risk of strong 
thunderstorms on Thursday. Temperatures will not be too far from
normals through the period, but could be a little cooler than 
normal Friday and Saturday in the wake of a cold front.


Frontal boundary slowly sagging southward across CWA this
afternoon and evening. Risk of showers/tstms with potential for
heavy rain has shifted to southern half of CWA. Bit of a
nebulous forecast for just how much convection will fire over
southern half late this afternoon/evening, with higher
likelihood further to our S and E where a severe thunderstorm
watch is currently in effect. But even scattered convection in
this anomalously high PWAT air will be capable of producing
torrential downpours with potential for a quick 1-2 inches of
rain which may lead to localized flooding issues. 

The threat of flash flooding lingers into the evening hours over
the SE. But, that area has been much drier than expected the 
past two days - this is the heaviest rain for many places these 
last few days. Little consensus exists among the model QPF for 
later today and this evening over the south. Thus, without a 
clear signal either way to tip the scales, we will ride the 
watch. Ending time of 06Z looks good. 

Consensus forecast is for the convection to die down and slide 
south of the area for the balance of tonight. A few isolated 
cells may pop up again over the north central mtns later in the 
day if the sun can break through there in the aftn. The NAM and 
a few CAMs play this out. Have nudged PoPs below 30pct for the 
second half of the night. Little clearing is expected tonight 
except in the north. If it does clear out, fog will develop 
again. Lows will stay several degs above normal.


Wet pattern with repeat rounds of rain along nearly stationary
frontal zone will continue to bring an increased flood risk to 
south central PA through midweek. 

A strong low pressure system for June will track across the area
on Thursday, and could bring a significant threat of severe
storms and flash flooding. SPC and WPC severe weather and
excessive rainfall outlooks on day 3 now reflect the increased
risk levels. Rain continues into Thursday night before shifting
east/decreasing coverage into Friday morning.


Breezy and drier/less humid conditions will arrive Friday on 
the backside of the departing system. Expect a break from the
persistent rain for at least 1-2 days before more showers and 
storms return to the forecast later in the weekend and into next


Abundant low level moisture and light wind in vicinity of a
stalled frontal boundary will lead to developing low cigs and
fog across central Pa overnight, along with the chance of
showers. Latest SREF probability charts indicate IFR conditions
will become likely late tonight over the high terrain of the 
Alleghenies from KBFD south through KJST. Further east,
thickening mid level cloudiness could limit the extent of fog 
formation, but can't rule out patchy IFR vsbys. 

Diurnal heating and resulting mixing of drier air aloft will
yield improving cigs/vsbys Wednesday, with predominantly VFR 
conditions by afternoon. However, a brief reduction will remain
possible from scattered showers/thunderstorms during the the
afternoon and evening hours.


Thu...AM rain/low cigs possible. Scattered PM tsra impacts.

Fri...AM low cigs possible W Mtns.

Sat-Sun...No sig wx expected.


Astronomical summer (solstice) begins Friday, June 21st at
1154AM EDT (1554 UTC).


Flash Flood Watch until 2 AM EDT Wednesday for PAZ017>019-


SHORT TERM...Dangelo
LONG TERM...Steinbugl