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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 192251

Area Forecast Discussion
National Weather Service State College PA
651 PM EDT Fri Apr 19 2019

A slow moving cold front will move through the region later
this evening and overnight. Unsettled weather will hang around 
through the weekend as the associated upper air disturbance 
crawls eastward. Much of the time from later Sunday into mid 
week will be dry, but no long term dry spells are seen at this 


SVR Thunderstorm Watch #93 in effect until 03z for southeast
quarter of our area. Convection lifting from northern VA/MD into
high shear low CAPE environement over S Central Mtns and Lower 
Susq River Valley this evening. It won't take much bouyancy to 
support bowing line segments and isolated tornadoes but the big
question is the bouyancy in the relatively stable llvl se flow
thus far. Threat will last through the mid evening hours. 

The threat for locally heavy rain will accompany the convection as
PW in excess of 1.5" surge north on the nose of a southerly 
35-60kt LLJ, which the ensembles show to be some 3-5 Sigma above

Increasingly negative tilted upper trough and strengthening 
deep layer shear will lead to moderately strong upper 
diffluence/large scale uvvel. Selective areas of higher CAPE 
will cause scattered thunderstorms capable of heavy rainfall 
rates in excess of 2 inches per hour. The window of heaviest 
rain looks like it will be closing by around midnight with the 
HRRR taking the deepest convection east of the CWA. Scattered 
showers will continue into Saturday however.


Dry slot should bring a decrease in shower activity east of the
Alleghenies to start the weekend. Despite some clouds, high
temps should manage to peak around 70 degrees from the central
mountains into the Susquehanna Valley. Cooler temps and most
likely area of showers should be across western PA. Saturday
looks like the better day for the upcoming holiday weekend. 

Falling heights and gradually cooling temps aloft associated
with slow moving upper level low will spread shower risk to the
east across most of central PA on Easter Sunday into Sunday 
night. Temperatures will trend cooler but max climo departures 
are only about 5 degrees from mid April averages.


Expect improving conditions/dry wx early next week as high 
pressure moves into the area behind departing upper level low. 
Look for a nice rebound in temperatures with highs in the 65 to 
75 degree range on Tuesday. 80F not out of the question in the 
Lower Susquehanna Valley Tuesday afternoon. 

There is decent model agreement in the next frontal system
moving into or through the area around midweek. Beyond
Wednesday, guidance shows a large divergence in the evolution of
the boundary and overall precipitation pattern. Trends seem to
lean toward wet vs. dry into the second half of next week but
confidence is low. Temperatures are likely to cool off from
Tuesday's highs before trending warmer into next weekend.


Showers and embedded thunderstorms will continue to overspread
the flying area into the evening hours. Localized downpours are
expected, and a few of the thunderstorms could produce strong winds.
Expect widespread flight restrictions into tonight.

Unsettled, showery weather will persist into Saturday and 
possibly Sunday as well.


Sat...Widespread restrictions in the morning with some 
improvement despite continued chc of showers.

Sun...Scattered showers and areas of sub-VFR.

Mon-Wed...Mainly VFR with scattered showers.


Flash flood watch expanded westward earlier today coincident
with shift/trend in the hires models and HREF mean QPF. 

River (small stream) flooding threat remains largely predicated
on exactly where (location) the heavy rain falls. That said, 
still expecting widespread 1-2 inches across most of central PA.
Hydro models still show minor flooding on the Swatara Creek at 
Harper Tavern and Middletown. The lower mainstem Susq. small 
streams/tribs remain very vulnerable to quick rises and most
susceptible/likely to experience short duration flooding. 
Smaller, quick responding streams in the Juniata and WB Susq. 
should also be monitored for potential flooding. 

Several-foot rises are fcst on larger rivers with fcst crests
above caution/action levels at Harrisburg and Williamsport later
Saturday into Sunday.


Flash Flood Watch through Saturday morning for PAZ012-018-019-


NEAR TERM...DeVoir/La Corte
SHORT TERM...Steinbugl
LONG TERM...Martin/Steinbugl