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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 200119

Area Forecast Discussion
National Weather Service State College PA
919 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/TOR threat is starting to wind down across the southeast
quarter of my area, but hydro/FF threat is ramping up as line of
locally training convection in rich PW environment is targeting
eastern/southeastern portions of my area late evening through 
the early morning hours. PW in excess of 1.5" surging north on 
the nose of a southerly 35-60kt LLJ ahead of negative tilted 
upper trough and strong upper diffluence/large scale uvvel. 
Selective areas of higher CAPE support scattered thunderstorms 
capable of heavy rainfall rates in excess of 2 inches per hour. 
The window of heaviest rain 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