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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 191845
AFDCTP

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

.SYNOPSIS...

A slow moving cold front will move through the region later
today 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 point.

&&

.NEAR TERM /THROUGH TONIGHT/...

Look for the showers to continue becoming more widespread 
through the afternoon into the evening hours. The threat for 
locally heavy rain will increase as PWATs 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 normal.

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.

We moved the Flash Flood Watch back to the west a layer of
counties given the latest CAMs depiction of an axis of heavy
rain back over central PA as well as over ERN areas. The 
strong, southerly wind aloft will be easily tapped by 
thunderstorms with wet microbursts and localized strong to 
damaging gusts possible within the broad Marginal Risk area that
covers the southern two-thirds of the forecast area. 

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. 

&&

.SHORT TERM /SATURDAY/...
Falling heights and gradually cooling temps aloft ahead of a
slowly filling upper trough and weakening/elongating sfc low
will mean plenty of multi-layered clouds and sctd-numerous rain
shower coverage for much of Saturday into Sat night. 

QPF will average anywhere from several hundredths of an inch in
some locations, up to around 2 tenths of an inch in others. a
few clusters of locally heavier showers and even a low top tsra
can't be ruled out Sat afternoon and evening, which could bring
a few locations between 0.25 and 0.50 of an inch.

Max temps Sat will cool by just 2-5 deg F, and will still be 
several deg or more above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
While it will start off mild, the Easter weekend looks to be 
cold and wet. Best chance of dry and sunnier conditions will be 
later on Easter Sunday.

Another cold front expected on Monday, followed by high 
pressure trying to build southward. Still some chance of showers
at times, given the front being nearby.

See hydro section below for more detail on the potential for 
heavy rain.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...

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.


.Outlook...

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.

&&

.HYDROLOGY...
Only minor changes made to the QPF at this point.

Flash flood watch remains in effect for this afternoon into 
Saturday morning for the central and eastern portions of of the 
CWA.

Rainfall from showers and thunderstorms today and tonight  
could be enough to produce flooding, though mainly on tribs of 
the Susq Mainstem and North Branch, where MMEFS shows 4-5 points
of concern for exceedance of minor FS. 

Storm total QPF via model consensus and EFSs has decreased
slightly since 24 hours ago, but still in the 1-1.5 range across
much of Central and Western PA, with locally 2-3 inches expected 
across the east between Noon Friday and noon Saturday. 

Latest runs having that convective look to the precip with big 
stripes of heavy/intense rain and gaps in between. No solution 
in particular should be followed verbatim when it comes to QPF. 
Model solutions generally keep the heaviest rain over the east, 
with relatively lighter amounts elsewhere. 

The larger waterways (Susq, Juniata) should be fine until at 
least Saturday or Sunday if they ever get high.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday morning for PAZ012-018-019-
026>028-035>037-041-042-045-046-049>053-056>059-063>066.

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Lambert
LONG TERM...Lambert/Martin
AVIATION...La Corte
HYDROLOGY...