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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 162336
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
736 PM EDT Thu May 16 2019

.SYNOPSIS...
Daytime high temperatures will continue to be slightly above 
normal today through Saturday, before likely jumping to 10 
degrees or more above normal for Sunday and Monday. 
A period of showers is expected to impact the western third or 
Pennsylvania late tonight through the mid morning hours Friday.
Otherwise, isolated to scattered showers, mainly of the brief 
variety, will continue to threaten almost daily as a frontal 
boundary meanders north and south across Pennsylvania.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A ridge of high pressure at the surface and aloft will drift
across the CWA late this afternoon and this evening providing
fair, dry weather with diminishing wind. As cirrus clouds spread
in from the NW, the previous fair weather to Mdt cu will
dissipate. 

Variable amounts of cirrus followed by sct-bkn Altocu clouds
will be the rule tonight with winds becoming light south to
southwest as the sfc ridge slides to the Mid Atlantic Coast. 

High res/CAMS data indicates that an area of slowly weakening 
convection (forming over the Western Glakes this evening) will
reach the Alleghenies of Western PA around or shortly after 
daybreak then break up between 12-14Z Friday across the central
third of the state.  

The increasing clouds and 4-8kt SW breeze will lead to overnight
min temps generally in the low-mid 50s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
GEFS indicates Highest PWAT air (30-35MM over Western and 
Central PA early Friday) will sag south to the Southern Tier 
counties of PA by 18Z Friday, with negative LLVL Theta-E 
advection across the Central and North. PWAT values by late
Friday afternoon will dip to under 20 MM along the PA/NY border. 

Will layer pops for Friday afternoon from only 20-30 percent 
across the northern tier of PA where ML capes will be nil, 
to near 60 Percent across the Laurels, where CAPE will be on the
order of 1500-2000 J/KG.

Granted, there will likely be a sharper gradient, but there is 
still some uncertainty near and just south of the I-80 corridor 
whether a few stray showers could wet the ground or we'll see 
dry conditions after the brief bout of dissipating morning 
showers/isolated TSRA. 

Thunder chances are probably highest late tonight (west) and 
then again in the aftn, but mainly in the Scent and SW. SPC does
have much of the southern tier counties in our CWA within their
MRGL risk for svr storms on Friday (DY2).

Temps should rebound to the m60s in the N, but get close to 80F
along the MD border.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
*Trending warmer and more humid Saturday-Monday
*Dry breaks but still can't rule out a couple of showers or 
 t-storm through Monday
*Tuesday looks cooler/less humid with increasing chance for rain
 into midweek

Rising heights and building upper level ridging will spell a
warmer and more humid sensible wx trend through the weekend 
into early next week. While there will be plenty of dry breaks,
we still cannot rule out a few spotty showers or isolated 
t-storm during this time. Expect sparse coverage with limited
rainfall. 

We are fairly confident that Tuesday will be dry and 
and bit cooler/less humid. Model and ensemble guidance shows an
increase in rain risk heading into the middle of next week.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
A weak ridge of high pressure will supply predominantly VFR 
conditions through the remainder of this evening. After that, 
clouds will gradually thicken and lower overnight. Ceilings 
should drop to MVFR (possibly IFR) over the western highlands 
/KJST and KBFD/ after midnight, with brief vsby reductions 
possible in showers.

Included LLWS at all airfields overnight into Friday morning, 
as a 30-45 kt WSW low-level jet is expected to push across 
central PA.

.Outlook...

Fri...AM low cigs possible NW Mtns. Isolated PM tsra impacts
possible, mainly across southern Pa.

Sat...Isolated PM tsra impacts possible western highlands.

Sun...Scattered PM tsra impacts possible area-wide.

Mon...AM low cigs possible NW Mtns. Scattered PM tsra impacts
possible eastern PA.

Tue...mainly VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Steinbugl
AVIATION...Evanego