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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 152019
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
419 PM EDT Sat Jun 15 2019

.SYNOPSIS...
The weather pattern will turn unsettled and stormy into Father's
Day with the potential for rounds of heavy thunderstorms across
parts of Central Pennsylvania into next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Latest radar imagery shows isolated showers developing across 
south central counties, likely in response to increasing warm 
advection pattern. Also an west to east band of showers filling
in across the northern tier counties along a convergence zone.
Accordingly, introduced isloated pops across the south central 
region, though showers are very light and speeded up pops 
across the north.

Pops in general will be on the uptick, as expected, across the
region into Sunday. A few heavy downpours are possible with 
mean QPF in the 0.50 to 0.75 inch range. Hires models show a 
better signal for heavy rainfall across the Ohio Valley.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
Isolated strong to severe storms may occur across parts of
central PA Sunday and Monday afternoon. Periods of heavy rain 
will also pose a marginal risk for localized/isolated flash 
flooding. 

A weak surface front should be located just south of Lake Erie
on Sunday. Conditional instability to the southeast of this
boundary yields thunderstorm development with potential for 
sufficient CAPE/shear combination to support isolated strong to 
severe storms. If confidence increases in destablization, SPC 
may increase categorical risk from marginal to slight. 

The aforementioned frontal boundary should sink slowly southward
across CPA Sunday-Monday and become quasi-stationary near the 
Mason Dixon line. Above normal precipitable water along the 
frontal zone could lead to rounds of heavy rainfall. There is 
low confidence in the location of heavy rain given uncertainty 
in the position of the frontal boundary. WPC excessive rainfall
outlook places a marginal risk across most of the area on 
Sunday and over the southern tier on Monday. 

Total rainfall forecast through 12Z Tuesday has 1-2 inches
across most of the area.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
A showery and muggy week in store as several waves ride along a
lingering frontal boundary that will remain nearly stationary 
near the Mason/Dixon line.

Latest guidance indicates a persistent southeast Canada trough
with confluent flow along the southern periphery in the OH
Valley to the northern Mid Atlantic. This persistent pattern 
will allow a quasi-stationary frontal system and waves of low 
pressure to maintain stormy weather across CPA much of next 
week with multiple rounds of heavy t-storms possible. Timing and
location of multiple episodes of convection will be difficult 
given low predictability especially at this range. But looks
like best chances for most sig rains will be Mon/Tue across the
west and Thursday areawide (though best prob in the NW).

Models hint at a drier period toward the end of the week into
first half of the weekend, which translates to just isolated 
showers focused on the NW half. But precip chances increase
again with another storm system by Sunday.

Though elevated dewpoints will keep muggy conditions in place
with above average low temps, highs will top out a bit below
normal each day.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
Light rain showers, generally isolated in coverage attm, will 
be on the increase into Sunday ahead of a weather system 
approaching from the west.

Despite increasing clouds, expect VFR conditions to hold at 
least into the evening hours. Lower CIGS expected tonight and
Sunday across the northwest mtns.

.Outlook...

Sun...AM low cigs poss N Mtns. Scattered PM tsra impacts poss.

Mon...AM fog possible, mainly north. Scattered PM tsra poss.

Tue...AM low cigs/fog possible. Scattered PM tsra impacts
possible south.

Wed and Thu...Rain/low cigs possible, especially south.

&&

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

&&

$$
SYNOPSIS...Gartner
NEAR TERM...Gartner
SHORT TERM...Gartner/Steinbugl
LONG TERM...RXR/Steinbugl
AVIATION...Gartner/Martin