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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 170555
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
155 AM EDT Mon Jun 17 2019

.SYNOPSIS...
An unsettled and stormy weather pattern is expected across 
central Pennsylvania this week. There will be multiple rounds 
of heavy downpours with the potential for localized flooding 
and isolated severe storms. Temperatures and humidity levels are
forecast to remain near average for mid to late June.

&&

.NEAR TERM /THROUGH TODAY/...
A bit of clearing has allowed vsby to drop well over the 
central mountains and NW. A balancing factor may come in the 
form of thickening/lowering cloud cover as convection slides 
through far SWrn PA and will likely spread at least mid clouds 
in from the S. This area will continue to be monitored for need 
for a dense fog advy.

The showers and isold patches of thunder over the SW will likely
weaken some, but continue to march slowly north and east through
morning. One hour FFG is generally 1.5-2" in the SW, though, as
they have seen only very light rain over the last 24-36 hrs.
Temps not going anywhere until sunrise. Dewpoints in the north 
are in the u50s, with 70F at KLNS. Don't see much change through
morning. Even after sunrise, temp rise will likely be hampered 
by all the clouds and rainfall over the srn half of the area. 
Will take a notch off the maxes for today and keep them within a
couple degs of 70F. The exception will be the srn tier of 
counties where sun is more possible. Will keep them in the 
m-u70s. 

Prev SWODY2 has srn tier in a slight risk for severe tstms.
Threat of excessive rain also exists, mainly across the southern
half of the CWA. But, the ground will have to get primed at
first this morning (see above), and see some extremely heavy
downpours. Instability is in question with the cloud cover
forecast as it is. Shear, esp low level shear, is Our PWATs 
will be above normal for mid June, running 1.5-1.8" from I-80 to
the MD border. MBE vector magnitudes will be very small in the 
aftn and evening even if storm motion is 15-20KTs. Therefore, 
flooding may be the bigger concern today. Will need to chat with
the neighbors about the need for a flood/flash flood watch for 
today (and perhaps Tues).

&&

.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
An active wx pattern continues with an east-west frontal 
boundary waggling north and south, but seemingly never out of 
PA, during the entire week. Little change is in the forecast for
this time period, as minute differences are all that is seen
between the going forecast grids and what the newest guidance
would suggest. Again, there is a threat for severe wx and
excessive rainfall/flooding during this period. 

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Fairly relentless stream of showers and scattered thunderstorms
in store for much of central PA Mon into Thu as an E-W oriented 
frontal boundary wiggles over the region. Though it won't be
raining the entire time, it will definitely be a soggy and
cloudy run of weather.

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 as another storm is progged to lift into the Great Lakes 
Sunday brushing our western areas.

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 /06Z MONDAY THROUGH FRIDAY/...
Main problem overnight will be pockets of fog.

Other issue will be the very narrow band of showers lifting
north and east into the southwest part of central PA.

06Z TAFS sent.

Earlier discussion below.

A dying cold front sagging into southern Pa will be the focus 
for scattered showers late tonight. However, the main concern 
overnight will be low clouds and fog developing just north of
this boundary. 03Z surface analysis shows IFR cigs/vsbys across
the northern mountains, with mainly VFR conditions noted across
the rest of the region. SREF/HREF probability charts support 
the continued likelihood of low cigs across the northern 
mountains overnight, with the Laurel Highlands also likely to 
experience IFR/LIFR cigs toward dawn Monday. Elsewhere, plenty 
of low level moisture, a diminishing wind and breaking clouds 
support the idea of patchy fog. However, confidence is not high 
in significant fog formation due to an approaching area of low 
pressure and associated return of cloud cover late tonight, 
which would diminish the threat of radiation fog.

Models indicate an area of low pressure will track across
southern Pa Monday, producing rain and low cigs across the
central part of the state. Somewhat more favorable conditions
are possible along the southern tier of the state, where
precipitation will fall as scattered showers, rather than a
steady rain, and cigs are likely to be higher. More favorable 
conditions are likely over the northeast corner of the state, 
where little rain is expected and VFR cigs appear likely.

.Outlook...

Tue...AM low cigs/fog possible. 

Wed...AM rain/low cigs possible.

Thu...AM rain/low cigs possible. Scattered PM tsra impacts
possible.

Fri...AM low cigs possible W Mtns.

&&

.CLIMATE...
Astronomical summer (solstice) begins Friday, June 21st at
1154AM EDT (1554 UTC).

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo/Evanego
LONG TERM...RXR/Steinbugl
AVIATION...Fitzgerald/Martin
CLIMATE...