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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 060950
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
550 AM EDT Thu Aug 6 2020

.SYNOPSIS...
-- Changed Discussion --
A ridge of high pressure will stretch from Michigan to the New
England state today and Friday, while a stationary front will
be located just south of the Mason-Dixon line. A few weak waves
of surface low pressure developing over the Central Appalachians
and Delmarva region today and Friday will bring scattered to
numerous showers and thunderstorms southeast of I-99 today and
Friday. For the weekend, plenty of sunshine and dry weather will
precede the arrival of warmer, more humid air and daily
thunderstorm chances during the first part of next week.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A very dry airmass with mainly clear skies and light wind across
much of the northern and western mountains was leading to
anomalously cool temperatures in the upper 40s to low 50s with
areas of valley fog, while a well-defined and persistent jet
entrance region over Central PA was leading to large scale lift
of the warmer and more unstable airmass across SE PA and points
south. This is leading to shield of thick clouds and an area of
showers and scattered TSRA (in the Baltimore/D.C. area before
daybreak) lifting NE.

Several hours of high POPS between 80-100 percent during the mid
to late morning hours today across our SE zones will capture
this initial weak wave of low pressure, and the associated minor
drift nwd of the llvl Quasi Stnry front. Convection-allowing
models produce upwards of a quarter to one half inch of rain
with the few isolated storms. This shouldn`t be anywhere
near enough to cause any flooding issues, even with 3"+ falling
on Tuesday in the eastern parts of the CWA.

As the jet entrance region weakens and broadens out a bit and
shifts a bit further north into central PA this afternoon and
early this evening, the large scale weak ascent and areas of sfc-
based CAPE of just over 1000 J/KG will support the formation of
isolated to scattered SHRA/TSRA further north to near a KIDI t
KUNV and KSEG line for this afternoon.

Max temps today will be in a fairly tight range (upper 70s to
Low 80s) due to the greater amount of clouds in the typically
warmer valleys of central and SE PA, and abundant late
morning/early afternoon sunshine across much of the Laurel
Highlands and Northern Mtns.

Winds will be light and mainly from the northeast this morning,
then southeast this afternoon.
-- End Changed Discussion --


&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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Mostly cloudy to overcast skies will be spread across the
forecast area tonight with min temps mainly in the mid to upper
60s. Temps across the northern mtns could dip into the upper
50s.

The upper trough moving out of the Ohio valley will weaken as
it approaches tonight into Fri, but create enough forcing (via
the formation of a sharp and compact upper level jet streak) to
maintain a weak sfc low over Maryland and keep unsettled
weather in the forecast.

Went with scattered to numerous showers tonight and scattered
showers and tstms Fri afternoon, adding up to about 0.25 to
locally 0.50 inch in the Lower Susq, with lesser amounts
elsewhere.

Max temps Friday will vary form the low to mid 70s over the
Northern Mtns to around 80F in the larger metro areas across the
Lower Susq Valley.
-- End Changed Discussion --

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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High pressure will build in for the weekend, with increasing
sunshine and just a slight chance of a stray shower on Saturday.
Temps will climb back to a few degrees above normal, with highs
in the 80s, but humidity will be on the low side.

The longer term will feature a return of warmer weather, with
temperatures generally 5-10 degrees above average from Mon
through Wed as an upper ridge builds over the Eastern US.
Dewpoints climb back to the upper 60s and 70s for Mon and Tue,
and perhaps even the mid 70s in the Lower Susq on Tue and Wed.
Combined with temps in the upper 80s to near 90, this would mean
Heat Index values take a run at the upper 90s to near 100 Tue
and Wed afternoon, so long as the low level moisture doesn`t mix
out in the afternoon and cause the dewpoint to drop. Boundary
layer mixing and entrainment of drier midlevel air was something
that was noted on many of the hotter days in July, but a wetter
ground and increased moisture flux from vegetation after Isaias
may result in the dewpoint remaining elevated during peak
heating next week, at least across the Lower Susq.

Scattered airmass thunderstorms are possible each afternoon
from Mon through Wed. This stretch of weather looks like
"typical summer", with no strong fronts or highly anomalous
features to speak of, other than increased heat and humidity.
-- End Changed Discussion --

&&

.AVIATION /09Z THURSDAY THROUGH MONDAY/...
VFR conditions most of the area. Clouds will spread north into
the area from the south across the PA/MD border. Fog is possible
across northern valleys for a couple hours near sunrise. A few
showers are possible in SE airfields before daybreak and
continuing through the day. Don`t expect long- lasting
reductions but could see brief cig/vis reductions if a heavy
shower moves over an airfield. A few SHRA may pop up over the
Laurels/wrn Alleghenies in the aftn, too. But, those will be few
and far between. Not expecting much TS, but the highest chc of
that will be for MDT and LNS during peak heating but before the
minor wave moves to the east of the area.


A series of weak low pressure systems will track just south of
of our area later this week into the upcoming weekend. Almost
everyone will get wet at some point Thurs PM-Fri. High pressure
just to our north will then press southward and settle overhead
for the weekend.

Outlook...

Sat-Sun...VFR. AM fog poss nrn valleys.
Mon...Mainly VFR with local impacts from sct aftn/eve TS/SHRA.

&&

.CLIMATE...
Although the current pattern with below-normal temperatures is
not record-setting, a couple stats are worth noting. Low
temperatures Thursday morning are expected to be the lowest
since late June at a few sites:

SITE8/6 FORECAST LOWLAST OCCURRENCE
Harrisburg64June 26 (41 days)
State College58June 25 (42 days)
Bradford46June 17 (50 days)

The high at MDT on Thursday is forecast to be 79 degrees. If the
temperature fails to reach 80, it will be the first time since
June the. The current stretch of 48 days is tied for 5th
longest at that site.

&&

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

&&

$$
SYNOPSIS...Lambert/Banghoff
NEAR TERM...Lambert/Banghoff
SHORT TERM...Lambert/Banghoff
LONG TERM...Colbert/Banghoff
AVIATION...Ross
CLIMATE...