-- Discussion containing changed information from previous version are highlighted. --
506
FXUS61 KCTP 021721
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
121 PM EDT Thu May 2 2024

.SYNOPSIS...
-Warm/dry weather with lower humidity continues for today and
 most or all of Friday

-Trending unsettled into the weekend with some periods of rain
 and thunderstorms Sat/Sun

&&

.NEAR TERM /UNTIL 10 PM THIS EVENING/...
The only cu that have popped thus far are over far srn Somerset
Co. Dewpoints are dropping across most of the area, but still
holding in the u50s in the SE. Still expecting those to dip a
little, too. Fcst rolling along nicely.

Prev...
Tranquil conditions with mainly clear skies cover the entire
forecast area early this morning. Surface T/Td spreads of
several deg F or more are negating any notable valley fog
development.

Temps to start the day will be close to 10 degrees above climo
in the warm advection regime ahead of a weak/dry cold front
front that was sliding across the NW Mtns of PA at 09Z.

Daybreak readings will range from 45F to 50F throughout the
higher rural valleys of Central PA, to the mid and upper 50s
across the Lower Susq Valley.

The aforementioned weak cold front will bring primarily a few to
several deg F drop in sfc dewpoints today, yielding another
excellent vsby day with abundant sunshine. This frontal
boundary will settle just south of the Mason Dixon Line by this
afternoon as the associated shortwave passes off the New England
Coast and upper level ridging sharpens and crests over PA
tonight.

Vertical mixing of model 850mb temps in the 12-14C range will
equate to highs ranging from the mid 70s over the N Mtns, to
the mid 80s in the Southern Valleys, which are 10-15 degrees
higher than what we normally see for early May.

A nearly east/west band of low level convergence and higher
humidity is depicted via the latest HREF near the Mason/Dixon
line this afternoon yielding MU CAPE values of a few to several
hundred j/kg.

A weak capping inversion and very dry air above 800mb suggests
any convection is very unlikely there.

The very dry air above the weak inversion aloft supports
undercutting NBM dewpoints this afternoon over the central and
northern part of the forecast area. We continued to employ a
blend of the NBM and the much lower numbers obtained from the
MixedDewpoint Tool.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Sfc and upper level ridge of high pressure will remain over PA
for most or all of the daylight hours Friday. Clouds will
increase across the Western part of the CWA later Friday
afternoon, bringing the chance of a few showers near and to the
west of the RT 219 corridor after 21Z Friday.

Southeasterly flow will develop across much of the CWA Friday
as the center of sfc high pressure exits stage right off the Mid
Atlantic Coast. This will lead to cooler daytime highs - mainly
in the mid to upper 70s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
-Noticeably cooler this weekend with periods of rain
-Trending warmer/above climo but remaining unsettled next week

A slow moving frontal system combined with anomalous pwats will
bring periods of rain to central PA this weekend. A few non-
severe thunderstorms are possible, most likely along and west
of the Alleghenies on the edge of warmer air surging into the
upper Ohio Valley. The eastern slopes of the Alleghenies into
the Susquehanna Valley will noticeably cooler with rain, low
clouds and moist southeast flow. We trimmed max temps on
Saturday due to the CAD pattern setup. Rain/showers continue on
Sunday with highs recovering ~10F on the western and southern
periphery of the CWA. Despite the relatively high moisture
available, overall stability should limit rain rates especially
east of the mtns and preclude flooding risk. 48hr blended mean
QPF ranges from 0.50-0.75" with spot amounts up to 1 inch
possible.

The front stalls near or south of the MD line before lifting to
the northeast (as a warm front) into midweek. The favors the
best chance for rain the SW zones on Monday before POPs increase
to 50-70% Tuesday into Wednesday. After a weekend cooldown,
temps are forecast to trend warmer/back above climo into the 70s
to low 80s next week.
-- End Changed Discussion --

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
A weak area of low pressure passing to our north has pushed a
weak/dry cold front into srn PA. The front shouldn`t move too
much more to the south today. An upper ridge will crest
overhead, keeping the sky clear, except for a few cu, mainly in
the Laurels. WNW sfc winds are already gusting into the teens.

Tranquil weather will persist through tonight with diminishing
winds thanks to the high pressure aloft and to our NE. Expect a
return/srly flow to develop in the morning on Friday. This will
help generate more cu, and decrease stability, esp in the W.
SHRA/TSRA are expected late aftn/evening Friday at JST and BFD.
A warm front will rise into wrn PA on Friday, but stall out
there until Sat when a cold front catches up and pushes it
eastward. This will push the SHRA/TSRA to the east and across
the rest of Central PA. Widespread SHRA/TSRA are expected
Friday night into Sunday. The heaviest rain will be Fri night
over the W and Saturday aftn/evening in the SE. IFR
restrictions will be possible Fri PM into Sunday.

Outlook...

Sat PM-Sun...Widespread restrictions across the central and
western mountains due to low cigs. SHRA likely with a chance of
TSRA.

Mon-Tues...AM fog/clouds poss. PM -SHRA possible areawide.

&&

.CLIMATE...
Near-record highs are forecast for some locations in south
central PA this afternoon. The daily records are listed below.

Harrisburg88 in 1913
Altoona87 in 1954
State College86 in 1938

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Lambert/Fitzgerald
LONG TERM...Steinbugl
AVIATION...Evanego/Colbert
CLIMATE...Steinbugl