171
FXUS61 KCTP 141043
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
643 AM EDT Tue May 14 2024

.SYNOPSIS...
An area of low pressure over Missouri early today will drift
slowly east and weaken, while a second low forms to the south of
Pennsylvania later tonight and Wednesday.

These two weather features, along with a slow moving front
drifting southeast from the Lower Great Lakes, will bring
periods of showers today through Wednesday.

Drier conditions will follow for expected Thursday into early
Friday before the chance of rain increases headed into the
upcoming weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Mainly clear skies over much of Central PA were sandwiched
between variable amounts of clouds over Northern PA and
increasing/thickening clouds spreading into the Southern Tier
counties of the state.

Comfortable nocturnal sfc dewpoints in the mid 40s to low 50s
and associated PWAT values of 0.6-0.8 inch early today will be
followed by PWATS increasing to around 1.0 inch during the
midday hours today and up to 1.1-1.3 inches this evening
through Wednesday.

Mid level lapse rates are moderate at best and the overnight
clear skies followed by mid to late morning increasing clouds
should greatly limit instability and the chc for any TSRA
today. Trimmed (or removed in certain periods and locations)
chcs for TSRA this afternoon through Wednesday as latest HREF
and Operational Models indicate MU CAPE of only a few to several
hundred J/KG at most.

Max temps today will be in the U60s across the higher terrain
of the North and West and in the low 70s throughout the valleys
of Central and Southern PA.

Southerly winds will be highest near and to the east of the
Susq Valley beneath a moderately strong southerly LLJ. Sfc wind
gusts in that part of our CWA will be in the upper teens to low
20s (KTS) with gusts further west only in the low to mid teens.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
The Mid Miss/Lower Ohio River Valley sfc low will weaken with a
secondary surface low developing over N Carolina/Southern VA
later tonight/early Wednesday ahead of an approaching shortwave.

This storm track will result in gradually backing llvl flow
keeping mainly overcast skies, relatively cool and stable air
with occasional showers across the CWA through Wednesday.

Slightly higher, but still unimpressive instability will occur
in a relatively narrow channel along and ahead of a quasi-stnry/slow
moving cold front across NW PA tonight and Wednesday.

Ensemble plumes suggest generally around a half inch of rain or
less for most spots by Wednesday evening. There could be a few
locations that see around 0.75 inch of rain over the 36 hour
period ending at 00Z Thu.

Lows tonight between 55 and 60 will be notably milder than early
Tuesday`s mins. Temps Wednesday will only climb (at best) by
8-10 Deg F as the 850 mb low center via the GEFS drifts over the
Delmarva region and the nose of an approx -2 sigma
Southeasterly 925-850 mb jet drifts N over the Mid Atlantic
Piedmont region. Current forecast maxes Wednesday may even need
to be trimmed by a few to several deg F. Strongly doubt we`ll
see much in the way of breaks that could lead to warmer highs
than expected.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Rain/frequent showers will taper to scattered showers with areas
of drizzle and fog for Wed night as the low exits the Mid
Atlantic coast.

Thursday still has the possibility of being dry for most
locations. Some guidance is depicting somewhat of a ring of fire
feature across western and northern areas with isold diurnal
shra or tsra possible, but for most areas the shortwave ridging
should keep it dry. Left the 20-30 PoPs in for Thurs given by
the National Blend respecting the low predictability of timing
and strength of mesoscale features, like the aforementioned
small ridge aloft, at this range.

On the large-scale, a fairly zonal upper-level flow pattern is
expected across the CONUS from late this week into the early
portion of next week. Within this zonal flow, an energetic
northern stream will keep frequent short-waves and surface
frontal passages traversing the northern tier of states,
including PA.

Although the above described pattern is not likely to feature
any complete washouts or widespread heavy rainfall, not many
completely dry days are foreseen either, with at least hit and
miss showers likely to prevail.

The most widespread shower activity could occur on Saturday,
with a surface wave anticipated to track south of the
Commonwealth, and a relatively cool E-SE flow pattern in place
in the lower levels. Outside of that, as alluded to above,
showers should be mostly scattered in nature and diurnally
centered on the afternoon and evening hours.

Temperatures should average close to seasonal normals for mid-
May, with mostly upper 60s-70s foreseen by day. The one
exception is Saturday, when upper 50s and 60s are most
probable. Given lots of clouds and shower activity, any
frost/freeze conditions appear highly unlikely, with night-time
lows mostly in the 50s.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The day will begin with VFR conditions across the board; however,
expect thicker clouds to begin advecting into the region with
gradual lowering throughout the late morning into early
afternoon. MVFR ceilings will move in from southwest to
northeast during the afternoon as occasional showers and a few
thunderstorms drift across the region. Ceiling heights will
generally continue to lower through the afternoon and into the
evening with most sites likely to see IFR cigs after 0Z
Wednesday.

A few rumbles of thunder could be possible with some
of these showers this afternoon and tonight, but instability is
the limiting factor and confidence in the coverage of thunder is
relatively low. Patchy fog development is also expected
overnight tonight and into Wednesday morning making IFR
conditions likely to stick around to start tomorrow.

Outlook...

Wed...Restrictions in showers/t-storms and low ceilings.

Thu...Slow improvement, with a few lingering showers possible.

Fri...Deteriorating conditions with showers increasing.

Sat...Showers continuing with reductions.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Guseman/Jurewicz/Dangelo
AVIATION...Banghoff/Bowen