130
FXUS61 KCTP 130755
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
355 AM EDT Mon May 13 2024

.SYNOPSIS...
A warm front will brush northern PA on Monday before a cold
front pushes through on Tuesday. A wave of low pressure
tracking south of the Commonwealth will continue showery
conditions on Wednesday with drier conditions expected
Thursday and Friday.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
Nighttime Microphysics Channel shows a dendritic pattern of
valley fog across much of Central PA early this morning, the
result of mostly clear skies, light wind and wet ground.
Further east, pooling of low level moisture along and east of a
weak surface trough in the Susq Valley has resulted in broken
stratus over the eastern counties. A light upsloping flow should
result in ridgetop fog early this morning over this part of the
forecast area, particularly Sullivan and Schuylkill counties.

A weak area of low pressure and its attendant warm front lifting
across the Eastern Grt Lks is producing scattered showers/tsra
early this morning over Michigan into Southern Ontario. Latest
convection-allowing model guidance suggests a few of these
showers could reach Warren County by around 12Z.

Based on latest observations, expect min temperatures at dawn to
range from the mid 30s in the coldest valleys of Somerset
County, where patchy frost is possible, to around 50F in the
Lower Susq Valley.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
Upper level ridging building over PA should result in a warmer
and drier Monday overall. However, a weak area of low pressure
and its attendant warm front lifting through the Eastern Grt Lks
could produce a few morning showers or afternoon tsra across
the northern half of PA. Partly to mostly sunny skies and a developing
southwest flow should push readings well into the 70s.

High pressure passing off of the east coast and the resulting
southerly breeze should result in a significantly milder Monday
night, with lows in the 50s. Generally fair weather should hold
tonight with upper level ridging over the state. However, a
weakening shortwave lifting out of the Ohio Valley could support
a late night shower over primarily the southwest part of the
forecast area.

Expect an increasing chance of showers and possible tsra Tuesday
associated with an approaching southern stream shortwave lifting
northeast from the Southern Miss Valley. Model RH profiles
support mainly overcast skies, which should act to limit heating
and the chance of tsra. However, surging low level moisture,
combined with modest diurnal heating, should support fairly
widespread showers and isolated tsra by late afternoon based on
the 00Z HREF.

All guidance tracks the surface low linked to the approaching
shortwave south of PA Tuesday night into Wednesday, resulting in
another period of rain. Latest ensemble plumes suggest around a
half inch of rain is likely in most spots by Wednesday evening.
Have tweaked temps downward slightly from NBM guidance Wednesday
due to the expected rain and easterly flow. Raw NAM/GFS surface
temps peak in the 60s over most of the region Wed. Expect rain
to end Wed evening, as the low exits the Mid Atlantic coast.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Late evening update holds no big changes to the long range fcst.
Thursday-ish still has the possibility of being dry for most
locations. The S may have isold diurnal convection - but
shortwave ridging will likely 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.

Prev...
Lingering unsettled weather is possible into Wednesday, as
upper-level low pressure passes overhead.

Medium range models diverge a bit late this week. The ECMWF
continues to show unsettled weather persisting into Thursday,
as the upper- level low pressure very slowly pulls to our east.
The GFS/GEFS is a bit more optimistic, showing an upper- level
ridge bringing a period of dry weather from Wednesday night
through early Friday.

Both medium range models are in agreement in bringing our next
weather maker into the area later Friday into Saturday with
another round of showers and thunderstorms. The result would be
another Saturday with rain, easterly winds, and below average
temperatures - a beloved tradition over the last couple months
in Central PA.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
High pressure, clearing skies, and light winds will be the story
of the night across much of Pennsylvania. Given the conditions
for efficient radiational cooling fog has already begun
developing in the valleys across the north east and the Lower
Susquehanna Valley. Fairly strong signal for IFR conditions due
to low clouds or fog at MDT, LNS, and IPT. It`s possible these
sites could see 1/2 mile visibility restrictions in the pre dawn
hours. UNV has a small chance (~10%) of lowered conditions
toward daybreak.

After fog lifts/mixes out, VFR conditions prevail for everyone
on during the day on Monday. High pressure riding will become
dominant; however, a few light showers will impact northern
airfields Monday (BFD, UNV, and IPT), but no restrictions are
expected at this time.

Outlook...
Tue...Showers/tstms and reductions developing.

Wed...Showery weather and reductions continue.

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

Fri...Deteriorating conditions with showers increasing.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Dangelo/Banghoff
AVIATION...Bowen