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000
FXUS61 KCTP 211633
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1233 PM EDT Sun Apr 21 2024

.SYNOPSIS...
An upper level trough with unseasonably cold air aloft will
swing through eastern Canada and the northeastern states late
this weekend. A frost or freeze is expected in many areas of
Central and Northern PA this morning and again Monday morning
as high pressure moves overhead and the sky clears. Showers
return to the forecast for late Tues through Wed.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
Widespread,multi-layered and predominantly non-precipitating
clouds covered the entire CWA this midday hour. A weak northern
stream trough dropping SE across the Glakes and a more amplified
and slightly wwd lagging southern stream short wave was
responsible for higher based (altostratus and cirrostratus)
clouds across the SE third of the CWA with some weak
echoes/virga seen across the Lower Susq Valley.

A weak, secondary sfc cold front was crossing the Alleghenies of
Northern and Western PA ATTM and will move across the Ridge and
Valley region of the state this afternoon leading to a subtle
wind shift from the west to the west-northwest.

A few deg C of neg theta-E advection in the 925-850 mb layer
will help to create some breaks in the high based strato cu deck
present across the NW half of the CWA as we journey through the
afternoon hours.

High temps this afternoon will vary from the mid to upper 40s
over the Northern and Western Mtns to the mid 50s throughout the
Mid and Lower Susq Valley.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM MONDAY/...
 *Freeze Warning for the Ridge and Valley Region and Middle
  Susq Valley with temps as low as 25 to 32F, while a Frost
  Advisory has been posted for the Lower Susq Valley with mins
  of 33 to 35 and some 30-32F mins possible in the coldest rural
  valleys.

Clearing skies will follow for tonight. Thicknesses and 9H/8H
temps remain static thru Mon PM. Therefore, we could see temps
very similar to Sun AM again on Monday morning. Now, there won`t
be clouds (high or low altitude) like Sun AM which should allow
them to go even a deg or two colder still. The one trick may be
how much wind is left overnight - there may be a little breeze.
Therefore, we don`t have quite enough confidence to post
another frost advy for Mon morning just yet. However, the
progged mins are between 31-33F for the ridge and valley region
(which is roughly the part of PA that is SE of the Allegheny
Front and NW of the Lower Susquehanna Valley). Therefore, even
if the wind stays up, they could get a freeze (without any
visible frost).

High pressure nosing in from the west crests over the
Appalachian Mountains on Mon Temps rise nicely on Mon aftn-
night. This should keep clouds away, but allow for a light WNW
wind. 8H temps rise a bit back to near 0C. All this should help
temps into the 50s over most of the area and lower 60s in the SE
where they`ll have a downslope llvl flow.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Model guidance all supports dry conditions Monday night through
most of Tuesday, as high pressure and an associated low-pwat
air mass overhead starts to slip a little to the east. However,
upper level troughing does support below average temperatures on
Tues. Some frost is again possible Tues AM, but as slight warm
advection starts aloft, the temps might not be able to get quite
as cold as Mon AM. The wind does look light for most of the CWA.

A decent warmup looks likely Tuesday, as high pressure moves
off the east coast. Medium range guidance all points to a
chance of showers and a subsequent cool down associated with a
cold front passage Tuesday night into Wed AM. The moisture
return ahead of the front looks unimpressive, but strong forcing
ahead of a potent upper level shortwave suggests a good chance
of rain. Latest plumes support a general 0.2 to 0.4 inch
rainfall.

It appears there will be another chance of a frost/freeze Thu
and Fri AM, as Canadian High Pressure builds over the region.
Those with agricultural interests should keep an eye on the
forecast for the end of next week.

The next chance of rain will come Friday night into Saturday
associated with low pressure lifting into the Grt Lks and the
associated warm front approaching PA.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
VFR conds are expected to continue through 00Z Monday with high
(> 90%) confidence. Some brief borderline MVFR CIGS will occur
INVOF KBFD.

Stratocu, topped by Altocu will have bases mainly between 045
and 060 this afternoon across the Ridge and Valley Region, with
BKN-OVC CIGS based AOA 10000 FT AGL in the SE.

West to WNW winds will increase slightly this afternoon as a
weak cold front crosses the region. There is moderate (50-60%)
confidence in gusts between 15-20kts after 18Z today at all
airfields outside of MDT/LNS. Peaks gusts at KMDT and KLNS
should be around 15KT as the clouds begin to break up later this
afternoon.

Outlook...

Mon...No sig wx expected.

Tue...Slight chance of evening showers/cig reductions NW Mtns.

Wed...Showers move in west-to-east from rain early, continues
throughout the day. TSRA possible SW late PM.

Thu...Clearing as high pressure builds into the area.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 2 AM to 8 AM EDT Monday for PAZ019-025>028-
034>036-045-046-049>053.
Frost Advisory from 2 AM to 8 AM EDT Monday for PAZ056-057-059-
063>066.

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Lambert
SHORT TERM...Lambert/Dangelo
LONG TERM...Fitzgerald
AVIATION...Lambert