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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 211908
AFDCTP

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

.SYNOPSIS...
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An upper level trough with unseasonably cold air aloft will
drift through eastern Canada and the northeastern states to
close out this weekend. A widespread frost or freeze is
expected across portions of the Commonwealth that have started
the growing season recently across Central and Southern PA, as
high pressure moves overhead and the sky clears. After a sun-
filled Monday, clouds increase and thicken up on Tuesday with
showers returning to the forecast for late Tues through Wed.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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*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.

Widespread, multi-layered and predominantly non-precipitating
clouds kept temps nearly 10 deg F below normal in many locations
with highs limited to only around 40 across the ridgetops of the
North and West and mid 40s to low 50s respectively, from the
Central Mountains to the Lower Susq Valley.

Drier air advecting east in the wake of a weak, secondary cold
front that extended from near KELM, SSW to KUNV and KCBE will
slowly break up the clouds late this afternoon across the NW
zones, between 22-23Z throughout much of the Central Ridge and
Valley Region and 01-02Z over the Lower Susq Valley.

Clearing skies will follow for tonight with temps dropping to
the quite chilly levels noted above.
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&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
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Surface high pressure building in from the Ohio Valley will
crest over the Appalachian Mountains on Mon. Temps will rebound
nicely Mon aftn. 8H temps rise a bit back to near 0C. All this
should help temps peak in the 50s over most of the area and
lower 60s in Central and SE valleys where the best warming will
occur via a light to moderate WNW wind. Vertical mixing up to
around 6 kft agl will bring the likelihood of lower dewpoints
than model guidance (by a few to several deg F).

Clear skies early Monday night will be followed by increasing
(but mainly thin) cirrus late Monday night early Tuesday.

Low temps early Tuesday should average about 3 deg F warmer than
early Monday, which should diminish the threat for sub-freezing
conditions, but won`t eliminate the potential for frost.
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&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
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Model guidance all supports dry conditions 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.
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&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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VFR conds are expected to continue through 00Z Monday with high
(> 90%) confidence. Some brief borderline or high end MVFR CIGS
will occur INVOF KBFD through 22Z.

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 gust between 15-20 kts across the Central
and NW Mtns, in the wake of a weak cold front crossing the
region. Winds will be notably lighter across the Susq Valley
until picking up by 5-10 kts for up to several hours late this
afternoon/evening in the wake of the Cfropa.

WNW Winds diminish to under 6 KTS overnight and skies clear
out.

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.
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&&

.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...Dangelo
LONG TERM...Fitzgerald
AVIATION...Lambert