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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 210821
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
421 AM EDT Sun Apr 21 2024

.SYNOPSIS...
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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.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Low cloud cover has spread across the northern half of the CWA
and some of the Laurel Highlands as of 08Z. The temperature
fall has just about halted there. These clouds will try to get
into the frost advy area, but it has likely already formed even
if it does go away before sunrise. Temps should start to warm
up everywhere after sunrise despite the thickening high clouds.
The high clouds will slide to the east later this morning as the
wave over the Carolinas scoots off the coast. Nothing more than
a sprinkle is possible without good forcing this morning/early
aftn over the nrn tier. Maxes should be 45-55F.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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Clearing should be just about complete 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.
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&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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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.
-- End Changed Discussion --

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
VFR conds are expected to continue through 00Z Monday with high
(> 90%) confidence. Some SCT low-level clouds (5000-8000ft AGL)
will continue for the next couple of hours across NW PA before
giving way to SKC conditions. Some low-level clouds are expected
to return during the morning/early afternoon hours on Sunday
with ceilings above 5000ft AGL expected.

Winds will slowly be on the decrease overnight at 300-340 with
recent observations outlining some gusts up to 20-25kts across
SE PA. Winds are expected to dip below 10kts sustained by 2Z
Sunday and continue into the early afternoon hours. Later in the
TAF period, there is moderate (50-60%) confidence in gusts
between 15-20kts at 280-320 after 18Z Sunday at all airfields
outside of MDT/LNS.

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...
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Frost Advisory until 8 AM EDT this morning for PAZ019-025>028-
034-035-045-046-049>053-056-057.
Freeze Watch from late tonight through Monday morning for
PAZ019-025>028-034>036-045-046-049>053.
-- End Changed Discussion --

&&

$$

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