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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 222328
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
728 PM EDT Mon Apr 22 2024

.SYNOPSIS...
A Frost Advisory is in effect from 2 AM to 8AM Tuesday where
the official growing season recently started across Central
and Southern PA, while near to sub-freezing temperatures will
occur tonight across the Northern Mountains.

A ridge of high pressure at the surface and aloft will build
over the region today supplying abundant sunshine and milder
daytime temperatures, followed by mainly clear skies and light
wind tonight.

Light rain along and ahead of a cold front will arrive late
Tuesday across the Northwest half of the state and spreads
southeast Tuesday night with scattered showers lingering on
Wednesday, followed by another frost/freeze risk for both
Thursday and Friday morning.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
* Coordinated one more Frost Advisory for tonight (3rd night in
  a row) with Neighboring WFOs - PHI and LWX for all of the
  Central Ridge and Valley Region and Mid/Lower Susq Valley for
  06-12Z Tuesday. Next round of Frost/Freeze products is likely
  Wed night and Thursday night.

Essentially cloud-free skies and unlimited visibility kicked off
the start of the new work/school week thanks to ridging at the
surface and aloft building over the region and roots of the
airmass descending off the Northern U.S. and Canadian Rockies.

Temps will climb a few more deg F (from their 19Z readings in
the low-mid 50s across the higher terrain of the North and
West, and upper 50s to low 60s in the Central and Southern
Valleys) and anomalously low sfc dewpoints will remain steady or
fall another few degrees late this afternoon.

Conditions will stay favorable for near optimal radiational
cooling (particularly early tonight) throughout the decoupled
central and southeastern valleys. Expect areas of frost to form
with low temps in the low to mid 30s (and some mid to upper 20s
possible in the higher mountain valleys to the North and
Northeast of KIPT.

HREF and BUFKIT time/height cross-sections indicate that high
clouds will gradually increase after midnight and could offset
the diurnal cooling a bit, but they probably will stay thin
enough in most areas (and for the duration of the predawn hours)
that they`ll have little impact on the cooling.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Increasing llvl p-gradient following the departure of high
pressure sliding off the Eastern Seaboard will result in a
gusty south to southwesterly breeze kicking up later Tuesday
morning, leading to a warmer day on Tuesday. Max temps will
rebound to the 60s across the Northern and Western Mtns and
upper 60s to Low 70s in the Central and Southern Valleys.

There are still some fire wx concerns especially given an
increase in wind speeds (see fire wx section).

All guidance then points to light rain and a subsequent cool
down associated with a cold front passage Tuesday night into
Wednesday. The moisture return ahead of the front is rather
unimpressive (pw <1 inch), but strong forcing ahead of a potent
upper level shortwave supports a measurable rainfall. The
latest multi model ensemble blend produces most likely rainfall
amounts ranging from around 0.05 inches over the Lower Susq
Valley, to 0.25 to 0.50 inches over the NW Alleghenies.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
It appears there will be another chance of a frost/freeze Thu
and Fri AM, as Canadian High Pressure builds over the region.
Thursday morning temperatures are likely to be the coldest of
the week with lows ranging from the upper 20s in the north to
mid 30s across the southeast. Those with agricultural interests
should keep an eye on the forecast for the end of this week.
The renewed frost/freeze risk will continue to be highlighted
in the HWO.

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. Both the EPS and GEFS
indicate the warm front will lift north of the region by Sunday,
resulting in markedly warmer and more humid conditions with
scattered PM convection possible. Mean progged 850mb temps south
of the warm front are around 12C, supportive of highs in the
75-80F range.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
VFR conds are expected to prevail through 00Z Wednesday with
high (>90%) confidence. A SCT-BKN high-level (20,000ft+ AGL)
cloud deck will move into the area in the 00Z-02Z Tuesday
timeframe with some breaks of SKC expected to overnight. Winds
overnight will be light/variable with any sustained winds
expected to drop below 5kts sustained after 01Z Tuesday.

Later in the TAF period (after 18Z Monday), some lower clouds
will begin moving into central PA. At this time, model soundings
and the bulk of guidance suggests all airfields to stay above
VFR thresholds. If any airfields do manage to drop towards high-
end MVFR cigs, KBFD will be the most likely after 22Z within
stratiform rain, but low (< 20%) confidence on this occurring in
this TAF package at this time.

Outlook...

Wed...RA early with some MVFR cigs possible, Cloudy PM with
lingering showers and periods of MVFR Cigs and Vsbys.

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

Fri...Mainly dry, but increasing clouds late.

Sat...Rain moves in W early AM and continues throughout the day
with restrictions possible. TSRA possible W PA in PM hours.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Marginal fire wx conditions to start the week. MinRH 15-25%
across most of the area this afternoon with wind gusts from the
northwest gusting 15-20 mph at times. The wind will increase
Tuesday with gusts 20-30 mph from the south/southwest. MinRH
should increase by 5-10%, but still bottom near or below 30%
over particularly over south central PA. The low humidity and
breezy conditions Monday & Tuesday could result in an elevated
risk of wildfire spread.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM EDT Tuesday for PAZ019-
025>028-034>036-045-046-049>053-056-057-059-063>066.

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert/Steinbugl
LONG TERM...Fitzgerald/Banghoff
AVIATION...NPB
FIRE WEATHER...Steinbugl