000
FXUS61 KCTP 230531
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
131 AM EDT Tue Apr 23 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 THIS MORNING/...
Conditions remain favorable for radiational cooling tonight,
with surface ridging/dry air lingering over the state. Have
therefore blended the lower MAV min temps with those of the NBM.
Expect areas of frost with low temps in the low to mid 30s over
most of Central PA. A Frost Advisory remains in effect for
tonight (3rd night in a row) for all active growing season
counties in the Central Ridge and Valley Region and Mid/Lower
Susq Valley.

HREF and BUFKIT time/height cross-sections indicate that high
clouds associated with an upstream trough will gradually
increase after midnight and could offset the diurnal cooling a
bit, but they probably will stay thin enough in most areas
that they`ll have little impact on the cooling.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
High pressure passing off of the east coast and the return
southwest flow will result in a breezy and warmer Tuesday.
Mixing down model 850mb temps of around 6C yields expected max
temps ranging from the low 60s over the NW Mtns, to near 70F
across the Lower Susq Valley.

Model soundings continue to show some fairly dry air above a
weak inversion Tuesday, a signal that supports undercutting NBM
dewpoints by a few degrees. This will have fire wx implications
(see fire wx section below).

All guidance points to a round of showers and a subsequent cool
down associated with a cold front passage Tuesday night into
Wed AM. Latest convection-allowing models indicate the showers
will reach the NW Mtns before sunset Tue evening. The moisture
return ahead of the front looks unimpressive (no positive PWAT
anomalies), but strong forcing ahead of a potent upper level
shortwave supports a good chance of measurable rainfall. Latest
plumes indicate most likely rainfall ranging from around 0.05
inches over the Lower Susq Valley, to around 0.3 inches over the
NW Mtns.

&&

.LONG TERM /WEDNESDAY NIGHT 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.
Ensemble plumes suggest Thursday morning is likely to be the
coldest of the week with lows ranging from the mid 20s in the
north to mid 30s across the southeast. However, the southeast
counties may be equally cold Fri morning, due to the proximity
of the retreating surface high. 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. Medium range guidance
indicates large scale forcing will be weak, with upper level
ridging over PA. Therefore, any rainfall should be on the light
side.

Both the EPS and GEFS indicate the warm front will lift north
of the region by Sunday and Monday, 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 /06Z TUESDAY THROUGH SATURDAY/...
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 Tuesday), 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. Highest confidence in MVFR cigs will be near
06Z Wednesday behind the passage of a cold front.

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.

&&

.FIRE WEATHER...
Low humidity and breezy conditions could result in an elevated
risk of wildfire spread Tuesday afternoon. The strongest winds
with gusts of 25-30 mph should be over the northern mountains,
where relative humidity should stay above 30 percent. Afternoon
RH values should dip below 30 percent over central and southern
PA, but winds will be somewhat lighter there.

&&

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

&&

$$

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