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000
FXUS61 KPBZ 230147
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
947 PM EDT Mon Apr 22 2024

.SYNOPSIS...
An overnight frost for insulated valleys in Pennsylvania and
northern West Virginia will be followed by seasonably warm
temperature Tuesday. A passing front will bring rain overnight
Tuesday before a warming trend closes out the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
KEY MESSAGES:

- Frost Advisory is in effect for portions of Pennsylvania and
  West Virginia tonight from 2am to 9am.
------------------------------------------------------------------

The forecast remains on track this evening. Just a few minor
touch ups to hourly temperatures that have run a couple degrees
warmer than forecast, but should still drop off as wind has
dipped to less than 5 mph.

High clouds are expected to progressively advect overnight with
the arrival of upper moisture, although these clouds appear
optically thin when looking upstream on daytime visible
satellite. Overnight, gradient winds will also increase from the
south with the approach of a surface trough.

A frost advisory has been issued for zones in PA and WV where
temperature less than or equal to 36 are forecast, though
hazards should be confined to insulated valleys where winds will
remain calm. Allegheny County has been excluded owing to urban
heat island influences.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Marginal fire weather tomorrow, primarily south of I-70.
- Rainfall returns with a cold front overnight Tuesday.
- Additional frost/freeze headlines possible Wednesday night.
----------------------------------------------------------------

Warm, southerly flow returns for the day on Tuesday. As the
morning inversion breaks, a sharp increase in temperature is
progged as daytime highs push above seasonable normals.
Lingering high clouds may inhibit the most efficient warming,
but scattered to broken decks in warm advection resulted in a
slight upward adjustment in daytime high temperatures.

With an increasing pressure gradient, and mixing up to 850mb,
daytime wind gusts of up to 20mph to 30mph are possible,
particularly south of the Pittsburgh metro where less cloud
cover is forecast. Since soil moistures have had a chance to
recover, and with relative humidity observations from Monday in
the 20s and 30s, marginal fire weather is forecast for fine
fuels, particularly south of I-70.

Concerns will be squashed abruptly overnight as a passing cold
front allows for a low-QPF rainfall event. Probabilistic QPF
ranges from 0.05 to 0.15 inches on the low end to 0.4 to 0.8
inches on the high end. Virtually all of the probabilistic
distribution does not allow for any flooding concerns. Chances
of passing the all-time maximum April rainfall for Pittsburgh
are roughly 50/50 for this event (only need 0.26 more inches).

Temperature will dip below average Wednesday and Wednesday night
behind the cold front with mostly dry weather. Additional
frost/freeze headlines possible at the end of the short term
period. Probabilities of dropping below 32 degrees are already
greater than 50% for most of PA and OH.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
KEY MESSAGES:

- A warming trend is forecast into the weekend.
- Showers are possible once again by late Friday.
-------------------------------------------------------------------

Upper ridging is forecast into the weekend with daytime highs
rising as much as 25 to 30 degrees from Wednesday to Sunday
coincident with 500mb height rises of up to 240m. Clustering
shows little variability through Sunday, indicating high
confidence in a warm weekend ahead.

Ridging should limit a complete washout, but moist, warm
advection through the on the upwind side of the upper tough
axis may allow for some showers along a passing surface warm
front late Friday, and in the warm sector of a couple passing
upper Great Lakes lows Saturday and Sunday.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
VFR conditions will prevail under high pressure. Wind will be
considered light to variable after sunset with the loss of
diurnal heating.

Wind gusts will increase after sunrise Tuesday with an
approaching cold front and a lagging upper-level trough from
the northwest. Deep diurnal mixing is expected to occur with
lingering dry air in the boundary layer and cigs will continue
to remain VFR cross the region. However, mid to upper-lvl
clouds will build throughout the day from anticipated convection
upstream.

Probability of rain with VFR cigs are expected to increase near
the end of the TAF period.

Probability of rain along with MVFR cigs increases above 50%
for areas north and west of PIT after 06Z Wednesday. Cig
restrictions will heavily depending on how fast low-lvl moisture
advances into the region from the northwest.

.Outlook...

Widespread MVFR to potential IFR (DUJ/FKL) conditions are
expected to increase between 09Z to 12Z Wednesday with the
passage of a cold front.

Cig improvements will likely develop late evening Wednesday with
incoming dry, cold air in the wake of the front.

The probability of showers and isolated thunderstorms increases
Saturday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 2 AM to 9 AM EDT Tuesday for PAZ008-009-
     014>016-022-029-031-073>078.
OH...None.
WV...Frost Advisory from 2 AM to 9 AM EDT Tuesday for WVZ021-
     509>512.

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...MLB/Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek
AVIATION...Hefferan