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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 222237
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
637 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/...
-- Changed Discussion --
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. With the loss of
mixing and daytime heating, fair weather cumulus has largely
dissipated and we`ll see mostly clear skies for the next couple
hours ahead of approaching cirrus.

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.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.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 /00Z TUESDAY THROUGH SATURDAY/...
VFR is expected under the influence of high pressure through the
TAF period. Diurnal heating has resulted in a few afternoon cu
around 4-5kft and W-NW wind around 10kts. Warm advection aloft
ahead of the next shortwave will increase cirrus by 00Z across
the area. It is possible to see some influence in lowering cigs
as the next front begins to impact the area by the end or just
after the end of the TAF period.

.Outlook...
Expect some restrictions with the approach and passage of a low
pressure system late Tuesday into Wednesday creates increased
restriction potential along with widespread rain. There is high
confidence in high pressure supporting VFR conditions to end the
work week.

&&

.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...Shallenberger