917
FXUS61 KPBZ 170445
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1245 AM EDT Thu Apr 17 2025

.SYNOPSIS...
Frost is expected tonight and Thursday morning. Mainly dry
weather continues through Friday, with isolated chances Thursday
night. Thunderstorms are then possible this weekend with a
crossing cold front.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KEY MESSAGES:

- Gusty wind diminishes this evening
- Clear, calm, and cold overnight
- Frost Advisory tonight for areas south of Pittsburgh
-------------------------------------------------------------------

Relaxing pressure gradient as high pressure builds will allow
wind gusts to quickly diminish this evening. Clear skies and
calm winds tonight open the door for efficient radiational
cooling across the area and high probability of frost
development. Probabilities for temperatures to drop below
freezing are largely above 80% areawide and near 100% north of
Pittsburgh and along the ridges. A Frost Advisory is in effect
for areas where the growing season has begun (most areas near
and south of I-70).

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:

- Gradual warming Thursday before bigger warmup Friday
- Dry until shower chances return Thursday night and Friday
- Marginal Risk of storms Friday night
-------------------------------------------------------------------

High pressure continues dry weather on Thursday. 500mb height
rises and warm advection support a temperature recovery towards
normal. A subtle shortwave trough looks to traverse and slightly
flatten the ridge as it drags a surface warm front north
Thursday night into Friday. Shower chances return as this wave
crosses, but limited deep layer moisture precludes widespread
rain chances. Dry weather returns Friday afternoon as the wave
and front exit north.

Warm advection and largely clear skies are expected to result in a
surge in high temperatures 10 to 15 degrees above average on Friday.
NBM 25th percentile cloud cover (a reasonable clearer solution) has
skies clear across much of the region and NBM 75th percentile cloud
cover (a reasonable cloudier solution) still has skies largely less
than 50% cloud cover, with the clearest areas south of I-70. NBM
probabilities of temperatures greater than 80 degrees are largely
above 60% south of I-70 and even see some 40-60% probabilities sneak
into downtown Pittsburgh.

Another shortwave advances out of the Midwest region Friday night,
dragging a surface cold front eastward. Shower chances increase
again, mainly late, as this wave and front approach. There exists a
chance to see some thunderstorms along and ahead of this front, but
any thunderstorm risk would likely be late Friday night. SPC has
included some of our far western counties in a Marginal Risk for
severe weather Friday/Friday night, with hail and damaging wind the
most likely threats. LREF joint probabilities of CAPE (250 J/kg) and
Shear (30 KTS) remain largely in the 20-30% range with the axis of
best severe ingredients far to our west across the OH/IN border,
near SPCs Slight Risk.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
KEY MESSAGES:

- Showers and possible thunderstorms Saturday
- Periodic shower chances continue through early next week
- Above average temperatures through much of the period
-------------------------------------------------------------------

Ensembles continue to indicate the initial shortwave and surface
front crosses the area on Saturday with showers and storms. Time of
day looks to be a much bigger help to the severe threat on Saturday
as the front could be crossing the region during peak diurnal
heating, allowing for more potent storm production along and ahead
of it. Uncertainty in exact placement still exists this far away but
our same joint probability from the LREF shows an axis of elevated
probabilities between 40-60% south and east of Pittsburgh,
coinciding with the center of SPCs Day 4 Risk polygon.

Differences in the upper-air pattern begin to tick up from the end
of this weekend well into next week. Most ensembles favor upper
ridging across the area on the day Sunday pushing our surface
boundary to the south bringing cooler conditions Sunday. Heading
into next week, clustered ensembles seem to indicate a flatter, more
progressive but active pattern with near-daily chances to see
measurable rain as upper-level waves cross the region.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
VFR is expected through the TAF period as high pressure slides
east across the region. Calm wind tonight will pick up from the
SSW on Thursday at around 5kt. Increasing high level clouds are
expected Thursday night ahead of an approaching warm front. Some
LLWS potential is also possible late with an approaching low
level jet.

Outlook...
VFR and gusty SSW winds are expected Friday after the passage of
a warm front. Restriction potential, along with increasing
shower and thunderstorm chances, are expected late Friday night
and Saturday as a slow moving cold front approaches.
Restrictions and showers are still possible Sunday as the front
sinks slowly south, though more restrictions and widespread
showers/tstms are likely Monday with another crossing cold
front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory until 9 AM EDT this morning for PAZ029-031-075.
OH...Frost Advisory until 9 AM EDT this morning for OHZ057>059-068-
     069.
WV...Frost Advisory until 9 AM EDT this morning for WVZ003-004-012-
     021-509>511.

&&

$$

SYNOPSIS...Rackley
NEAR TERM...Rackley/AK
SHORT TERM...AK
LONG TERM...AK
AVIATION...WM