000
FXUS61 KPBZ 240346
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1146 PM EDT Tue Apr 23 2024

.SYNOPSIS...
A crossing cold front will increase precipitation chances
tonight and early tomorrow. A warming trend is expected to close
out the week.

&&

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

- Showers tonight with a passing cold front.
- Rumble of thunder, brief gusts to 30-40 mph possible.
------------------------------------------------------------------

Minor adjustments were made for the late evening update based on
the latest observations and near term model output.

Previous...
Rain showers are moving across the area this evening in a zone
of pre-frontal convergence and along a cold front. Plenty of
near-surface dry air evident on the 00z PIT sounding is
resulting in sporadic wind gusts of 30-40 mph (51 mph at KHLG)
right before and at precipitation onset, especially south of
Pittsburgh where the lowest RHs are. Expect that this threat
will continue to the east as the showers keep moving, but with
saturation the gusts are and will continue to diminish in the
showers. Wouldn`t rule out a few low confidence rumbles of
thunder overnight, especially toward daybreak as mid-level drier
air noted on water vapor imagery and the core of a 500 mb
thermal trough slide overhead and allow for some modest
instability to develop with latest hi res ensemble guidance
placing 100-200 J/kg of CAPE, especially north of Pittsburgh.

Precipitation totals have trended down slightly with
the latest update. The best chance (40-50%) to exceed a quarter
of an inch will be along the ridges with upslope enhancement.
There is only about a 30% chance of exceeding a quarter of an
inch along I-80 and a 15% to 25% chance elsewhere. This means
Pittsburgh will likely not exceed its all-time April rainfall
with this event.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Few showers possible Wednesday, followed by a frost/freeze
  Wednesday night.
- Dry and warmer Thursday.
----------------------------------------------------------------

Post-frontal cold advection will force saturation in a low deck
on Wednesday. This, combined with the cold advection itself,
will keep daytime high temperatures a few degrees below average
on Wednesday. Quasi-unstable, low-level thermodynamic profiles
in saturation may lend to a few shallow daytime showers,
enhanced by a couple passing 500mb shortwaves.

Overnight, drier air will advect in from the north, reducing
cloud cover along with it. Clearing combined with calm surface
conditions and anomalously cool low levels will lead to
moderate confidence in a freeze north and west of Pittsburgh
(greater than 50%), with a frost possible elsewhere. A Freeze
Watch has been issued accordingly.

The return of surface high pressure on Thursday will lend to
another dry day with mostly clear skies. Surface heating will
allow a slight rebound in high temperatures.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Much warmer and unsettled through the weekend.
- Forecast uncertainty increases considerably next Tuesday.
-------------------------------------------------------------------

Model ensembles indicate ridging, warm advection, and rising
1000-500mb heights will result in dry and warmer weather on
Friday. The ridge will shift east of the area Friday night and
Saturday, as a shortwave trough embedded in southwest flow aloft
crosses the region. Showers will return with the approach and
passage of the wave.

The ridge is then progged to become reestablished across much
of the Eastern CONUS through Sunday night. Dry weather is
expected most of the period from Saturday night through Sunday
night, through diurnal instability could be sufficient for
isolated to scattered showers and thunderstorms.

Rising 1000-500mb heights, and 850mb temperatures around 14 deg
C, should result in highs as much as the upper 70s on Saturday
(most likely for eastern Ohio), and the mid 80s on Sunday (most
likely for the lowlands).

Multi-model clusters are incredibly consistent with the 500mb
pattern through Monday, but uncertainty increases considerably
thereafter. Some clusters have the maintain the eastern ridge
which would allow for continued warm weather; other clusters
develop quasi-zonal flow or eastern troughing, which would tend
cooler and more unsettled.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
High pressure will keep VFR conditions in place through this
afternoon and evening. Winds gusting from the west-southwest up
to 25 knots will continue before decoupling just after 00Z.
Expect cigs to begin lowering with the approach of a cold front.
Showers are expected to impact ZZV by 03Z and then PIT by 06Z.
MVFR at terminals will worsen to IFR and below through the
remainder of the overnight and into Wednesday morning. Frontal
passage is expected by 12Z but IFR and below conditions may
remain through the end of the TAF period.

.Outlook...
Widespread MVFR to potential IFR (DUJ/FKL) conditions are
expected to increase 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...Freeze Watch from Wednesday evening through Thursday morning
     for PAZ007>009-013>016-020-022-077.
OH...Freeze Watch from Wednesday evening through Thursday morning
     for OHZ039>041-048-057.
WV...None.

&&

$$

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