286
FXUS61 KPBZ 272014
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
414 PM EDT Thu Jun 27 2024

.SYNOPSIS...
High pressure building across Pennsylvania and New York tonight
will bring quiet weather that should last into Friday. A warm
front will lift north Friday night with increasing chances of
showers. Showers and thunderstorms are then expected Saturday
and Saturday night as a cold front pushes south into the warm
and humid airmass.

&&

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

- Dry weather and light wind expected overnight.

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Surface high over Michigan should build across SW Ontario this
evening and then New York and Pennsylvania later tonight. Quiet
weather will continue as a result. Lows will be near normal with
850 mb temps in the 12-14C range.

&&

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

- Dry weather continues.
- Temperature rises above normal again Friday.

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Surface high pressure transitions over New England and heights
rise ahead of the next upper-level shortwave trough. Heights
will end up around 70 meters higher than this evening, and 850
mb temps are forecast to rise to about 18C.

Positioning of the high will support weak warm, moist advection
amid mostly clear skies to raise area temperature about 5
degrees above the daily average solidly into the 80s. Broad
ascent may increase mid- to high-level clouds and even offer
low probability of showers Friday night as a warm front
approaches. Precipitable water is shown to increase to about
1.8" by late Friday night, supporting the potential for
precipitation.

&&

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

- Shower and thunderstorm chances return Saturday into Sunday
  with the next low pressure system.
- Severe and Flash Flood threat returns Saturday.

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Broad ascent within warm, moist southwesterly flow ahead of the
main upper-level trough will support increasing shower and
thunderstorm probabilities starting early Saturday morning as
the associated sfc low moves across the upper Great Lakes.
Saturday afternoon and evening is likely to be active with a
crossing shortwave trough and a cold front approaching from the
west.

Severe weather will once again be a possibility as increasing
mid-level flow overspreads an increasingly moist warm sector
with 850 mb theta-e increasing into the 345-350K range. Latest
ensembles show CAPE values from 1000-2000 J/kg with effective
shear ~30-40 kt. Machine learning output shows 5% probs for
both wind and tornadoes, which is not surprising looking at
forecast hodographs.

Flash Flooding will also be a threat with anomalously high
PWAT (>2"), abundant buoyancy, and warm cloud depths >13kft,
which would all lead to very efficient warm-rain processes, and
torrential downpours in storms. Corfidi vectors show the
classic ridging pattern over Ohio with values decreasing to 5-10
knot range during the evening, indicating potential for slow-
moving or backbuilding storms with heavy rainfall. WPC has
noted a >5% risk for excessive rain while machine learning
output highlights >15% risk.

Dry weather and seasonable temperature are likely by late
Sunday into next week as the upper trough axis moves east and
high pressure builds in from the western Great Lakes.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Scattered boundary-layer cumulus will gradually diminish this
afternoon and evening and then mainly clear sky with light wind
expected tonight as surface high builds across NY and PA. River
valley fog is possible but is not expected to impact the TAF
sites.

The high will push to the Atlantic Friday evening, and southerly
wind will begin to bring moisture back north. However, VFR is
expected through the period and winds will be relatively light.


.Outlook...

VFR is expected through Friday amid high pressure. Restrictions
are possible Friday night with a crossing warm front.

Restrictions are likely Saturday and Saturday night with
showers and thunderstorms ahead of and along a crossing cold
front. VFR returns Sunday under high pressure and is likely to
persist Monday and Tuesday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Craven
NEAR TERM...Craven
SHORT TERM...Craven
LONG TERM...Craven
AVIATION...Craven