PBZ issues Area Forecast Discussion (AFD) at Aug 4, 3:28 AM EDT888
FXUS61 KPBZ 040728
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
328 AM EDT Sun Aug 4 2024
.SYNOPSIS...
After a couple of morning showers east of Pittsburgh, mainly
dry weather is expected today and tonight as high pressure
builds in. Shower and thunderstorm chances return later Monday
and Tuesday with a crossing cold front.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
- Isolated morning showers ending
- Areas of fog early this morning
- Mainly dry weather for much of the day
-------------------------------------------------------------------
A shortwave trough axis was analyzed from near DUJ to AGC to
MGW. A few showers continue to develop east of the trough axis,
and this should continue this morning as the wave tracks
eastward. Clearing behind the trough, and plenty of low level
moisture in place, will continue to support fog across the area
early this morning. THe fog will dissipate as mixing begins
after sunrise.
Otherwise, dry weather is expected today after the passage of
the trough, and as high pressure builds in. High temperatures
will be around 5 degrees above average. Dew points are expected
to fall into the lower to mid 60s for most areas, with somewhat
less humid conditions than in recent days.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Dry tonight under high pressure
- Shower and thunderstorm chances return Monday and Tuesday
- Strong to severe storms possible Monday mainly north of
Pittsburgh
-------------------------------------------------------------------
High pressure will maintain dry weather tonight as it shifts
east of the region. A shortwave trough in NW flow aloft, and
its associated surface cold front, will approach the Upper Ohio
Valley region on Monday. Scattered showers and thunderstorms are
expected to develop through the day as the shortwave
approaches.
A band of 1500-2000 j/kg MU CAPE is depicted ahead of the front
in the latest HREF output, with 0-6km shear increasing to around
30kt. This could be enough to spark a severe storm potential
mainly north of Pittsburgh Monday afternoon and evening, if
storms become organized. This potential should quickly wane
Monday evening as instability diminishes. Currently the NAM was
the most aggressive with instability and shear across the area,
when compared to other CAMS and global models. Machine learning
was also showing a minimal potential for strong to severe
storms.
Isolated showers and thunderstorms will still be possible Monday
night under limited ascent in vorticity advection. Shower and
thunderstorm activity should increase again on Tuesday as
another shortwave trough embedded in the NW flow aloft
approaches and crosses the region. These should continue into
Tuesday night, with decreasing coverage as the wave exits late.
Warm advection ahead of the approaching shortwave should return
temperatures to near 90 degrees for most locations south of I 80
on Monday, with more seasonable readings behind the surface
boundary on Tuesday.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Unsettled through the period
- Seasonable temperatures expected
-------------------------------------------------------------------
Model ensembles indicate a broad upper trough will persist
across the northeast CONUS through the period. Rain chances will
continue into Wednesday as a shortwave slowly exits the region.
Low showers chances are expected east of Pittsburgh Thursday as
ensembles push some moisture northward from Tropical System
Debby. These chances extend further westward on Friday as the
low drifts northward. A high degree of uncertainty exits in the
exact track and strength of the tropical system by that time, so
stayed close to the National Blend of Models (NBM) output. Low
shower/storm chances continue Saturday with the area under the
broad upper troughing.
Temperatures are expected to average near seasonable levels
through the long term period.
&&
.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Low probability isolated rain showers will taper off through
12z as the upper level trough exists east of the region. Dry
advection aloft already occurring will continue to erode mid-
level decks, clearing the way for strong radiational cooling at
the surface. There is some uncertainty in timing and degree of
restrictions, but MVFR/IFR vsbys are likely with fog formation
with areas of lower stratus also possible. Probabilities favor
HLG/FKL/DUJ/MGW for LIFR impact, which are included in TAFs.
Confidence is high that VFR conditions will return to all
terminals by 14z, with the only potential linger MVFR stratocu
with daytime heating occurring around MGW/LBE and the higher
terrain. Expect only a few to scattered afternoon CU around 4kft
with light W/NW wind.
.Outlook...
A series of shortwaves within the NW flow will create periodic
storm chances Monday (primarily the I-80 corridor) through
Wednesday (more widespread by then).
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Aug 4, 3:28 AM EDT---------------
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