PBZ issues Area Forecast Discussion (AFD) at May 5, 7:48 AM EDT056
FXUS61 KPBZ 051148
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
748 AM EDT Mon May 5 2025
.SYNOPSIS...
Slow moving low pressure will maintain periodic shower and
thunderstorm chances across the area through mid week. A few
storms could be severe this afternoon and evening. A cold front
will maintain shower chances Thursday before generally dry and
warmer weather returns for the weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Areas of dense fog and stratus this morning
- Shower and thunderstorm chances increase this afternoon
- Severe storms possible with damaging wind and large hail
-------------------------------------------------------------------
Areas of fog and stratus has developed across the region this
morning as clearing has occurred, with low level moisture in
place. Issued a Dense Fog Advisory through 9am for much of the
area with several areas reporting vsbys of 1/4 mile or less.
The fog and stratus will quickly dissipate this morning as
mixing and surface heating begins. Areas to the north have seen
more stratus as opposed to fog, keeping vsbys up in those areas.
A mid and upper low will drift across Kentucky today, as a
surface low redevelops across the Upper Ohio Valley region.
Vorticity maximums rotating around the low will maintain
periodic showers and thunderstorms across the region today,
mainly this afternoon. Convective temperatures are low, and this
should also enhance the showers/storm coverage. Similar to
yesterday, the mid and upper level flow is progged to increase
today, enhancing the 0-6km shear(40-50kt.) MUCAPE is expected to
range from 750-1500 J/kg this afternoon as well. This should
result in a potential for severe storms again this afternoon and
early evening. Similar to Sunday, as any storm becomes more
organized with a taller core, it will tap in to the stronger
shear aloft. Large hail and damaging wind remain the primary
hazards today. The Storm Prediction Center has expanded the
Marginal Risk to include the entire forecast area, and this
appears reasonable.
Precipitable water is expected to be slightly lower today,
mainly under 1.0 inches. This should result in a decreased
potential for flooding, except in areas that saw heavy rain
Sunday. Will include the mention of localized flooding in this
area (generally N-NE of PIT) in the Hazardous Weather Outlook.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:
- Severe weather potential ends this evening
- Periodic showers and possible thunderstorms continue Tuesday
- Dry for much of the area on Wednesday
-------------------------------------------------------------------
The mid and upper low will continue to spin across far southern
Ohio tonight, as the surface low rotates around it. Showers and
thunderstorms will continue this evening as a stronger vort max
and band of moisture rotates around the upper low. Enough shear
and instability should continue into the evening to maintain the
potential for severe storms.
The vort max should exit by late evening, as instability wanes.
Showers and storms should diminish in intensity and coverage by
late evening, with the severe weather potential ending. The
mid/upper low is progged to track NE Tuesday, reaching SW PA by
late in the day. Expect another diurnal increase in showers and
possible storms. Instability and shear should be much less on
Tuesday, with the severe weather potential staying east of the
area.
The upper low is progged to reach NE PA Wednesday. Moisture
rotating around the low should result in low chances for showers
mainly east of PIT during the day. The remainder of the area is
expected to be dry. Dry weather is expected in the region
Wednesday night as the low exits the New England coast.
Below average temperatures are expected under the upper low on
Tuesday, moderating to seasonable levels by Wednesday.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Unsettled weather on Thursday
- Generally dry and warmer through the weekend
-------------------------------------------------------------------
A digging trough is progged to drop SE across the Upper Ohio
Valley region on Thursday, with slight to low chance POPs for
showers.
The forecast becomes more uncertain late week and early in the
weekend as the trough deepens into another cutoff low. Ensembles
indicate the low should be just east of our area, with mainly
slight chances of showers across portions of the region. Some
operational models do indicate a further westward position with
the low. Stayed close to the ensemble blend to smooth out some
of this uncertainty in the forecast. Confidence is higher on a
dry and warmer forecast for Sunday, as the upper low opens and
is absorbed into the northern stream flow.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Low clouds/fog in place over much of the region in the wake of
yesterday's storms, with several terminals experiencing LIFR
conditions. The onset of daytime mixing will lift most of the
low ceilings/visibility by the 13Z/14Z window. This will return
most sites to VFR, although FKL and DUJ may hold on to MVFR
ceilings a bit longer.
The stubborn upper low will lift slowly northward across the
Middle Ohio Valley today. Continued moisture advection to its
east along with support for lift and instability will provide
another round of scattered to numerous showers and thunderstorms
this afternoon and evening. Onset today should be a bit earlier
than yesterday as convective temperatures will be reached a bit
more quickly - say by the 18Z to 20Z window. Have used PROB30
groups to try to time the most likely window of impact at each
terminal. The heavier storms will be capable of brief IFR to
LIFR visibility, along with hail and gusty wind.
Storms will largely fade by the late evening or midnight with
diurnal stabilization. With lower levels remaining quite moist,
another round of MVFR to IFR ceilings seems likely. West of a
DUJ/PIT/HLG line, the HREF shows a 50 to 80 percent chance of
IFR ceilings. Fog development is possible as well, although
better mixing may prevent a repeat of particularly dense fog.
Outlook...
Periodic restrictions, along with scattered showers and
thunderstorms, are expected again Tuesday as the upper low
finally crosses the Upper Ohio Valley region. VFR largely returns
by Wednesday, although a few scattered showers remain possible
that day.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Dense Fog Advisory until 9 AM EDT this morning for PAZ014-
020>022-029-031-073>078.
OH...Dense Fog Advisory until 9 AM EDT this morning for OHZ039>041-
048>050-057>059-068-069.
WV...Dense Fog Advisory until 9 AM EDT this morning for WVZ001>004.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...CL
Source:
PBZ issues Area Forecast Discussion (AFD) at May 5, 7:48 AM EDT---------------
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