Severe Thunderstorm Warning 65, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
1240 PM EDT Sat May 11 2024

.SYNOPSIS...
Rain showers and scattered thunderstorms are likely through
tonight with passage of a cold front. Dry and more seasonable
weather will develop through Monday before the next round of
upper level disturbances increase precipitation chances midweek.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Showers and thunderstorms expected through tonight, favoring
  NW PA
- Low probability for small hail and gusty wind through this
  evening
-------------------------------------------------------------------

A warm front, centered on the 700mb layer, will continue to
push a swath of light to moderate rain showers through the
region during the afternoon period. Dry slotting will promote
quick precipitation dissipation after passing of that warm
front. The surface cold front will quickly cross the region
thereafter as the 500mb trough axis drifts over the Great Lakes.
Scattered convection will develop ahead of this boundary (with
light showers lingering with trough axis) through the evening
before tapering off overnight.

Cold advection aloft will increase lapse rates over the region
and create a low probability potential for small hail/gusty wind
dependent upon degree of heating that occurs behind the warm
frontal band. Latest HREF modeling suggests instability/shear
will be best aligned along/south of I-70, but drier air and
weaker forcing should limit much in the way of convective
development. Stronger convection is more likely over northwest
PA given greater cooling aloft and stronger forcing, but weak
shear and more limited instability development is likely to keep
convection sub-severe.

High pressure and subsidence will slowly clear out showers and
area cloud cover from SW to NE overnight, though NW flow may
persist such conditions longest over northwest PA. Low
temperature will be near the seasonal average.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Dry weather likely, saving for passing disturbances near far
  northwest PA.
- Above normal temperature likely by Monday.
-------------------------------------------------------------------

Shortwave ridging ahead of a deepening central CONUS upper
trough will promote dry weather and rising temperature through
Monday. Residual NW flow Sunday with the surface high just to
the west will limit the degree of temperature rebound. But as
heights further increase Monday and the surface high positions
along the eastern coast, warm advection in southwest flow will
drive temperature to about 5 degrees above the daily average.

Any precipitation chances during this period will be tied to
shortwave movement well to the north and the positioning of a
developing warm front near the region. Latest trends lift the
warm front and upper wave north of the region, but will
maintain low probability chances in northwest PA in case those
trends change.

&&

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

- Midweek showers and thunderstorms likely, with limited severe
  and flooding threats.
- Dry conditions likely to end the week.
-------------------------------------------------------------------

The sagging central plains trough will meander eastward across
the TN River Valley Tuesday into Wednesday, with weak shortwaves
likely traversing the Upper Ohio River Valley ahead of the wave.
Showers and thunderstorms are likely through the
afternoon/evening Tuesday, though positioning of forcing and
potential influence of shortwave ridging in the mid-Atlantic
could alter the areal coverage/probabilities. Early analysis
suggests that the instability/shear parameters are unlikely to
promote much severe threat, while forcing/deep moisture should
remain south of region and limit a flooding threat (only 20%
probability of seeing greater than 1" of rain over 24 hours at
any location).

The trough will progress towards the eastern coast Wednesday,
with low positioning and depth dictating how long precipitation
will linger in the Upper Ohio River Valley. Ensembles are
confident in ridging developing over the lower Ohio River
Valley late week that should promote a few day period of dry
weather and above normal temperature.

&&

.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
After the exit of a mid-level warm frontal rain band, dry
advection aloft may create a window of drier weather at TAF
onset before scattered to numerous showers and thunderstorms
develop along the cold front. Upper level support and greater
moisture depth will favor northwest PA for this convective
activity, with decreasing probabilities moving towards KZZV.
Sufficient wind flow aloft, and a low freezing level, should
result in gusty wind and small hail in some of the storms.

Shower activity will slowly dissipate overnight (ending later in
NW PA) with the exit of the surface cold front and upper level
trough axis. Cold advection by Sunday morning should return MVFR
to localized IFR stratocu to most terminals before high pressure
and subsidence lift area cigs to VFR levels.

.Outlook...
VFR favoring through Monday under the influence of high
pressure.  Slow progression of the next upper level trough
system means increases precipitation and restriction potential
Monday night through Wednesday night, peaking Tuesday night into
Wednesday.

&&

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

&&

SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Frazier

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
225 AM EDT Sat May 11 2024

OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>022-029-
031-073>078-WVZ001>004-012-021-509>514-120630-
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH-
Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest-
Lawrence-Butler-Clarion-Jefferson PA-Beaver-Allegheny-Armstrong-
Washington-Greene-Westmoreland-Higher Elevations of Westmoreland-
Fayette-Higher Elevations of Fayette-Indiana-
Higher Elevations of Indiana-Hancock-Brooke-Ohio-Marshall-Wetzel-
Marion-Monongalia-
Ridges of Eastern Monongalia and Northwestern Preston-Preston-
Eastern Preston-Western Tucker-Eastern Tucker-
225 AM EDT Sat May 11 2024

This Hazardous Weather Outlook is for east central Ohio, western
Pennsylvania, and northern West Virginia.

.DAY ONE...Today and tonight.

Areas of dense valley fog should lift after 8 am. Showers and
thunderstorms are expected during the afternoon and early evening
hours and could produce small hail and gusty winds to 40 mph.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Craven

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