502
FXUS61 KPBZ 211658
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1258 PM EDT MON APR 21 2025
SYNOPSIS
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS MORNING AS
A WARM FRONT LIFTS NORTH ACROSS THE REGION. MORE WIDESPREAD
SHOWERS AND THUNDERSTORMS ARE EXPECTED LATER TODAY WITH THE
APPROACH AND PASSAGE OF A COLD FRONT. DRY WEATHER THEN RETURNS
THROUGH MID WEEK UNDER HIGH PRESSURE.
NEAR TERM /UNTIL 10 PM THIS EVENING/
KEY MESSAGES:
- SCATTERED SHOWERS/THUNDERSTORMS EARLY THIS MORNING WITH A WARM
FRONT
- COLD FRONT BRINGS MORE WIDESPREAD SHOWERS/STORMS LATER TODAY
- MARGINAL RISK FOR SEVERE STORMS THIS AFTERNOON
-------------------------------------------------------------------
MID-MORNING UPDATE: FORECAST REMAINS LARGELY ON TRACK WITH ONLY
VERY MINOR TWEAKS.
PRE-FRONTAL SHOWERS ARE INCREASING IN COVERAGE ACROSS OHIO.
THESE SHOWERS WILL LIKELY INFLUENCE OUR ENVIRONMENT FOR
THUNDERSTORMS LATER IN THE DAY. POTENTIAL BACKING AT THE SURFACE
COULD HELP TO PRODUCE MORE CURVED HODOGRAPHS, MORE AMPLE
MOISTURE AT THE SURFACE COULD ALSO HELP TO LOWER LCLS BUT
COOLING AT THE SURFACE COULD LIMIT INSTABILITY.
CURRENT SATELLITE DEPICTIONS SHOW A CLOUDY ENVIRONMENT BETWEEN
THE BACK EDGE OF THE SHOWERS AND THE LEADING EDGE OF THE COLD
FRONT, LEAVING LESS TIME TO DESTABILIZE BEHIND THE SHOWERS AND
AHEAD OF THE FRONT. WE WILL CONTINUE TO KEEP AN EYE ON HOW THESE
FACTORS EVOLVE AND INTERACT WITH EACH OTHER AS WE MOVE INTO THE
EARLY AFTERNOON HOURS, BUT THUNDERSTORMS REMAIN LIKELY WITH THE
POSSIBILITY THAT SOME BRING SEVERE THREATS OF DAMAGING WIND
GUSTS, HAIL AND POSSIBLY A TORNADO. PREVIOUS DISCUSSION BELOW:
THE WARM FRONT SHOULD LIFT NORTH OF THE REGION LATER THIS
MORNING, AS A PREFRONTAL TROUGH DEVELOPS AHEAD OF THE
APPROACHING COLD FRONT. SOME DESTABILIZATION IS EXPECTED AFTER
THE PASSAGE OF THE WARM FRONT, AND BEFORE THE ARRIVAL OF THE
PREFRONTAL TROUGH LATE THIS MORNING INTO THE AFTERNOON. IN
GENERAL, 500-750 J/KG OF MU CAPE IS PROGGED IN MOST OF THE CAMS
THIS AFTERNOON AND EARLY EVENING, WITH 40-50KT OF 0-6KM SHEAR,
ENHANCED BY A MID LEVEL JET. A FEW STORMS COULD BE SEVERE, BOTH
WITH THE PREFRONTAL TROUGH FROM EARLY TO MID AFTERNOON, AND WITH
ANY POTENTIAL REDEVELOPMENT ALONG THE SURFACE COLD FRONT LATER
THIS AFTERNOON AND EARLY EVENING. THE MAIN LIMITING FACTOR IN
SEVERE STORM DEVELOPMENT WILL BE THE AMOUNT OF INSTABILITY THAT
DEVELOPS, DEPENDING ON HOW THE FORECAST CONDITIONS EVOLVE
THROUGH THE DAY.
THE STORM PREDICTION CENTER HAS INCLUDED MUCH OF OUR REGION IN A
MARGINAL RISK FOR SEVERE STORMS. THE MAIN HAZARD IS EXPECTED TO
BE THE POTENTIAL FOR DAMAGING WIND GUSTS WITH INCREASING FLOW
ALOFT, THOUGH ISOLATED EMBEDDED QLCS TORNADOES ARE POSSIBLE AS
0-3KM HELICITY INCREASES WITH A VEERING WIND PROFILE.
HIGH TEMPERATURES ARE EXPECTED TO BE 10 TO 15 DEGREES ABOVE
AVERAGE WITH THE AREA IN THE WARM SECTOR.
SHORT TERM /10 PM THIS EVENING THROUGH WEDNESDAY NIGHT/
KEY MESSAGES:
- SHOWERS/STORMS END THIS EVENING WITH THE PASSAGE OF A COLD
FRONT
- DRY WEATHER THEN RETURNS THROUGH WEDNESDAY NIGHT
-------------------------------------------------------------------
THE PREFRONTAL TROUGH IS EXPECTED TO BE JUST EAST OF THE AREA
EARLY THIS EVENING, AS THE SURFACE COLD FRONT CROSSES THE
REGION. A POTENTIAL FOR STRONG TO SEVERE STORMS WILL CONTINUE
UNTIL FROPA, THOUGH THIS WILL DEPEND ON THE AMOUNT OF
INSTABILITY ABLE TO OCCUR BEHIND THE PREFRONTAL TROUGH. SHOWER
AND THUNDERSTORM CHANCES WILL END AFTER FROPA, WITH DRY WEATHER
RETURNING THE REMAINDER OF THE NIGHT.
SURFACE HIGH PRESSURE WILL SLIDE EAST ACROSS THE UPPER OHIO
VALLEY REGION LATER TONIGHT THROUGH WEDNESDAY NIGHT UNDER ZONAL
FLOW ALOFT, MAINTAINING DRY WEATHER THROUGH WEDNESDAY NIGHT.
AFTER A BRIEF COOL DOWN ON TUESDAY BEHIND THE COLD FRONT,
TEMPERATURES WILL RETURN TO READINGS AROUND 10 DEGREES ABOVE
AVERAGE BY WEDNESDAY.
LONG TERM /THURSDAY THROUGH SUNDAY/
KEY MESSAGES:
- INCREASING SHOWER CHANCES THROUGH LATE WEEK INTO SATURDAY
- DRY WEATHER RETURNS FOR THE END OF THE WEEKEND
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MODEL ENSEMBLES INDICATE ZONAL FLOW ALOFT EARLY IN THE PERIOD
WILL BECOME MORE AMPLIFIED BY LATE WEEK. A TROUGH IS EXPECTED TO
DEVELOP ACROSS THE CENTRAL CONUS ON THURSDAY. INCREASING
MOISTURE AND WARM ADVECTION AHEAD OF THIS TROUGH SHOULD RETURN
SHOWER CHANCES TO THE AREA LATE THURSDAY AND THURSDAY NIGHT. THE
TROUGH, AND ITS ASSOCIATED SURFACE COLD FRONT, IS EXPECTED TO
TRACK ACROSS THE UPPER OHIO VALLEY REGION FRIDAY AND FRIDAY
NIGHT, WITH THE HIGHEST CHANCES FOR SHOWERS AND POSSIBLE
THUNDERSTORMS. THE TROUGH AND FRONT SHOULD EXIT THE REGION EARLY
SATURDAY, WITH SHOWERS ENDING FROM W-E.
RIDGING, BETWEEN THE EXITING TROUGH TO THE EAST, AND A
DEVELOPING WESTERN CONUS TROUGH, SHOULD RETURN DRY WEATHER TO
THE REGION SATURDAY NIGHT AND SUNDAY AS IT BUILDS ACROSS THE
UPPER OHIO VALLEY REGION. ABOVE AVERAGE TEMPERATURES ARE
EXPECTED TO RETURN TO SEASONABLE LEVELS AFTER THE PASSAGE OF THE
TROUGH.
AVIATION /18Z MONDAY THROUGH SATURDAY/
BROAD ASCENT IN THE PRESENCE OF A 300MB JET WILL INDUCE
GENERALLY LIGHT RAIN A FEW HOURS AHEAD OF INCOMING SURFACE COLD
FRONT. LIMITED MOISTURE CONTENT FAVORS MAINTENANCE OF VFR
CONDITION, THOUGH A PERIOD OF MVFR CIGS JUST AHEAD OF THE FRONT
IS POSSIBLE DUE TO MOISTURE CONVERGENCE.
A BROKEN LINE OF LOW-TOPPED SHOWERS WITH EMBEDDED THUNDERSTORMS
WILL BETWEEN 3PM-8PM EDT AHEAD OF A SURFACE COLD FRONT.
UNCERTAINTY IN THE DEGREE OF INSTABILITY AHEAD OF THIS LINE
CONTINUES TO LIMIT FORECASTER CONFIDENCE IN DEVELOPMENT OF
30-45KT GUSTS, BUT LOCALIZED SPEEDS TO THAT OR APPROACHING 50KTS
CAN'T BE RULED OUT. STORM MOTION SHOULD BE FAST ENOUGH THAT
TERMINAL IMPACTS LAST NO MORE 1-2 HOURS BEFORE THE LINE EXITS
EAST.
PASSAGE OF THE UPPER SHORTWAVE AXIS AND SURFACE COLD FRONT WILL
SEE A QUICK END TO CONVECTIVE ACTIVITY IN THE REGION. A
SLIGHTLY DELAY BEFORE THE ONSET OF WEAK COLD ADVECTION MAY
CREATE INITIAL CIG COVERAGE VARIATION, BUT LOW VFR AND SPOTTY
MVFR SHOULD DEVELOP/PERSIST OVERNIGHT AND FAVOR FKL/DUJ/LBE/MGW.
DRY ADVECTION WITHIN COLUMN WESTERLY FLOW WILL ERODE STRATOCU
WEST TO EAST NEAR DAWN, WITH VFR AND NO MORE THAN SCATTERED CU
AT ALL TERMINALS BY 16Z.
OUTLOOK...
HIGH PRESSURE AND WEAK RIDGING ALOFT WILL FAVOR VFR THROUGH
MUCH OF THE DAYTIME HOURS THURSDAY.
WEAK SHORTWAVE MOVEMENT WITHING SOUTHWESTERLY FLOW IS EXPECTED
TO INCREASE SHOWER AND THUNDERSTORM CHANCES LATE THURSDAY INTO
THE EARLY WEEKEND WHERE CONVECTIVE ACTIVITY BECOMES THE MAIN
DRIVER FOR TERMINAL RESTRICTIONS.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...WM
NEAR TERM...WM/AK
SHORT TERM...WM
LONG TERM...WM
AVIATION...FRAZIER
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