071
FXUS61 KPBZ 011730
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
130 PM EDT TUE APR 1 2025
SYNOPSIS
DRIER WEATHER AND COOL TEMPERATURES ARE EXPECTED TODAY. SEVERE
WEATHER AND HEAVY RAINFALL ARE POSSIBLE WEDNESDAY THROUGH THE
END OF THE WORK WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- DRY CONDITIONS, CLEARING SKIES, AND BELOW NORMAL TEMPERATURES
EXPECTED TODAY, FOLLOWED BY INCREASING CLOUDS AND NEAR-NORMAL
TEMPERATURES TONIGHT.
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UPDATE...
CLOUDS HAVE BEEN SLOW TO CLEAR, WITH MOISTURE UNDER A STRONG
TEMPERATURE INVERSION. INCREASING SUBSIDENCE UNDER BUILDING HIGH
PRESSURE SHOULD RESULT IN A DECREASE IN CLOUD COVER THROUGH THE
AFTERNOON. LOWERED HIGH TEMPERATURES A COUPLE OF DEGREES WITH
THE DELAY IN CLEARING.
PREVIOUS DISCUSSION...
CLOUDS RETURN FROM THE WEST OVERNIGHT AS HIGH PRESSURE MOVES
OFF TO THE EAST, ALLOWING DEEP-LAYER SOUTHWEST FLOW AND MOISTURE
RETURN TO SET BACK UP AHEAD OF THE NEXT APPROACHING LOW
PRESSURE SYSTEM. LOW TEMPERATURES HOVER AROUND OR A DEGREE OR
TWO ABOVE NORMAL, IN THE LOW 30S NEAR I-80 AND MID TO UPPER 30S
FARTHER SOUTH.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- ABOVE NORMAL TEMPERATURES RETURN.
- SEVERE THUNDERSTORMS AND LOCALLY HEAVY RAINFALL POSSIBLE
WEDNESDAY INTO WEDNESDAY NIGHT.
- FLOOD WATCH FOR PORTIONS OF OHIO
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ENSEMBLES ARE MAINTAINING HIGH CONFIDENCE IN RIDGING SETTING UP
OFF OF THE SOUTHEAST CONUS COAST STARTING WEDNESDAY. THIS WILL
SET UP PERSISTENT DEEP-LAYER SOUTHWEST FLOW FROM THE SOUTH
PLAINS UP INTO THE OHIO VALLEY. AS A RESULT, A FRONTAL
BOUNDARY CURRENTLY PROGGED TO ADVANCE EASTWARD ACROSS THE
MIDWEST AND OHIO VALLEY ON WEDNESDAY WILL STALL IN THE VICINITY
OF THE LOCAL AREA BY THURSDAY. POTENTIAL FOR BOTH SEVERE
WEATHER AND FLOODING THREATS INCREASE AHEAD OF AND ALONG THIS
FRONT THROUGHOUT THE SHORT TERM PERIOD.
LATEST CONVECTIVE-ALLOWING ENSEMBLE GUIDANCE STILL SUGGESTS A
STRONGLY-FORCED LINE OF STORMS IN OR NEAR EASTERN OHIO
APPROACHING AS EARLY AS WEDNESDAY AFTERNOON. ENSEMBLES HAVE
LITTLE DOUBT THAT THERE WILL BE SUFFICIENT DEEP-LAYER SHEAR FOR
ORGANIZED CONVECTION, WITH THE HREF SUGGESTING AT LEAST 60
KNOTS IN THE SURFACE TO 500MB LEVEL WITH HIGH CONFIDENCE (NEAR
100%). IN FACT, THE INNER QUARTILE SPREAD IS ONLY ~5 KTS IN
MOST PLACES, WITH ~67 KTS AND ~72 KTS AS THE 25TH AND 75TH
PERCENTILES, RESPECTIVELY. INSTABILITY (MORE SPECIFICALLY,
SURFACE-BASED INSTABILITY) IS MORE UNCERTAIN WITH THIS INITIAL
LINE OF STORMS. STRONG WAA AROUND 850MB RESULTS IN A RATHER
STOUT WARM NOSE (>10C) THAT KEEPS ANY AVAILABLE POTENTIAL ENERGY
ELEVATED. IN FACT, HREF PROBABILITIES FOR SBCAPE>100 J/KG ARE
NEAR ZERO THROUGH THE MID TO LATE AFTERNOON HOURS, AND EVEN THE
MORE OPTIMISTIC NBM PROBABILITIES FOR THE SAME THRESHOLD ARE
ONLY 20-40% ACROSS EASTERN OHIO AND NEAR ZERO FARTHER EAST.
MEANWHILE, AN INTERROGATION OF HREF SOUNDINGS SHOW MEAN MUCAPE
ABOVE 600 J/KG WITH AN INNER QUARTILE OF ROUGHLY 450-750 J/KG.
ALL OF THESE SIGNS POINT TO A LINE OF ELEVATED THUNDERSTORMS,
WHICH MAY BE "LOUD AND PROUD" BUT OTHERWISE PRESENT A RATHER
LIMITED SEVERE THREAT.
A GREATER SEVERE THREAT WOULD BE PRESENT FOR ANY THUNDERSTORMS
ABLE TO DEVELOP WITH THE HELP OF DIURNAL HEATING LATER IN THE
AFTERNOON OR EVENING, AS THOSE WOULD HAVE A BETTER CHANCE OF
BECOMING SURFACE-BASED. ALL MODES OF SEVERE WEATHER (DAMAGING
WINDS, LARGE HAIL, TORNADOES) WOULD BE POSSIBLE WITH THOSE
STORMS. THE GREATEST PROBABILITIES FOR THAT OCCURRING STILL
ALIGN WITH WHERE SPC HAS MAINTAINED A SLIGHT RISK (LEVEL 2 OF 5)
IN THEIR DAY 2 OUTLOOK, PRIMARILY ALONG AND WEST OF I-77.
LONG TERM /FRIDAY THROUGH TUESDAY/
KEY MESSAGES:
- ABOVE NORMAL TEMPERATURES CONTINUE INTO THE WEEKEND.
- POTENTIAL FOR SEVERE THUNDERSTORMS CONTINUES THURSDAY.
- POTENTIAL FOR FLOODING DUE TO HEAVY RAIN INCREASES THURSDAY
THROUGH SATURDAY.
- QUIETER WEATHER POSSIBLE SUNDAY/MONDAY, HOWEVER RIVERS MAY
REMAIN ELEVATED.
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ONLY MINOR DEVIATIONS IN THE POSITION OF THE STALLED FRONT ARE
EXPECTED THURSDAY THROUGH THE WEEKEND. IF ENOUGH INSTABILITY IS
ABLE TO MATERIALIZE ON THE WARM SIDE OF THE BOUNDARY, THE
POTENTIAL FOR SEVERE WEATHER WILL CONTINUE WITH ANY STORMS THAT
DEVELOP. DAMAGING WIND GUSTS IN ANY LARGER CLUSTERS OF STRONGER
STORMS WOULD BE THE PRIMARY THREAT THERE.
DESPITE THE GRADUALLY DIMINISHING SEVERE THREAT, SIGNALS FOR
HEAVY RAIN WITH THIS STALLED FRONT ARE CERTAINLY THERE. AN
EXTENDED PERIOD OF PRECIPITABLE WATER VALUES NEAR OR ABOVE THE
TOP END OF CLIMATOLOGY IS POSSIBLE FROM THROUGH SATURDAY, AND
WITH LIKELY PERIODS OF CONVERGENT FLOW WITH THE FRONT, THERE IS
POTENTIAL FOR SOME IMPRESSIVE 72-HOUR RAINFALL TOTALS,
PARTICULARLY IN EASTERN OHIO. GEFS M-CLIMATE PROGS ALSO SHOW THE
POTENTIAL FOR AN AXIS OF RAINFALL EXTENDING INTO FAR WESTERN PA
THAT COULD EXCEED THE 20-YEAR CLIMATOLOGY RELATIVE TO GEFS
REFORECASTS - BOTTOM LINE, A POTENTIALLY SIGNIFICANT RAINFALL
EVENT FOR THE OHIO VALLEY. WHILE THE RAINFALL TOTALS SHOULD
GENERALLY REMAIN HIGHER TO OUR SOUTHWEST, NBM PROBABILITIES OF
2 INCHES OR MORE OF TOTAL RAIN FROM 8 AM THURSDAY THROUGH 8 AM
SATURDAY ARE 50 PERCENT OR GREATER IN EASTERN OHIO, AND SLOWLY
DROP OFF EAST OF THE PA/OH BORDER. 90TH PERCENTILE VALUES OF 3
TO 4 INCHES CONTINUE TO SHOW UP DURING THIS PERIOD, WHICH COULD
REPRESENT VALUES IN A RELATIVELY SMALL BAND WHERE CONVECTION
ENDS UP BEING MOST FAVORED. FLASH FLOODING MAY BECOME A CONCERN
IN SPOTS DEPENDING ON WHERE THE HEAVIER AXIS OF CONVECTION SETS
UP. LONG-RANGE ENSEMBLE RIVER GUIDANCE ALSO SHOWS THE POTENTIAL
FOR RISES ON AREA RIVERS, WITH AT LEAST ACTION STAGES POSSIBLE
FOR MUCH OF THE AREA AS WELL AS SOME POTENTIAL FOR MINOR FLOOD
STAGES IN AT LEAST EASTERN OHIO. IT'S STILL A BIT TOO EARLY FOR
A FLOOD WATCH, BUT IT WILL LIKELY BECOME NECESSARY OVER THE
NEXT 12 TO 24 HOURS.
ABOVE-NORMAL TEMPERATURES WILL ACCOMPANY ALL OF THIS RAIN INTO
THE WEEKEND. IMPROVEMENT IN THE WEATHER PATTERN IS POSSIBLE BY
SUNDAY OR MONDAY AS A STRONGER GREAT LAKES SHORTWAVE COULD
FINALLY KICK THE BOUNDARY TO THE EAST, ALTHOUGH THERE IS MODEL
DISAGREEMENT THIS FAR OUT ON TIMING AND STRENGTH. BELOW-NORMAL
TEMPERATURES COULD RETURN WITH SOME OF THESE SOLUTIONS, ALONG
WITH A DRIER PATTERN.
AVIATION /17Z TUESDAY THROUGH SATURDAY/
WANING COLD ADVECTION AND DRIER AIR WORKING IN WITH BUILDING
HIGH PRESSURE HAS ERODED THE LOW STRATUS DECK ALBEIT QUITE
SLOWLY AS MOISTURE REMAINED STUBBORN UNDER A STRONG INVERSION
AROUND 850 MB. SOME SCATTERED LOW-LEVEL COVERAGE WILL LINGER
THROUGH THE AFTERNOON, BUT INCREASING CIRRUS THIS EVENING WILL
BECOME THE STORY OVERNIGHT AS IT THICKENS AND LOWERS WITH
INCREASING UPPER LEVEL MOISTURE AHEAD OF OUR NEXT SYSTEM ON
WEDNESDAY.
THE MORNING HOURS WEDNESDAY WILL BE DRY, BUT LATEST GUIDANCE IS
EXTENDING A SHIELD OF SHOWERS AND STORMS AS FAR SOUTH AS MGW IN
THE EARLY AFTERNOON HOURS. CONFIDENCE IS NOT HIGH ON THE
SOUTHERN EXTENT OF IT, BUT TRENDS HAVE BEEN TOWARD A SOUTHWARD
SHIFT. INTRODUCED A PROB30 GROUP AT ZZV AND PIT, BUT IT WILL BE
JUST OUTSIDE THE CURRENT TAF PERIOD AT ALL OTHER SITES.
SOUNDINGS SUGGEST AN ELEVATED NATURE TO THE CONVECTION, SO NOT
EXPECTING MIXING DOWN OF STRONGER WIND GUSTS WITH IT AT THIS
TIME, THOUGH WITH AN INCREASING LOW-LEVEL JET, A PERIOD OF LLWS
IS POSSIBLE IN THE AFTERNOON HOURS. SOME IMPROVEMENT IS
POSSIBLE IN THE EVENING HOURS AHEAD OF A COLD FRONT THAT WILL
BRING ANOTHER ROUND OF SHOWERS AND STORMS OVERNIGHT WEDNESDAY
NIGHT.
WIND OUT OF THE NORTH THIS AFTERNOON WILL GRADUALLY VEER
THROUGH THE TAF PERIOD BECOMING NORTHEASTERLY TONIGHT AND
ULTIMATELY EASTERLY EARLY WEDNESDAY MORNING. DESPITE SHALLOW
DECOUPLING OVERNIGHT ON FORECAST SOUNDINGS, A TIGHTENING
PRESSURE GRADIENT WILL KEEP A LIGHT FLOW PREVAILING.
OUTLOOK...
RESTRICTIONS WILL CONTINUE EARLY THURSDAY AND THROUGH THE
WEEKEND WITH THE COLD FRONT PASSAGE AND ADDITIONAL ROUNDS OF
RAIN MOVING THROUGH THE AREA OVER THE NEXT SEVERAL DAYS.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...FLOOD WATCH FROM WEDNESDAY EVENING THROUGH SUNDAY MORNING FOR
OHZ039-040-048-049-057>059-068-069.
WV...NONE.
SYNOPSIS...CERMAK
NEAR TERM...CERMAK/WM
SHORT TERM...CERMAK
LONG TERM...CERMAK/CL
AVIATION...MLB
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