779
FXUS61 KPBZ 021933
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
333 PM EDT WED APR 2 2025
SYNOPSIS
RAIN AND THUNDERSTORMS RETURN TODAY AND CONTINUE THROUGH THE
WEEKEND. STORMS COULD BE SEVERE OVERNIGHT THURSDAY NIGHT.
MULTIPLE DAYS OF RAIN WILL LEAD TO RIVER RISES AND LOCALIZED
FLOODING CONCERNS. A FLOOD WATCH REMAINS IN EFFECT FOR EASTERN
OHIO.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
KEY MESSAGES:
- ANOTHER ROUND OF THUNDERSTORMS, POSSIBLY SEVERE, OVERNIGHT TONIGHT.
- A FLOOD WATCH IS IN EFFECT FOR PORTIONS OF EASTERN OHIO.
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A BROKEN LINE OF ELEVATED THUNDERSTORMS HAS MAINTAINED ITSELF INTO
THE PENNSYLVANIA RIDGES THIS AFTERNOON. IT CONTINUES RIDING A
GRADIENT OF 1000 J/KG MUCAPE AND MID-LEVEL LAPSE RATES AROUND 6.5-
7C. WITH THE LOW FREEZING LEVEL AND EBWD NEARING 60 KNOTS, THIS IS
SUPPORTING EFFICIENT HAIL GROWTH IN THE STRONGEST UPDRAFTS WHICH
HAVE AT TIMES PUSHED 60 DBZ TO 25KFT AND 50 DBZ TO 35KFT AND
PRODUCING HALF DOLLAR TO GOLF BALL SIZE HAIL. IN THE WAKE OF THIS
BATCH, WE SHOULD SEE A LULL IN THE ACTION INTO THE EVENING HOURS
AHEAD OF ANOTHER ROUND OF STORMS OVERNIGHT TONIGHT.
GUSTY WIND IN THE RIDGES SHOULD RELAX THIS AFTERNOON AS DIRECTION
VEERS MORE WEST OF SOUTH AND CUTS OFF THE DOWNSLOPE EFFECTS. DESPITE
THE STRONG FLOW JUST OFF THE SURFACE, A WARM ADVECTION DRIVEN
INVERSION WILL PREVENT MIXING DOWN TO THE GROUND.
SHOWERS AND THUNDERSTORMS WILL MOVE THROUGH OVERNIGHT AS A COLD
FRONT AND SHORTWAVE TROUGH APPROACH. THE POTENTIAL FOR SEVERE STORMS
INCREASES ALONG A PRE-FRONTAL TROUGH WITH A SQUALL LINE MOVING
ACROSS OHIO WITH UPSCALE GROWTH SUPPORTED BY PARALLELING DEEP LAYER
SOUTHWESTERLY FLOW. AGAIN THOUGH, WE LOOK TO BE IN A SETUP WHERE THE
STORMS WILL MOVE IN LOCALLY IN AN UNFAVORABLE DIURNAL TIMING WINDOW
FOR SURFACE-BASED INSTABILITY; HREF PROBABILITY FOR >100 J/KG OF
SBCAPE DOESN'T EXCEED 20% IN OUR AREA OVERNIGHT WITH A WARM NOSE
EXTENDING UP TO 850 MB. CAM POINT SOUNDINGS SUGGEST SOME MORE MUCAPE
(POTENTIALLY UP TO 750 J/KG) AVAILABLE ATOP THE LOW LEVEL WARM NOSE.
SHEAR WILL NOT BE AN ISSUE WITH A LOW LEVEL JET MAXIMUM NEARING 70
KNOTS AT 850 MB, AND THUS THE 0-3 KM SHEAR VALUES ARE PROGGED IN
EXCESS OF 40 KNOTS WITH DEEP LAYER SHEAR NEARING 60 KNOTS. WHAT THIS
ALL MEANS IS THAT THERE'S AGAIN A CONDITIONAL PROBABILITY, DEPENDENT
ON STORMS BEING SURFACE BASED, FOR DAMAGING WIND AND AN EMBEDDED
TORNADO GIVEN THE LOW LEVEL SHEAR PARAMETERS AND VEERING IN THE
LOWEST FEW KM. THE SEGMENTS OF THE LINE TO PAY CLOSE ATTENTION TO
WOULD BE THOSE ORIENTED MORE NORTHWEST TO SOUTHEAST TO BEST
INGEST THE AVAILABLE LOW LEVEL SHEAR. SHOULD THE STORMS BE
ELEVATED, THOUGH, THREATS WOULD LIKELY BE LIMITED TO SMALL HAIL
AND HEAVY RAIN. SPC HAS MAINTAINED THE SLIGHT RISK (2/5) WEST OF
I-79 AND A MARGINAL RISK (1/5) FARTHER EAST.
SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/
KEY MESSAGES:
- SHOWERS AND THUNDERSTORMS CONTINUE THROUGH THE REST OF THE
WORK WEEK AS A FRONT STALLS NEAR THE LOCAL AREA.
- SOME STORMS COULD BE SEVERE ON THURSDAY.
- A FLOOD WATCH REMAINS IN EFFECT FOR PORTIONS OF EASTERN OHIO.
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THE FORWARD PROGRESS OF THE FRONT IS EXPECTED TO SLOW AND STALL ON
THURSDAY AS THE UPPER LEVEL FLOW ESTABLISHES OUT OF THE SOUTHWEST
AND TRANSPORTS ANOMALOUSLY HIGH (+3 TO 4 STANDARD DEVIATIONS)
PRECIPITABLE WATER INTO THE REGION. UNCERTAINTY IN THE EXACT
POSITION OF THE FRONT EXISTS, WHICH WILL IMPACT AREAS WHERE
CONVERGENCE IS STRONGEST AND HEAVY RAIN FALLS, AND ALSO WHICH AREAS
HAVE THE POTENTIAL FOR SEVERE STORMS. AT THIS TIME, THE SOUTHERN
HALF OF THE AREA (ESPECIALLY SOUTH OF I-70) IS FAVORED FOR HAVING A
MORE CONDUCIVE ENVIRONMENT FOR ORGANIZED DEEP CONVECTION AND SEVERE
POTENTIAL ON THURSDAY, BUT THERE WILL LIKELY BE SOME WIGGLE ROOM AS
MODELS STILL TRY TO PIN DOWN THE PLACEMENT OF THE BOUNDARY. THIS
THREAT CONTINUES TO BE HIGHLIGHTED BY SPC WITH A SLIGHT RISK (2/5)
WHICH HAS BEEN PULLED SOUTH OF THE MASON-DIXON LINE WHILE A MARGINAL
RISK (1/5) EXTENDS UP TO US-422. HREF PROBS ARE AROUND 50-70% FOR
ANOTHER HALF AN INCH, BUT COULD BE LOCALLY HIGHER IN HEAVIER
THUNDERSTORMS.
THE FRONT IS PROGGED TO DRIFT SOUTH OF THE AREA LATE THURSDAY OR
THURSDAY NIGHT, WHICH WILL LEAD TO A DECREASE IN POPS FROM NORTH TO
SOUTH DURING THAT TIME AS THE PRIMARY AXIS OF SHOWERS AND
THUNDERSTORMS SHIFTS SOUTH OF THE MASON-DIXON LINE. THIS IS ALSO THE
WINDOW WHEN THE STRONGEST UPPER FORCING FOR LARGE-SCALE ASCENT EXITS
THE REGION, FURTHER SUPPORTING A BRIEF DECREASE IN HEAVY RAIN AND
THUNDERSTORM POTENTIAL (ESPECIALLY NORTH OF I-70) DURING THE DAY
FRIDAY.
YET ANOTHER SURFACE LOW IS THEN EXPECTED TO TRACK NE OUT OF THE
MISSISSIPPI VALLEY REGION FRIDAY NIGHT, PUSHING THE FRONT BACK NORTH
THIS TIME AS A WARM FRONT. SHOWERS AND THUNDERSTORMS ONCE AGAIN
INCREASE IN COVERAGE AS THE FRONT AND SURFACE LOW MOVE ACROSS THE
UPPER OHIO VALLEY REGION FRIDAY NIGHT INTO EARLY SATURDAY. AMOUNTS
THROUGH THE DAY ON SATURDAY LOOK TO BE HIGHEST FROM PITTSBURGH AND
NORTH WITH FORCING ALONG THE WARM FRONT AND ENHANCED CONVERGENCE ON
THE NOSE OF AN IMPINGING 850 MB JET. WE'LL BRIEFLY RESIDE IN THE
WARM SECTOR BEFORE THE COLD FRONT COMES THROUGH IN THE LATTER HALF
OF THE DAY BRINGING YET ANOTHER ENHANCEMENT IN RAIN COVERAGE ALONG
IT. THE SEVERE WEATHER POTENTIAL SHOULD BE LIMITED DUE TO WEAK
INSTABILITY, HOWEVER WITH REPEATED ROUNDS OF HEAVY RAIN AND A
SATURATED GROUND, FLOODING POTENTIAL WILL INCREASE, ESPECIALLY WITH
RISES ON AREA RIVERS.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
KEY MESSAGES:
- SHOWERS/THUNDERSTORMS WITH POTENTIAL FOR HEAVY RAINFALL CONTINUE
THIS WEEKEND.
- A COLD FRONT MOVES THROUGH SUNDAY FINALLY BRINGING AN END TO THE
HEAVY RAINFALL.
- COLDER NEXT WEEK WITH LIGHTER RAIN/SNOW CHANCES EACH DAY.
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SHOWERS AND THUNDERSTORMS CONTINUE SATURDAY NIGHT AS THE SURFACE LOW
TRACKS THROUGH THE AREA, YET IS STILL UNABLE TO EFFECTIVELY MOVE THE
STALLED FRONTAL BOUNDARY. ENSEMBLES SUGGEST ANOTHER HEAVIER PERIOD
OF RAIN ON THE NOSE OF ANOTHER LOW LEVEL JET SATURDAY NIGHT INTO
SUNDAY MORNING FALLING ON A THEN VERY SATURATED GROUND. HOWEVER,
ENSEMBLE CLUSTERS ALL AGREE ON A DEEP UPPER TROUGH SWINGING ACROSS
THE EASTERN CONUS ON SUNDAY INTO MONDAY WHICH WILL FINALLY SHUNT THE
SURFACE RIDGE THAT HAD BEEN FIRMLY PLANTED OVER THE SOUTHEAST CONUS
COAST AND ALLOW A COLD FRONT TO ADVANCE THROUGH THE AREA AND OFF TO
THE EAST BRINGING AN END TO THE HEAVY RAIN AND STORM POTENTIAL.
THERE'S SOME DISCREPANCY IN THE TIMING OF THE UPPER PATTERN AND HOW
QUICKLY THE TROUGH AXIS ARRIVES WITH THE CLUSTER DOMINATED BY THE
GEPS SUGGESTING A SLOWER CESSATION OF THE RAIN IN THE MONDAY MORNING
HOURS.
THE UPPER TROUGH IS THEN EXPECTED TO PERSIST ACROSS THE NE CONUS
EARLY NEXT WEEK, RESULTING IN TEMPERATURES DIPPING TO BELOW NORMAL
VALUES AND DAILY RAIN/SNOW CHANCES, ALBEIT NOT NEARLY AS INTENSE AS
WHAT WE'RE EXPERIENCING THIS WEEK.
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
A WARM FRONT WILL CONTINUE TO LIFT ACROSS THE REGION THIS
AFTERNOON, SPREADING SHOWERS AND THUNDERSTORMS ACROSS THE AREA.
TIMED THESE AT INDIVIDUAL AIRPORTS OVER A 1-2 HOUR PERIOD AS
THESE MOVE THROUGH. TEMPORARY MVFR RESTRICTIONS AND HAIL ARE
POSSIBLE.
VFR SHOULD RETURN AFTER THE WARM FRONT EXITS THIS EVENING.
ANOTHER LINE OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO MOVE
ACROSS THE AREA OVERNIGHT AS A COLD FRONT APPROACHES.
INSTABILITY DIMINISHES SOME OVERNIGHT, THOUGH ENOUGH UPPER
LEVEL AND JET SUPPORT SHOULD MAINTAIN THIS LINE THROUGH THE
OVERNIGHT PERIOD.
OUTSIDE OF ANY STORMS, EXPECT GUSTY SSE WIND TODAY AND TONIGHT,
SHIFTING TO THE SSW OVERNIGHT. THE HIGHEST GUSTS ARE EXPECTED AT
LBE, WHERE SOME DOWNSLOPING IS EXPECTED.
OUTLOOK...
SHOWERS AND THUNDERSTORMS, ALONG WITH MVFR CONDITIONS, WILL
CONTINUE INTO THURSDAY AS THE COLD FRONT SLOWLY CROSSES THE
REGION. THIS FRONT IS EXPECTED TO STALL THURSDAY NIGHT, AND
RETURN NORTH FRIDAY AND SATURDAY WITH ANOTHER WAVE OF
SHOWERS/THUNDERSTORMS. RESTRICTIONS ARE EXPECTED TO CONTINUE
INTO SUNDAY AS THE FRONT TRACKS EAST AS A COLD FRONT, AND
CROSSES THE UPPER OHIO VALLEY REGION.
HYDROLOGY
THE POTENTIAL FOR HEAVY RAINFALL WILL EXIST BEGINNING TONIGHT
AND CONTINUING INTO SUNDAY. AT THIS TIME, AREAS ACROSS OHIO HAVE
THE POTENTIAL TO SEE THE HEAVIEST RAINFALL, WHERE A FLOOD WATCH
HAS BEEN ISSUED. CURRENT NBM VALUES INDICATE A 60 PERCENT
CHANCE OR GREATER OF AT LEAST 2 INCHES OF RAIN OVER A 72 HR
PERIOD IN THIS REGION. LESSER PROBABILITIES EXIST FURTHER EAST,
THOUGH A TREND UP HAS BEEN NOTED IN THE LATEST ENSEMBLE GUIDANCE
AND WILL NEED TO BE MONITORED FOR ANY POTENTIAL EXPANSION OF THE
FLOOD WATCH. THE EXACT LOCATION OF THE HEAVIEST RAIN WILL
DEPEND ON THE POSITION OF A QUASI-STATIONARY SURFACE FRONT.
PRECIPITABLE WATER IS EXPECTED TO REMAIN ELEVATED THROUGH
SUNDAY, WITH SOME PERIODIC JET ENHANCED ASCENT. EVEN AFTER THE
HEAVY RAIN POTENTIAL ENDS, RIVER LEVELS WILL LIKELY REMAIN
ELEVATED FOR A FEW DAYS. CURRENT ENSEMBLE RIVER FORECAST
PROJECTIONS ALSO FOCUS THE MOST SIGNIFICANT RIVER RISES ACROSS
OHIO.
WILL MONITOR FURTHER TRENDS FOR ANY FUTURE ADJUSTMENTS TO THE
WATCH.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...FLOOD WATCH FROM 8 PM EDT THIS EVENING THROUGH SUNDAY MORNING
FOR OHZ039-040-048-049-057>059-068-069.
WV...NONE.
SYNOPSIS...CERMAK/MLB
NEAR TERM...MLB
SHORT TERM...CERMAK/MLB
LONG TERM...CERMAK/MLB
AVIATION...WM
HYDROLOGY...MLB/WM
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