277
FXUS61 KPBZ 040604
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
204 AM EDT MON MAY 4 2026
WHAT HAS CHANGED
NO MAJOR CHANGES WERE MADE TO THE FORECAST.
KEY MESSAGES
1) SHOWER AND THUNDERSTORM CHANCES INCREASE LATE THIS
AFTERNOON/EVENING.
2) AN ACTIVE PATTERN WILL KEEP SHOWER AND/OR THUNDERSTORM
CHANCES IN THE FORECAST THROUGH THE WEEKEND.
3) POTENTIAL FOR FROST RETURNS THURSDAY NIGHT, MAINLY ACROSS
I-80 CORRIDOR AND IN THE RIDGES.
DISCUSSION
KEY MESSAGE 1...
MAINLY DRY WEATHER IS EXPECTED INTO THIS AFTERNOON, THOUGH A FEW
SPRINKLES OR ISOLATED LIGHT SHOWERS ARE POSSIBLE WITH WARM
ADVECTION. DIURNAL INSTABILITY IS EXPECTED TO BUILD IN THE WARM
SECTOR ON THROUGH THE DAY AS A SHORTWAVE TROUGH APPROACHES. ML
CAPE IS PROGGED TO REACH AROUND 1,000 J/KG ACROSS OHIO DURING
THE AFTERNOON, WITH LESSER AMOUNTS TO THE EAST. SHEAR IS ALSO
EXPECTED TO INCREASE, WITH 30-35KT FROM 0-6KM. A FEW STRONG
STORMS WITH WIND AND HAIL WILL BE POSSIBLE, ESPECIALLY ACROSS
OHIO, BEFORE A GENERAL DECREASING TREND OCCURS THROUGH THE
EVENING AND OVERNIGHT AS INSTABILITY GRADUALLY WANES. LATEST
CAMS HAVE BEEN FAIRLY RELUCTANT TO INITIALIZE SHOWERS/STORMS
OVER EASTERN OHIO LATE THIS AFTERNOON/EVENING, SO IT IS POSSIBLE
WE SEE ONLY A FEW ISOLATED NON-SEVERE THUNDERSTORMS.
KEY MESSAGE 2...
SURFACE LOW PRESSURE WILL CROSS NORTH OF THE GREAT LAKES TODAY
AND TUESDAY, SLOWLY DRAGGING A COLD FRONT INTO THE REGION
TUESDAY. BOUNDARY-PARELLEL FLOW WILL SLOW PROGRESSION OF THE
FRONT AS IT SINKS ACROSS OUR AREA LATE TUESDAY AND WEDNESDAY.
TUESDAY SHOULD BE THE WARMEST DAY OF THE WEEK, WITH GUSTY SOUTH
WIND AHEAD OF THE FRONT. INSTABILITY IS EXPECTED TO BE LIMITED
AS THE FRONT CROSSES THE REGION, THOUGH A FEW THUNDERSTORMS ARE
POSSIBLE. AT THIS TIME THERE IS AN 80-90 PERCENT PROBABILITY OF
SEEING AT LEAST A HALF INCH OF RAIN WITH THIS SYSTEM, WITH
PROBABILITIES AROUND 70 PERCENT FOR AN INCH OF RAIN NORTH OF
PIT.
SHOWER CHANCES WILL CONTINUE ON THURSDAY AS THE FRONT BECOMES
QUASI-STATIONARY ACROSS THE LOWER OHIO VALLEY AND MID-ATLANTIC
REGION AND AS A WAVE OF LOW PRESSURE TRACKS ALONG IT. A
SHORTWAVE TROUGH SHOULD FINALLY DRIVE THE FRONT OUT THE AREA
THURSDAY NIGHT INTO FRIDAY, BUT LINGERING UPPER TROUGHING WILL
MAINTAIN SHOWER CHANCES THROUGH THE WEEKEND. AFTER A WARM START
TO THE WEEK, COOLER THAN AVERAGE TEMPERATURES ARE EXPECTED
BEHIND THE MID WEEK COLD FRONT.
KEY MESSAGE 3...
POTENTIAL FOR LIGHT WIND AND TEMPERATURES BELOW 37F RANGES FROM
50-70% ACROSS THE I-80 CORRIDOR AND IN THE RIDGES THURSDAY
NIGHT/EARLY FRIDAY MORNING. THIS COULD LEAD TO FROST
DEVELOPMENT FOR THOSE AREAS, BUT WILL LARGELY BE DEPENDENT
WHETHER OR NOT SKIES CLEAR OVERNIGHT.
AVIATION /06Z MONDAY THROUGH FRIDAY/
VFR IS VERY LIKELY TO PREVAIL THROUGH THE ENTIRE PERIOD.
OVERNIGHT, LIGHT SOUTHWEST GRADIENT WIND WILL PREVAIL AROUND
5 KNOTS. WITH THE PASSAGE OF WEAK MID-LEVEL DISTURBANCE, DECKS
HAVE GONE BROKEN AROUND 5-6 KFT, BUT EXPECT AN EVENTUAL
TRANSITION BACK TO SCT AFTER DAYBREAK AND MIXING ALLOWING FOR
SOME CU DEVELOPMENT.
WIND WILL PICK UP NOTABLY ON MONDAY OUT OF THE SOUTHWEST WITH A
TIGHTENING GRADIENT AND MOMENTUM TRANSFER WITH MIXING
SUGGESTING AT LEAST 20 KNOT GUSTS THROUGH THE AFTERNOON HOURS.
THE STRONGEST LOW LEVEL FLOW LIKELY DOESN'T ARRIVE UNTIL THE
EARLY EVENING HOURS AS THE SURFACE BEGINS TO DECOUPLE, SO WE
LOOK TO BE SPARED FROM MIXING DOWN STRONGER GUSTS AT THIS TIME,
BUT WITH LOWER PROBABILITY EARLIER ARRIVAL, CAN'T RULE OUT A
BRIEF PERIOD OF ENHANCED GUSTS. WHAT THIS MAY RESULT IN IS A
FAVORABLE SETUP FOR LOW LEVEL WIND SHEAR AFTER 00Z AS 925 MB
FLOW RAMPS UP TO AROUND 40 KNOTS AND 850 MB FLOW TO 45-50 KNOTS.
NBM AND HREF SEEM TO BOTH BE OVERDOING GUSTS OVERNIGHT AS MODEL
SOUNDINGS SUPPORT WAA REINFORCING THE DECOUPLED SURFACE LAYER.
STILL, A FEW MODELS SUGGEST THAT THE PROFILE IS MORE ISOTHERMAL
THAN STABLE AND ALLOWING FOR SOME HIGHER GUSTS, SO HAVE
EXCLUDED LLWS MENTION IN THE TAFS AT THIS TIME. BUT, INCLUSION
IS MORE LIKELY THAN NOT, ESPECIALLY IF SUBSEQUENT MODEL RUNS
INCREASE CONFIDENCE THAT SURFACE FLOW REMAINS LOW ENOUGH THAT
CRITERIA WILL BE MET.
WITH INCREASING WARM ADVECTION, SOME SHOWERS MAY DEVELOP IN THE
EARLY EVENING, BUT THE SCATTERED NATURE AND RUN TO RUN MODEL
INCONSISTENCY WITH OCCURRENCE AT ALL CONTINUES TO WARRANT A
PROB30 MENTION AT ALL SITES FOR NOW. THUNDER IS POSSIBLE AS
WELL, THOUGH WITH SOME UNCERTAINTY WITH AVAILABLE INSTABILITY
AND UPDRAFTS EXCEEDING -10C IN DRIER MID-LEVEL AIR.
OUTLOOK...
A FEW THUNDERSTORMS ARE POSSIBLE ON TUESDAY. MORE WIDESPREAD
RESTRICTIONS IN SHOWERS ARE LIKELY TUESDAY NIGHT INTO WEDNESDAY
AS A WAVE OF LOW PRESSURE TRACKS ALONG THE COLD FRONT.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...WM/RACKLEY
AVIATION...MLB
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