560
FXUS61 KPBZ 050512
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
112 AM EDT FRI SEP 5 2025
SYNOPSIS
AFTER AREAS OF FOG DISSIPATE THIS MORNING, ANOTHER ROUND OF
SHOWERS AND LOW PROBABILITY THUNDERSTORMS WILL OVERSPREAD MOST
OF THE REGION TONIGHT INTO SATURDAY AND RESULT IN WELL BELOW
AVERAGE TEMPERATURE. DRY WEATHER WITH SLOWLY RISING TEMPERATURE
IS FAVORED SUNDAY THROUGH EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- AREAS OF FOG WILL DISSIPATE AFTER SUNRISE
- SHOWERS AND LOW PROBABILITY THUNDERSTORMS RETURN LATE THIS
EVENING, WITH A NON-ZERO DAMAGING WIND THREAT
---------------------------------------------------------------
THE COMBINATION OF LIGHT WIND AND ABUNDANT NEAR SURFACE MOISTURE
HAS AIDED IN AREAS OF FOG DEVELOPING FOR MUCH OF THE FORECAST
AREA WITH LOCALLY DENSE CONDITIONS BEING OBSERVED. A DENSE FOG
ADVISORY WAS ISSUED TO HIGHLIGHT WESTERN PA WHERE MORE
WIDESPREAD DENSE FOG CONDITIONS ARE LIKELY TO PERSIST. THE ONLY
RESERVATION IS HI-RES MODEL GUIDANCE SUGGESTING SOME VISIBILITY
IMPROVEMENTS WITH SUBTLE WARM ADVECTION IN SOUTHERLY SURFACE
FLOW THAT MAY END DENSE CONCERNS QUICKER.
AFTER DIURNAL HEATING AND INCREASED MIXING ERODES AREA FOG, THE
REGION WILL EXPERIENCE DRY CONDITIONS WITH MORE SEASONABLE
TEMPERATURE FOR MOST OF THE DAYLIGHT HOURS. THESE CONDITIONS ARE
LIKELY TO BE SHORT-LIVED AS A DEEP UPPER LEVEL SHORTWAVE ENTERS
THE LOWER OHIO RIVER VALLEY AND ITS ASSOCIATED STRONG MID-LEVEL
JET LIFTS NE TOWARDS THE AREA. JET-INDUCED ASCENT WILL BE STRONG
ENOUGH TO INDUCE SHOWERS AND LOW PROBABILITY THUNDERSTORMS
GENERALLY AFTER 6PM AHEAD OF THE NEXT SURFACE COLD FRONT. THE
MAIN QUESTIONS ARE WHETHER CONVECTIVE INITIATION CAN BE EARLY
ENOUGH TO TAP INTO SOME SURFACE BASED BUOYANCY AND IF THERE IS
ENOUGH SURFACE HEATING TO OVERCOME WARM MID-LEVEL AIR TO
INCREASE BUOYANCY SO THAT ANY STORM UPDRAFT ISN'T IMMEDIATELY
SHEARED. AT THIS TIME, THE PROBABILITY OF GENERATING AROUND 1000
J/KG CAPE ALONG WITH THE 40KTS 0-6KM SHEAR IS LOW (10-15%) BUT
MATCHES THE CONDITIONAL THREAT NEEDED TO HIGHLIGHT POTENTIAL FOR
DAMAGING WINDS. HAZARDOUS CONDITIONS ARE LIKELY TO EASE BY
MIDNIGHT, BUT WAVES OF SHOWER ACTIVITY WILL PERSIST AS EMBEDDED
SHORTWAVES CONTINUE TO LIFT NE THROUGH THE STRONG SW FLOW ALOFT.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
KEY MESSAGES:
- ROUNDS OF RAIN POSSIBLE, THOUGH TRENDS SHIFT THE PRECIPITATION
AXIS EAST FOR SATURDAY
- WELL BELOW AVERAGE TEMPERATURE SATURDAY WILL TREND CLOSER TO
NORMAL SUNDAY
--------------------------------------------------------------
THE UPPER OHIO RIVER VALLEY WILL CONTINUE TO SIT EAST OF THE
MAIN UPPER TROUGH AXIS THAT IS EXPECTED TO SEE ADDITIONAL
SHORTWAVE MOVEMENT SATURDAY. THESE WAVES WILL HELP PUSH A
NOMINAL COLD FRONT SE THROUGH THE REGION DURING THE VERY EARLY
MORNING HOURS SATURDAY AS WELL AS PROMOTE PERIODS OF GENERALLY
LIGHT TO OCCASIONALLY MODERATE RAIN SHOWERS THROUGH THE EVENING.
ENSEMBLE MODEL TRENDS SUGGEST THE SLIGHTEST SHIFT EAST OF THE
AXIS OF PRECIPITATION EXPECTED TO OCCUR IN RESPONSE TO EASTWARD
EDGING OF THE UPPER DRY SLOT (AND ULTIMATELY THE TROUGH AXIS).
THIS SHIFT MAY ALLOW FOR THE FAR NORTHWEST FORECAST LOCATIONS
(LOCATED IN NE OH) TO MORE QUICKLY SEE RAIN CHANCES END AND A
RETURN OF SOME SUNSHINE TO BOOST AFTERNOON TEMPERATURE; OTHER
AREAS IN RAIN WILL STRUGGLE TO SEE WARMING. THE RESULT IS ALL
LOCATIONS WILL BE WELL BELOW NORMAL, WITH THE DEGREE OF
AFTERNOON TEMPERATURE RISING CORRELATED WITH THE PERSISTENCE OF
RAIN THROUGH THE DAY.
THERE IS HIGH CONFIDENCE IN DRY WEATHER DEVELOPING SATURDAY
NIGHT INTO SUNDAY MORNING JUST PRIOR TO THE UPPER TROUGH AXIS
PASSAGE. THESE DRY CONDITIONS ARE LIKELY TO CONTINUE INTO SUNDAY
WITH DRY WESTERLY (SHIFTING EVENTUALLY NORTHWESTERLY FLOW) AND
INCREASING HIGH PRESSURE. HOWEVER, LIFT ASSOCIATED WITH THE
TROUGH AXIS AND COLD TEMPERATURES ALOFT MAY BE ENOUGH TO DEVELOP
LAKE ENHANCED SHOWERS NORTH OF PITTSBURGH SUNDAY AFTERNOON;
LATEST GUIDANCE SUGGESTS 850MB FLOW WILL BE WESTERLY ENOUGH THAT
MOST SHOWER DEVELOPMENT SHOULD REMAIN ALONG/NORTH OF I-80.
TEMPERATURE WILL REMAIN WELL BELOW NORMAL AS MOST CITIES
STRUGGLE TO REACH 70 DEGREES FOR A HIGH (AVERAGE TEMPERATURE IS
78 DEGREES IN PITTSBURGH SUNDAY, FOR REFERENCE).
LONG TERM /MONDAY THROUGH THURSDAY/
KEY MESSAGES:
- RISING TEMPERATURE THROUGH MIDWEEK WITH DRY WEATHER
- NEXT RAIN CHANCES NOT UNTIL LATE NEXT WEEK.
-------------------------------------------------------------------
ENSEMBLE MODELS ARE HIGHLY CONFIDENT THAT THE COMBINATION OF
SURFACE HIGH PRESSURE AND GRADUAL HEIGHT RISES ALOFT WILL
PROMOTE DRY WEATHER, TEMPERATURE RETURNING TO SEASONAL AVERAGES
BY WEDNESDAY.
THE NEXT WEATHER SYSTEM MAY NOT OCCUR UNTIL THE LATE WEEK PERIOD
AND WILL BE DEPENDENT ON DEPTH/TIMING OF TROUGH MOVEMENT AS A
WESTERN CONUS TROUGH, CENTRAL CONUS RIDGE, AND EASTERN CONUS
TROUGH TYPE PATTERN DEVELOPS.
AVIATION /05Z FRIDAY THROUGH TUESDAY/
IFR CONDITIONS WILL BE LARGELY ACROSS THE REGION OVERNIGHT WITH
A COMBINATION OF LOW-LEVEL STRATUS AND PATCHY DENSE FOG AFTER
EARLIER SHOWERS/STORMS HAVE LEFT LOW LEVELS SATURATED UNDER THE
OVERNIGHT INVERSION. LOW CONFIDENCE IN EITHER FOG OR STRATUS AT
ANY GIVEN PLACE GIVEN FORECAST MRI VALUES BEING ON THE FENCE,
BUT IN ANY CASE IFR OR LOWER RESTRICTIONS SHOULD PREVAIL UNTIL
MID- MORNING WITH INCREASED MIXING.
VFR CONDITIONS WILL THEN PERSIST UNTIL ADDITIONAL SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH A CROSSING FRONT PASS THROUGH THE
REGION LATER THIS EVENING AND OVERNIGHT.
THE
OUTLOOK.
VFR IS EXPECTED SATURDAY AFTERNOON THROUGH THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK (OUTSIDE OF SOME RIVER VALLEY MORNING FOG)
WITH HIGH PRESSURE THE DOMINANT FEATURE ACROSS THE REGION.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ008-009-
013>016-020>022-073-074-077-078.
OH...NONE.
WV...NONE.
SYNOPSIS...FRAZIER
NEAR TERM...FRAZIER
SHORT TERM...FRAZIER
LONG TERM...FRAZIER
AVIATION...88
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