013
FXUS61 KPBZ 210524
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1224 AM EST SAT FEB 21 2026
WHAT HAS CHANGED
- WINTER STORM WATCH IN EFFECT FROM 1AM SUNDAY TO 1AM TUESDAY
FOR THE HIGH TERRAIN, WITH EXTENDED-DURATION UPSLOPE SNOW.
- FLOOD WATCH CONTINUES FOR MOST SUSCEPTIBLE ICE-JAM AREAS
THROUGH 9AM SATURDAY.
KEY MESSAGES
1) GUSTY WINDS LESSEN SOMEWHAT TONIGHT.
2) ICE JAM FLOOD WATCH CONTINUES THROUGH TOMORROW.
3) WINTER STORM LIKELY FOR HIGH TERRAIN. LOWER CONFIDENCE IN
SNOW TOTALS ELSEWHERE.
DISCUSSION
KEY MESSAGE 1...
GUSTY WINDS BETWEEN 35MPH AND 45MPH ON AVERAGE ACROSS THE REGION
(LOCALLY HIGHER GUSTS WILL STILL BE POSSIBLE THIS EVENING)
WILL BEGIN TO LESSEN TONIGHT AS THE PRESSURE GRADIENT BEGINS TO
RELAX AND THE BOUNDARY LAYER BECOMES LESS DEEP. HOWEVER, WINDS
OVERALL WILL REMAIN GUSTY OVERNIGHT AS LATEST FORECAST
SOUNDINGS GIVE NO INDICATION OF DECOUPLING. THE WIND ADVISORY
FOR EASTERN TUCKER REMAINS IN EFFECT THROUGH MIDNIGHT TONIGHT.
KEY MESSAGE 2...
THE FLOOD WATCH HAS BEEN EXTENDED FOR CERTAIN COUNTIES UNTIL
SATURDAY MORNING DUE TO PERSISTENT ICE JAM PROBLEMS IN THE UPPER
ALLEGHENY RIVER BASIN.
CURRENT SITUATION: AS OF THIS MORNING, AN ICE JAM WAS CONFIRMED NEAR
EMLENTON, PA AND FOXBURG, PA. MINOR FLOODING IS ANTICIPATED IN THE
VICINITY OF THE JAM; FLOOD WARNING IN EFFECT THROUGH 4PM TODAY.
ONGOING MONITORING: DUE TO WARM TEMPERATURES TODAY AND HIGH STREAM
LEVELS FROM RECENT RAINFALL, CONTINUOUS MONITORING FOR NEW ICE
JAMS DOWNSTREAM WILL LIKELY BE NECESSARY OVER THE NEXT 24HRS.
AREAS OF CONCERN INCLUDE EAST BRADY, TEMPLETON, AND REEDSDALE.
KEY MESSAGE 3...
A COMPLICATED INTERACTION OF A DIGGING 500MB TROUGH AND
RECURVING MID-ATLANTIC SURFACE LOW WILL BRING AREA-WIDE SNOW
CHANCES TO THE REGION SUNDAY THROUGH MONDAY. HERES WHAT WE KNOW:
HIGH CONFIDENCE: ACCUMULATING, IMPACTFUL SNOW FOR THE HIGH
TERRAIN OF PENNSYLVANIA AND WEST VIRGINIA. IRRESPECTIVE OF THE
MID-ATLANTIC LOW TRACK, THE DIGGING 500MB TROUGH, STEEP LAPSE
RATES ALOFT THROUGH THE DENDRITIC LAYER AND RIDGETOPS TEMPS
AROUND OR BELOW FREEZING FOR THE EVENT. THERE WAS A >50% OF >6"
OF SNOW FOR THE 48 HOUR PERIOD ENDING MONDAY NIGHT. NOTE: TOTALS
MAY VARY GREATLY FROM RIDGETOP TO VALLEY WITH WARMER
TEMPERATURES AT LOWER ELEVATIONS.
MEDIUM CONFIDENCE: ACCUMULATIONS FOR THE LOWLANDS. DUE TO A
NUMBER OF FACTORS, SNOW RATIOS IN MOST ENSEMBLE GUIDANCE
OVERESTIMATE REALITY, PIRATICALLY FOR THE DAYTIME HOURS SUNDAY
(DURING THE PEAK ACCUMULATION WINDOW). THIS IS RELATED TO A
DIFFERENCE BETWEEN SNOW RATIOS IN THE SNOW GROWTH LAYER, AND
RATIOS UPON CONTACT WITH THE WARM SURFACE. WITH THE NBM 10TH TO
90TH MAX T SPREAD BETWEEN THE MID-30S AND LOW 40S, THIS SPANS
EVERYTHING FROM A WETTER SNOW TO EVEN PERIODS OF RAIN FOR THE
VALLEYS. TO DOWNTREND NBM RATIOS, KEPT 10:1 MEAN ACCUMULATION
THROUGH THE EVENT. EVEN WITH A MOST LIKELY FORECAST OF 1" TO 3",
TOTALS MAY TREND LOWER IF SNOW IS LIGHTER AND TEMPERATURES ARE
WARMER. MOST ACCUMULATIONS ARE FAVORED ON GRASSY SURFACES, WITH
CHANCES OF ACCUMULATIONS ON UNTREATED ROADS INCREASING SUNDAY
NIGHT AS TEMPERATURES DROP BELOW FREEZING.
LOW CONFIDENCE: SNOW TOTALS MAY TREND HIGHER IN THE MID-
ATLANTIC LOW CURVES INLAND AS A NOR- EASTER (THOUGH MOST OF THIS
UNCERTAINTY IS EAST OF PITTSBURGH). THE MOST LIKELY SCENARIO
(80% CHANCE) IS THAT THE MID-ATLANTIC LOW INFLUENCE STAYS SOUTH
AND HAS LITTLE EFFECT ON AREA SNOW TOTALS. IN THE LOW
PROBABILITY EVENT THAT THIS TRENDS WEST, BIG SNOWS REMAIN
POSSIBLE EAST OF PITTSBURGH AND INTO THE HIGH TERRAIN (LONG,
HIGH-END TAIL ON THE SNOWFALL DISTRIBUTION). IN THE PREFECT
SCENARIO WHERE THE LOW TRENDS WEST AND A FRONTOGENETICAL BAND
FORMS ON THE WESTERN PERIPHERY OF THE LOW, UP TO 6 TO 10" IS
ENTIRELY POSSIBLE FOR THE LOWLANDS EAST OF PITTSBURGH, WITH UP
TO 15" TO 20" FOR THE HIGH TERRAIN. AGAIN, THIS IS A LOW-
PROBABILITY BUT HIGH-IMPACT SCENARIO THAT WILL NEED TO CONTINUE
TO BE MONITORED.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
KEY MESSAGES...
- BREEZY WINDS TO CONTINUE BEFORE SLACKENING SATURDAY MORNING
- MVFR SETTLING IN FROM THE NORTH OVERNIGHT
- MVFR SCATTERS FROM S TO N TOMORROW, FKL/DUJ UNLIKELY TO CLEAR
------------------------------------------------------------
WHAT WERE VERY GUSTY WINDS EARLIER TODAY HAVE SLACKENED SOME AS
EXPECTED OVERNIGHT. BREEZY CONDITIONS ARE EXPECTED TO CONTINUE
INTO SATURDAY MORNING BEFORE SLACKENING FURTHER. WINDS GO LIGHT
AND VARIABLE AT MANY LOCATIONS BY THE END OF THE 24HR TAF
WINDOW.
LOW CLOUDS FILTERING IN ARE SLOWLY LOWERING AND MVFR IS
CREEPING SOUTHWARD ACROSS THE REGION AT THIS TIME. PIT AND AGC
ARE EXPECTED TO FALL SHORTLY, WITH HLG NOT FAR BEHIND. ZZV WILL
BE NEAR THE EXPECTED SOUTHERN EXTENT OF THESE CLOUDS. HREF
PROBABILITIES FOR MVFR AT ZZV PEAK NEAR 40% BUT HAVE ERRED ON
THE SIDE OF CAUTION GIVING A FEW HOURS OF MVFR BEFORE SCATTERING
OUT AGAIN BEFORE SUNRISE. MGW IS FAR ENOUGH SOUTH THAT IT
LIKELY REMAINS VFR THROUGHOUT THE PERIOD. IFR PROBABILITIES ARE
HIGHEST (NEAR 90%)OVERNIGHT FOR FKL/DUJ BUT THE NEAR 80% CHANCE
THEY HAVE OF OCCURRENCE AT THIS TIME CERTAINLY ISN'T PANNING OUT
SO I HAVE INITIALIZED A LITTLE MORE OPTIMISTICALLY FOR THESE
PORTS.
A GENERAL S TO N CLEARING BEGINS BY EARLY MORNING AT ZZV THEN
PROGRESSES THROUGH THE MORNING AND MIDDAY HOURS AS FAR NORTH AS
BVI, RETURNING VFR TO ALL PORTS NOT NAMED FKL OR DUJ. FKL/DUJ
LIKELY REMAIN LOCKED INTO MVFR IF NOT IFR THROUGH MUCH OF THE
DAY.
BKN VFR CIGS AND LIGHT SNOW RETURN TO MOST PORTS BY THE CLOSE
OF THE CURRENT 24HR TAF PERIOD.
OUTLOOK... WIDESPREAD, LIGHT SNOW IS EXPECTED LATE SATURDAY
NIGHT THROUGH MONDAY WITH A CROSSING UPPER LOW. PROBABILITIES
FAVOR A 1-3 INCH SNOWFALL OUTSIDE OF THE RIDGES. VFR SHOULD
GRADUALLY RETURN TUESDAY AS HIGH PRESSURE BEGINS TO BUILD IN.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...FLOOD WATCH UNTIL 9 AM EST THIS MORNING FOR PAZ008-014>016-022.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE MONDAY NIGHT
FOR PAZ074-076.
OH...NONE.
WV...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE MONDAY NIGHT
FOR WVZ510>514.
DISCUSSION...HEFFERAN/MILCAREK/88
AVIATION...AK
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