801
FXUS61 KPBZ 170926
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
426 AM EST MON FEB 17 2025
SYNOPSIS
SNOW AND BLOWING SNOW CONTINUES FOR SOME THIS MORNING,
WITH SOME GUSTS UP TO 25 TO 35MPH LINGERING TODAY. WIND CHILLS
BETWEEN 5 AND 20 BELOW ARE EXPECTED TONIGHT. BELOW AVERAGE
TEMPERATURES CONTINUE THIS WEEK WITH ADDITIONAL SNOW POTENTIAL
WEDNESDAY INTO THURSDAY. A "WARMUP" IS FAVORED BY THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- BLIZZARD CONDITIONS LINGER IN THE HIGH TERRAIN THIS MORNING.
- WIND GUSTS OF UP TO 25MPH TO 35MPH EXPECTED TODAY.
- WIND CHILLS OF -5 TO -20 OVERNIGHT; A COLD WEATHER ADVISORY IS
IN EFFECT FOR PORTIONS OF THE AREA.
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SNOW AND BLOWING SNOW CONTINUES FOR PORTIONS OF THE AREA THIS
MORNING WITH ADIABATIC NEAR-SURFACE PROFILES, COURTESY OF COLD
ADVECTION. SHORTWAVE ASCENT AND MOISTURE FROM UPSTREAM GREAT
LAKES APPEAR TO BE THE MAIN FUEL TO THE FIRE FOR SNOW BANDING.
THIS IS EXPECTED TO DRAW NORTHEAST THROUGHOUT THE MORNING AS
RIDGING ENSUES BEHIND AN OVERNIGHT SHORTWAVE PASSAGE, ORIENTING
WIND MORE OUT OF THE WEST ALOFT. THOUGH PRECIPITATION CHANCES
DECREASE, THEY COLD NOT BE RULED OUT COMPLETELY IN THE TYPICAL
SPOTS IN HIGH TERRAIN WITH OROGRAPHIC LIFT AND IN THE I-80
CORRIDOR IN THE LEFT EXIT REGION OF A DEVELOPING UPPER JET THIS
MAY BE JUST ENOUGH ASCENT TO INVIGORATE THE ALREADY-PRIMED LOW
LEVELS.
THERE IS HIGH CONFIDENCE IN MAINTAINED WIND GUSTS THROUGHOUT THE
DAY DUE TO CONTINUED COLD ADVECTION ENFORCING ADIABATIC PROFILES
IN A STRONG GRADIENT BETWEEN THE LOW AND ENCROACHING HIGH.
THERE IS NEARLY AN 80% TO 100% CHANCE THE MAX GUSTS FOR EXPOSED
HILLTOPS EXCEEDS 30MPH, WITH A 30% CHANCE OF EXCEEDING 40MPH.
THIS INCREASES TO 100% AND 70% RESPECTIVELY FOR HIGH TERRAIN.
WHILE THESE ARE MAX GUSTS, IS IS FORECAST THE LOWLANDS WILL
GUST FROM 25MPH TO 35MPH FOR THE MOST PART, WHILE THE RIDGES MAY
BE UP TO 45MPH. WIND WILL COMBINE WITH SNOW ON THE GROUND TO
CONTINUE TO ALLOW FOR BLOWING SNOW HAZARDS, PARTICULARLY FOR
THE RIDGES. WITH ADDITIONAL SNOW CHANCES AND BLOWING SNOW
CHANCES, THE BLIZZARD WARNING FOR THE HIGH TERRAIN REMAINS.
INTO TOMORROW NIGHT, WINDS ARE EXPECTED TO RELAX WITH THE
STRONGEST WINDS ABOVE THE MIXED LAYER, BUT 15MPH TO 25MPH STILL
SEEMS REASONABLE. COMBINED WITH THE COLD TEMPERATURES, THIS WILL
GENERATE WIND CHILL HAZARDS. A COLD WEATHER ADVISORY HAS BEEN
HOISTED ACCORDINGLY IN AREAS WITH A >50% CHANCE OF -10F "FEELS-
LIKE" VALUES OR BELOW. FOREST AND VENANGO WERE LEFT OUT DUE TO
THEIR LOWER (-15F) CRITERIA. LOWS ARE FORECAST IN THE SINGLE
DIGITS FOR MOST.
SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/
KEY MESSAGES:
- DRY AND COLD TUESDAY.
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TUESDAY APPEARS TO BE LIKELY THE COLDEST DAY OF THE WEEK, WITH
A ROUGHLY >50% CHANCE OF A MAX TEMPERATURE BELOW 20F NORTH OF
I-70. FOR REFERENCE, THIS IS NEARLY 20F BELOW NORMAL FOR THIS
TIME OF YEAR. ZONAL FLOW UNDER A STRONG UPPER JET SHOULD KEEP
PRECIPITATION CHANCES >10%.
TUESDAY NIGHT, LOWS RETURN TO THE LOW 10S AND SINGLE DIGITS, BUT
WIND IS MUCH LESS LIKELY SURFACE HIGH PRESSURE OVERHEAD. THIS
WOULD KEEP WIND CHILL CONCERNS A BIT LOWER THAN THE NIGHT PRIOR,
BUT THERE IS STILL ROUGHLY A 25% CHANCE OF HITTING COLD WEATHER
ADVISORY CRITERIA FOR PARTS OF THE I-80 CORRIDOR AND THE HIGH
TERRAIN.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGES:
- SNOW CHANCES WEDNESDAY INTO THURSDAY
- HIGHER CHANCES OF DRY WEATHER AND "WARMING" TEMPERATURES INTO
THE WEEKEND.
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INTO WEDNESDAY, THERE IS SURPRISINGLY HIGH CONFIDENCE THAT THE
UPPER LEVEL PATTERN WILL SHAPE UP TO BE A CLOSED 500MB LOW OR
ELONGATED TROUGH EXTENDING FROM THE CANADIAN MARITIMES TO THE
NORTHERN GREAT PLAINS. THE MAIN, SUBTLE UNCERTAINTY, IS HOW THE
TROUGH PROGRESSES. THIS TRICKLES INTO UNCERTAINTY ON THURSDAY
IN THE PROGRESSION SPEED AND SHAPE OF HOW THE TROUGH SWEEPS THROUGH.
THIS RELATES TO A COUPLE FACETS OF THE FORECAST:
1) THERE IS INCREASING CONFIDENCE THAT THE FIRST SURFACE LOW
DEVELOPING ON THE INITIAL TROUGH DIPPING SOUTH, REMAINS
PRIMARILY TO THE SOUTH OF THE FORECAST AREA. THROUGH 1AM
THURSDAY, THERE IS ONLY ROUGHLY A 15% CHANCE OF >1" IN
PITTSBURGH. THIS INCREASES TO THE SOUTH, UP TO A 30% TO 50%
CHANCE FOR EASTERN TUCKER COUNTY. THE MOST LIKELY TIMING OF THIS
SNOWFALL AT THIS POINT WOULD BE BETWEEN ROUGHLY 4AM AND 4PM
WEDNESDAY.
2) BECAUSE OF DIFFICULTY IN RESOLVING HOW THE TOUGH PIVOTS
THROUGH THERE ARE A COUPLE SCENARIOS. IN THE FIRST ONE, THE
UPPER LOW REJOINS THE FLOW AS A TROUGH, PROGRESSES THROUGH
RAPIDLY, AND CYCLOGENESIS REMAINS FAVORED IN THE MID-ATLANTIC,
SOUTH OF THE AREA. IN THE SECOND SCENARIO, THE LOW REMAINS OR
BECOMES CLOSED AND PROGRESSES A BIT SLOWER THURSDAY, ALLOWING A
BIT OF CONVERGENCE AHEAD OF IT, AND RESULTING IN HIGHER SNOW
CHANCES. JUST HOW HIGH? ROUGHLY A 30% (<5%) CHANCE OF >1" (>3")
IN PITTSBURGH. CHANCES INCREASE TO THE SOUTHEAST, UP TO A 50%
(10%) CHANCE OF >1" (>3") FOR THE HIGH TERRAIN OF WEST VIRGINIA.
IN EITHER SCENARIO, ALL PRECIPITATION WILL FALL AS SNOW.
THE MAIN IMPACTS THIS WEEK APPEAR TO LIKELY BE THE CONTINUED
COLD, WITH TEMPERATURES REMAINING IN THE BALLPARK OF 15F TO 20F
BELOW NORMAL FROM LATE MONDAY INTO EARLY THURSDAY. THE IS HIGH
CONFIDENCE IN RIDGING INTO THE WEEKEND, BUT THE MAIN
UNCERTAINTY IS HOW STRONG EMBEDDED TROUGHING MAY BE, WHICH WILL
CORRELATE TO JUST HOW "WARM" THINGS GET. WE DON'T HAVE A >50%
CHANCE OF BREAKING NORMAL UNTIL MONDAY.
AVIATION /09Z MONDAY THROUGH FRIDAY/
SNOW BANDS ARE EXPECTED TO CONTINUE INTO EARLY MONDAY MORNING.
WITHIN THESE BANDS YOU COULD OBS VISIBILITY AS LOW AS 1/2SM AND
LOW IFR TO POTENTIALLY LIFR CIGS FOR A BRIEF PERIOD OF TIME.
BAND INTENSITY IS EXPECTED TO WANE BETWEEN 10Z TO 13Z WITH
INCREASE SUBSIDENCE.
WINDS GUSTS ARE EXPECTED TO CONTINUE WITH A STRONG PRESSURE
GRADIENT, 25-35 KNOTS, BUT THEN TAPERING SOME MONDAY AFTERNOON.
DRY AIR WORKING INTO THE REGION MONDAY AFTERNOON IS EXPECTED TO
BEGIN TO ERODE CIGS BEGINNING IN OH AND MOVING EAST. MODEL SOUNDINGS
DISAGREE ON WHERE MOISTURE TRAPPED BENEATH THE SUBSIDENCE INVERSION
WILL CONTINUE MVFR CIGS. AT THIS TIME PROBABILITIES OF MVFR CIGS
DROP BELOW 50% FOR ZZV/BVI/PIT/AGC BY LATE MONDAY AFTERNOON, WITH
ZZV THE MOST LIKELY TO SEE THE RETURN OF VFR.
OUTLOOK...
LOW PROBABILITY FOR MVFR RESTRICTIONS EXPECTED AT ALL
OTHER TERMINALS THROUGH TUESDAY. BY WEDNESDAY, REGION WIDE
RESTRICTIONS EXPECTED TO RETURN AS ANOTHER STORM IMPACTS THE
REGION.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR PAZ009-
015-016-021-022-073-077-078.
COLD WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
TUESDAY FOR PAZ014>016-022-074-076>078.
BLIZZARD WARNING UNTIL 3 PM EST THIS AFTERNOON FOR PAZ074-076.
OH...NONE.
WV...COLD WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
TUESDAY FOR WVZ512-514.
BLIZZARD WARNING UNTIL 3 PM EST THIS AFTERNOON FOR WVZ512>514.
WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR
WVZ510-511.
SYNOPSIS...MILCAREK
NEAR TERM...MILCAREK
SHORT TERM...MILCAREK
LONG TERM...MILCAREK
AVIATION...HEFFERAN/AK
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