974
FXUS61 KPBZ 211225
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
725 AM EST SUN DEC 21 2025
SYNOPSIS
DRY, QUIET, AND BREEZY CONDITIONS TODAY. RAIN CHANCES, MIXED
WITH A WINTRY MIX, ARE EXPECTED LATE MONDAY INTO EARLY TUESDAY.
WARM PATTERN EXPECTED LATE THIS WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- PASSING COLD FRONT OFFERS LITTLE PRECIPITATION BUT BREEZY
CONDITIONS TODAY
- SEASONABLY OVERNIGHT LOWS
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TEMPERATURES ARE EXPECTED TO FALL THROUGHOUT THE DAY, DESPITE
THE SUNSHINE, DUE TO A COLD FRONT PASSING OVER THE GREAT LAKES.
SNOW IS UNLIKELY, GIVEN THE WEAK MOISTURE PROFILE ALOFT, ONLY
SOME LOW-LEVEL CLOUDS ARE ANTICIPATED NORTH OF PITTSBURGH.
SURFACE HIGH PRESSURE WILL CENTER OVER THE UPPER
OHIO RIVER VALLEY OVERNIGHT AS NORTHWEST FLOW ALOFT WANES
SLIGHTLY. THE RESULTANT CLEAR AND CALM CONDITIONS FAVOR STRONG
RADIATIONAL COOLING THAT DROPS AREA TEMPERATURE BELOW SEASONAL
AVERAGES (AND COULD END UP A FEW DEGREES LOWER THAN FORECASTED).
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
KEY MESSAGES:
- TEMPERATURE MODERATION MONDAY WITH INCREASING CLOUDS
- MONITORING FREEZING RAIN POTENTIAL NE OF PITTSBURGH EARLY
TUESDAY MORNING
- RAIN AREAWIDE THROUGH THE DAY TUESDAY BEFORE TAPERING OFF AT
NIGHT
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A DEVELOPING UPPER LEVEL SHORTWAVE WITHIN NORTHWEST FLOW WILL
ENCROACH THE AREA THROUGH THE DAY MONDAY, FOSTERING WARM
ADVECTION ALOFT THAT HELPS INCREASE MID TO HIGH LEVEL CLOUDS. A
COOL START TO THE DAY IS EXPECTED TO WARM AS ENOUGH SOUTHERLY
SURFACE FLOW DEVELOPS WITH HIGH PRESSURE SLIDING EAST; THAT
SAID, EXCESSIVE CLOUD COVER COULD STUNT SOME OF THIS WARMING
(NOTABLY ACROSS WEST CENTRAL TO NORTHWEST PA) UNTIL LATE IN THE
EVENING WHEN SW FLOW BETTER DEVELOPS. THE REGION IS LIKELY TO
REMAIN DRY WITH HIGH PRESSURE INFLUENCE BUT A WARM-NOSE ALOFT
WITH ENOUGH JET LIFT COULD SQUEEZE SOME LIGHT RAIN OR SNOW
(DEPENDING LOCATIONS THERMAL PROFILES) DURING THE LATE AFTERNOON
AND EVENING HOURS.
THE FOCUS WILL BE A MORE NOTABLE PUSH OF THE SHORTWAVE AND LOW
MOVEMENT OVERNIGHT MONDAY INTO TUESDAY MORNING, WHICH WILL
FEATURE A LIFTING SURFACE WARM FRONT AIDING IN PRECIPITATION
PRODUCTION. MODEL MEAN 850MB TEMPERATURES WILL RISE TOWARD 2 TO
5 DEGREES CELSIUS WHILE SURFACE TEMPERATURE STARTS TO RISE AS
WELL AND CAUSE FALLING PRECIPITATION TO BE RAIN FOR A VAST
MAJORITY OF THE REGION. THE LATER ARRIVAL OF THIS WARM NOSE, AN
INITIAL DRIER LOWER PROFILE RIPE FOR WET-BULBING, AND SOME
VARIANCES IN LOW POSITIONING THAT COULD ALLOW FOR E TO SE FLOW
TO REINFORCE SUB-FREEZING SURFACE AIR ALL PAINT A PICTURE FOR
MORE OF A WINTRY MIX FOR PORTIONS OF NORTHWEST PA. CURRENT
ENSEMBLE MODEL MEANS AN INITIAL PERIOD OF SNOW THAT TRANSITIONS
TO RAIN, WITH SNOW ACCUMULATIONS LIKELY TO BE LESS THAN 1"
(85-95% PROBABILITY). HOWEVER, THERE ARE SOME LOW PROBABILITIES
(10-20%) SUGGESTING A PERIOD OF FREEZING RAIN PRIOR TO THAN RAIN
TRANSITION THAT COULD LEND TO A GLAZE OF ICE ACCUMULATION. WILL
ADD A MENTION FOR THESE ZONES AS WELL AS EASTERN TUCKER THAT
CAN BE MORE PRONE/STUBBORN IN HOLDING SUB-FREEZING TEMPERATURE
IN THESE REGIMES AS IT BEARS MONITORING MOVING FORWARD.
THE GENERALLY LIGHT RAIN AREAWIDE BY THE AFTERNOON WILL TAPER
OFF SLOWLY THROUGH TUESDAY EVENING AS THE SYSTEM DIVES TOWARD
NEW ENGLAND AND THE SURFACE COLD FRONT PUSHES THROUGH. ENSEMBLE
MEANS FAVOR DRY CONDITIONS OVERNIGHT BUT EVEN THERE, LINGERING
MOISTURE WITH UPSLOPE FLOW COULD CREATE AREAS OF LIGHT RAIN,
DRIZZLE, AND EVEN FREEZING DRIZZLE IN PLAY FOR THE HIGHER
ELEVATIONS.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
KEY MESSAGES:
- SEASONABLY WARM PATTERN FAVORED THROUGH FRIDAY BUT REMAINS
HIGHLY VARIABLE ON DEGREE OF WARMING
- PERIODIC PRECIPITATION CHANCES DRIVEN BY SUBTLE SHORTWAVE
MOVEMENT
- NON-ZERO LIGHTNING PROBABILITY OVERNIGHT WEDNESDAY
INTO CHRISTMAS MORNING SOUTHWEST OF PITTSBURGH
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THERE IS HIGH CONFIDENCE IN THE DEVELOPMENT OF RIDGING OVER THE
CENTRAL CONUS WEDNESDAY THROUGH FRIDAY WITH THE UPPER OHIO RIVER
VALLEY SITTING ON ITS NE PERIPHERY UNDERNEATH NORTHWEST FLOW. IF
THE CALENDAR DIDN'T SAY 'DECEMBER', YOU'D ALMOST THINK THIS WAS
A SUMMER-ESQUE PATTERN WHERE SUBTLE SHORTWAVES ROUNDING THE
RIDGE AXIS COULD POSE VARIOUS THUNDERSTORM OR SEVERE WEATHER
RISKS FOR THE FORECAST AREA. WELL, IT WILL BE TRUE BUT WILL NOT
FEATURE 'SEVERE WEATHER' CONCERNS; IT WILL FEATURE TEMPERATURE
BECOME ABOVE TO WELL ABOVE NORMAL WHILE EMBEDDED SHORTWAVES
(THE FIRST OF WHICH ARRIVES LATER ON CHRISTMAS EVE INTO
CHRISTMAS DAY) GENERATES PRECIPITATION (VERY LIKELY RAIN) AND A
NON-ZERO LIGHTNING THREAT. IT IS ALSO A PATTERN THAT CAN BE
HIGHLY VARIABLE AS SUBTLE CHANGES COULD DRASTICALLY ALTER THE
DEGREE OF WARMING, THE FAVORED AREAS FOR PRECIPITATION, AND THE
PATH OF SUBSEQUENT SHORTWAVES.
MONITORING THE PROGRESSION OF TUESDAY'S SHORTWAVE TROUGH AND
HOW DEEP IT BECOMES JUST OFF THE ATLANTIC COAST IS KEY FOR
IRONING SOME OF THE VARIANCES. IN GENERAL, A DEEPER TROUGH WILL
STUNT THE INFLUENCE OF THE EASTWARD-MOVING RIDGE AND DELAY THE
MEAN TEMPERATURE RISE WEDNESDAY/THURSDAY WHILE PUSHING THE
FAVORED PRECIPITATION AREA MORE SOUTHWEST OF THE CURRENT POP
PEAKS. A SHALLOWER, MORE PROGRESSIVE TROUGH WOULD ALLOW THAT
EASTWARD RIDGE MOVEMENT AND PUSH TEMPERATURE NEAR/ABOVE CURRENT
FORECASTED VALUES WEDNESDAY/THURSDAY WHILE CENTERING
PRECIPITATION OVER THE AREA. THIS IS BEST EXEMPLIFIED IN LOOKING
AT ENSEMBLE MODEL MAXT SPREADS WEDNESDAY/THURSDAY THAT SHOW
LARGE RANGE OFF OUTCOMES WITHIN A ZONE THAT IS APPROXIMATELY
ALONG/NORTH OF I-70 AND MEANS FLUCTUATION IN FORECASTED VALUES
IS LIKELY TO OCCUR FOR THIS PERIOD AS IT APPROACHES UNTIL THESE
DETAILS BETTER COALESCE.
VARIABILITY IN THE SYNOPTIC PATTERN ONLY GROWS FRIDAY INTO
SATURDAY IN PART DUE TO HOW WEDNESDAY/THURSDAY'S SYSTEM PLAYS
OUT, BUT THE CURRENT CONSENSUS MAINTAINS THE ABOVE NORMAL
TEMPERATURE WITH PERIODIC PRECIPITATION CHANCES.
AVIATION /12Z SUNDAY THROUGH THURSDAY/
KEY MESSAGES:
- VFR CONDITIONS
- RESTRICTIONS LIKELY AT BVI, DUJ, AND FKL SUNDAY.
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CONDITIONS ACROSS THE AREA FAVOR A VFR FORECAST THROUGH MUCH OF
THE PERIOD. A PASSING COLD FRONT WILL PROVIDE SOME LOW-LEVEL
CLOUDS NORTH OF PIT. AS WELL, WITH A MID LEVEL JET CROSSING THE
FORECAST AREA, THERE MAY BE A PERIOD OR TWO OF SOME LOW LEVEL
WIND SHEAR. HOWEVER, THERE HAVE BEEN SOME INSTANCES OF GUSTS AT
THE SURFACE THROUGH 06Z SO WILL HOLD OFF ON THE LLWS THREAT FOR
NOW.
SFC GUSTS WILL DECREASE LATE THIS EVENING/OVERNIGHT AND
TURN VARIABLE. EXPECT WINDS TO GUST UP TO 25 KNOTS FROM THE
NORTHWEST BEFORE DECOUPLING TONIGHT.
OUTLOOK...
VFR RETURNS AREAWIDE SUNDAY NIGHT INTO MONDAY. WIDESPREAD
RESTRICTIONS RETURN OVERNIGHT MONDAY INTO TUESDAY WITH CHANCES
OF RAIN AND A WINTRY MIX (MAINLY NORTHEAST OF PIT).
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...HEFFERAN
NEAR TERM...HEFFERAN/FRAZIER
SHORT TERM...FRAZIER
LONG TERM...FRAZIER
AVIATION...SHALLENBERGER/HEFFERAN
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