716
FXUS61 KPBZ 220658
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
158 AM EST MON DEC 22 2025
SYNOPSIS
A PERIOD OF SNOW OR WINTRY MIX MAY DEVELOP BY EARLY TUESDAY
MORNING FOR PORTIONS OF NORTHWEST PENNSYLVANIA AND ALONG THE
HIGHER TERRAIN AHEAD OF A LIFTING WARM FRONT. OTHERWISE, THE
REST OF THE REGION WILL SEE RAIN CHANCES INCREASE ALONG WITH
SLOWLY RISING TEMPERATURE. SEASONABLY WARM CONDITIONS AND
PERIODIC PRECIPITATION CHANCES CHARACTERIZE THE WEATHER EXPECTED
INTO NEXT WEEKEND.
NEAR TERM /THROUGH TODAY/
KEY MESSAGES:
- SEASONABLE TEMPERATURE AMID INCREASING CLOUD COVER
- LOW PROBABILITY FOR RAIN/SNOW DURING THE AFTERNOON
-----------------------------------------------------------
SURFACE HIGH PRESSURE CURRENTLY SITUATED OVER THE REGION SHIFTS
TOWARD THE ATLANTIC COAST TODAY IN RESPONSE TO WEAK LOW
DEVELOPMENT UNDERNEATH THE APEX OF THE CENTRAL CONUS UPPER
RIDGE. THOUGH A DEVELOPING UPPER SHORTWAVE WILL STREAM MID TO
HIGH LEVEL CLOUDS FROM THE NORTHWEST, WEAK SURFACE WARM
ADVECTION IS LIKELY TO OFFSET CLOUD COOLING TO PUSH AREA
TEMPERATURE BACK TOWARD THE DAILY AVERAGE. THOUGH THE SURFACE
HIGH AND DRY SUB-CLOUD LAYER FAVORS THE REGION STAYING DRY,
THERE MAY BE ENOUGH LIFT AMID WARM/MOIST MID-LEVEL ADVECTION FOR
A NARROW BAND OF RAIN TO SNOW MIX WITH THE DEGREE OF WET-BULBING
DICTATING COVERAGE OF SNOW OCCURRENCE.
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
KEY MESSAGES:
- WIDESPREAD RAIN PLUS A NORTHWEST PA WINTRY MIX EXPECTED BY
EARLY TUESDAY MORNING
- WARM ADVECTION LENDS TO NEAR OR ABOVE NORMAL TEMPERATURE
DESPITE PRECIP
----------------------------------------------------------------
THERE IS LIKELY TO BE A BRIEF LULL BETWEEN THE PREVIOUSLY
MENTIONED NARROW BAND OF RAIN/SNOW MIX CROSSING WEST-TO-EAST
MONDAY AFTER BEFORE MORE WIDESPREAD PRECIPITATION DEVELOPS OVER
THE REGION BY EARLY TUESDAY MORNING. THE COMBINATION OF WEAK JET
ASCENT WITH A LIFTING WARM FRONTAL BOUNDARY WILL DRIVE
PRECIPITATION GENERATION WITH 850MB/SFC WARM ADVECTION RESULTING
IN PREDOMINANTLY RAIN FOR MOST OF THE REGION. THERE REMAINS
SIGNAL FOR MORE OF A WINTRY MIX NEAR THE I-80 CORRIDOR AND ALONG
THE HIGHER ELEVATIONS EAST/SOUTHEAST OF PITTSBURGH DUE TO WET-
BULBING AND WEAKER/SLOWER ARRIVAL OF THE SURFACE WARM ADVECTION.
LEANING ON HI-RES MODELING FOR BETTER TERRAIN RESOLUTION, THE
LIKELY PROGRESSION OF P-TYPES IN THIS REGION WILL BE A FEW HOURS
OF SNOW BEFORE TRANSITIONING TO RAIN. HOWEVER, THERE REMAINS
30-40% PROBABILITIES OF A FREEZING RAIN PERIOD NEAR THE MORNING
COMMUTE IN BETWEEN THAT POSES THE GREATEST IMPACT RISK, AS THAT
MAY LEAD TO A GLAZE OF ICE ACCUMULATION (50-70% PROBABILITY OF A
GLAZE OR MORE OF ICE ACCUMULATION IF THIS P-TYPE OCCURS). DUE
TO THE LOWER CONFIDENCE OF P-TYPE OCCURRENCE (OR ITS POTENTIAL
TOO SHORT OF DURATION), WILL FORGO HEADLINES AT THIS TIME BUT
MAINTAIN MESSAGING VIA HWO AND OTHER AVENUES.
THE REST OF TUESDAY FAVORS LIGHT RAIN AND PERIODS OF DRIZZLE
WHILE WARM ADVECTION PUSHES TEMPERATURE 5-10 DEGREES ABOVE THE
DAILY AVERAGE. SHORTWAVE/SURFACE LOW EXIT TUESDAY EVENING SHOULD
DIMINISH AREAL COVERAGE OF RAIN BUT THE LACK OF STRONG DRY
ADVECTION PLUS POTENTIAL FOR SLOW SE MOVEMENT OF THE NOMINAL
SURFACE COLD FRONT MEANS DRIZZLE COULD PERSIST INTO WEDNESDAY
MORNING (ESPECIALLY SE OF PITTSBURGH). LOW TEMPERATURE MAY ALSO
REMAIN ABOVE NORMAL WITH STAUNCH CLOUD COVER.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGES:
- LAKE ERIE HIGH PRESSURE PROMOTES DRY WEATHER CHRISTMAS EVE.
- SHOWERS AND LOW PROBABILITY THUNDERSTORMS FAVORED CHRISTMAS
DAY.
- PATTERN UNCERTAINTY REMAINS HIGH HEADING INTO THE POST-HOLIDAY
WEEKEND.
-------------------------------------------------------------------
ENSEMBLE MODELS ARE COALESCING AROUND SURFACE HIGH PRESSURE
CROSSING LAKE ERIE WEDNESDAY THAT SQUELCHES ANY LINGERING LIGHT
RAIN/DRIZZLE AND PROMOTES DRY WEATHER FOR THE REST OF CHRISTMAS
EVE. COOLER AIR WORKING AROUND THE HIGH PLUS JET-INDUCED
MID/HIGH LEVEL CLOUD LAYERS KEEP TEMPERATURE CLOSER TO
SEASONABLE AVERAGES; THE EXCEPTION MAY BE SOUTH OF I-70 WHERE
ENOUGH INSOLATION AND SOUTHERLY RETURN FLOW COULD RAISE
TEMPERATURE ABOVE THE DAILY AVERAGE.
THEREAFTER, EMBEDDED SHORTWAVE MOVEMENT WITHIN NW FLOW CROSSES
DURING THE EARLY MORNING TO AFTERNOON HOURS OF
CHRISTMAS/THURSDAY AND GENERATES SHOWERS THAT HAVE 15%
PROBABILITIES OF DEVELOPING LIGHTNING AMID ELEVATED INSTABILITY.
THERE ARE SOME VARIANCES AMONGST MODELS ON THE TIMING OF THIS
WAVE AND ITS WARM FRONT POSITIONING BUT CURRENT TRENDS FAVOR THE
CENTER OF THIS RAIN TO CROSS NEAR TO SW OF PITTSBURGH. THE
VARIANCES RELATED TO THE WARM FRONT ARE BEST SEEN IN THE RANGE
OF POTENTIAL HIGH TEMPERATURE AS LOCATIONS ALONG/NORTH OF I-70
EXHIBIT 7-10 DEGREE SPREADS BETWEEN THE 25TH-75TH PERCENTILES.
MORE SIMPLY, HIGH TEMPERATURE CHRISTMAS DAY ARE HIGHLY
PREDICATED ON THE NORTH-SOUTH POSITIONING OF THE WARM FRONT WITH
THE CURRENT FORECAST SETTLING ON IT BEING LOCATION NE OF
PITTSBURGH (COLDER NORTH OF IT/WARMER SOUTH).
ENSEMBLE MODELS GENERALLY FAVOR THE DEVELOPMENT OF ANOTHER LOW
PRESSURE SYSTEM FRIDAY THAT WOULD QUICKLY TRAVEL THROUGH THE
GREAT LAKES; HOWEVER, THERE IS NOTABLE SPREAD IN THE LARGER
SYNOPTIC PATTERN THAT MAY CHANGE TIMING/AMOUNTS/FAVORED AREAS
AMONGST OTHER DETAILS. THEY ALL DO AGREE ON WARM FRONTAL
POSITIONING TO BE NORTH OF THE AREA UNDERNEATH ELEVATED 500MB
HEIGHTS SUCH THAT AREA TEMPERATURE CONFIDENTLY WILL BE 15 TO 25
DEGREES ABOVE THE DAILY AVERAGE. THAT CONFIDENCE ENDS BY
SATURDAY AS THOSE SYNOPTIC PATTERN DIFFERENCES WIDEN TO WHERE
ALL THAT CAN BE SAID IS PERIODIC PRECIPITATION CHANCES ARE
LIKELY WITH TEMPERATURE BEING NEAR TO ABOVE NORMAL.
AVIATION /06Z MONDAY THROUGH FRIDAY/
KEY MESSAGES:
- VFR CONDITIONS AND LIGHT WINDS TONIGHT THROUGH 00Z TUESDAY
- RESTRICTIONS RETURN AFTER 063Z TUESDAY WITH PASSING LOW
PRESSURE; WINTRY MIX (ALONG/NORTH OF I-80) AND RAIN EXPECTED
------------------------------------------------------------
THERE WILL BE HIGH CONFIDENCE THAT VFR CONDITIONS WILL BE IN
PLACE THROUGH MUCH OF THE TAF PERIOD WITH LIGHT AND VARIABLE
WINDS. HIGH PRESSURE WILL KEEP MAINLY CLEAR SKIES AND DRY
CONDITIONS AT LEAST THROUGH 00Z TUESDAY. AN APPROACHING WARM
FRONT WILL BRING SOME LIGHT RAIN INTO THE AREA BY THE 00Z TO 06Z
TIMEFRAME TO THE TAF SITES. SOME MVFR CIGS WILL LIKELY SET IN
DURING THIS TIME. HAVE USED PROB30S TO COVER THIS APPROACH OF
MOISTURE GIVEN THE DRY SURFACE LAYER AND TIME FOR THE COLUMN OF
AIR TO SATURATE. A WINTRY MIX IS ALSO POSSIBLE DURING THIS TIME
AT THE FKL AND DUJ SITES.
OUTLOOK...
VFR MAY RETURN BRIEFLY DURING THE DAY WEDNESDAY
BEFORE ANOTHER SYSTEM BRINGS PRECIPITATION AND RESTRICTION
CHANCES BACK TO THE REGION WEDNESDAY NIGHT INTO THURSDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...FRAZIER
NEAR TERM...FRAZIER
SHORT TERM...FRAZIER
LONG TERM...FRAZIER
AVIATION...CERMAK/SHALLENBERGER
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