636
FXUS61 KPBZ 201644
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1144 AM EST SAT DEC 20 2025
SYNOPSIS
A "MOSTLY DRY" COLD FRONT PASSES OVERNIGHT, WITH DRIZZLE
CHANCES IN THE HIGH TERRAIN. COOL AND DRY SUNDAY WITH THE NEXT
DISTURBANCE FORECAST MONDAY NIGHT INTO TUESDAY, ACCOMPANIED BY
A WARMUP. ODDS OF A "WHITE CHRISTMAS" ARE NULL THIS YEAR WITH
ABOVE AVERAGE TEMPERATURES.
NEAR TERM /THROUGH SUNDAY/
KEY MESSAGES:
- WARM/DRY TODAY, DRIZZLE POSSIBLE OVERNIGHT IN THE RIDGES.
-----------------------------------------------------------
TEMPERATURES WILL CONTINUE TO CLIMB ABOVE AVERAGE FOR HIGHS
TODAY IN SOUTHERLY FLOW BEHIND A EASTWARD MOVING SURFACE HIGH
PRESSURE. HIGH CLOUDS WILL CONTINUE TO INCREASE THROUGHOUT THE
DAY AND OVERNIGHT, GIVING WAY TO A "MOSTLY DRY" SURFACE COLD
FRONT PASSAGE OVERNIGHT.
AT THIS TIME, FORCING APPEARS TO WEAK AND THE LOW LEVELS TO DRY TO
SUPPORT ANY PRECIPITATION ALONG IT, UNTIL IT REACHES THE RIDGES
WHICH AID IN OROGRAPHIC LIFT. SOUNDINGS HAVE HIGH CONFIDENCE IN
SATURATION LESS THAN -10C AT ONSET, DEDICATING DRIZZLE MAY BE
THE PRIMARY PRECIPITATION TYPE IN THE RIDGES. THE ONLY QUESTION
BETWEEN DRIZZLE AND FREEZING DRIZZLE IS WHETHER THE RIDGES WILL
BE BELOW FREEZING BY THEN (FORECAST TO DROP BY 06Z TO 08Z).
NONETHELESS, EVEN THE WARM SURFACE FROM TODAY, IMPACTS TO
SIDEWALKS OR ROADWAYS SEEM MINIMAL, EVEN SHOULD IT OCCUR.
AT THIS TIME, THERE APPEARS TO BE A SECONDARY AND "MOSTLY DRY" COLD
FRONT PASSAGE SUNDAY WHICH WILL INCREASE LOW CLOUDS FROM THE NORTH.
THERE MAY BE SHALLOW ENOUGH SATURATION TO SUPPORT SOME FLURRIES
NORTH OF I-80, BUT NO IMPACTS EXPECTED. BECAUSE OF THE SHORT BOUT OF
SURFACE TROUGHING, TEMPERATURES ARE EXPECTED TO REMAIN A FEW
DEGREES BELOW NORMAL.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/
KEY MESSAGES:
- COOL MONDAY MORNING; CLOUDS AND WARMING TREND AFTERWARD.
- LOW CHANCE OF FREEZING RAIN NORTH OF PITTSBURGH MONDAY NIGHT.
----------------------------------------------------------------
BEHIND THE SHORTWAVE TROUGH PASSAGE WILL ENSUE SHORTWAVE RIDGING
AND A BRIEF BOUT OF SURFACE HIGH PRESSURE SUNDAY NIGHT INTO
EARLY MONDAY. THIS WILL ACT TO CLEAR THE SKIES AND LEND TO AN
EFFICIENT RADIATIVE COOLING NIGHT, BRINGING LOWS AROUND 10
DEGREES BELOW NORMAL, THROUGH LIGHT TO CALM WINDS SHOULD KEEP
WIND CHILLS AT BAY. WARMING TEMPERATURES AND INCREASING CLOUDS
ARE EXPECTED FOR THE DAY MONDAY AS THE NEXT DISTURBANCE
APPROACHES FROM THE WEST. HIGHS ARE EXPECTED TO BE NEAR NORMAL.
MONDAY NIGHT, A SYSTEM IS EXPECTED TO SWEEP THROUGH THE AREA AS
A WARM FRONT BRINGS PRECIPITATION. THIS IS >90% LIKELY TO FALL
AS ALL RAIN OUTSIDE OF THE I-80 CORRIDOR. IN VENANGO, FOREST,
CLARION, JEFFERSON, AND INDIANA COUNTIES, THERE IS SOME
UNCERTAINTY IN PRECIPITATION TYPE. WHILE MOST ENSEMBLES FAVOR
RAIN, MODELS TEND TO PREFORM POORLY WITH EVACUATING EXISTING
COLD AIR.
IN THE WARM SCENARIO WHERE THE WARM FRONT ARRIVES AFTER
DAYBREAK TUESDAY, THE AFOREMENTIONED COUNTIES MAY REMAIN ALL
RAIN AND HAVE NO IMPACTS. IN THE COOLEST SCENARIO, WHERE THE
WARM FRONT ARRIVES EARLY OVERNIGHT, COUNTIES COULD SEE T-1" OF
SNOW, WHICH TRANSITIONS TO A LIGHT COATING OF FREEZING RAIN. IN
THE CURRENT FORECAST, WE MAINTAIN MORE OF A MEDIAN SOLUTION OF A
LIGHT COATING OF FREEZING RAIN RAPIDLY OVERRODE BY RAIN.
LONG TERM /TUESDAY THROUGH FRIDAY/
KEY MESSAGES:
- RAIN CHANCES TUESDAY AFTERNOON
- ABOVE-NORMAL TEMPERATURES OVER CHRISTMAS
-------------------------------------------------------------------
LONG-RANGE GUIDANCE STRONGLY FAVORS A WARM PATTERN FROM TUESDAY
AFTERNOON INTO FRIDAY, SUPPORTED BY A PRONOUNCED RIDGE OVER THE
GREAT PLAINS. DURING THIS PERIOD, ANY DISTURBANCE THAT ADVANCES
THROUGH THE REGION WILL MAINLY FALL AS RAIN, WITH PERHAPS A
BRIEF RAIN/SNOW MIX NORTH OF PITTSBURGH WITH NO IMPACTS. SOME
MODEL SOUNDINGS EVEN SUGGEST THE POTENTIAL OF THUNDERSTORMS
EARLY CHRISTMAS MORNING ALONG A WARM FRONT, DRIVEN BY ELEVATED
INSTABILITY. AS THE EVENT APPROACHES, CONFIDENCE WILL INCREASE
IN ASSESSING ANY THREATS BEYOND THE POTENTIAL FOR LIGHTNING.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
KEY MESSAGES:
- VFR WITH LLWS OVERNIGHT.
- RESTRICTIONS LIKELY AT BVI, DUJ, AND FKL SUNDAY.
------------------------------------------------------------
THERE IS HIGH CONFIDENCE IN VFR THROUGHOUT THE DAY. THIS WILL
BE ACCOMPANIED BY A LIGHT SOUTHERLY WIND, THAT WILL GRADUALLY
VEER SOUT-SOUTHWEST THROUGHOUT THE DAY.
OVERNIGHT, DECOUPLING IS EXPECTED ALONG WITH AN ENHANCED
PRESSURE GRADIENT AS HIGH PRESSURE MOVES TO THE EAST. FURTHER,
LOW-LEVEL WIND SHEAR WAS NOTED FOR NOW WITH DECOUPLING FAVORED
OVER GUSTS.
A DRY COLD FRONT IS EXPECTED TO PASS, RE-COUPLING SOME PORTS
(ACCOMPANIED BY GUSTS) FROM 06Z TO 12Z WITH ENCROACHING LOWER
DECKS. THERE CURRENTLY A 80% CHANCE OF MVFR OR LOWER AND A 30%
CHANCE OF IFR AT DUJ/FKL. ELSEWHERE, CHANCES OF MVFR ARE LESS
THAN 50% (SAVE BVI).
OUTLOOK...
WIDESPREAD RESTRICTIONS RETURN OVERNIGHT MONDAY INTO TUESDAY
WITH CHANCES OF RAIN (AND -FZRA AT DUJ).
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...MILCAREK
NEAR TERM...MILCAREK
SHORT TERM...MILCAREK
LONG TERM...HEFFERAN
AVIATION...MILCAREK
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page