753
FXUS61 KPBZ 230520
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1220 AM EST THU JAN 23 2025
SYNOPSIS
WIND CHILLS ON EITHER SIDE OF ZERO CONTINUE TONIGHT BUT ARE
EXPECTED TO REMAIN ABOVE HEADLINE CRITERIA OUTSIDE OF EASTERN
TUCKER COUNTY. DRY WEATHER OTHERWISE TODAY WITH LIGHT SNOW
RETURNING THURSDAY NIGHT AND SOME MODIFICATION TO TEMPERATURES
FOR THE WEEKEND AHEAD.
NEAR TERM /UNTIL 6 AM THIS MORNING/
KEY MESSAGES:
- DRY WITH INCREASING MID/UPPER CLOUD COVERAGE.
- COLD OVERNIGHT LOWS, BUT NOT AS COLD AS RECENT NIGHTS.
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ONLY MINOR CHANGES TO THE OVERNIGHT PERIOD...CLOUD COVER WAS
ADJUSTED FOR A LITTLE MORE OF AN INCREASE THIS EVENING WITH AN
AREA OF MID CLOUDS PASSING THROUGH WITH THE WARM AIR ADVECTION.
THIS AREA SHOULD SHIFT NORTHWARD LATER TONIGHT ALLOWING SKIES TO
CLEAR BEFORE SUNRISE. OVERNIGHT LOWS WERE UPDATED WITH THE
LATEST BLENDED GUIDANCE.
PREVIOUS DISCUSSION...
HEADED INTO TONIGHT, LOW TEMPERATURES WILL BE SOME 15-20 DEGREES
WARMER THAN WEDNESDAY NIGHT THANKS TO MODEST WARM ADVECTION AND
INCREASED CLOUD COVER, THOUGH THAT STILL ONLY PUTS THE AREA
INTO THE LOW TO MID SINGLE DIGITS WITH A <20% CHANCE OF
REMAINING ABOVE 10 DEGREES. LIGHT SOUTHERLY WIND WILL DROP
APPARENT TEMPERATURES INTO THE NEGATIVE SINGLE DIGITS AND ARE
LIKELY TO REMAIN ABOVE HEADLINE CRITERIA, BUT IT WILL STILL BE
QUITE COLD. THE EXCEPTION WILL BE EASTERN TUCKER COUNTY WHERE
COLDER OVERNIGHT LOWS, MORE ELEVATED WIND, AND THE POTENTIAL FOR
SOME PERIODS OF BREAKS IN THE CLOUDS WILL RESULT IN WIND CHILLS
DIPPING BELOW -10F. THE BEST CHANCE FOR THIS WILL BE THE
HIGHEST ELEVATIONS, AND FOR THAT REASON, HAVE ISSUED A NEW COLD
WEATHER ADVISORY COVERING 7PM TONIGHT - 10AM THURSDAY.
SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/
KEY MESSAGES:
- TEMPERATURES WILL BEGIN TO MODERATE THURSDAY.
- LIGHT SNOW RETURNS THURSDAY EVENING WITH MINIMAL ACCUMULATION.
- MOSTLY DRY FRIDAY WITH TEMPERATURES SLIGHTLY COLDER.
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THE AFOREMENTIONED SHORTWAVE WILL STRUGGLE TO BRING MUCH SNOW TO THE
GROUND EARLY IN THE MORNING THURSDAY WITH DRY AIR TO OVERCOME.
ENSEMBLE SOUNDINGS SHOW SOME MID-LEVEL MOISTURE ADVECTION, BUT STILL
DRY LOW LEVELS FROM ~800 MB DOWN. FOR MOST, THE DAY WILL BE DRY AS
ESTABLISHING SOUTHERLY FLOW MODIFIES THE AIRMASS WITH A 60+% CHANCE
OF >25F FOR HIGHS EXTENDING UP TO PITTSBURGH. THE BEST CHANCE
FOR SOME SNOW SHOWERS WILL COME LATER THURSDAY INTO THE
OVERNIGHT HOURS WHEN BETTER MOISTURE WORKS IN AND A DECAYING
BOUNDARY PASSES THROUGH. DISPLACEMENT OF UPPER SUPPORT MOVING
THROUGH JUST AHEAD OF THE BOUNDARY WON'T HELP OUR SNOW CHANCES.
THE NAM IS A BIT MORE AGGRESSIVE WITH SATURATION OCCURRING
QUICKER AND SUGGESTS A COUPLE TENTHS OF AN INCH POSSIBLE, THOUGH
THIS IS LIKELY MORE REPRESENTATIVE OF THE WORST CASE SCENARIO.
AS A WHOLE, HREF PROBABILITY FOR A HALF AN INCH OF SNOW THROUGH
THURSDAY NIGHT IS UP TO ~40% IN THE RIDGES WHERE OROGRAPHIC
ASCENT MAY AID IN ENHANCED FORCING, THOUGH THE MOISTURE ISSUE
STILL REMAINS. ELSEWHERE, CHANCES ARE LOW AND THE NATURE LIKELY
REMAINS LIGHT AND SCATTERED.
SNOW CHANCES TAPER OFF ON FRIDAY AS SURFACE RIDGING RE-
ESTABLISHES FROM THE SOUTHWEST AND WE'RE SANDWICHED BETWEEN TWO
MID-LEVEL WAVES. HIGHS WILL TAKE A HIT BACK DOWN A FEW DEGREES
AS SOME COLDER AIR WORKS IN IN WEST-NORTHWEST FLOW. A SHALLOW,
NEAR DRY-ADIABATIC LAYER WITH COLD ADVECTION AT THE 850 MB LEVEL
WILL STEEPEN LAPSE RATES AND TAP INTO ELEVATED FLOW ALOFT.
MOMENTUM TRANSFER ISN'T ALL THAT IMPRESSIVE WITH ONLY 15-20 KNOT
FLOW, SO WIND MAY TAKE ON MORE OF A 5-10 MPH SUSTAINED NATURE
WITH SPORADIC GUSTS.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
KEY MESSAGES:
- BELOW AVERAGE TEMPS ARE EXPECTED TO LINGER THROUGH EARLY NEXT
WEEK.
- ROUNDS OF WEAK DISTURBANCES WILL PRODUCE SCATTERED SNOW
CHANCES.
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A LEAD SHORTWAVE WILL SLIDE THROUGH ZONAL FLOW LOCALLY ON SATURDAY
WITH RELATIVELY GOOD AGREEMENT AMONG THE ENSEMBLES. SURFACE HIGH
PRESSURE PROGGED ACROSS THE CAROLINAS IS FAVORED TO KEEP US DRY,
THOUGH CAN'T ENTIRELY RULE OUT VERY LOW-END SNOW SHOWER CHANCES
CONFINED NORTH OF I-80 IN THE EVENING AS A WARM FRONT LIFTS THROUGH.
THE BETTER CHANCE, ALBEIT WITH LOW ACCUMULATION POTENTIAL, WILL COME
ON SUNDAY. ENSEMBLES BRING A SECOND WAVE WITH MINOR DISAGREEMENT ON
ITS DEPTH, AS SURFACE LOW PRESSURE DRAGS A COLD FRONT THROUGH. ONE
ENSEMBLE CLUSTER WITH A DEEPER SHORTWAVE SUGGESTS SLIGHTLY HIGHER
PROBABILITY OF >0.5" EXTENDING DOWN OFF OF THE LAKE, BUT EVEN IN
THIS SCENARIO, THE CHANCE OF REACHING 1" IS LESS THAN 20%. THE
PRIMARY ISSUE LOOKS TO BE AVAILABLE MOISTURE AS THE LACK OF
AMPLIFICATION WITH WESTERLY MID-LEVEL FLOW ISN'T PULLING FROM A
GREAT MOISTURE SOURCE REGION.
WEEKEND TEMPERATURES WILL MODERATE IN COMPARISON TO THE PAST
WEEK, BUT CONTINUE TO REMAIN BELOW AVERAGE WITH AFTERNOON HIGHS
IN THE UPPER 20S/LOW 30S AND OVERNIGHT LOWS IN THE LOW 20S
THROUGH SUNDAY. PROBABILITIES TO ECLIPSE THE FREEZING MARK FOR
HIGHS ARE BETTER ON SUNDAY EXTENDING A 50-70% CHANCE AS FAR
NORTH AS PITTSBURGH.
ENSEMBLES EJECT YET ANOTHER SHORTWAVE ON MONDAY THROUGH THE STILL
ESTABLISHED WESTERLY ZONAL FLOW. NOTED DISAGREEMENT COMES INTO PLAY
AT THIS POINT WITH THE PROGRESSION OF THE UPPER LEVELS AS SOME
CLUSTERS EXHIBIT A POTENTIALLY PHASED SOLUTION WITH A SOUTHERN
STREAM AND NORTHERN STREAM SHORTWAVE. OTHERS KEEP THEM UNPHASED AND
WEAKER WITH QUICK PROGRESSION THROUGH THE AREA. MOST OF THE GUIDANCE
IS NOT BULLISH ON MUCH WITH THIS DISTURBANCE EITHER AS WE AGAIN LACK
SUFFICIENT DEEP LAYER MOISTURE. THE MEAN QPF FROM 3/4 CLUSTERS
THROUGH MONDAY NIGHT IS GENERALLY <0.10" AREAWIDE, WITH THE 90TH
PERCENTILE AS HIGH AS 0.15", WHICH WOULD SUGGEST LOW-END SNOW
ACCUMULATION POTENTIAL. THE OUTLIER AT THIS POINT IS ONE CLUSTER
THAT SUGGESTS A MUCH DEEPER, PHASED, AND SLOWER TROUGH. THIS
SOLUTION POINTS TOWARD MORE QPF AND MORE REPRESENTATIVE OF THE
CURRENT NBM 90TH PERCENTILE SUGGESTING 1-2 INCHES OR SO IN THE
RIDGES. OVERALL CONFIDENCE IS LOW, BUT THE TREND POINTS TOWARD
A LESSER IMPACT EVENT.
AVIATION /05Z THURSDAY THROUGH MONDAY/
VFR IS EXPECTED THROUGH THIS AFTERNOON, THOUGH MID LEVEL CLOUD
CIGS WILL INCREASE AHEAD OF AN APPROACHING COLD FRONT. WIND
WILL ALSO INCREASE THROUGH THE DAY WITH A TIGHTENING PRESSURE
GRADIENT AHEAD OF THE FRONT, WITH GUSTS AROUND 20KT FROM THE SW
BY THIS AFTERNOON.
THE FRONT WILL CROSS THE REGION LATE THIS AFTERNOON AND
EVENING, WITH MVFR CIGS. MOISTURE IS LIMITED WITH THE FRONT,
THOUGH ENOUGH SATURATION IN THE DENDRITIC ZONE COULD RESULT IN
SCATTERED SNOW SHOWERS. INCLUDED A PROB30 MENTION OF SNOW
SHOWERS IN THE TAFS AS THE FRONT CROSSES. MVFR CIGS ARE EXPECTED
TO CONTINUE THURSDAY NIGHT AFTER FROPA.
OUTLOOK...
MVFR CIGS ARE LIKELY TO CONTINUE THROUGH FRIDAY UNDER COLD NW
FLOW AND A CROSSING UPPER TROUGH. VFR RETURNS LATE FRIDAY
THROUGH EARLY SATURDAY UNDER HIGH PRESSURE. RESTRICTIONS AND
SNOW SHOWERS ARE THEN POSSIBLE THROUGH SUNDAY WITH A CROSSING
COLD FRONT. VFR RETURNS MONDAY UNDER HIGH PRESSURE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...COLD WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR WVZ514.
SYNOPSIS...MLB
NEAR TERM...22/MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...WM
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