478
FXUS61 KPBZ 231336
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
836 AM EST THU JAN 23 2025
SYNOPSIS
BELOW NORMAL TEMPERATURES WILL CONTINUE THE REMAINDER OF THE WEEK
WITH A SLIGHT CHANCE OF LIGHT SNOW SHOWERS LATER THIS AFTERNOON
AND INTO THE EVENING. TEMPERATURES WILL MODERATE SOME FOR THE
WEEKEND BUT STILL REMAIN BELOW NORMAL.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- TEMPERATURES WILL BEGIN TO MODERATE TODAY.
- LIGHT SNOW POSSIBLE DURING THE EVENING WITH MINIMAL
ACCUMULATION.
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PASSING MID-LEVEL CLOUD COVERAGE KEPT OVERNIGHT LOWS SOME 10-15
DEGREES "WARMER" THAN TUESDAY NIGHT WITH READINGS IN THE UPPER
SINGLE DIGITS AND TEENS. CLEARING OF THE CLOUDS IN THE FEW HOURS
BEFORE DAYBREAK ALLOWED FOR A LAST GASP OF RADIATIONAL COOLING
WHICH HAS RESULTED IN WIND CHILL VALUES AS LOW AS THE UPPER
NEGATIVE SINGLE DIGITS. READINGS ACROSS EASTERN TUCKER COUNTY
WILL CONTINUE TO HOLD BELOW -10F THIS MORNING, SO THE COLD
WEATHER ADVISORY REMAINS IN EFFECT THERE UNTIL 10 AM THIS
MORNING.
CLOUD COVERAGE WILL AGAIN INCREASE FROM WEST TO EAST TODAY IN
TANDEM WITH A PASSING MID-LEVEL WAVE. MOISTURE IN THE LOW LEVELS
WILL BE SCARCE WITH THE PASSAGE, AND THE BEST CHANCES FOR SNOW
SHOWERS WILL LIKELY COME LATER THIS AFTERNOON AND EVENING ALONG
AND AHEAD OF A WEAK BOUNDARY AS OPPOSED TO THE IMPULSE. LATEST
GUIDANCE STILL OFFSETS THE PASSAGE OF THE WAVE AND THE BOUNDARY,
SO THE OVERLAP OF FORCING WILL BE DISPLACED. BETTER MOISTURE
RETURN WILL COME JUST AHEAD OF THE BOUNDARY WITH A MORE
SATURATED DGZ AND AT THIS POINT HREF HOURLY PROBABILITIES FOR
MEASURABLE SNOWFALL REACH 30-60%, HIGHEST IN THE HIGHER
ELEVATIONS. THE MORE PERSISTENT SNOW WILL BE ACROSS THE RIDGES
WITH OROGRAPHIC ASCENT, BUT THE MOISTURE ISSUE WILL STILL
REMAIN. OVERALL ACCUMULATION WILL BE GENERALLY A HALF INCH OR
LESS (POTENTIALLY UP TO LOCALLY 1" IN THE RIDGES). TIMING LOOKS
TO BE AFTER THE EVENING RUSH, SO TRAVEL SHOULDN'T SEE A NOTABLE
IMPACT.
SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/
KEY MESSAGES:
- MOSTLY DRY FRIDAY WITH SLIGHTLY COLDER TEMPERATURES.
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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 /14Z THURSDAY THROUGH MONDAY/
VFR IS EXPECTED THROUGH THIS AFTERNOON/EVENING, THOUGH STRATOCU
CIGS WILL OVERSPREAD THE AREA 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 TONIGHT 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...88
NEAR TERM...MLB/88
SHORT TERM...MLB/88
LONG TERM...MLB/88
AVIATION...WM/SHALLENBERGER
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