131
FXUS61 KPBZ 220002
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
702 PM EST SAT DEC 21 2024
SYNOPSIS
LAKE ENHANCED SNOW SHOWERS WILL CONTINUE TO DECREASE IN COVERAGE
AND INTENSITY, MOSTLY ENDING BY SUNRISE ON SUNDAY. WITH THE
EXCEPTION OF LATE MONDAY AND TUESDAY MORNING, DRY CONDITIONS ARE
LARGELY EXPECTED NEXT WEEK WITH AN INCREASING TREND IN
TEMPERATURES.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
KEY MESSAGES:
- LAKE ENHANCED SNOW SHOWERS WILL CONTINUE TO DECREASE IN
COVERAGE AND INTENSITY THROUGH THE NIGHT.
- COLD OVERNIGHT LOWS IN THE FROM THE UPPER SINGLE DIGITS INTO
THE MIDDLE TEENS.
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THE LAKE-EFFECT BAND HAS DEVOLVED INTO MAINLY SCATTERED SNOW
SHOWERS BY THIS POINT, GENERALLY NEAR AND NORTH/EAST OF PIT
CURRENTLY. THE IN-PROGRESS PBZ SOUNDING SHOWS THAT THE
INVERSION HEIGHT HAS LOWERED FROM AROUND 750MB AT 12Z TO 800MB
AT 00Z, AND THIS SLOW PROCESS WILL CONTINUE TONIGHT, WITH
COVERAGE AND INTENSITY CONTINUING ITS SLOW DECLINE. STILL, THE
TOP OF THE MOIST LAYER REMAINS AROUND -20C CURRENTLY, SO SOME OF
THE SNOW SHOWERS ARE STILL TAKING ADVANTAGE OF THIS AND
PRODUCING BRIEFLY MODERATE SNOW RATES.
MOST ACTIVITY IS CURRENTLY LOCATED NEAR AND NORTH/EAST OF PIT.
CONSIDERING THIS, AND WITH THE EXPECTED CONTINUED DOWNWARD
TREND, HAVE TRIMMED A FEW COUNTIES FROM THE SOUTHERN SIDE OF THE ONGOING
WINTER WEATHER ADVISORY. LEFT IT UP FOR THE REST OF THE AREA
WHERE AT LEAST SCATTERED SNOW SHOWERS CONTINUE, WHERE VERY BRIEF
VISIBILITY/ROAD IMPACTS REMAIN POSSIBLE.
ALSO OF NOTE: OVERNIGHT LOWS WERE LOWERED SLIGHTLY. MOST OF THE
REGION WILL SEE MORNING LOWS BETWEEN 10 AND 16, WITH SOME SINGLE
DIGITS NORTH OF I-80 AND ON THE HIGHER RIDGES. AS A RESULT, SOME
ICE FORMATION IS POSSIBLE ON ANY ROADS THAT CURRENTLY REMAIN
WET, ESPECIALLY UNTREATED ROADS. EVEN A FEW TREATED ROADS MAY
SEE A BIT OF ICE IN THE COLDER LOCATIONS, AS BRINE SOLUTIONS
START TO LOSE A BIT OF EFFECTIVENESS.
SNOW SHOWERS WILL CONTINUE TO WANE OVERNIGHT AS SHORTWAVE
TROUGHING LIFTS OUT AND SUBSIDENCE INCREASES. THEY SHOULD
MOSTLY CEASE BY SUNRISE, ALTHOUGH THIS WILL NEED TO BE MONITORED
FOR THE POSSIBLE NEED OF AN EXTENSION.
SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/
KEY MESSAGES:
- COLD AND DRY SUNDAY AND MONDAY MORNING.
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BY SUNDAY, HIGH PRESSURE IS EXPECTED TO BE JUST TO THE NORTH OF
THE FORECAST AREA AS THE CORE OF THE COLDEST AIR FINALLY
DESCENDS ON THE UPPER OH VALLEY. TEMPERATURES IN OUR FAR
NORTHEASTERN COUNTIES ADVERTISE A 60% TO 80% CHANCE OF LESS THAN
10 DEGREES FOR A LOW SUNDAY MORNING. ITS EVEN COLDER FOR MONDAY
MORNING AS THE PROBS IN THE NORTHEAST (FOREST COUNTY) NOW
INCREASES TO AROUND 90% BUT ALSO SHOWING AROUND 40% FOR THE
RIDGES AND SOUTH INTO THE WV COUNTIES. HIGHS ARE EXPECTED TO BE
BELOW NORMAL FOR SUNDAY BUT THE AIR MASS WILL MODIFY
SIGNIFICANTLY AFTER A COLD MORNING ON MONDAY AS HIGHS SOAR INTO
THE LOW 40S. THE NBM ENSEMBLE SUGGESTS A 40% TO 60% PROBABILITY
OF HIGH TEMPERATURES ABOVE 40 DEGREES FOR MONDAY. THIS PROVIDES
QUITE A SHIFT IN TEMPERATURES JUST BEFORE CHRISTMAS.
ENSEMBLE GUIDANCE CONTINUES TO INDICATE FLAT MID-LEVEL RIDGING
MOVING ACROSS THE UPPER OHIO VALLEY ON MONDAY, WITH CONTINUED DRY
WEATHER LIKELY. WARM ADVECTION AND RISING HEIGHTS SHOULD LEAD TO
THE PREVIOUSLY DISCUSSED WARMER TEMPERATURES, WITH MAX VALUES
PERHAPS AROUND 10 DEGREES HIGHER THAN SUNDAY, DEPENDING ON HOW
QUICKLY CLOUDS THICKEN AHEAD OF THE NEXT SYSTEM.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
KEY MESSAGES:
- GENERALLY LIGHT PRECIPITATION APPEARS LIKELY MONDAY NIGHT INTO
CHRISTMAS EVE DAY, WITH A MINOR SNOW ACCUMULATION POSSIBLE
NORTH OF PITTSBURGH.
- A WARMING TREND AND LOWER PRECIPITATION CHANCES MAY FOLLOW FOR
CHRISTMAS DAY THROUGH THE END OF THE WEEK.
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A FAIRLY WEAK SHORTWAVE APPEARS MOST LIKELY TO CROSS THE AREA MONDAY
NIGHT INTO CHRISTMAS EVE DAY. MODEL CLUSTERING SHOWS GENERALLY MINOR
DIFFERENCES IN STRENGTH AND TIMING, BUT MOST AGREE THAT QPF WILL
GENERALLY BE LIGHT AND FOCUSED NORTH OF PITTSBURGH CLOSER TO THE
WAVE TRACK. PROBABILITIES OF ACCUMULATING SNOW ARE BEING MODULATED
BY TEMPERATURE, WITH HIGHS LIKELY IN THE MID TO UPPER 30S FROM
PITTSBURGH NORTH AND IN THE RIDGES, AND IN THE LOWER 40S TO THE
SOUTH. THESE LIKELIHOODS RANGE FROM NEAR 10 PERCENT AT ZANESVILLE,
TO 40 PERCENT AT PITTSBURGH, AND 90 PERCENT AT DUBOIS.
PROBABILITIES OF AN INCH OR MORE REMAIN CONFINED TO AREAS NORTH
OF I-80 AND MAX OUT AT AROUND 40-50%. THIS WOULD BE THE AREA
THAT HAS THE BEST CHANCE OF HAVING AN INCH OF SNOW ON THE GROUND
COME CHRISTMAS MORNING, BUT THE ABOVE-FREEZING TEMPERATURE
COULD PLAY A ROLE IN LIMITING SNOW DEPTH.
THEREAFTER, ENSEMBLES CONTINUE TO SHOW GOOD PROBABILITIES OF RIDGING
DURING THE MIDWEEK PERIOD, WHICH WILL CONTINUE THE WARMING TREND
THROUGH CHRISTMAS DAY AND THE REMAINDER OF THE WEEK. TEMPERATURES
COULD PERHAPS RISE TO AROUND 10 DEGREES ABOVE NORMAL BY FRIDAY. A
MINORITY OF ENSEMBLE MEMBERS ARE SHOWING LOWER HEIGHTS/FLATTER
RIDGING, PERHAPS LEADING TO LESS OF A WARMUP. ALONG WITH THE
WARMING, THE MAJORITY MODEL OPINION WOULD LEAD TO FAIRLY LOW CHANCES
OF LIGHT PRECIPITATION AT BEST FOR THE SECOND HALF OF THE HOLIDAY
WEEK.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
WINDS LIGHTEN FROM THE NORTHWEST OVERNIGHT WITH HIGH PRESSURE
MOVING IN OVERHEAD. SATELLITE COVERAGE SHOWS BROKEN DECKS
MAINTAINED FROM THE NORTHWEST, WITH THE 00Z SOUNDING SHOWING
SHALLOW SATURATED LAYERS AT 4KFT AND 6KFT. WITH A 50% TO 60%
CHANCE OF VFR OVERNIGHT FOR PIT, AGC, BVI, LBE, MGW, AND FKL,
OPTED TO LEAN THAT WAY IN THE FORECAST GIVEN THE CURRENT TRENDS,
THOUGH MVFR IS 40% TO 50% LIKELY OVERNIGHT. AT ZZV AND HLG, VFR
IS 75% MEANWHILE, AT DUJ MVFR IS 65% LIKELY OVERNIGHT. SNOW IS
EXPECTED TO TAPER FOR MOST PORTS NORTH AND WEST OF PIT BY 04Z
NORTHWEST FLOW WEAKENS.
THOUGH SOME LOWERING IS POSSIBLE SUNDAY MORNING, MOST GUIDANCE
MAINTAINS SCATTERED COVERAGE, WITH HIGH CONFIDENCE IN LIFTING
AND SCATTERING AFTER NOON-TIME. WINDS TURN LIGHT OUT OF THE
SOUTHEAST OVERNIGHT.
OUTLOOK...
VFR UNDER THE INFLUENCE OF HIGH PRESSURE IS FAVORED SUNDAY AFTERNOON
INTO MONDAY BEFORE THE NEXT UPPER LEVEL SYSTEM CROSSES INTO THE REGION
LATE MONDAY INTO TUESDAY, BRINGING ANOTHER ROUND OF LIGHT SNOW
AND AREAWIDE RESTRICTIONS.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR PAZ013-
014-020-021-073-074-076.
OH...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR OHZ041.
WV...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ001-
510>512.
SYNOPSIS...CL/88
NEAR TERM...88
SHORT TERM...SHALLENBERGER/88
LONG TERM...SHALLENBERGER/88
AVIATION...MILCAREK
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