895
FXUS61 KPBZ 221823
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
123 PM EST SUN DEC 22 2024
SYNOPSIS
DRY WEATHER CONTINUES WITH THE NEXT CHANCE OF PRECIPITATION
MONDAY NIGHT INTO TUESDAY MORNING. TEMPERATURES WILL BEGIN A
MODERATING TREND INTO THE COMING WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- DRY UNDER HIGH PRESSURE.
- COLD WITH HIGHS IN THE 20S AND OVERNIGHT LOWS IN THE TEENS.
--------------------------------------------------------------------.
DRY CONDITIONS WILL PREVAIL AS HIGH PRESSURE REMAINS THE
DOMINANT FEATURE. GRADUAL WARM ADVECTION ALOFT AND INCREASING
SUBSIDENCE WILL CONTINUE TO LESSEN STRATOCU CLOUD COVERAGE
THROUGH THE AFTERNOON, FOLLOWED BY MAINLY CLEAR SKIES OVERNIGHT.
WITH LIGHT WIND AND MINIMAL CLOUD COVERAGE, IT WILL BE
RELATIVELY COLD OVERNIGHT WITH AN IDEAL SETUP FOR EFFICIENT
RADIATIONAL COOLING. WITH THAT IN MIND, TIPPED THE HAT TOWARDS
THE COLDER SIDE OF THE DISTRIBUTION FOR OVERNIGHT LOWS.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
KEY MESSAGES:
- LIGHT PRECIPITATION RETURNS MONDAY NIGHT WITH SOME
SNOW ACCUMULATION POSSIBLE NORTH AND EAST OF PITTSBURGH.
- WARMER ON CHRISTMAS EVE WITH AFTERNOON HIGHS CHALLENGING THE
CHANCES OF A WHITE CHRISTMAS.
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MOST OF THE DAYTIME HOURS ON MONDAY ARE LIKELY TO BE DRY WITH THE
INFLUENCE OF DEPARTING HIGH PRESSURE. ENSEMBLES ARE IN
RESPECTABLY GOOD AGREEMENT ON THE PROGRESSION OF A TROUGH
CROSSING THE AREA MONDAY NIGHT INTO TUESDAY MORNING WITH LITTLE
DEVIATION ON ITS STRENGTH OR TIMING LENDING HIGHER CONFIDENCE. A
WEAK ATTENDANT SURFACE LOW WILL TRACK EAST ACROSS THE GREAT
LAKES PULLING A WEAK BOUNDARY THROUGH AS IT PASSES BY.
PRECIPITATION PROBABILITIES ARE HIGH AT 80%+ WITH THIS FEATURE,
BUT MOISTURE RETURN AHEAD OF IT APPEARS PALTRY GIVEN A LACKING
MERIDIONAL COMPONENT TO THE FLOW AHEAD OF ITS ARRIVAL.
PRECIPITABLE WATER VALUES ONLY HAVE AROUND A 50-60% CHANCE OF
EXCEEDING 0.5". THAT SAID, WITH THE TIMING BEING IN THE
OVERNIGHT HOURS, PROBABILITY OF DOMINANT PRECIP TYPE TO BE SNOW
IS HIGHEST NORTH AND EAST OF PITTSBURGH COINCIDENT WITH THE
COLDER AIR WHERE OVERNIGHT LOWS <32F ARE 80-100% (30-50% IN THE
URBAN AREAS). PROBABILITY OF TOTAL LIQUID >0.10" IS AS HIGH AS
60-70% NORTH OF PITTSBURGH CLOSER TO THE BEST FORCING. IN TERMS
OF SNOW, NBM PROBABILITY FOR 1" IS UP TO ABOUT 60% CONCENTRATED
IN FOREST, CLARION, AND JEFFERSON COUNTIES; THE REASONABLE HIGH
END OF THE GOAL POSTS SITS AT AROUND 3" AT THIS POINT WITH THE
LOW END <1", SO THERE'S STILL SOME UNCERTAINTY IN AMOUNTS, BUT
GENERALLY ARE FAVORING THE 1-3" RANGE. ELSEWHERE, RAIN OR A
RAIN/SNOW MIX ARE MORE LIKELY GIVEN THE WARMER TEMPERATURES.
IF AT LEAST 1" OF SNOW DOES FALL OVERNIGHT AND PROVIDE AT LEAST THAT
MUCH SNOW DEPTH HEADED INTO THE DAY ON CHRISTMAS EVE, WE'RE LOOKING
AT A HIGH PROBABILITY FOR AFTERNOON HIGHS TO EXCEED THE FREEZING
MARK, SO SNOW DEPTH MAY BE CHALLENGED AS COULD A WHITE CHRISTMAS (1"
OF SNOW ON THE GROUND AT 7AM ON CHRISTMAS DAY). A TRANSITION TO RAIN
SHOWERS THEN BECOMES MORE LIKELY ON TUESDAY WITH LINGERING MOISTURE
AND SHORTWAVE PASSAGES AS THE TROUGH EXITS, BUT ADDITIONAL
MEASURABLE RAIN CHANCES ARE ONLY PEAKING AROUND 50%.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
KEY MESSAGES:
- LOW PRECIPITATION CHANCES ON CHRISTMAS DAY.
- WARMING TREND THROUGH THE END OF THE WEEK.
- UNCERTAINTY IN THE PATTERN BY NEXT WEEKEND.
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IN THE WAKE OF THE CHRISTMAS EVE DISTURBANCE, ENSEMBLES CONVERGE ON
A BRIEF RIDGING SOLUTION DOWNSTREAM OF ANOTHER QUICKLY APPROACHING
TROUGH ACROSS THE MIDWEST THAT IS FAVORED TO WEAKEN AND FLATTEN OUT
AS IT APPROACHES LOCALLY ON CHRISTMAS DAY. SOME UNCERTAINTY COMES
INTO PLAY WITH POTENTIAL PHASING OF A NORTHERN STREAM WAVE
TRAVERSING NORTH OF THE GREAT LAKES WITH THE WEAKENING SOUTHERN
WAVE, BUT THIS IS ONLY REPRESENTED BY ONE ENSEMBLE CLUSTER WHILE THE
OTHERS SUGGEST HIGHER HEIGHTS. THIS WOULD BE A NON-TRIVIAL SOLUTION
THOUGH SHOULD IT COME TO FRUITION AND PROVIDE GREATER MOISTURE
RETURN IN A BIT MORE AMPLIFIED FLOW COMPARED TO OTHER SOLUTIONS THAT
SUGGEST ONLY LOW-END PROBABILITY SCATTERED RAIN SHOWERS. IF PRECIP
DOES OCCUR, PROFILES AREN'T FAVORABLE FOR SNOW WITH PROBABILITY NEAR
100% TO EXCEED 32 DEGREES FOR HIGHS.
FOR THE LATTER HALF OF THE WEEK, ALL CLUSTERS SUGGEST BUILDING
RIDGING BY THURSDAY, AGAIN SAVE ONE SOLUTION THAT HANGS BACK THE
UPPER DISTURBANCE AND ASSOCIATED PRECIPITATION CHANCES INTO EARLY
THURSDAY MORNING. REGARDLESS, RIDGING WILL FINALLY TAKE HOLD WITH
570+ DAM HEIGHTS PRESENTING AS INCREASING PROBABILITY. DEEP LAYER
SOUTHERLY COMPONENT FLOW WILL SUPPORT A WARMING AND MOISTENING TREND
AS HIGHS RISE ABOVE 50 DEGREES SOUTH OF PITTSBURGH WITH A 40-60%
CHANCE ON THURSDAY AND INCREMENTALLY STEPPING UP FURTHER NORTH
INTO THE WEEKEND. CONFIDENCE IN A WARMING TREND IS INCREASING.
ANOTHER DISTURBANCE IS POSSIBLE COME NEXT WEEKEND, BUT DEVIANCE
FROM THE GRAND ENSEMBLE SOLUTION INCREASES SUBSTANTIALLY IN
REGARD TO PRECIPITATION CHANCES.
AVIATION /19Z SUNDAY THROUGH FRIDAY/
THE SITES AT FKL AND DUJ HAVE BEEN HANGING ON TO MVFR LONGER BUT
SHOULD IMPROVE BY 22Z. WINDS WILL CONTINUE TO LIGHTEN THROUGHOUT THE
REMAINDER OF THE DAY AS HIGH PRESSURE SITS OVERHEAD. FROM TONIGHT
THROUGH TOMORROW EVENING, VFR CONDITIONS ARE EXPECTED TO PERSIST.
TOMORROW, WINDS WILL FRESHEN UP TO 7-10 KNOTS OUT OF THE SOUTH AND
GUSTY CONDITIONS WILL BEGIN DEVELOPING TOMORROW AFTERNOON. IN
EASTERN OHIO, GUSTS ARE EXPECTED TO BE 18-20 KNOTS WHILE AREAS
ACROSS WESTERN PENNSYLVANIA AND NORTHERN WEST VIRGINIA WILL SEE
GUSTS OF UP TO 15-17 KNOTS.
OUTLOOK...
THE NEXT UPPER LEVEL SYSTEM CROSSES INTO THE REGION
TOMORROW NIGHT INTO TUESDAY, BRINGING ANOTHER ROUND OF LIGHT SNOW
AND AREAWIDE RESTRICTIONS. BETWEEN EARLY TUESDAY MORNING THROUGH
TUESDAY AFTERNOON, THERE IS A 40%-55% PROBABILITY FOR IFR CONDITIONS
ACROSS A MAJORITY OF THE REGION. THERE IS A 30%-45% CHANCE THAT DUJ
AND FKL HOLD ON TO IFR CONDITIONS THROUGH LATE NIGHT ON TUESDAY
WHILE MAJORITY OF OTHER TERMINALS WILL RETURN TO MVFR CONDITIONS.
TOMORROW NIGHT, THERE IS A CHANCE FOR LOW-LEVEL WIND SHEAR ACROSS
WESTERN PENNSYLVANIA AND PARTS OF EASTERN OHIO. THE POTENTIAL THREAT
ENDS BY EARLY TUESDAY MORNING.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...MLB/88
LONG TERM...MLB/88
AVIATION...LUPO
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