271
FXUS61 KPBZ 161832
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
132 PM EST MON DEC 16 2024
SYNOPSIS
WIDESPREAD RAIN IS LIKELY THIS AFTERNOON AND EVENING AS WELL AS
WEDNESDAY IN ASSOCIATION WITH FAST MOVING UPPER LEVEL TROUGHS,
WHILE ARE TEMPERATURE IS ABOVE NORMAL. A LATE WEEK PATTERN SHIFT
IS FAVORED TO BRING BELOW NORMAL TEMPERATURE BUT SNOW CHANCES
MAY BE LIMITED TO NEAR LAKE ERIE AND THE HIGHER TERRAIN/
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- LIGHT TO OCCASIONALLY MODERATE RAIN IS EXPECTED THIS
AFTERNOON/EVENING.
- AREA TEMPERATURE WILL REMAIN ABOVE NORMAL.
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AN UPPER LEVEL TROUGH APPROACHING THE WESTERN GREAT LAKES WILL
LIFT A PLUME OF WARM, MOIST AIR THROUGH THE OHIO RIVER VALLEY
TODAY, RESULTING IN WIDESPREAD LIGHT TO MODERATE RAIN THIS
AFTERNOON/EVENING. THE INITIAL WAVE OF RAIN THIS AFTERNOON WILL
BE AHEAD OF THE 700MB WARM FRONT WHILE THE SECOND WAVE LATE
TONIGHT IS EXPECTED AHEAD OF THE SURFACE COLD FRONT. RAINFALL IS
LIKELY TO BE FAIRLY CONSISTENT FOR MULTIPLE HOURS, THOUGH
PROBABILITIES SUGGEST A POTENTIAL FEW HOUR BREAK BETWEEN THE TWO
WAVES. MOST AREAS ARE LIKELY TO SEE TOTAL AMOUNTS IN EXCESS OF
0.5" (60-90% PROBABILITY), WITH THE AXIS OF HIGHEST TOTALS
FAVORING SOUTHEAST OH TOWARDS THE MASON-DIXON LINE.
PRECIPITATION WILL QUICKLY END/SHIFT EAST BEHIND THE OVERNIGHT
FRONTAL PASSAGE AMID DRY ADVECTION ON THE SOUTHERN SIDE OF THE
TROUGH AXIS. STEEPENED LAPSE RATES AND TIGHTENED PRESSURE
GRADIENT MAY MAKE FOR 25-35 MPH GUSTS OUT OF THE SW BY DAWN
TUESDAY.
SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- ABOVE NORMAL TEMPERATURE LIKELY TUESDAY INTO PORTIONS OF
WEDNESDAY.
- THE NEXT LOW PRESSURE SYSTEM ARRIVES WEDNESDAY WITH RAIN BEING
THE FAVORED PRECIPITATION TYPE.
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HIGH PRESSURE WILL BUILD IN FROM THE SOUTHWEST TUESDAY AMID
HEIGHT RISES ALOFT. THOUGH CLOUDS MAY LINGER OVER NORTHWEST PA
AS FLOW TRAVERSES THE WARMER LAKE ERIE, THE OVERALL PATTERN WILL
SUPPORT DRY WEATHER, ABOVE NORMAL TEMPERATURE AND SUNNY SKIES.
THE NEXT WEATHER SYSTEM WILL ARRIVE WEDNESDAY AND FEATURES A
DEEPENING TROUGH TRAVERSING THE GREAT LAKES REGION WHILE A WEAK
SURFACE LOW LIFTS FROM THE TN RIVER VALLEY TOWARDS THE MID-
ATLANTIC. BROAD JET ASCENT IS EXPECTED TO DEVELOP OF PLUME OF
PRECIPITATION THAT CROSSES THE UPPER OHIO RIVER VALLEY DURING
THE DAY AND EVENING HOURS WEDNESDAY. ENSEMBLE MODEL
DISCREPANCIES POINT TO SOME VARIATION IN TROUGH DEPTH AND
POSITIONING (I.E. ITS FORWARD SPEED), BUT THESE ALTERATIONS
AREN'T LIKELY TO OFFER HIGHER/LOWER IMPACT SCENARIOS. WHY?
CURRENT ENSEMBLE MEANS SHOW 850MB TEMPS BETWEEN 2-4 DEGREES C
(LIMITING/ELIMINATING ANY SNOW ACCUMULATION) AND THE PROBABILITY
OF SEEING PRECIPITATION AT THE SAME TIME AS BELOW FREEZING
TEMPERATURE IS GENERALLY LESS THAN 10% (ELIMINATING FREEZING
RAIN CONCERN).
CONFIDENCE IS HIGH FOR DRY WEATHER TO RESUME THURSDAY UNDER THE
INFLUENCE OF HIGH PRESSURE, THOUGH COLD ADVECTION BEHIND
WEDNESDAY NIGHT'S FRONT WILL FAVOR MORE SEASONABLE TEMPERATURE
AND CLOUD COVER.
LONG TERM /FRIDAY THROUGH SUNDAY/
KEY MESSAGES:
- HIGH PROBABILITY FOR TEMPERATURES AROUND 10 DEGREES BELOW
NORMAL FOR THE WEEKEND.
- SNOWFALL POTENTIAL CONTINUES TO APPEAR LOW END THREAT WITH ANY
IMPACTS LIKELY NEAR LAKE ERIE.
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ANOTHER UPPER LEVEL TROUGH IS LIKELY TO DEVELOP OVER THE EASTERN
CONUS FRIDAY INTO THE WEEKEND AS IT DROPS SOUTHEAST FROM CENTRAL
CANADA. THIS PATTERN SHIFT WILL SUPPORT ANOTHER PERIOD OF
PRECIPITATION (MAINLY SNOW) WITH THE INITIAL WAVE PASSAGE FRIDAY
INTO SATURDAY) AND BELOW AVERAGE TEMPERATURE INTO THE WEEKEND.
MODEL VARIATIONS REMAIN FAIRLY HIGH ON THE OVERALL DEPTH OF THE
TROUGH AS WELL AS THE SHORTWAVE MOVEMENT WITHIN IT; THESE
FACTORS WILL PLAY LARGER ROLES IN HOW ACTIVE LAKE EFFECT SNOW
DEVELOPS AND THE BOUNDARY LAYER FLOW ANGLE FOR THOSE BANDS.
DEEPER/COLDER LEADS TO MORE EFFECTIVE SNOW BANDS (MEANING
GREATER ACCUMULATION POTENTIAL FOR FAR NORTHWEST PA AND THE
HIGHER TERRAIN) WHILE LESS DEEP/SLIGHTLY WARMER KEEPS THE REGION
DRIER AND LEADS TO MORE INCONSEQUENTIAL SNOWFALL TOTALS. STAY
TUNED AS SMALL-SCALE VARIATIONS FOR THIS WEEKEND PERIOD WILL
DETERMINE IF IMPACTS MAY DEVELOP OR NOT.
AVIATION /19Z MONDAY THROUGH SATURDAY/
CURRENTLY, AN UPPER TROUGH DIGGING INTO THE LOWER OHIO RIVER
VALLEY WILL SUPPORT BROAD ASCENT/WARM ADVECTION LEADING TO
AREAWIDE RAIN STARTING THIS AFTERNOON AND EARLY EVENING. THERE
IS A HIGH PROBABILITY (GREATER THAN 80%) FOR MOST TERMINALS
(EXCLUDING LBE AND MGW) TO FALL BACK TO IFR OR LOWER LEVELS
DURING THIS PERIOD. A BRIEF PERIOD OF LLWS IS LIKELY TO OCCUR
FOR A COUPLE HOURS AT ALL TERMINALS BETWEEN 00Z-05Z WITH THE
ARRIVAL OF A STRONG LOW-LEVEL JET AND THE MIXING OF GUSTIER
WINDS TO THE SURFACE.
PASSAGE OF A WEAK COLD FRONT LATE THIS EVENING WILL AID
DISSIPATION OF RAINFALL, ENCOURAGE DEEPER MIXING TO LIFT AREA
CIGS, AND OFFER INCREASED WIND GUSTS OUT OF THE WSW. BY TOMORROW
AFTERNOON, THERE ARE EXPECTED TO BE NO CEILING RESTRICTIONS FOR
ALL TERMINALS ASIDE FROM FKL.
OUTLOOK...
FROM WEDNESDAY MORNING TO THURSDAY MORNING, RESTRICTIONS WILL
RETURN ASSOCIATED WITH ANOTHER DISTURBANCE MOVING THROUGH THE
AREA. VFR CONDITIONS EXPECTED DURING THE DAY ON THURSDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...FRAZIER
NEAR TERM...FRAZIER
SHORT TERM...FRAZIER
LONG TERM...FRAZIER
AVIATION...FRAZIER/LUPO
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