922
FXUS61 KPBZ 171133
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
633 AM EST TUE DEC 17 2024
SYNOPSIS
A DRY DAY WITH NEAR NORMAL TEMPERATURES. RAIN RETURNS ON
WEDNESDAY, WITH COLDER TEMPERATURES FOR THE END OF THE WEEK AND
THROUGH THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- DRY DAY WITH NEAR NORMAL TEMPERATURES.
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MINOR UPPER LEVEL HEIGHT RISES ARE EXPECTED TODAY AS A SURFACE
HIGH MOVES TOWARD THE MID-ATLANTIC REGION. THIS SHOULD PROVIDE A
DRY DAY WITH ABOVE NORMAL TEMPERATURES. EXPECT TO SEE LOTS OF
SUN FOR AT LEAST THE SOUTHERN HALF OF THE REGION AS THE LOWER
CLOUDS WILL BE SHUNTED NORTHWARD WITH THE COLDER AIR ALOFT.
LOCATIONS ALONG AND NORTH OF I-80 WILL LIKELY HAVE TO DEAL WITH
A BLANKET OF LOW CLOUDS FROM TIME TO TIME TODAY AS A STRATOCU
DECK, ASSOCIATED WITH THE COLDER AIR ALOFT, WILL REST OVER THOSE
LOCALES.
HIGH TEMPERATURES TODAY WILL COOL FROM MONDAY, BUT WILL STILL
REMAIN ABOVE NORMAL.
GUSTY SURFACE WINDS ARE ALSO ANTICIPATED THIS MORNING AS
STRONGER WINDS ALOFT MIX DOWN TO THE SURFACE. NBM PROBS FOR WIND
GUSTS > 25MPH ARE GENERALLY 60 TO 90% ACROSS THE REGION, WITH
THE HIGHEST OF THESE OVER THE RIDGES AND THE I-80 CORRIDOR. THE
STRONGEST WIND GUSTS ARE EXPECTED OVER TUCKER COUNTY WV WHERE
PROBS OF GUSTS > 40 MPH ARE 60-80%.
SHORT TERM /WEDNESDAY THROUGH THURSDAY/
KEY MESSAGES:
- ABOVE NORMAL TEMPERATURE LIKELY WEDNESDAY.
- RAIN RETURNS ON WEDNESDAY.
- COLDER TEMPERATURES ON THURSDAY.
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THE NEXT WEATHER SYSTEM WILL ARRIVE WEDNESDAY AND FEATURE 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 A PLUME OF
PRECIPITATION THAT CROSSES THE UPPER OHIO RIVER VALLEY 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'S FRONT WILL FAVOR MORE SEASONABLE TEMPERATURE AND
CLOUD COVER.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
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 /12Z TUESDAY THROUGH SATURDAY/
FAIRLY HIGH CONFIDENCE FORECAST OF VFR THROUGH THE TAF PERIOD
WITH INCREASING INFLUENCE OF SURFACE HIGH PRESSURE IN A POST-
FRONTAL ENVIRONMENT. COLD, DRY ADVECTION WILL LIMIT LOW CIG
DEVELOPMENT WITH ONLY A FEW/SCT DIURNAL CU DEVELOPING THIS
AFTERNOON. THE BIGGEST UNCERTAINTY LAYS IN THE CUT OFF LINE OF
A MORE ENTRENCHED MVFR STRATUS DECK ASSOCIATED WITH COLDER AIR
TO THE NORTH. FKL/DUJ MAY SEE PERIODS OF BKN 3KFT DECKS BUT
TIMING AND DURATION OF IMPACT IS HIGHLY UNCERTAIN.
THE MIXED BOUNDARY LAYER PLUS SURFACE PRESSURE GRADIENT WILL
CONTINUE TO FOSTER 15 TO 25KT GUSTS OUT OF THE WSW THROUGH THIS
AFTERNOON BEFORE WANING TONIGHT.
OUTLOOK...
WIDESPREAD RAIN AND RESTRICTIONS ARE LIKELY WEDNESDAY AMID WARM,
MOIST ADVECTION AHEAD OF THE NEXT UPPER LEVEL DISTURBANCE,
FAVORING 15Z-20Z FOR ONSET OF CONDITIONS.
ENSEMBLE MODELS ARE BEARISH FOR A REPRIEVE OF MVFR CIGS (MOST
TERMINALS WITH 50-80% PROBABILITY OF PERSISTENCE) UNTIL THURSDAY
EVENING; THIS LIKELY MEANS ANY PERIOD OF VFR WILL BE SHORT-LIVED
BEFORE THE NEXT LOW PRESSURE SYSTEM ARRIVES FRIDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22/FRAZIER
LONG TERM...FRAZIER
AVIATION...FRAZIER
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