169
FXUS61 KPBZ 160851
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
351 AM EST SAT NOV 16 2024
SYNOPSIS
INTERMITTENT DRIZZLE MAY LINGER DURING THE MORNING HOURS,
ESPECIALLY NORTH OF PITTSBURGH AND IN THE RIDGES. DRY CONDITIONS
WILL THEN RESUME OVER THE COURSE OF THE DAY. A MORE ACTIVE
PATTERN IS THEN EXPECTED NEXT WEEK WITH SEVERAL CHANCES FOR
PRECIPITATION.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- LIGHT RAIN/DRIZZLE WILL LINGER EARLY IN THE AM.
- PATCHY DENSE FOG EXPECTED ALONG THE RIDGES.
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ANY INTERMITTENT / PATCHY DRIZZLE WILL END THIS MORNING AS
STRATUS CEILINGS LIFT, HOWEVER, CLOUD COVERAGE SHOULD PERSIST
UNDER COOL NORTHWESTERLY FLOW. COVERAGE MAY LESSEN SLIGHTLY
LATER IN THE AFTERNOON AS FLOW ALOFT BECOMES MORE NORTHERLY, BUT
A SUBSTANTIAL AMOUNT OF MOISTURE WILL REMAIN IN THE BOUNDARY
LAYER. DAYTIME HIGHS SHOULD TOP OFF A DEGREE OR TWO WARMER THAN
OBSERVED FRIDAY.
SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/
KEY MESSAGES:
- DRYING AND WARMING TREND BEGINS AND LASTS THROUGH THE WEEKEND.
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LATER TONIGHT INTO SUNDAY MORNING, EXPECT CLOUDS TO BRIEFLY
LESSEN MORE AS THE RIDGE AXIS MOVES OVERHEAD. LIGHT WINDS AND
POTENTIALLY LESS CLOUD COVERAGE RAISES THE POTENTIAL FOR MORE
WIDESPREAD FOG DEVELOPMENT EARLY SUNDAY MORNING. WITH THE RIDGE
AXIS EAST OF THE REGION, FLOW WILL SHIFT TO THE SOUTHWEST AND
RESULT IN INCREASED WARM ADVECTION, DRIVING TEMPERATURES BACK
INTO THE UPPER 50S TO LOWER 60S ON SUNDAY AFTERNOON.
LONG TERM /MONDAY THROUGH FRIDAY/
KEY MESSAGES:
- RAIN RETURNS TUE/WED WITH ADDITIONAL CHANCES THROUGH LATE WEEK
- HIGH UNCERTAINTY REMAINS WITH A LATE WEEK SYSTEM
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ENSEMBLES SHOW FAIRLY HIGH CONSISTENCY MONDAY INTO TUESDAY WITH
SIGNIFICANT UNCERTAINTY THEREAFTER.
BY MONDAY, SFC LOW PRESSURE COINCIDENT WITH A MID-LEVEL
SHORTWAVE WILL EJECT OUT OF THE SOUTHERN PLAINS AND INTO THE
UPPER MIDWEST AND ACROSS THE GREAT LAKES ON TUESDAY. THIS SHOULD
BRING A ROUND OF RAINFALL PRECEDING A COLD FRONT THROUGH THE
AREA ON TUESDAY. HIGH TEMPERATURES WILL RUN 10-15 DEGREES ABOVE
AVERAGE MON/TUE, PUTTING MUCH OF THE AREA IN THE LOWER 60S
(UPPER 50S NORTH OF PITTSBURGH).
BREAKDOWN IN THE FORECAST OCCURS IN THE WEDNESDAY THROUGH
FRIDAY TIMEFRAME. GENERALLY, MODELS SHOW A MORE POTENT
WAVE/CLOSED LOW DEVELOPING OVER THE CENTRAL US BY WEDNESDAY AND
DIVING OVER THE EAST BY THURSDAY/FRIDAY. STRENGTHENING LOW
PRESSURE AT THE SURFACE WOULD BRING AN INITIAL ROUND OF
PRECIPITATION FOLLOWED BY WRAP-AROUND MOISTURE WITH A FETCH OF
COLD AIR ADVECTION.
GREATEST UNCERTAINTY STEMS FROM THE TIMING, STRENGTH, AND
PLACEMENT OF THE TROUGH WHICH WILL DEPEND ON THE STRENGTH OF THE
DOWNSTREAM RIDGE OVER THE EAST COAST. ENSEMBLES CURRENTLY FAVOR
TWO CLUSTERED SCENARIOS: A MORE AMPLIFIED RIDGE AND THEREFORE
WEAKER/SLOWER TROUGH PROGRESSION (SLIGHTLY FAVORED BY ENS), OR
LESS AMPLIFIED RIDGE WITH QUICKER, DEEPER TROUGHING (FAVORED BY
MORE GEFS/GEPS MEMBERSHIP). ENSEMBLE FORECAST ELEMENTS ACROSS
THESE DAYS SHOW THIS BIMODAL VARIANCE, FAVORING EITHER A COLDER
OR WARMER SOLUTION. THIS BIMODAL DISTRIBUTION MAKES A
DETERMINISTIC FORECAST PARTICULARLY DIFFICULT FOR THE TIME
PERIOD, SINCE NBM MEAN VALUES FALL BETWEEN THE TWO SOLUTIONS AND
ARE METEOROLOGICALLY UNLIKELY. FOR NOW, HAVE HEDGED SLIGHTLY
TOWARD THE COLDER SOLUTION, GIVEN FAVORED ENSEMBLE MEMBERSHIP.
THIS DOES INTRODUCE THE POSSIBILITY OF RAIN/SNOW (GASP) INTO THE
FORECAST FOR THE THURSDAY/FRIDAY TIMEFRAME, BUT THIS WILL
OBVIOUSLY BE TEMPERATURE DEPENDENT. THE 25-75TH PERCENTILE RANGE
IN TEMPS ON THURSDAY IS ROUGHLY 20 DEGREES. STAY TUNED FOR MORE
DETAILS...
AVIATION /09Z SATURDAY THROUGH WEDNESDAY/
STOUT MOISTURE TRAPPED BENEATH A POST-FRONTAL INVERSION WILL
HELP TO MAINTAIN MVFR TO LOCALIZED IFR CONDITIONS THROUGH THE
MORNING. THOUGH HIGH PRESSURE WILL KEEP THE REGION DRY,
LINGERING NORTHWEST FLOW AND THE LACK OF DRY ADVECTION IS LIKELY
TO LIMIT CIG IMPROVEMENTS THROUGH THE AFTERNOON. BY 00Z, HI-RES
MODELING SUGGESTS 60-80% PROBABILITIES OF MVFR OR LOWER CEILINGS
REMAINING OVER THE REGION. TAFS FAVOR THE PESSIMISTIC OUTLOOK
WITH SOME POTENTIAL FOR BREAKS IN THE OVERCAST STRATOCU LAYER.
CONFIDENCE FALLS AFTER 21Z TOWARD THE END OF THE TAF AS VARIANCE
IN CLOUD COVERAGE AT HEIGHTS INCREASES; SOME SUGGEST SCATTERING
TO OCCUR WHILE OTHERS SUGGESTS LIFTING AND EVEN SE TO NW
EROSION. WITH LITTLE AIRMASS CHANGING, TRENDED TOWARD
PERSISTENCE THAT WOULD MAINTAIN MVFR STRATOCU AT ALL TERMINALS.
HOWEVER, IF SCATTERING/CLEARING WERE TO CLEAR, A NON-ZERO FOG
THREAT MAY DEVELOP BETWEEN 06Z-12Z SATURDAY DUE TO MOIST
GROUNDS, LIGHT WINDS, AND POTENTIAL FOR STRONG RADIATIONAL
COOLING.
OUTLOOK....
GREATER MIXING AND DRIER SOUTHWEST FLOW IS HIGHLY LIKELY (ABOVE
90% PROBABILITY) TO ERODE ANY RESIDUAL MVFR STRATOCU, LEADING TO
VFR AND DRY CONDITIONS SUNDAY.
A WEAK SHORTWAVE AND SURFACE FRONT WILL SUPPORT LOWER
PROBABILITY RAIN CHANCES AND CEILING REDUCTIONS (FAVORING
NORTHWEST PA). THERE IS INCREASING LIKELIHOOD FOR AN ACTIVE MID
TO LATE WEEK WEATHER PATTERN THAT LENDS TO MULTIPLE WAVES OF
PRECIPITATION AND PROLONGED RESTRICTIONS.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...88/LUPO
LONG TERM...RACKLEY
AVIATION...FRAZIER
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