206
FXUS61 KPBZ 161734
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1234 PM EST SAT NOV 16 2024
SYNOPSIS
DRY BUT DREARY WEATHER CONTINUES TODAY AS CLOUD COVER PERSISTS.
TEMPERATURES WILL WARM INTO EARLY NEXT WEEK. RAIN CHANCES RETURN
ON TUESDAY, WITH SEVERAL CHANCES FOR PRECIPITATION THROUGH NEXT
WEEKEND.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- LITTLE CHANGE IN TEMPERATURE TODAY AS OVERCAST CONDITIONS
PERSIST.
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PATCHY DRIZZLE HAS LARGELY ENDED THIS MORNING AS STRATUS
CONTINUES TO SLOWLY LIFT. SOME PATCHY BREAKUP OF OVERCAST SKIES
IS EXPECTED THIS AFTERNOON AS FLOW ALOFT BECOMES MORE
NORTHERLY, BUT CLOUDY CONDITIONS ARE EXPECTED TO PERSIST AS
SUBSTANTIAL BOUNDARY LAYER MOISTURE REMAINS TRAPPED UNDER A
STOUT POST-FRONTAL INVERSION. DAYTIME TEMPERATURES REMAIN
SUPPRESSED GIVEN LITTLE INSOLATION.
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 /18Z SATURDAY THROUGH THURSDAY/
MVFR CEILINGS REMAIN LOCKED OVER THE REGION, AS MOISTURE REMAINS
TRAPPED UNDERNEATH A POST-FRONTAL INVERSION. THE MOISTURE LAYER
IS RELATIVELY THIN, AND SOME MODEST CLOUD BREAKUP IS ALREADY
OCCURRING NORTH OF PIT. IT STILL APPEARS THAT MIXING WILL
LIKELY BE INSUFFICIENT TO REMOVE CEILINGS IN MOST CASES TODAY
GIVEN THE STOUTNESS OF THE INVERSION. SUCH CEILINGS WILL LINGER
INTO THE EVENING AS WELL. INDEED, THE HREF SHOWS 50 TO 80
PERCENT PROBABILITY OF MVFR CEILINGS LINGERING THROUGH 06Z ACROSS
SOUTHWEST PA/NORTHERN WV. PROBABILITIES ARE A TOUCH LOWER IN
EASTERN OHIO. WILL ALLOW FOR A LOW VFR CEILING AT ZZV THIS
EVENING, BUT PLAN ON MAINTAINING MVFR CEILINGS INTO THE EVENING
AT MOST LOCATIONS.
HREF MEMBERS CONTINUE TO SHOW VARIANCE IN CLOUD COVERAGE AFTER
06Z, MAINLY SOUTH OF I-70, AS WARM ADVECTION TRIES TO EAT AWAY
AT THE LOW CLOUDS. THINK THAT AT LEAST ZZV AND MGW HAVE A
DECENT CHANCE OF SCATTERING OUT LATE TONIGHT - BUT DO NOT HAVE
ENOUGH CONFIDENCE TO GO FURTHER NORTH THAN THIS AT THE MOMENT.
ASSUMING THIS CLEARING DOES OCCUR, THERE IS A THREAT OF FOG
DEVELOPMENT DUE TO MOIST GROUNDS, LIGHT WINDS, AND POTENTIAL FOR
STRONG RADIATIONAL COOLING. HAVE INCLUDED TEMPO POSSIBILITIES
AT THE TWO SITES MENTIONED ABOVE.
THE DISSIPATION OF THE STRATOCUMULUS WILL CONTINUE PAST SUNRISE,
AIDED BY DAYTIME MIXING. EXPECT ALL SITES TO ACHIEVE VFR BY LATE
MORNING. AREAS THAT LOSE STRATOCUMULUS WILL STILL BE COVERED BY
A VEIL OF HIGHER CLOUDS, THANKS TO SOUTHWEST FLOW AHEAD OF A
GREAT LAKES SHORTWAVE.
NORTHWEST WIND WILL CONTINUE TODAY, GENERALLY AT 5 TO 10 KNOTS
OR SO, BEFORE DIMINISHING TONIGHT.
OUTLOOK....
ANY REMAINING STRATOCUMULUS WILL DISSIPATE SUNDAY AFTERNOON,
WITH CONTINUED VFR AND DRY CONDITIONS.
SUNDAY NIGHT, A WEAK SHORTWAVE AND SURFACE FRONT WILL SUPPORT
LOWER PROBABILITY RAIN CHANCES AND CEILING REDUCTIONS (FAVORING
NORTHWEST PA). VFR THEN LIKELY RETURNS ON MONDAY. 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...RACKLEY
NEAR TERM...RACKLEY
SHORT TERM...88/LUPO
LONG TERM...RACKLEY
AVIATION...CL
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