882
FXUS61 KPBZ 171524
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1024 AM EST SUN NOV 17 2024
SYNOPSIS
DRY CONDITIONS ARE EXPECTED INTO THIS EVENING. A WEAK FRONT
BRINGS SCATTERED SHOWERS MAINLY NORTH OF PITTSBURGH LATE
TONIGHT. A MORE ACTIVE PATTERN DEVELOPS THEREAFTER, WITH
MULTIPLE PRECIPITATION CHANCES INTO NEXT WEEKEND.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- DRY WEATHER CONTINUES TODAY WITH MID AND UPPER LEVEL CLOUD
COVERAGE.
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MID-LEVEL RIDGING CONTINUES TO CROSS THE AREA TODAY, WITH
CONTINUED DRY WEATHER. MORNING VALLEY FOG HAS LARGELY
DISSIPATED. THROUGH THE AFTERNOON, MID AND UPPER CLOUD COVER IS
EXPECTED ON SOUTHWEST FLOW ALOFT. WITH RISING HEIGHTS AND WARM
ADVECTION, DAYTIME HIGHS WILL TOP OUT AROUND 5 DEGREES WARMER
THAN OBSERVED SATURDAY.
SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/
KEY MESSAGES:
- WARMING TREND INTO NEXT WEEK.
- QUICK SHOWER CHANCE OVERNIGHT INTO EARLY MONDAY MAINLY NORTH
OF PGH.
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THE UPPER RIDGE AXIS WILL SHIFT DIRECTLY OVERHEAD BY SUNDAY
MORNING AS HIGH PRESSURE CENTERED OVER THE SOUTHEAST BUILDS INTO
THE AREA. THIS WILL BACK FLOW MORE SOUTHWESTERLY, RESULTING IN
INCREASED WARM ADVECTION AND HELPING TO BREAK AND LIFT THE CLOUD
DECK THROUGH THE DAY. WARM ADVECTION WILL LEAD TO A 5-10 DEGREE
BOOST IN AFTERNOON HIGHS, WITH MUCH OF THE REGION IN THE
MID/UPPER 50S.
A QUICK-MOVING SHORTWAVE WILL CROSS WELL TO THE NORTH OF THE
AREA SUNDAY NIGHT INTO EARLY MONDAY AS A WEAK COLD FRONT CROSSES
THE OHIO VALLEY. THIS WILL ALLOW LIGHT SHOWERS TO DEVELOP
OVERNIGHT, PRIMARILY NORTH OF PITTSBURGH AND IN THE PA RIDGES,
BUT LOW-PROBABILITY CHANCES ELSEWHERE. LINGERING SHOWERS SHOULD
EXIT BY SUNRISE MONDAY.
DESPITE COOLING 850S, BETTER INSOLATION ON MONDAY AS CLOUD COVER
BREAKS WILL HELP HIGH TEMPERATURES GAIN ANOTHER ~5 DEGREES.
OTHERWISE, DRY WEATHER CONTINUES INTO MONDAY NIGHT.
LONG TERM /TUESDAY THROUGH SATURDAY/
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 THROUGH TUESDAY AS SFC
LOW PRESSURE COINCIDENT WITH A MID-LEVEL SHORTWAVE EJECTS OUT
OF THE SOUTHERN PLAINS MONDAY AND INTO THE GREAT LAKES ON
TUESDAY. THIS SHOULD BRING A ROUND OF RAINFALL AS EARLY AS
TUESDAY MORNING IN ADVANCE OF A CROSSING COLD FRONT. RAIN WILL
LIKELY LINGER INTO THE EVENING/OVERNIGHT PERIOD. HIGH
TEMPERATURES WILL ANOTHER FEW DEGREES ABOVE MONDAY (10-15
DEGREES ABOVE AVERAGE), PUTTING MUCH OF THE AREA IN THE LOWER
60S (UPPER 50S NORTH OF PITTSBURGH).
MORE SIGNIFICANT 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
COINCIDENT WITH SIGNIFICANT 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. TWO CLUSTERED SCENARIOS
REMAIN: A MORE AMPLIFIED RIDGE AND THEREFORE WEAKER/SLOWER
TROUGH PROGRESSION, OR LESS AMPLIFIED RIDGE WITH QUICKER,
DEEPER TROUGHING. HOWEVER, PROBABILITY FOR THE LATTER (AND
COLDER) SOLUTION IS INCREASING. THERE REMAINS A BIMODAL
DISTRIBUTION IN FORECAST ELEMENTS (YIELDING NON-
METEOROLOGICALLY SENSIBLE MEAN VALUES), BUT THE LEFT-MOST PEAK
(COLDER SOLUTION) CONTINUES TO GROW AT EXPENSE OF THE WARMER
SOLUTION.
GIVEN INCREASING CONFIDENCE, HAVE HEDGED TOWARD THE COLDER
SOLUTION. THIS DOES INCREASE THE POSSIBILITY OF SNOW FOR THE
THURSDAY/FRIDAY TIMEFRAME, BUT THIS WILL OBVIOUSLY BE
TEMPERATURE DEPENDENT. THE 25-75TH PERCENTILE SPREAD IN TEMPS
ON THURSDAY/FRIDAY IS ROUGHLY 20 DEGREES. STAY TUNED FOR MORE
DETAILS...
AVIATION /16Z SUNDAY THROUGH THURSDAY/
AFTER PATCHY FOG ENDS THIS MORNING, VFR IS THEN HIGHLY LIKELY
THROUGH THE MAJORITY OF THE TAF PERIOD WITH 5-10KT SOUTHERLY
WINDS DEVELOPING AND STREAMS OF CIRRUS CROSSING THE REGION. A
SHORTWAVE AND ASSOCIATED SURFACE BOUNDARY WILL APPROACH FROM THE
NORTHWEST AFTER 06Z AND INCREASE MVFR POTENTIAL, THOUGH NOT
FAVORED UNTIL LATER MONDAY MORNING. A FEW ISOLATED SHOWERS OR
DRIZZLE MAY BE POSSIBLE WITH THIS FEATURE EARLY MONDAY MORNING.
OUTLOOK....
MVFR (60-80% PROBABILITY) TO LOCALLY IFR (20-40% PROBABILITY)
CEILINGS SOUTHEAST RESTRICTIONS BECOME MORE LIKELY AFTER 12Z
MONDAY WITH THE CROSSING SHORTWAVE AND FRONT. THE SURFACE
BOUNDARY MAY STALL ACROSS WESTERN PA AND CAUSE RESTRICTIONS TO
LINGER THROUGH THE DAY BEFORE IT SLOWLY LIFTS NORTHWARD AS A
WARM FRONT (WITH VFR RETURNING BEHIND IT).
A SERIES OF INCREASINGLY POTENT LOW PRESSURE SYSTEMS WILL BRING
BOUTS OF RESTRICTIONS, GUSTY WIND, AND RAIN TURNING INTO
POTENTIAL SNOW SHOWERS FOR THE SECOND HALF OF THE WEEK.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...88
NEAR TERM...CL/88
SHORT TERM...RACKLEY/88
LONG TERM...RACKLEY/88
AVIATION...RACKLEY/FRAZIER
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