894
FXUS61 KPBZ 170650
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
150 AM EST SUN NOV 17 2024
SYNOPSIS
CLOUD COVERAGE WILL PERSIST, BUT A WARMING TREND IN
TEMPERATURES CAN BE EXPECTED THROUGH MIDWEEK. UNSETTLED
CONDITIONS WILL RESULT IN PERIODIC PRECIPITATION CHANCES TUESDAY
AND INTO NEXT WEEKEND.
NEAR TERM /UNTIL 6 AM THIS MORNING/
KEY MESSAGES:
- DRY WEATHER CONTINUES THROUGH TONIGHT WITH PERSISTENT CLOUD
COVER.
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OVERCAST STRATUS CONTINUES ACROSS THE AREA WITH NORTHWEST FLOW
AND SUBSTANTIAL BOUNDARY LAYER MOISTURE TRAPPED UNDER A STOUT
POST-FRONTAL INVERSION. RECENT PIT ACARS SOUNDINGS SHOW A
GRADUAL VEERING TREND TO MORE NORTHERLY BETWEEN 850-800 MB WHICH
EXPLAINS THE LOCALIZED BREAKS IN COVERAGE ESPECIALLY EAST OF
PITTSBURGH, BUT ANY BREAKS WILL BE FAIRLY SHORT-LIVED AND
GENERAL OVERCAST CONDITIONS WILL LIKELY CONTINUE INTO THE
OVERNIGHT. SOME GREATER ENSEMBLE SPREAD COMES INTO PLAY ACROSS
SOUTHEAST OHIO AND NORTHERN WEST VIRGINIA WHERE SOME WEAK WARM
ADVECTION ALOFT MAY ALLOW FOR MORE SCATTERED TO BROKEN COVERAGE
AS FLOW WEAKENS AND TURNS SOUTHERLY WITH A BUILDING RIDGE.
STILL, WITH GENERALLY BROKEN TO OVERCAST CONDITIONS CONTINUING
OVERNIGHT, AND DEW POINTS IN THE UPPER 30S/NEAR 40, LOWS WILL
REMAIN JUST ABOVE-NORMAL. PATCHY FOG IS POSSIBLE WITH LINGERING
MOISTURE, WHERE CLOUD COVERAGE IS MINIMAL.
SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/
KEY MESSAGES:
- WARMING TREND INTO NEXT WEEK.
- QUICK SHOWER CHANCE SUNDAY NIGHT 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 /07Z SUNDAY THROUGH THURSDAY/
SUBSIDENCE IS RAPIDLY ERODING AREA STRATOCU EARLY THIS MORNING,
RESULTING IN CLEARING SKIES WITH PASSING HIGH CIRRUS. THERE IS A
LOW PROBABILITY FOR PATCH FOG TO DEVELOP BETWEEN 10Z-13Z AS WIND
REMAINS LIGHT AND RADIATIONAL COOLING BEGINS, BUT CONFIDENCE IS
LOW WHILE PASSING CIRRUS LIKELY WILL INSULATE THE REGION ENOUGH
FROM FOG.
VFR IS HIGHLY LIKELY THROUGH THE VAST 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.
OUTLOOK....
THE AFOREMENTIONED SHORTWAVE AND FRONT IS FAVORED TO SPREAD LOW
PROBABILITY RAIN/DRIZZLE CHANCES AND MVFR (60-80% PROBABILITY)
TO LOCALLY IFR (20-40% PROBABILITY) CEILINGS SOUTHEAST MONDAY
MORNING. 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.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...RACKLEY
LONG TERM...RACKLEY
AVIATION...FRAZIER
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