399
FXUS61 KPBZ 201727
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1227 PM EST THU FEB 20 2025
SYNOPSIS
AN UPPER LEVEL DISTURBANCE WILL BRING SNOW SHOWERS TO THE AREA
TODAY. DRY AND WARMER FOR THE WEEKEND.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- WINTER WEATHER ADVISORY FOR PA/WV RIDGES.
- HEAVIER CONVECTIVE SNOW SHOWERS MAY CREATE LOCALIZED IMPACTS
THIS AFTERNOON AND EVENING.
- COLD WEATHER ADVISORY FOR E.TUCKER TODAY.
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UPDATE...
THE LATEST SURFACE AND UPPER AIR ANALYSIS SHOWS AN UPPER LOW
CENTERED ACROSS OHIO, WITH A SURFACE TROUGH ACROSS SOUTHERN
ONTARIO. THE UPPER LOW WILL DRIFT EASTWARD ACROSS THE UPPER OHIO
VALLEY REGION TODAY, WITH OCCASIONAL SNOW SHOWERS. STEEPENING
LAPSE RATES THROUGH THE DENDRITIC LAYER COULD RESULT IN A FEW
HEAVIER SNOW SHOWERS OR POSSIBLE SQUALLS THIS AFTERNOON AND
EARLY EVENING. SOME LAKE ENHANCEMENT IS ALSO POSSIBLE THIS
AFTERNOON, MAINLY FROM LAKE HURON, AS LAKE ERIE IS MOSTLY ICE
COVERED. ALSO LOWERED TEMPERATURES CLOSER TO GFS LAMP GUIDANCE,
WITH LITTLE IF ANY TEMPERATURE RISE EXPECTED TODAY.
PREVIOUS DISCUSSION...
500MB LOW WILL SLOWLY MOVE ACROSS THE REGION TODAY. LIGHT SNOW
WILL SPREAD ACROSS THE AREA FROM WEST TO EAST THIS MORNING AHEAD
OF THE LOW. THE LOW WILL BRING A COLD POOL ALOFT EASTWARD WITH IT,
INCREASING INSTABILITY AS IT PASSES. A STRENGTHENING OF THE NW
FLOW WILL ALSO OCCUR AND THE DGZ WILL LOWER INTO THE SATURATED
LAYER. THERE WILL ALSO BE AN INCREASE IN LOW-LEVEL LAPSE RATES
THIS MORNING. ALL OF THIS IS POINTING TO MORE CONVECTIVE SNOW
SHOWERS DEVELOPING UNDER AND BEHIND THE UPPER LOW. LATEST SNOW
SQUALL PARAMETERS ARE SHOWING THE BEST TIME FOR SQUALLS TO BE THIS
AFTERNOON, MAINLY OVER OHIO AND THE SOUTHERN HALF OF PA. THE
PARAMETER IS NOT EXCEPTIONAL, BUT THE THREAT FOR SQUALLS IS THERE.
IN ADDITION TO THE RISK FOR HEAVIER SNOW SHOWERS, LAKE ENHANCED
BANDS MAY ALSO DEVELOP.
THE HIGHEST ACCUMULATIONS ARE EXPECTED OVER THE RIDGES WHERE
WINTER WEATHER ADVISORIES REMAIN POSTED.
TEMPERATURES WILL AGAIN BE WELL BELOW NORMAL.
SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/
KEY MESSAGES:
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LOSS OF INSTABILITY AND FURTHER EROSION OF UPPER SUPPORT SHOULD
CAUSE A DOWNWARD TREND IN COVERAGE AND INTENSITY OF SNOW SHOWERS
TONIGHT. HOWEVER, WITH CONTINUED NW FLOW AND A LOW DGZ, LAKE
ENHANCED SNOW BANDS CANNOT BE COMPLETELY RULED OUT TONIGHT. THE
THREAT FOR THESE SHOULD DECREASE LATE TONIGHT AS HEIGHT RISES
ALOFT AND SURFACE HIGH PRESSURE INCREASE SUBSIDENCE.
ANY LINGERING SNOW SHOWERS SHOULD DISSIPATE FRIDAY MORNING AS
DRIER AIR OVERSPREADS THE REGION.
HIGH PRESSURE WILL KEEP SATURDAY DRY AND ALLOW TEMPERATURES TO
MODERATE.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
KEY MESSAGES:
- HIGH PROBABILITY IN RIDGING AND TEMPERATURE MODERATION SUNDAY.
- PRECIPITATION CHANCES TETHERED TO SHORTWAVE MOVEMENT WITHIN
THE BROADER NW FLOW PATTERN.
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RIDGING AND WARMING IS EXPECTED FOR SUNDAY.
THAT PATTERN IS FAVORED TO BECOME MORE ACTIVE BY THE START OF
NEXT WEEK WITH A SERIES OF SHORTWAVES MOVE ACROSS THE GREAT
LAKES REGION AND PROMOTE INCREASED PRECIPITATION CHANCES. TIMING
OF THE PRECIPITATION AND DEPTH OF THE COLD ADVECTION WILL
GREATLY INFLUENCE PRECIPITATION TYPE AND WINTRY ACCUMULATIONS,
BUT THIS IS LIKELY TO BE THE START OF ANOTHER PERIOD OF BELOW
AVERAGE TEMPERATURE THAT SHOULD GENERALLY PERSIST THROUGH THE
END OF THE MONTH.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
MVFR CIGS AND MVFR/IFR VSBYS WITH SNOWFALL RATES LESS THAN
0.5"/HR (AROUND 90% PROBABILITY) CAN BE EXPECTED THROUGH THE TAF
PERIOD AS AN UPPER LOW CROSSES THE REGION. THE HIGHEST
PROBABILITY OF IFR VSBYS WILL BE DURING THE AFTERNOON AS STRONG
COLD ADVECTION ON THE BACK SIDE OF THE TROUGH STEEPENS LAPSE
RATES AND SNOW BECOMES MORE CONVECTIVE. LATEST GUIDANCE SHOWS A
60% CHANCE OF IFR CIGS THROUGH THE TAF PERIOD.
THE MENTIONED CONVECTIVE SHOWERS LOOK LIKELY TO BEGIN BY EARLY
AFTERNOON (18Z) AND LASTING THROUGH 00Z. ON AND OFF WIDESPREAD
HEAVIER SNOW SHOWERS THAT CAN QUICKLY DROP VISIBILITY TO LESS
THAN 1 MILE AND HAVE SNOWFALL RATES BETWEEN 0.5"-1"/HR (30-50%
PROBABILITY OF THOSE RATES) WILL BE POSSIBLE. SHORT-DURATION
BURSTS CAN BE EXPECTED BUT TIMING OF IMPACTS AND LOCATION OF
HEAVIEST BANDS IS TOO DIFFICULT BEYOND TEMPO GROUPS TO NOTE THE
THREAT. INCREASED NW WIND WILL DEVELOP DURING THE AFTERNOON WITH
25-30KT PEAK GUSTS.
LOSS OF HEATING AND SLOWLY INCREASING SUBSIDENCE WILL TAPER OFF
SHOWERS BY 00Z, BUT RESIDUAL COLD ADVECTION IN NW FLOW MAKES IT
LIKELY THAT A LAKE-ENHANCED BAND OR TWO PERSISTS THROUGH THE END
OF THE TAF PERIOD. THERE IS HIGH UNCERTAINTY IN THE POSITIONING
OF THESE BANDS (IF THEY DEVELOP) AND THE POTENTIAL RATES WITHIN
THEM. IN GENERAL, THE COLD ADVECTION AND RESIDUAL BOUNDARY
LAYER MOISTURE WILL FOSTER MVFR TO SPOTTY IFR CIGS OVERNIGHT,
WITH VSBY ISSUES TETHERED TO THESE LAKE BANDS.
OUTLOOK...
INCREASING SUBSIDENCE AND DRY ADVECTION IN NW WILL ERODE
REMAINING LIGHT SNOW SHOWERS THROUGH FRIDAY MORNING AND SLOWLY
LIFT/SCATTER MVFR STRATOCU DECK. AREAS SOUTHEAST OF KPIT ARE
FAVORED FOR A RETURN TO VFR BY FRIDAY AFTERNOON (LESS THAN 30%
PROBABILITY OF MVFR PERSISTENCE), BUT MODELS SUGGEST SOME
POTENTIAL FOR LINGERING STRATOCU FOR NORTHERN SITES LIKE FKL/DUJ
INTO SATURDAY MORNING (40-60%).
DRY WEATHER IS EXPECTED SATURDAY INTO SUNDAY BEFORE A SERIES OF
SHORTWAVES DROP OUT OF THE GREAT LAKES EARLY NEXT WEEK, BRINGING
RESTRICTIONS AND PERIODIC PRECIPITATION CHANCES.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR PAZ074-076-
078.
OH...NONE.
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR WVZ510>514.
COLD WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ514.
SYNOPSIS...22
NEAR TERM...WM/22
SHORT TERM...22/SHALLENBERGER
LONG TERM...22/FRAZIER/SHALLENBERGER
AVIATION...88
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