Area Forecast Discussion
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000
FXUS61 KPBZ 041645
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1145 AM EST WED MAR 4 2015

.SYNOPSIS...
RAIN AND MIXED PRECIPITATION WILL TURN TO SNOW ACROSS THE ENTIRE
REGION THIS EVENING...WITH SEVERAL INCHES OF SNOW EXPECTED INTO
NORTHERN WEST VIRGINIA. TEMPERATURES WILL BE UNSEASONABLY COLD
INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
HAVE CLEARED THE NORTHERN TIER OF COUNTIES FROM FLOOD WATCH AS NO
ADDITIONAL RAIN OR SIGNIFICANT RUNOFF EXPECTED NORTH OF
PITTSBURGH. NO CHANGES AT THIS TIME FOR WINTER HEADLINES OR SNOW
AMOUNTS. PREVIOUS DISCUSSION BELOW.

BULK OF HEAVIER PRECIPITATION NOW HEADING INTO THE SOUTHEAST
RIDGES AS COLDER AIR ABOVE THE SURFACE PUSHES SOUTHEAST. EXPECT
RAIN ALONG I-70 TO MIX OVER TO SNOW OR A BIT OF SLEET BEFORE
DIMINISHING FOR A TIME. BOUNDARY INTO CENTRAL OHIO WITH LEADING
EDGE OF MUCH COLDER AIR WILL SAG SOUTH THIS AFTERNOON AS SURFACE
WAVE WITH SHORTWAVE ALOFT MOVES NORTHEAST ALONG BOUNDARY. SNOW
WILL REDEVELOP SOUTHWEST TO NORTHEAST ACROSS AREAS FROM
PITTSBURGH SOUTH TOWARD SUNSET AND CONTINUE INTO EARLY THURSDAY.
STILL APPEARS BEST LIFT AND QPF WILL BE ACROSS THE FAR SOUTH WHERE
WARNING IS IN PLACE. NORTH OF THIS REGION MAY BE A SHARPER CUTOFF
TO SNOW AND AMOUNTS IN THE NORTHERN SECTIONS OF ADVISORY AREA MAY
BE LOWERED A BIT LATER TODAY DEPENDING ON INCOMING DATA.

SNOW WILL DIMINISH THURSDAY MORNING WITH COLD HIGH PRESSURE
BUILDING IN THURSDAY AFTERNOON.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
THE MAIN CHANGEOVER FROM RAIN TO SNOW WILL HAPPEN DURING THE LATE
AFTERNOON INTO EARLY EVENING. ALTHOUGH THE COLDER AIR WILL MOVE IN
BEHIND THE COLD FRONT...THE FRONT ITSELF WILL TAKE ITS TIME MOVING
OUT OF THE REGION...ALLOWING PRECIPITATION TO CONTINUE TONIGHT INTO
THURSDAY. MOST DIFFICULT PART OF THE FORECAST WILL BE DETERMINING
THE WESTERN EDGE OF THE HEAVIEST SNOWFALL...AS A TIGHT GRADIENT IS
EXPECTED. ALL COUNTIES PREVIOUSLY UNDER THE WINTER STORM WATCH
HAVE BEEN PUT INTO A WINTER WEATHER ADVISORY OR WINTER STORM
WARNING...WITH A FEW ADDITIONAL COUNTIES ADDED INTO THE ADVISORY
AS WELL. HAVE GONE SOMEWHAT CONSERVATIVE WITH THE AREA IN THE
WARNING...AND AM CONCERNED THAT HIGHER SNOW TOTALS COULD EDGE A
LITTLE BIT FARTHER NORTH AND WEST. AN ADDITIONAL CONCERN WAS
MODEL SOUNDINGS SHOWING THAT A WARM LAYER ALOFT COULD REMAIN FOR A
FEW HOURS ACROSS THE WV/MD RIDGES...WHICH COULD ALLOW FOR A BRIEF
PERIOD OF FREEZING RAIN DURING THE EVENING HOURS. IF FREEZING RAIN
DEVELOPS...IT WOULD CUT INTO OVERALL SNOWFALL TOTALS...BUT WOULD
PRESENT ITS OWN SET OF PROBLEMS DUE TO ICE ACCUMULATION.

SNOW SHOWERS WILL DIMINISH THROUGH THURSDAY AFTERNOON WITH ARCTIC
HIGH PRESSURE CLEARING OUT SKIES. WITH LIGHT WINDS TEMPERATURES
EXPECTED TO CRASH NEAR OR BELOW ZERO WITH FRESH SNOW COVER.

SUNSHINE BUT CONTINUED COLD FRIDAY WITH TEMPERATURES 15 TO 20
DEGREES BELOW SEASONAL AVERAGES.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE LONG TERM PERIOD LOOKS RELATIVELY QUIET WITH A PROGRESSIVE
PATTERN FEATURING PASSAGE OF A COUPLE OF SHORTWAVE TROUGHS. POPS
WERE FORECAST GENERALLY BELOW CHANCE CLIMO NUMBERS USING GFS
TIMING...BUT LONG TERM CONFIDENCE IS MINIMAL WITH DOUBTS ABOUT
TIMING AND MOISTURE SUPPLY. SEASONALLY COOL TEMPERATURES WERE
FORECAST VIA PERSISTENCE AND MOS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
IFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE MAJORITY OF THE
DAY AS LOW PRESSURE CROSSES THE GREAT LAKES REGION. A GRADUAL
CHANGEOVER TO SNOW IS EXPECTED FROM NORTH TO SOUTH THROUGH THE
MORNING WITH KMGW THE LAST TO CHANGE OVER JUST BEFORE NOON.  AN
IMPROVEMENT TO LOW END MVFR WILL BE POSSIBLE FROM PIT NORTH BY
AFTERNOON AS THE ASSOCIATED COLD FRONT PUSHES SOUTH.

.OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
WIDESPREAD RESTRICTIONS ARE EXPECTED INTO THURSDAY AS A WAVE OF
LOW PRESSURE MOVES ALONG A COLD FRONT...WITH SNOW MAINLY FROM PIT
SOUTH. RESTRICTIONS ARE POSSIBLE WITH A SUNDAY COLD FRONT.

&&

.HYDROLOGY...
THE COMBINATION OF SNOW MELT AND DEVELOPING RAIN IS EXPECTED TO
CAUSE SIGNIFICANT RISES ON THE CHEAT... MONONGAHELA AND
YOUGHIOGHENY RIVER BASINS. THESE RISES WILL AID IN MOVING ICE INTO
AREAS WHERE ICE JAMS ARE KNOWN TO DEVELOP. THE RISES WILL MOST
LIKELY PERSIST THROUGH THURSDAY. CONFIDENCE IN RAIN AMOUNTS
REMAINS LOW...BUT THE BETTER CHANCE FOR MORE SIGNIFICANT
ACCUMULATION IS EXPECTED TO BE ALONG AND SOUTH OF A ZANESVILLE TO
LATROBE LINE.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FLOOD WATCH UNTIL 7 PM EST THIS EVENING FOR MDZ001.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR MDZ001.
OH...FLOOD WATCH UNTIL 7 PM EST THIS EVENING FOR OHZ049-050-057>059-
     068-069.
     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR OHZ049-050-057>059-068.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR OHZ069.
PA...FLOOD WATCH UNTIL 7 PM EST THIS EVENING FOR PAZ021-029-031-
     073>076.
     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR PAZ021-023-029-031-073>075.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR PAZ076.
WV...FLOOD WATCH UNTIL 7 PM EST THIS EVENING FOR WVZ001>004-012-
     021>023-041.
     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR WVZ001>004.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST
     THURSDAY FOR WVZ012-021>023-041.

&&

$$









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