Areal Flood Warning 13, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
310 AM EST THU MAR 10 2011

.SYNOPSIS...
LOW PRESSURE MOVING ACROSS THE UPPER OHIO VALLEY WILL BRING
PERIODS OF RAIN THROUGH THURSDAY. COLDER TEMPERATURES WILL CHANGE
PRECIPITATION TO SNOW FOR THURSDAY NIGHT AND FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
A SLOW MOVING LOW PRESSURE SYSTEM WILL PUSH ACROSS OHIO THIS
MORNING AND INTO WESTERN PA BY THIS AFTERNOON. PERIODS OF RAIN
AHEAD THE LOW WILL CONTINUE THROUGH THE DAY INTO THIS EVENING. AS
THE LOW DRIFTS NORTH INTO NORTHWEST PA AND INTENSIFIES...COLD AIR
WILL WRAP AROUND THE LOW AND TURN THE RAIN TO SNOW BEHIND THE
STORM. SNOW WILL BECOME HEAVY AT TIMES AFTER MIDNIGHT WITH
SIGNIFICANT SNOW ACCUMULATION LIKELY BY OVERNIGHT.  AND INTO
A WINTER STORM WATCH IS IN PLACE FOR TONIGHT THROUGH FRIDAY.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
THE STORM WILL MOVE SLOWLY NORTH FRIDAY WITH PERIODS OF SNOW
CONTINUING TO BRING SIGNIFICANT SNOW ACCUMULATIONS. AS THE
INTENSIFYING LOW PRESSURE SYSTEM MOVES FARTHER AWAY TO THE
NORTHEAST, THE DEFORMATION PROCESSES WILL EXIT THE UPPER OHIO
VALLEY FRIDAY NIGHT ENDING THE STEADY SNOW. TEMPERATURES WILL BE
BELOW NORMAL.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
THERE ARE SOME MODEL DIFFERENCES IN THE STRENGTH AND LOCATION OF
THE UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW PROGGED TO MOVE
OVER THE GREAT LAKES SATURDAY AND SATURDAY NIGHT.

NUMEROUS RUNS OF THE ECMWF KEEP THIS SYSTEM FURTHER NORTH,
MAINTAINING THE BEST CHANCE FOR PRECIPITATION FURTHER NORTH. THE
GFS IN CONTRAST, DIGS THE UPPER LEVEL TROUGH FURTHER SOUTH, WHICH
WOULD BRING PRECIPITATION TO MOST OF OUR COUNTIES. HAVE OPTED TO
KEEP ONLY CHANCE POPS IN THE FORECAST AT THIS TIME WITH THE
UNCERTAINTY IN THE MODELS. WITH A NORTHWESTERLY FLOW AND COLD
ADVECTION HAVE KEPT THE POPS IN THE PERIOD THROUGH LATE SUNDAY
NIGHT, MAINLY NORTH OF I-80 AND ALONG THE RIDGES WITH ANY UPSLOPE
SHOWERS.

ON MONDAY, A RIDGE OF HIGH PRESSURE WILL BEGIN TO BRIEFLY BUILD IN
OVER THE REGION BEFORE THE NEXT SYSTEM PROGRESSES TOWARDS THE
REGION.

BOTH THE 00Z GFS/ECMWF AND THE 00Z GEFS HINT TO A LOW PRESSURE
SYSTEM MOVING SOUTH OF THE CWA ON MONDAY NIGHT BUT SLIGHT LOCATION
DIFFERENCES ARE APPARENT. GENERALLY EXPECT MOST OF THE
PRECIPITATION TO BE SOUTH OF THE REGION, AND LIGHT IN INTENSITY.

WITH CONTINUED LOW MODEL CONFIDENCE INTO WEDNESDAY AND THURSDAY,
HAVE OPTED TO REMAIN CLOSE TO HPC GUIDANCE.

TEMPERATURES THROUGH THE LONG TERM PERIOD WILL BE NEAR NORMAL.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
RAIN WILL CONTINUE TO OVERSPREAD THE REGION TODAY AS LOW PRESSURE
MOVES ACROSS. AS THE LOW MOVES EAST OF THE AREA THIS AFTERNOON...A
COLD FRONT WILL CROSS...TURNING SURFACE WINDS FROM THE WEST.

A LOW LEVEL JET AHEAD OF THIS LOW...COULD LEAD TO LOW LEVEL WIND
SHEAR EARLY IN THIS TAF PERIOD.

THE COMBINATION OF RAIN AND LOW LEVEL MOISTURE...WILL LEAD TO
WIDESPREAD IFR TO MVFR CONDITIONS...WITH A PERIOD OR TWO OF LIFR
ALSO POSSIBLE TODAY.

THE DEVELOPMENT OF WRAP AROUND PRECIPITATION ON THE COLD...WESTERN
END OF THE EXITING LOW PRESSURE SYSTEM CAN LEAD TO A PERIOD IFR OR
LIFR SNOW TONIGHT INTO FRIDAY AFTERNOON. FLIGHT CONDITIONS SHOULD
IMPROVE TO AT LEAST MVFR FRIDAY NIGHT AS SYSTEM COMPLETES ITS
EXIT.

AN UPPER LEVEL DISTURBANCE WILL CROSS THE AREA LATE ON SATURDAY WITH
RAIN AND SNOW WITH AN ADDITIONAL PERIOD OF RESTRICTIONS POSSIBLE.
VFR CONDITIONS WILL RETURN SUNDAY INTO MONDAY AS A HIGH PASSES
NORTH OF THE AREA.

&&

.HYDROLOGY...
ALTHOUGH WEDNESDAY EVENING RAINFALL WAS PATCHY AND RELATIVELY LIGHT,
IT APPEARS THAT ANOTHER 1.0 TO 1.5 INCHES OF RAIN, OR LIQUID
EQUIVALENT PRECIPITATION IS POSSIBLE DURING THE NEXT 48 HOURS AS
PER OHRFC GUIDANCE.

AS LOCAL STREAMS ARE RUNNING HIGH, THE POTENTIAL FOR AREAL
FLOODING CONTINUES THROUGH THURSDAY. THE RUNOFF WILL REACH THE
MAJOR RIVERS WITH CRESTS FORECAST ON FRIDAY AND SATURDAY. RIVER
FLOOD WARNINGS AND WATCHES ARE IN EFFECT FOR VARIOUS POINTS ALONG
THE TUSCARAWAS, MUSKINGUM, OHIO, AS WELL AS THE MONONGAHELA AND ITS
TRIBUTARIES. FORECASTS SHOULD BE MONITORED VIA THE INTERNET
HYDROLOGY PAGE.

ADDITIONALLY, WITH SO MUCH RECENT RAINFALL ACROSS THE REGION,
MANY RESERVOIRS IN EASTERN OHIO ARE TRYING TO HOLD WATER. SO
ANOTHER INCH, TO INCH AND A HALF OF LIQUID EQUIVALENT WOULD BRING
THE POSSIBILITY OF BACKWATER FLOODING TO MANY LOCATIONS CAUSING
ROAD CLOSINGS AND RESIDENTIAL RELOCATIONS.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FLOOD WATCH THROUGH THIS AFTERNOON FOR MDZ001.
     WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
     FOR MDZ001.
OH...FLOOD WATCH THROUGH THIS AFTERNOON FOR OHZ039>041-048>050-
     057>059-068-069.
     WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
     FOR OHZ039>041-048>050-057>059-068-069.
PA...FLOOD WATCH THROUGH THIS AFTERNOON FOR PAZ007>009-013>016-
     020>023-029-031-073>076.
     WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
     FOR PAZ007>009-013>016-020>023-029-031-073>076.
WV...FLOOD WATCH THROUGH THIS AFTERNOON FOR WVZ001>004-012-021>023-
     041.
     WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
     FOR WVZ001>004-012-021>023-041.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
450 AM EST THU MAR 10 2011

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021>023-041-111000-
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-VENANGO-
FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-ALLEGHENY-
ARMSTRONG-INDIANA-WASHINGTON-GREENE-WESTMORELAND-WESTMORELAND RIDGES-
FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-
MONONGALIA-PRESTON-TUCKER-
450 AM EST THU MAR 10 2011

...FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON...
...WINTER STORM WATCH IN EFFECT FROM THIS EVENING THROUGH FRIDAY
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST
CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA
AND NORTHERN PANHANDLE OF WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   FLOOD WATCH.
   WINTER STORM WATCH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   WINTER STORM WATCH.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.