Flood Potential Outlook
Issued by NWS

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
933 AM EST THU JAN 29 2015



...WINTER/SPRING FLOOD POTENTIAL OUTLOOK...

...THE FLOOD POTENTIAL FOR FLOODING IS NEAR NORMAL FOR THE UPPER
OHIO VALLEY...

A NORMAL FLOOD POTENTIAL MEANS SCATTERED FLOODING COULD OCCUR
WITH WATER LEVELS REACHING MINOR IMPACTS.

FOR THE LONG-RANGE RIVER OUTLOOKS AND THE PROBABILITY OF
EXCEEDING FLOOD STAGE OR THE CHANCES OF FLOODING RELATIVE TO
NORMAL AT SPECIFIC FORECAST POINTS DURING THE NEXT 90 DAYS...REFER
TO WWW.WEATHER.GOV/OHRFC AND CLICK ON THE 90-DAY RIVER OUTLOOK ON
THE LEFT HAND SIDE OF THE PAGE. CLICK ON FLOOD CHC VS NORMAL TO
VIEW THE RISK OF FLOODING WITH RESPECT TO NORMAL.

FLOOD OUTLOOKS ARE ISSUED BI-WEEKLY BY THE NATIONAL WEATHER
SERVICE DURING WINTER AND EARLY SPRING TO SUMMARIZE BASIN
HYDROMETEOROLOGICAL CONDITIONS AND TO ASSESS THE POTENTIAL FOR
WINTER/SPRING FLOODING. THE OUTLOOKS ARE BASED ON CURRENT AND
EXPECTED CONDITIONS DURING THE OUTLOOK PERIOD.

IN ADDITION 90-DAY WATER RESOURCES OUTLOOKS ARE ISSUED MONTHLY.

FACTORS CONSIDERED IN ASSESSING FLOOD POTENTIAL ARE...

ANTECEDENT CONDITIONS...
FACTORS CONSIDERED IN ASSESSING FLOOD POTENTIAL ARE (1)ANTECEDENT
CONDITIONS (2) PAST PRECIPITATION (3) RECENT STREAMFLOWS AND
RESERVOIR LEVELS (4) SOIL MOISTURE (5) WATER CONTENT OF THE SNOW
PACK (6) ICE CONDITIONS ON THE RIVERS AND (7) FUTURE
PRECIPITATION.

ICE CONDITIONS...
LARGE PORTIONS OF THE ALLEGHENY RIVER AND ITS TRIBUTARIES ARE ICE
COVERED WITH COVERAGE IS 50 TO 100 PERCENT ABOVE LOCK 4 ALLEGHENY WITH
THE ICE THICKNESS RANGING FROM 14 TO 36 INCHES. THERE ARE MINOR
ICE JAMS ALONG THE MIDDLE AND UPPER PORTIONS OF THE RIVER. ALL ICE
JAMS ARE CURRENTLY STABLE. NO IMPROVEMENT IN ICE CONDITIONS ARE EXPECTED.

METEOROLOGICALLY...
THE PREVAILING STORM TRACK HAS TAKEN ON AN EL NINO SIGNATURE
ACROSS THE U.S....PREDICTED SINCE THE SUMMER OF 2014...WITH
FREQUENT STORM SYSTEMS HITTING THE WEST COAST...THEN MOVING ACROSS
THE DEEP SOUTH BEFORE CURVING UP THE EAST COAST OR OUT INTO THE
WESTERN NORTH ATLANTIC BASIN. THE LACK OF PHASING OF THE POLAR AND
SUBTROPICAL JET STREAMS HAS RESULTED IN RELATIVELY LIGHT
PRECIPITATION EVENTS IN THE OHIO VALLEY DURING LATE AUTUMN/EARLY
WINTER. WITH THE EL NINO PATTERN IN PLACE...THE FAST FLOW ACROSS
THE U.S. HAS PREVENTED THE POLAR VORTEX FROM ESTABLISHING ITSELF
SEMI-PERMANENTLY OVER HUDSON BAY/JAMES BAY...THUS BLOCKING THE
FREQUENT INTRUSION OF ARTIC AIR MASSES INTO CONTINENTAL U.S. AS A
RESULT....A DEEP WINTER SNOWPACK HAS REMAINED NORTH OF THE U.S.
BORDER IN CANADA.

SOIL CONDITIONS...
SOILS ARE NORMALLY MOIST IN THE OHIO VALLEY.

RIVER FLOWS...
28-DAY AVERAGE STREAMFLOWS ARE NEAR NORMAL IN THE OHIO RIVER
BASIN WITH ISOLATED BELOW NORMAL STREAM FLOWS IN A FEW
WATERSHEDS.

SNOW COVER AND SNOW WATER EQUIVALENT...
A MINOR SNOWPACK (1-3 INCHES OF LOW WATER EQUIVALENT SNOW) EXISTS
ACROSS THE LAKE EFFECT SNOWBELT IN NORTHEAST OHIO...NORTHWEST
PENNSYLVANIA...AND SOUTHWEST NEW YORK STATE.

HYDROLOGIC OUTLOOK...
ATMOSPHERIC CIRCULATION WILL REMAIN LOCKED IN AN EL NINO PATTERN
DURING EARLY WINTER. FOR THE OHIO VALLEY...THE STORM TRACK WILL
BE PREDOMINANTLY ACROSS THE DEEP SOUTH...THEN CURVE UP THE
EASTERN SEABOARD OR OUT INTO THE WESTERN NORTH ATLANTIC BASIN.
WITHOUT PHASING OF THE POLAR AND SUBTROPICAL JET
STREAMS...SIGNIFICANT STORM EVENTS WILL NOT DEVELOP OR AFFECT THE
OHIO VALLEY.

HYDROLOGICALLY...
THE OUTLOOK FOR STREAMFLOWS WILL AVERAGE NEAR NORMAL WITH
OCCASIONAL ISOLATED MINOR FLOODING POSSIBLE IN THE OHIO RIVER
BASIN. MOST LIKELY CAUSE OF FLOODING WILL BE ICE JAMS.

SUMMARY...
ATMOSPHERIC CIRCULATION WILL REMAIN LOCKED IN AN EL NINO PATTERN
DURING EARLY TO MID WINTER. FOR THE OHIO VALLEY THE STORM TRACK
WILL BE PREDOMINANTLY ACROSS THE DEEP SOUTH...THEN CURVE UP THE
EASTERN SEABOARD OR OUT INTO THE WESTERN NORTH ATLANTIC BASIN.
WITHOUT PHASING OF THE POLAR AND SUBTROPICAL JET STREAMS...
SIGNIFICANT STORM EVENTS WILL NOT DEVELOP OR AFFECT THE OHIO
VALLEY.

THE NEXT WINTER/SPRING FLOOD POTENTIAL OUTLOOK WILL BE ISSUED BY
FEBRUARY 5 2015.



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