Note that if drought conditions are not being experienced, or in the case of river flooding or heavy rain, this statement may be used to indicate river flows or flood potential.
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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1238 PM EDT FRI MAR 5 2010
...WINTER/SPRING FLOOD POTENTIAL OUTLOOK 5...
INTRODUCTION.
DURING THE WINTER AND SPRING...THE NATIONAL WEATHER SERVICE ISSUES A
SERIES OF WINTER AND SPRING FLOOD POTENTIAL OUTLOOKS. THESE OUTLOOKS
ESTIMATE THE POTENTIAL FOR RIVER FLOODING (NOT FLASH FLOODING) ACROSS
CENTRAL PENNSYLVANIA BASED ON A CURRENT ASSESSMENT OF
HYDROMETEOROLOGICAL FACTORS WHICH CONTRIBUTE TO RIVER FLOODING.
ACROSS CENTRAL PENNSYLVANIA THESE FACTORS INCLUDE RECENT
PRECIPITATION...SOIL MOISTURE...SNOW COVER AND SNOW WATER
EQUIVALENT...RIVER ICE...STREAMFLOW...FUTURE WEATHER CONDITIONS AND
OTHERS. THIS OUTLOOK DOES NOT ADDRESS THE SEVERITY OR EXTENT OF ANY
FUTURE RIVER FLOODING.
IT SHOULD BE STRESSED THAT THIS OUTLOOK APPLIES ONLY TO THE
HYDROLOGIC FORECAST AREA COVERED BY THE NATIONAL WEATHER SERVICE
OFFICE IN STATE COLLEGE PA...AND INCLUDES:
* THE ENTIRE WEST BRANCH SUSQUEHANNA BASIN.
* THE ENTIRE JUNIATA RIVER BASIN.
* THE MAIN STEM SUSQUEHANNA RIVER FROM BLOOMSBURG THROUGH MARIETTA.
PORTIONS OF THE UPPER ALLEGHENY BASIN INCLUDING ELDRED...RUSSELL AND
WARREN.
* PORTIONS OF THE LOWER ALLEGHENY BASIN INCLUDING THE UPPER REACHES
OF THE CLARION RIVER...AND UPPER PORTIONS OF CONEMAUGH BASIN. ALSO
INCLUDED ARE THE FAR HEADWATERS OF THE MONONGAHELA BASIN INCLUDING
CONFLUENCE.
THIS OUTLOOK IS VALID FRIDAY MARCH 5TH THROUGH FRIDAY MARCH 19TH
2010.
IN CENTRAL PENNSYLVANIA...HEAVY RAINFALL IS THE PRIMARY FACTOR WHICH
LEADS TO RIVER FLOODING. IT IS IMPORTANT TO NOTE THAT HEAVY RAINFALL
CAN RAPIDLY CAUSE RIVER FLOODING ANY TIME OF THE YEAR...EVEN WHEN
OVERALL RIVER FLOOD POTENTIAL IS CONSIDERED LOW OR BELOW AVERAGE.
DETAILED DISCUSSION.
CURRENT RIVER FLOOD POTENTIAL...THE CURRENT POTENTIAL FOR RIVER
FLOODING IS CONSIDERED ABOVE AVERAGE FOR MUCH OF CENTRAL
PENNSYLVANIA.
CURRENT FLOODING...NONE.
RECENT PRECIPITATION...VARIABLE: ABOVE AVERAGE TO BELOW AVERAGE.
PRECIPITATION...ALL IN THE FORM OF SNOW...OVER THE STATE COLLEGE
HYDROLOGIC SERVICE AREA (HSA) DURING THE LAST 30 DAYS HAS GENERALLY
RANGED FROM SOMEWHAT ABOVE NORMAL ACROSS THE SOUTHERN TIER INCLUDING
THE JUNIATA AND LOWER SUSQUEHANNA BASINS...TO BELOW AVERAGE IN THE
NORTH INCLUDING THE WEST BRANCH AND MIDDLE SUSQUEHANNA BASINS.
PRECIPITATION SURPLUSES IN THE SOUTH WERE GENERALLY LESS THAN ONE
HALF INCH...WHILE PRECIPITATION DEFICITS IN CENTRAL AND NORTHERN
AREAS WERE BETWEEN ONE TO AS MUCH AS TWO INCHES BELOW NORMAL. MAPS
OF RECENT PRECIPITATION CAN BE FOUND ON THE WEB AT WEATHER.GOV/MARFC
AND CLICKING ON THE OBSERVED PRECIPITATION LINK.
SNOW CONDITIONS...AVERAGE TO MUCH ABOVE AVERAGE.
SNOW COVER IS BECOMING SPOTTY ACROSS MOST OF THE JUNIATA...WEST
BRANCH AND LOWER MAIN STEM SUSQUEHANNA BASINS. WHERE SNOW IS
FOUND...SNOW DEPTHS GENERALLY ARE 6 INCHES OR LESS. HOWEVER...ACROSS
THE HEADWATER PORTIONS OF THE JUNIATA AND WEST BRANCH...SOME
LOCATIONS ARE REPORTING BETWEEN 6 AND 24 INCHES. THESE VALUES ARE
WELL ABOVE AVERAGE FOR THIS TIME OF YEAR. HOWEVER...OF GREATEST
NOTE...WAS SNOW OVER THE LAUREL HIGHLANDS...THE HEADWATERS OF THE
MONONGAHELA AND LOWER ALLEGHENY BASINS. IN THESE AREAS...SNOW DEPTHS
OF MORE THAN 40 INCHES ARE PRESENT...WELL ABOVE NORMAL.
MUCH OF THE REGION HAS WATER EQUIVALENTS OF BETWEEN 1 AND 2
INCHES...WITH HIGHER ELEVATIONS BETWEEN 2 AND 4 INCHES. OVER CAMBRIA
AND SOMERSET COUNTIES...HOWEVER...WATER EQUIVALENTS ARE BETWEEN 4
AND 8 INCHES...WITH ISOLATED RIDGE LOCATIONS REPORTING NEARLY 10
INCHES. SNOW DATA AND INFORMATION SOURCES INCLUDE THE NOAA/NWS
OPERATIONAL HYDROLOGIC REMOTE SENSING CENTER
(WWW.NOHRSC.NOAA.GOV)...THE U.S. ARMY CORPS OF ENGINEERS...NWS
COOPERATIVE OBSERVERS...THE COMMUNITY RAIN, HAIL AND SNOW NETWORK
(COCORAHS) AND OTHERS. SNOW DEPTH AND BASIN AVERAGE WATER EQUIVALENT
ESTIMATES CAN BE SEEN AT WWW.ERH.NOAA.GOV/ER/MARFC AND
WWW.NOHRSC.NOAA.GOV.
RIVER ICE...AVERAGE.
NO HYDROLOGICALLY SIGNIFICANT ICE CURRENTLY EXISTS ACROSS
CENTRAL PENNSYLVANIA RIVERS AND STREAMS. THIS IS ABOUT NORMAL FOR
THIS TIME OF YEAR. ADDITIONAL ICE FORMATION IS NO LONGER EXPECTED
THIS SEASON.
STREAMFLOW CONDITIONS...VARIABLE: ABOVE TO BELOW AVERAGE.
STREAM FLOWS ARE RUNNING ABOVE TO MUCH ABOVE AVERAGE ACROSS MUCH OF
THE JUNIATA AND LOWER SUSQUEHANNA BASINS. OVER THE WEST BRANCH AND
MIDDLE SUSQUEHANNA BASINS...STREAMFLOWS ARE BELOW AVERAGE. OVER THE
UPPER AND LOWER HEADWATERS OF THE ALLEGHENY BASIN...STREAM FLOWS ARE
ALSO FOR THE MOST PART RUNNING BELOW AVERAGE. THESE STREAMFLOWS ARE
CLOSELY RELATED TO THE AMOUNT OF SNOW MELT EXPERIENCED ACROSS THE
AREA. AS TEMPERATURES CONTINUE TO WARM THIS WEEKEND AND INTO NEXT
WEEK...EXPECT STREAMFLOWS TO RISE. REAL TIME WATER DATA IS AVAILABLE
FROM THE UNITED STATES GEOLOGICAL SURVEY BY VISITING
HTTP://WATER.USGS.GOV ON THE INTERNET.
SOIL MOISTURE CONDITIONS...ABOVE AVERAGE TO MUCH ABOVE AVERAGE.
THE LATEST PALMER DROUGHT SEVERITY INDEX CHART IMPLIES THAT SOIL
MOISTURE CONDITIONS RANGED FROM UNUSUALLY MOIST TO EXTREMELY
MOIST...WITH THE WETTEST CONDITIONS ACROSS THE MIDDLE AND LOWER
SUSQUEHANNA BASINS. SOIL MOISTURE MONITORING CHARTS FROM NOAA`S
CLIMATE PREDICTION CENTER CAN BE FOUND AT
WWW.CPC.NCEP.NOAA.GOV/SOILMST/ AND WWW.DROUGHT.GOV.
GROUND WATER...AVERAGE TO ABOVE AVERAGE.
MONITORING WELLS INDICATE THAT CURRENT GROUND WATER LEVELS ARE
GENERALLY AVERAGE TO ABOVE AVERAGE OVER ALL OF CENTRAL PENNSYLVANIA.
CURRENT GROUND WATER CONDITIONS BASED ON A 30 DAY MOVING AVERAGE CAN
BE FOUND AT HTTP://PA.WATER.USGS.GOV/MONITOR/GW/INDEX.HTML
RESERVOIR CONDITIONS...AVERAGE TO ABOVE AVERAGE.
MOST WATER SUPPLY RESERVOIRS WITHIN CENTRAL PENNSYLVANIA ARE HOLDING
AVERAGE TO ABOVE AVERAGE STORAGES FOR THIS TIME OF YEAR...AS ARE
MOST FLOOD CONTROL RESERVOIRS.
FUTURE WEATHER CONDITIONS.
THE WEATHER DURING THE NEXT SEVERAL DAYS IS EXPECTED TO FEATURE
RELATIVELY MILD TEMPERATURES AND GENERALLY NO PRECIPITATION ACROSS
THE AREA. THE FAIRLY BENIGN WEATHER PATTERN SHOULD CONTINUE UNTIL
NEARLY MID WEEK NEXT WEEK...WHICH WILL ALLOW A GRADUAL YET
SIGNIFICANT DECREASE IN SNOW CONDITIONS ACROSS ALL AREAS...WHICH IS
FAVORABLE. A WETTER PATTERN MAY DEVELOP AFTER MID WEEK NEXT WEEK.
IT MUST BE REMEMBERED THAT BEYOND MID WEEK NEXT WEEK...WEATHER
PATTERNS ARE LESS PREDICTABLE.
THE 6 TO 10 DAY OUTLOOK FOR THE PERIOD MARCH 10 THROUGH MARCH 14 IS
FOR NORMAL TO ABOVE NORMAL TEMPERATURES AND NEAR NORMAL
PRECIPITATION. THE 8 TO 14 DAY OUTLOOK FROM MARCH 12 THROUGH MARCH
18 IS FOR NEAR NORMAL TEMPERATURES AND PRECIPITATION.
AHPS...VARIABLE: BELOW AVERAGE TO ABOVE AVERAGE.
ANOTHER TOOL USED TO ASSESS THE POTENTIAL FOR RIVER FLOODING IS THE
ADVANCED HYDROLOGIC PREDICTION SERVICE...AHPS. AHPS GENERATES
PROBABILISTIC RIVER FORECASTS BASED ON CURRENT BASIN CONDITIONS...
INCLUDING RIVER LEVELS...SOIL MOISTURE...EXTENT AND CONDITION OF ANY
SNOWPACK...ALONG WITH 50 YEARS OF HISTORIC TEMPERATURE AND
PRECIPITATION DATA. FOR THIS OUTLOOK PERIOD...AHPS INDICATES
THAT...IN GENERAL...THE LIKELIHOOD OF RIVER FLOODING IS SOMEWHAT
BELOW NORMAL COMPARED TO WHAT HAS BEEN HISTORICALLY OBSERVED DURING
THIS SAME TIME PERIOD ACROSS NORTHERN AND CENTRAL PORTIONS OF
CENTRAL PENNSYLVANIA...AND NEAR NORMAL ACROSS THE SOUTH. HOWEVER...
IT MUST BE EMPHASIZED THAT AHPS PROBABILISTIC FORECASTS DO NOT TAKE
INTO ACCOUNT FUTURE WEATHER CONDITIONS. WHETHER OR NOT RIVER
FLOODING ACTUALLY MATERIALIZES DURING THE NEXT TWO WEEKS WILL TRULY
DEPEND ON THE EXACT NATURE OF FUTURE WEATHER CONDITIONS, NOT
NECESSARILY ON WHAT HAS/HAS NOT OCCURRED IN THE PAST. RIVER
INFORMATION CAN BE FOUND WEATHER.GOV/AHPS
SUMMARY OF FLOOD POTENTIAL MARCH 5 - MARCH 19 2010:
MANY INDICATORS USED FOR DETERMINING FLOOD POTENTIAL OVER CENTRAL
PENNSYLVANIA RANGE FROM NEAR NORMAL ACROSS THE NORTHERN AND CENTRAL
PORTIONS OF THE REGION...TO ABOVE AVERAGE IN THE SOUTH FOR THIS TIME
OF YEAR. MOST SIGNIFICANTLY... SOME VERY HIGH SNOW DEPTHS AND SNOW
WATER EQUIVALENTS EXIST ACROSS THE SOUTHERN TIER OF CENTRAL
PENNSYLVANIA. EVEN WITH THESE ELEVATED SNOW AND SNOW-WATER
EQUIVALENT VALUES...A MODERATE TO HEAVY RAIN EVENT COUPLED WITH WARM
TEMPERATURES WOULD BE REQUIRED FOR SIGNIFICANT FLOODING.
THE OVERALL FLOOD OUTLOOK IS CONSIDERED ABOVE AVERAGE ACROSS MUCH OF
CENTRAL PENNSYLVANIA...ESPECIALLY IN THE SOUTHWEST WHERE THE SNOW
PACK IS GREATEST.
OVERVIEW:
CURRENT FLOODING...NONE.
RECENT PRECIPITATION...VARIABLE: ABOVE AVERAGE TO BELOW AVERAGE.
SNOW CONDITIONS...AVERAGE TO MUCH ABOVE AVERAGE.
RIVER ICE...AVERAGE.
STREAMFLOW CONDITIONS...AVERAGE TO BELOW AVERAGE.
SOIL MOISTURE CONDITIONS...ABOVE AVERAGE TO WELL ABOVE AVERAGE.
GROUND WATER...AVERAGE TO ABOVE AVERAGE.
RESERVOIR CONDITIONS...AVERAGE TO ABOVE AVERAGE.
AHPS...VARIABLE: BELOW AVERAGE TO ABOVE AVERAGE.
OVERALL FLOOD POTENTIAL...ABOVE AVERAGE.
THE NEXT REGULARLY SCHEDULED WINTER/SPRING FLOOD POTENTIAL OUTLOOK
OF THE SEASON WILL BE ISSUED ON MARCH 19TH. OTHER
HYDROMETEOROLOGICAL INFORMATION CAN BE FOUND BY VISITING THE STATE
COLLEGE INTERNET HOMEPAGE AT WEATHER.GOV/STATECOLLEGE.
$$
JUNG
