FGUS61 KRHA 071936 ESGRHA FLOOD POTENTIAL STATEMENT MIDDLE ATLANTIC RIVER FORECAST CENTER NATIONAL WEATHER SERVICE STATE COLLEGE PA 236 PM EST THU FEB 07 2008 WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK MIDDLE ATLANTIC RIVER FORECAST CENTER OUTLOOK NUMBER 08-3 FEBRUARY 7, 2008 INTRODUCTION - THE MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC) IS ONE OF 13 NATIONAL WEATHER SERVICE (NWS) RIVER FORECAST CENTERS LOCATED ACROSS THE CONTINENTAL UNITED STATES. MAJOR RIVER BASINS LOCATED WITHIN THE MARFC AREA OF RESPONSIBILITY INCLUDE THE SUSQUEHANNA, DELAWARE, RARITAN, PASSAIC, POTOMAC, SHENANDOAH, RAPPAHANNOCK, JAMES AND APPOMATTOX. STATES LOCATED WITHIN THE MARFC AREA OF RESPONSIBILITY INCLUDE ALL/PORTIONS OF NEW YORK, PENNSYLVANIA, NEW JERSEY, WEST VIRGINIA, MARYLAND, DELAWARE AND VIRGINIA. THE FOLLOWING OUTLOOK ESTIMATES THE POTENTIAL FOR RIVER FLOODING (NOT FLASH FLOODING) ACROSS THE MARFC AREA OF RESPONSIBILITY (MID-ATLANTIC REGION) BASED ON A CURRENT ASSESSMENT OF HYDROMETEOROLOGICAL FACTORS WHICH CONTRIBUTE TO RIVER FLOODING. ACROSS THE MARFC AREA, 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/EXTENT OF ANY FUTURE RIVER FLOODING. THIS OUTLOOK IS VALID FOR THE TWO WEEK PERIOD FEBRUARY 7-21, 2008, AND INCLUDES THE LATEST NWS EXTENDED-RANGE (6-10 DAY AND 8-14 DAY) WEATHER FORECASTS. FOR THE MARFC SERVICE AREA, THESE FORECASTS SUGGEST THAT BOTH TEMPERATURES AND PRECIPITATION AVERAGED OVER THE NINE-DAY PERIOD FROM FEBRUARY 12-20, 2008 WILL MOST LIKELY BE NORMAL TO ABOVE NORMAL. PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV/ TO VIEW MEDIUM AND LONG-RANGE WEATHER OUTLOOKS. AS RECENTLY SHOWN, IN THE MID-ATLANTIC REGION HEAVY RAINFALL IS THE PRIMARY FACTOR WHICH LEADS TO RIVER FLOODING. HEAVY RAINFALL CAN RAPIDLY CAUSE RIVER FLOODING ANY TIME OF THE YEAR, EVEN WHEN OVERALL RIVER FLOOD POTENTIAL IS CONSIDERED TO BE LOW OR BELOW AVERAGE. CURRENT RIVER FLOOD POTENTIAL - SOMEWHAT ABOVE AVERAGE TO THE NORTH, SOMEWHAT BELOW AVERAGE TO THE SOUTH. CURRENT FLOODING - SOME MINOR FLOODING WILL CONTINUE IN THE SUSQUEHANNA BASIN IN NEW YORK AND PENNSYLVANIA FOR ANOTHER DAY OR SO. RECENT PRECIPITATION - VARIABLE. DURING THE LAST 30 DAYS (01/08/08-02/06/08) PRECIPITATION WAS NORMAL TO BELOW NORMAL ACROSS VA, ABOUT NORMAL ACROSS MD, THE DELMARVA PENINSULA, SOUTHEASTERN PA AND NJ, AND ABOVE NORMAL TO MUCH ABOVE NORMAL ACROSS THE REST OF PA AND NY. IN GENERAL, MOST LOCATIONS RECEIVED 2-5 INCHES OF PRECIPITATION DURING THE LAST 30-DAYS. THE JAMES BASIN IN CENTRAL VA RECEIVED THE LEAST AMOUNT OF PRECIPITATION (2-3 INCHES) COMPARED TO NORMAL, WHILE THE SUSQUEHANNA AND UPPER DELAWARE BASINS RECEIVED THE MOST (3-5 INCHES). VISIT WWW.ERH.NOAA.GOV/ER/MARFC TO VIEW PRECIPITATION DEPARTURE MAPS. SNOW CONDITIONS - MUCH BELOW AVERAGE TO ABOUT AVERAGE. ACROSS THE ENTIRE MARFC SERVICE AREA, SNOW COVER REMAINS MINIMAL AND IS PRESENTLY HYDROLOGICALLY INSIGNIFICANT. MUCH OF THE SERVICE AREA HAS NO SNOW ON THE GROUND. WHERE SNOW DOES EXIST, IT IS PATCHY AND IS NO MORE THAN A FEW INCHES IN DEPTH, WITH WATER EQUIVALENT VALUES OF GENERALLY LESS THAN A HALF INCH. FOR NORTHERN AND WESTERN PORTIONS OF THE MARFC SERVICE AREA, CURRENT SNOW CONDITIONS ARE MUCH BELOW AVERAGE FOR THIS TIME OF YEAR. FOR SOUTHERN AND EASTERN AREAS, SNOW CONDITIONS ARE CLOSER TO AVERAGE SINCE THESE AREAS DO NOT TYPICALLY RECEIVE OR KEEP AS MUCH SNOW ANYWAY. SNOW DATA AND INFORMATION SOURCES INCLUDE THE NOAA/NWS NATIONAL OPERATIONAL HYDROLOGIC REMOTE SENSING CENTER (WWW.NOHRSC.NOAA.GOV), THE U.S. ARMY CORPS OF ENGINEERS, NWS COOPERATIVE OBSERVERS, THE COMMUNITY COLLABORATIVE RAIN, HAIL AND SNOW NETWORK (COCORAHS), THE NEW YORK CITY DEPT. OF ENVIRONMENTAL PROTECTION, AND OTHERS. BASIN-AVERAGE WATER EQUIVALENT ESTIMATES CAN BE SEEN AT WWW.ERH.NOAA.GOV/ER/MARFC. RIVER ICE - MUCH BELOW AVERAGE TO AVERAGE. ONCE AGAIN, MILDER TEMPERATURES AND RAINFALL HAVE VIRTUALLY ELIMINATED MOST, IF NOT ALL OF THE RIVER ICE WITHIN THE MARFC SERVICE AREA. ICE CONDITIONS ARE AGAIN CONSIDERED MUCH BELOW AVERAGE FOR THIS TIME OF YEAR FOR NORTHERN AND WESTERN AREAS. FOR SOUTHERN AND EASTERN AREAS, RIVER ICE CONDITIONS ARE CLOSER TO NORMAL FOR THIS TIME OF YEAR SINCE THESE RIVERS DO NOT TYPICALLY DEVELOP OR KEEP AS MUCH ICE ANYWAY. STREAMFLOW CONDITIONS - VARIABLE. COMPARED TO MEDIAN FOR THIS TIME OF YEAR, STREAMFLOW IS HIGHEST ACROSS NY AND MOST OF PA WHERE IT IS CURRENTLY AT OR NEAR RECORD HIGH LEVELS FOR THE DATE. HEADING SOUTH, STREAMFLOW DROPS OFF TO NEAR MEDIAN ACROSS MUCH OF NJ, SOUTHEASTERN PA, AND THE APPALACHIAN REGION. STREAMFLOW REMAINS BELOW TO MUCH BELOW MEDIAN ACROSS MUCH OF THE DELMARVA REGION AND VA. REAL-TIME WATER DATA CAN BE FOUND BY VISITING THE U.S. GEOLOGICAL SURVEY (USGS) WEB PAGES AT HTTP://WATER.USGS.GOV/. SOIL MOISTURE CONDITIONS - VARIABLE. THE FEBRUARY 2, 2008, PALMER DROUGHT SEVERITY INDEX CHART (FOUND BY NAVIGATING THE WEBSITE: WWW.CPC.NOAA.GOV/PRODUCTS) CONTINUES TO INDICATE WET TO EXTREMELY WET SOIL MOISTURE CONDITIONS ACROSS NY, MUCH OF PA AND NORTHERN NJ. ELSEWHERE WITHIN THE MARFC SERVICE AREA THE CHART INDICATES NEAR AVERAGE SOIL MOISTURE CONDITIONS FOR THIS TIME OF YEAR, EXCEPT FOR A PORTION OF THE DELMARVA PENINSULA WHERE MODERATE DROUGHT CONDITIONS ARE INDICATED. ACTUAL PALMER INDEX VALUES, HOWEVER, AS WELL AS OTHER SOIL MOISTURE AND DROUGHT-RELATED DATA INDICATES PORTIONS OF VA, MD AND DE STILL HAVE BELOW AVERAGE SOIL MOISTURE CONDITIONS FOR THIS TIME OF YEAR. SOIL MOISTURE AND DROUGHT RELATED DATA AND CHARTS CAN BE SEEN AT WWW.CPC.NCEP.NOAA.GOV/SOILMST/ AND WWW.DROUGHT.GOV. GROUND WATER - VARIABLE. SIMILAR TO OTHER CONDITIONS, CURRENT GROUND WATER LEVELS ARE GENERALLY ABOVE NORMAL ACROSS THE NORTH, NEAR NORMAL ACROSS THE CENTRAL REGION, AND BELOW NORMAL ACROSS THE SOUTH. RESERVOIR CONDITIONS - ABOVE AVERAGE TO BELOW AVERAGE. MOST LARGE WATER SUPPLY AND FLOOD CONTROL RESERVOIRS ARE HOLDING NEAR AVERAGE STORAGES FOR THIS TIME OF YEAR, ALTHOUGH RESERVOIR CONDITIONS ARE GENERALLY SOMEWHAT ABOVE AVERAGE ACROSS THE FAR NORTH, AND BELOW AVERAGE ACROSS PORTIONS OF VA. FUTURE WEATHER CONDITIONS - CHANGEABLE WEATHER CONDITIONS MORE TYPICAL OF LATER IN WINTER APPEAR LIKELY DURING THE NEXT WEEK OR SO ACROSS THE MARFC SERVICE AREA. INITIALLY FAIRLY SEASONABLE TEMPERATURES WITH GENERALLY LIGHT PRECIPITATION IS EXPECTED. ON SUNDAY, A STRONG COLD FRONT WILL CROSS THE SERVICE AREA ALSO ACCOMPANIED BY GENERALLY LIGHT PRECIPITATION. VERY COLD TEMPERATURES MONDAY WILL QUICKLY MODERATE BACK TO NEAR SEASONABLE LATER TUESDAY. MIDWEEK NEXT WEEK WILL SEE MILDER THAN NORMAL TEMPERATURES ALONG WITH A CHANCE OF MODERATE TO HEAVY PRECIPITATION. SEASONABLE TEMPERATURES AND DRIER WEATHER WILL FOLLOW THE MIDWEEK STORM SYSTEM FOR A COUPLE OF DAYS. IN SUMMARY, QUITE CHANGEABLE WEATHER IS ANTICIPATED DURING THE NEXT WEEK OR SO WITH A CHANCE OF SIGNIFICANT PRECIPITATION AROUND MIDWEEK NEXT WEEK. REPEATING THE EXTENDED RANGE WEATHER OUTLOOK FOR THE NINE DAY PERIOD FEBRUARY 12-20: NORMAL TO ABOVE NORMAL TEMPERATURES AND PRECIPITATION. AHPS FLOOD FORECASTS - VARIABLE. THE ADVANCED HYDROLOGIC PREDICTION SERVICE (AHPS) GENERATES PROBABILISTIC RIVER FORECASTS BASED ON CURRENT BASIN CONDITIONS (RIVER LEVELS, SOIL MOISTURE, EXTENT AND CONDITION OF ANY SNOWPACK ALONG WITH 50 YEARS OF HISTORIC TEMPERATURE AND PRECIPITATION DATA. FOR THE NEXT TWO WEEKS AHPS INDICATES THAT THE LIKELIHOOD OF RIVER FLOODING IS HIGHEST ACROSS PORTIONS OF THE UPPER SUSQUEHANNA BASIN, MAINLY BECAUSE FLOODING IS CURRENTLY ALREADY OCCURRING THERE. ONCE THIS FLOODING ENDS IN A COUPLE OF DAYS, AHPS SUGGESTS A SOMEWHAT ELEVATED RISK OF FLOODING, COMPARED TO HISTORY, WILL CONTINUE FOR THE REMAINDER OF THE NEXT TWO WEEKS. ELSEWHERE, AHPS INDICATES THE CHANCE OF RIVER FLOODING DURING THE NEXT TWO WEEKS IS NEAR OR SLIGHTLY LESS THAN WHAT HAS BEEN HISTORICALLY OBSERVED. IT SHOULD BE NOTED THAT, ACCORDING TO HISTORY, RIVER FLOODING DURING THIS NEXT TWO-WEEK PERIOD IS STILL NOT VERY LIKELY TO OCCUR TO BEGIN WITH. BUT AS THE LAST FEW DAYS HAVE SHOWN, HEAVY RAINFALL CAN RESULT IN FLOODING ANYWHERE WITHIN THE MARFC REGION, EVEN WHEN OVERALL RIVER FLOOD POTENTIAL IS CONSIDERED TO BE LOW OR BELOW AVERAGE. HISTORY DOES SHOW THAT THE CHANCES OF RIVER FLOODING WITHIN THE MARFC SERVICE AREA DO INCREASE IN LATE FEBRUARY AND THROUGHOUT MARCH. PLEASE VISIT WWW.WEATHER.GOV/AHPS/ FOR DETAILED AHPS INFORMATION. SUMMARY - RIVER FLOODING IS PRESENTLY OCCURRING IN PORTIONS OF THE SUSQUEHANNA BASIN DUE TO THE RECENT HEAVY RAIN. ONCE THIS FLOODING ENDS, THE RIVER FLOOD POTENTIAL FOR THE REMAINDER OF THE NEXT TWO WEEKS WILL REMAIN SOMEWHAT ABOVE NORMAL FOR THIS REGION DUE TO HIGH STREAMFLOW AND WET SOILS. BUT WITH LITTLE SNOW AND NO RIVER ICE, THE RIVER POTENTIAL IS NOT SIGNIFICANTLY HIGHER THAN NORMAL FOR MID FEBRUARY. MORE HEAVY RAIN WOULD STILL BE REQUIRED FOR ADDITIONAL WIDESPREAD RIVER FLOODING TO DEVELOP. ELSEWHERE, THE RIVER FLOOD POTENTIAL DURING THE NEXT TWO WEEKS IS NEAR NORMAL TO BELOW NORMAL. THE NEXT CHANCE FOR ANY HEAVY PRECIPITATION APPEARS TO BE AROUND MIDWEEK OF NEXT WEEK. LONGER-RANGE WEATHER OUTLOOKS SUGGEST THAT THE WEATHER CONDITIONS DURING THE PERIOD FEBRUARY 12-20 COULD BE WETTER THAN NORMAL FOR MUCH OF THE MARFC REGION. WATER SUPPLY OUTLOOK - MILD-SEVERE DROUGHT CONDITIONS LINGER ACROSS MUCH OF VA, MD AND THE DELMARVA REGION. AS SUCH, WATER SUPPLY SHORTAGES REMAIN POSSIBLE FOR THE SOUTHERN THIRD OF THE MARFC REGION DURING THE NEXT FEW MONTHS UNLESS PRECIPITATION AVERAGES ABOVE NORMAL. THE LATEST SEASONAL DROUGHT OUTLOOK (WWW.DROUGHT.GOV) RELEASED ON FEBRUARY 7, 2008, DOES SUGGEST CONTINUED SLOW IMPROVEMENT ACROSS THE DROUGHT AREA DURING THE NEXT TWO-THREE MONTHS. ELSEWHERE, ASSUMING NEAR NORMAL PRECIPITATION OCCURS, NO WATER SUPPLY SHORTAGES ARE ANTICIPATED ANYWHERE WITHIN THE MARFC REGION DURING THE NEXT FIVE MONTHS. THE NWS LONG-RANGE WEATHER OUTLOOK FOR THE MONTH OF FEBRUARY SUGGESTS ABOVE NORMAL TEMPERATURES AND NORMAL TO ABOVE NORMAL PRECIPITATION FOR THE MARFC SERVICE AREA. PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.ERH.NOAA.GOV/ER/MARFC FOR OTHER HYDROMETEOROLOGICAL INFORMATION. THE NEXT OUTLOOK WILL BE ISSUED BY MARFC IN TWO WEEKS ON FEBRUARY 21, 2008. SK $$ ....END MARFC.... NNNN