FGUS61 KRHA 081827 ESGRHA FLOOD POTENTIAL STATEMENT MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC) NATIONAL WEATHER SERVICE STATE COLLEGE PA 126 PM EST THU MAR 08 2012 WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK NWS MIDDLE ATLANTIC RIVER FORECAST CENTER OUTLOOK NUMBER 12-06 - MARCH 8, 2012 THIS OUTLOOK IS VALID FOR THE ONE-WEEK PERIOD MARCH 8-15, 2012. THIS OUTLOOK ESTIMATES THE POTENTIAL FOR RIVER FLOODING (NOT FLASH FLOODING) TO DEVELOP 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 INCLUDES THE LATEST NWS EXTENDED-RANGE (6-10 DAY) WEATHER FORECASTS DISCUSSED BELOW IN THE FUTURE WEATHER CONDITIONS SECTION. THIS OUTLOOK DOES NOT ADDRESS THE SEVERITY/EXTENT OF ANY FUTURE RIVER FLOODING. REMEMBER, 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. ONE-WEEK RIVER FLOOD POTENTIAL OUTLOOK - AVERAGE TO BELOW AVERAGE. THE RIVER FLOOD POTENTIAL ACROS THE MARFC SERVICE AREA FOR THE NEXT WEEK (THROUGH MARCH 15, 2012) IS CONSIDERED TO BE NORMAL TO BELOW NORMAL. FACTORS WHICH CONTRIBUTE TO RIVER FLOOD POTENTIAL ARE ADDRESSED INDIVIDUALLY BELOW. CURRENT FLOODING - NONE. RECENT PRECIPITATION - VARIABLE. PRECIPITATION WITHIN THE MARFC SERVICE AREA DURING THE LAST 30 DAYS (FEBRUARY 7-MARCH 7, 2012) WAS GENERALLY BELOW AVERAGE (25-80 PERCENT OF NORMAL) ACROSS THE NORTHEASTERN PORTION OF THE REGION, INCLUDING NORTHEASTERN MD, THE EASTERN HALF OF PA, NY AND NJ. ELSEWHERE, PRECIPITATION WAS FAIRLY CLOSE TO AVERAGE (70-130 PERCENT OF NORMAL). PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC FOR PRECIPITATION INFORMATION. SNOW CONDITIONS - MUCH BELOW AVERAGE TO NEAR AVERAGE. CURRENTLY THERE IS NO HYDROLOGICALLY SIGNIFICANT SNOW ON THE GROUND WITHIN THE MARFC SERVICE AREA. VERY LIMITED SNOW EXISTS ACROSS EXTREME NORTHEASTERN PA INTO THE CATSKILL REGION OF NY, AND ACROSS PORTIONS OF THE NORTH BRANCH SUSQUEHANNA BASIN. HERE NO MORE THAN A FEW INCHES OF SNOW IS ON THE GROUND WITH WATER EQUIVALENT VALUES OF MOSTLY UNDER AN INCH. HERE AND ACROSS MOST OF PA, NY AND NORTHERN NJ, SNOW CONDITIONS ARE CONSIDERED BELOW AVERAGE TO MUCH BELOW AVERAGE. ELSEWHERE, THE LACK OF SNOW IS NOT AS UNUSUAL AND THEREFORE SNOW CONDITIONS ARE NEAR AVERAGE. THE LIGHT-MODERATE SNOW THAT ACCUMULATED ACROSS THE SOUTH EARLIER THIS WEEK HAS MELTED. PLEASE VISIT WWW.NOHRSC.NOAA.GOV AND WWW.ERH.NOAA.GOV/ER/MARFC FOR SPECIFICS ON SNOW CONDITIONS. RIVER ICE - MUCH BELOW AVERAGE TO NEAR AVERAGE. NO HYDROLOGICALLY SIGNIFICANT RIVER ICE EXISTS WITHIN THE MARFC SERVICE AREA. THESE CONDITIONS ARE MUCH BELOW AVERAGE ACROSS THE NORTHWESTERN HALF OF THE REGION, BUT CLOSER TO AVERAGE ACROSS THE FAR SOUTH AND EAST WHERE THERE IS OFTEN LITTLE OR NO RIVER ICE DURING MANY WINTERS. STREAMFLOW CONDITIONS - BELOW MEDIAN TO MEDIAN. ACCORDING TO THE U.S. GEOLOGICAL SURVEY (USGS) STREAMFLOW FOR RIVERS WITHIN THE MARFC REGION CURRENTLY RANGES FROM BELOW MEDIAN TO MEDIAN. STREAMFLOW IN RIVERS IN EASTERN PA AND NORTHERN NJ IS LOWEST WITH RESPECT TO MEDIAN (15-75 PERCENT OF MEDIAN), WHILE THE JAMES RIVER BASIN IN VA HAS THE HIGHEST STREAMFLOW WITH RESPECT TO MEDIAN AT THE PRESENT TIME (75-175 PERCENT OF MEDIAN). REAL-TIME WATER DATA CAN BE FOUND BY VISITING THE USGS WEB PAGES AT HTTP://WATER.USGS.GOV/. SOIL MOISTURE CONDITIONS - NORMAL TO MUCH ABOVE NORMAL. THE LONG-TERM PALMER DROUGHT SEVERITY INDEX IS WIDELY USED TO INFER DEEP SOIL MOISTURE CONDITIONS. THE MARCH 3, 2012 INDEX CHART (WWW.CPC.NOAA.GOV/PRODUCTS WEBSITE) INDICATES VERY MOIST TO EXTREMELY MOIST SOILS ACROSS THE NORTH, WITH NEAR NORMAL TO VERY MOIST SOILS ACROSS THE SOUTH. FOR ADDITIONAL SOIL MOISTURE INFORMATION PLEASE SEE WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING. GROUND WATER - GENERALLY AROUND NORMAL. MOST USGS GROUND WATER MONITORING WELLS WITHIN THE MARFC REGION ARE INDICATING NEAR NORMAL LEVELS. HOWEVER, SOME MONITORING WELLS ACROSS PORTIONS OF THE CHESAPEAKE BAY REGION AND SOUTHEASTERN VA CONTINUE TO SHOW BELOW NORMAL LEVELS. CURRENT GROUNDWATER LEVELS CAN BE SEEN AT HTTP://GROUNDWATERWATCH.USGS.GOV/. RESERVOIR CONDITIONS - AVERAGE TO ABOVE AVERAGE. IN GENERAL, MOST MAJOR RESERVOIRS WITHIN THE MARFC REGION ARE HOLDING NORMAL TO ABOVE-NORMAL STORAGES FOR THIS TIME OF YEAR. FUTURE WEATHER CONDITIONS - A COLD FRONT WILL CROSS THE MARFC REGION TODAY AND TONIGHT ACCOMPANIED BY MOSTLY LIGHT-MODERATE RAINFALL. A CHILLY DAY FRIDAY BEFORE TEMPERATURES QUICKLY MODERATE TO UNSEASONABLY MILD AGAIN FOR MOST OF NEXT WEEK. THE NEXT COLD FRONT ARRIVES AROUND THURSDAY, MARCH 8. CURRENTLY, THERE ARE NO INDICATIONS OF ANY WIDESPREAD HEAVY RAIN EVENTS FOR THE NEXT WEEK, THOUGH ISOLATED HEAVY RAIN COULD OCCUR WITH THE CURRENT COLD FRONTAL PASSAGE. THE LATEST (MARCH 7, 2012) NWS 6-10 DAY WEATHER FORECAST FOR THE MARFC REGION SUGGESTS TEMPERATURES WILL MOST LIKELY BE ABOVE NORMAL WHEN AVERAGED OVER THE FIVE-DAY PERIOD MARCH 13-17, 2012, WHILE PRECIPITATION WILL MOST LIKELY BE BELOW NORMAL FOR THE SAME PERIOD. PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV. AHPS RIVER FORECASTS - GENERALLY BELOW NORMAL TO NORMAL. 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. REMEMBER, AHPS RIVER FORECASTS DO NOT TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER CONDITIONS. FOR THE NEXT TWO WEEKS (MARCH 8-22, 2012) AHPS RIVER FORECASTS INDICATE THAT THE LIKELIHOOD OF RIVER FLOODING WITHIN THE MARFC SERVICE AREA IS GENERALLY BELOW AVERAGE ACROSS THE SUSQUEHANNA, DELAWARE, PASSAIC AND RARITAN BASINS. MEANWHILE, TO THE SOUTH THE AHPS-GENERATED FORECASTS SUGGEST A NEAR-NORMAL TO BELOW-NORMAL CHANCE OF FLOODING DURING THE NEXT TWO WEEKS ACROSS THE POTOMAC, JAMES AND APPOMATTOX RIVER BASINS. PLEASE VISIT WWW.WEATHER.GOV/AHPS/. EXPERIMENTAL ENSEMBLE RIVER FORECASTS - NO RIVER FLOOD THREAT DURING ABOUT THE NEXT WEEK ACROSS THE MARFC SERVICE AREA. A RELATIVELY NEW TOOL IS CURRENTLY BEING TESTED BY THE NWS TO AID IN ASSESSING LONGER TERM RIVER FLOOD POTENTIAL. THE PROCESS USES PRECIPITATION AND TEMPERATURE DATA DERIVED FROM NUMEROUS NUMERICAL WEATHER PREDICTION MODELS DIRECTLY AS INPUT INTO HYDROLOGIC MODELS TO GENERATE RIVER FORECASTS FOR UP TO ONE WEEK INTO THE FUTURE FOR LOCATIONS WITHIN THE MARFC SERVICE AREA. THE RIVER FORECASTS ARE AUTOMATICALLY GENERATED FROM COMPUTER MODELS WITHOUT THE ADDED EXPERTISE AND EXPERIENCE OF HUMAN FORECASTERS, AND SEVERAL ASSUMPTIONS ARE MADE IN THE GENERATION OF THE FORECASTS. SINCE EACH NEW RUN OF WEATHER PREDICTION MODELS CAN GENERATE DRASTICALLY DIFFERENT FORECASTS OF PRECIPITATION AND TEMPERATURES, THE RESULTANT RIVER FORECASTS MAY ALSO SHOW DRAMATIC RUN-TO-RUN VARIABILITY, AS WELL AS VERY WIDE RANGES OF POSSIBILITIES. THESE EXPERIMENTAL FORECASTS SHOULD BE USED WITH CAUTION AND TREATED AS ANOTHER TOOL TO TRY TO ASSESS RIVER FLOOD POTENTIAL FOR UP TO ONE WEEK INTO THE FUTURE. WITH THIS IN MIND, THE MOST RECENT RUNS (MARCH 7, 2012) OF THE EXPERIMENTAL ENSEMBLE RIVER FORECASTS INDICATE ESSENTIALLY NO THREAT OF RIVER FLOODING WITHIN THE MARFC SERVICE AREA DURING THE NEXT 7-8 DAYS (THROUGH MARCH 15, 2012). PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS TO VIEW THESE EXPERIMENTAL FORECASTS. SUMMARY - THE RIVER FLOOD POTENTIAL DURING THE NEXT WEEK THROUGH MARCH 15, 2012 IS CONSIDERED NORMAL TO BELOW NORMAL. IN THE ABSENCE OF HEAVY RAIN, IT IS UNLIKELY THAT RIVER FLOODING WILL DEVELOP WITHIN THE MARFC REGION DURING THE NEXT WEEK. WHILE A FEW LOCATIONS COULD RECEIVE LOCALLY HEAVY RAIN DURING THE NEXT 24 HOURS, WIDESPREAD HEAVY RAIN IS NOT ANTICIPATED. UP NORTH, NOT ENOUGH SNOW EXISTS ON THE GROUND TO BE A CONCERN WITH RESPECT TO RIVER FLOODING, EVEN IF IT MELTS RAPIDLY. SO WHILE RISING RIVER LEVELS ARE ANTICIPATED FOR THE NEXT COUPLE OF DAYS, RIVER FLOODING IS UNLIKELY TO DEVELOP. WATER SUPPLY OUTLOOK - A SMALL AREA OF MODERATE DROUGHT CONDITIONS REMAINS OVER A PORTION OF THE DELMARVA PENINSULA, AND IT CONTINUES TO BE ABNORMALLY DRY ACROSS A LARGER AREA THAT INCLUDES SOUTHEASTERN VA, MUCH OF THE REST OF THE DELMARVA PENINSULA AND EXTREME SOUTHERN NJ. STILL, ASSUMING NEAR NORMAL PRECIPITATION DURING THE NEXT FEW MONTHS, NO WATER SUPPLY SHORTAGES ARE EXPECTED ANYWHERE WITHIN THE MARFC REGION THROUGH AT LEAST MAY, 2012. HOWEVER, IF BELOW AVERAGE RAINFALL CONTINUES ACROSS THE SOUTHEASTERN PORTIONS OF THE MARFC REGION DROUGHT CONDITIONS COULD EXPAND AND/OR WORSEN IN THE NEXT COUPLE OF MONTHS WHICH COULD EVENTUALLY LEAD TO SOME WATER SHORTAGES IN THE SUMMER MONTHS. THE LATEST NOAA U.S. SEASONAL DROUGHT OUTLOOK (MARCH 1) STILL SHOWS THE POTENTIAL FOR DROUGHT DEVELOPMENT ACROSS THE SOUTHEAST. PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV AND WWW.DROUGHT.GOV FOR DROUGHT-RELATED DATA AND CHARTS. PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.ERH.NOAA.GOV/ER/MARFC FOR OTHER HYDROMETEOROLOGICAL INFORMATION. THE NEXT WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED BY THIS OFFICE IN ONE WEEK ON THURSDAY, MARCH 15, 2012. SK $$ ....END MARFC.... NNNN