000 FGUS61 KRHA 191947 ESGRHA FLOOD POTENTIAL STATEMENT MIDDLE ATLANTIC RIVER FORECAST CENTER NATIONAL WEATHER SERVICE STATE COLLEGE PA 347 PM EDT THU MAR 19 2009 WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK MIDDLE ATLANTIC RIVER FORECAST CENTER OUTLOOK NUMBER 09-6 (FINAL). MARCH 19, 2009 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 MARCH 19-APRIL 02, 2009 AND INCLUDES THE LATEST NWS EXTENDED-RANGE (6-10 AND 8-14 DAY) WEATHER FORECASTS. FOR THE MARFC SERVICE AREA, THESE FORECASTS SUGGEST THAT BOTH TEMPERATURES AND PRECIPITATION ARE EXPECTED TO GRADUALLY TRANSITION FROM NORMAL/ABOVE NORMAL TO NORMAL/BELOW NORMAL DURING THE NINE-DAY PERIOD FROM MARCH 25-APRIL 02, 2009. TO VIEW NWS MEDIUM AND LONG-RANGE WEATHER OUTLOOKS, PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV/. 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. TWO-WEEK RIVER FLOOD POTENTIAL OUTLOOK - BELOW AVERAGE. CURRENT FLOODING - NONE. RECENT PRECIPITATION - NEAR AVERAGE TO MUCH-BELOW AVERAGE. PRECIPITATION WITHIN THE MARFC SERVICE AREA DURING THE LAST 30 DAYS (FEBRUARY 17-MARCH 18, 2009) WAS NEAR AVERAGE ACROSS NY AND EXTREME NORTHERN PA. PORTIONS OF THE JAMES RIVER BASIN IN VA ALSO RECEIVED NEAR-AVERAGE PRECIPITATION DURING THE LAST 30-DAY PERIOD, THANKS TO BENEFICIAL RAINFALL MAINLY DURING THE LAST 10 DAYS. ELSEWHERE, 30-DAY PRECIPITATION TOTALS WERE BELOW AVERAGE TO MUCH-BELOW AVERAGE. IN NY, NORTHERN PA, AND IN PORTIONS OF THE JAMES RIVER BASIN OF VA, 2.0-3.5 INCHES OF PRECIPITATION FELL DURING THE LAST 30 DAYS, WHICH IS 75-125 PERCENT OF NORMAL. ELSEWHERE, MOST LOCATIONS RECEIVED ONLY 0.5-2.0 INCHES OF PRECIPITATION DURING THE LAST 30 DAYS, WHICH IS 20-75 PERCENT OF NORMAL OR ABOUT 0.5-3.0 INCHES BELOW NORMAL FOR THE PERIOD. PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC TO VIEW PRECIPITATION DEPARTURE MAPS. SNOW CONDITIONS - BELOW AVERAGE IN NY AND IN PORTIONS OF NORTHERN/CENTRAL PA, OTHERWISE CLOSE TO AVERAGE. ALTHOUGH PATCHES OF SNOW REMAIN IN HIGHER ELEVATIONS, MAINLY IN NY, THE CURRENT SNOW CONDITIONS ARE HYDROLOGICALLY INSIGNIFICANT. 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), THE NEW YORK CITY DEPT. OF ENVIRONMENTAL PROTECTION, 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 - ABOUT AVERAGE. CURRENTLY NO RIVER ICE REMAINS WITHIN THE MARFC SERVICE AREA. FOR THE THIRD WEEK OF MARCH, THE LACK OF RIVER ICE IS NOT UNUSUAL FOR MOST AREAS. STREAMFLOW CONDITIONS - NORMAL TO MUCH-BELOW NORMAL. STREAMFLOW IS PRESENTLY NEAR NORMAL ACROSS PORTIONS OF NY AND NORTHERN PA (AND DOWN THE MAINSTEM SUSQUEHANNA AND DELAWARE RIVERS) DUE TO THE RECENT RAIN/SNOWMELT EVENTS. LIKEWISE, STREAMFLOW IS PRESENTLY NEAR NORMAL ACROSS PORTIONS OF THE JAMES RIVER BASIN DUE TO THE RECENT RAINFALL THERE. OTHERWISE, STREAMFLOW IS BELOW TO MUCH-BELOW NORMAL. 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 MARCH 14, 2009, PALMER DROUGHT SEVERITY INDEX CHART (NAVIGATE THE WWW.CPC.NOAA.GOV/PRODUCTS WEBSITE) SHOWS UNUSUALLY MOIST TO EXTREMELY MOIST SOIL MOISTURE CONDITIONS PERSIST ACROSS NY. THE CHART INDICATES MUCH OF THE REST OF THE MARFC REGION HAS NEAR AVERAGE SOIL MOISTURE CONDITIONS FOR THIS TIME OF YEAR, WITH THE EXCEPTION OF THE CHESAPEAKE BAY REGION WHICH IS SHOWING SOME MODERATE DROUGHT CONDITIONS. HOWEVER, ACTUAL PALMER INDEX VALUES AS WELL AS OTHER SOIL MOISTURE AND DROUGHT-RELATED DATA INDICATE DRY CONDITIONS ACTUALLY PERSIST ACROSS MOST OF THE SOUTHERN HALF OF THE MARFC REGION. ADDITIONALLY, THE LASTEST NOAA U.S. SEASONAL DROUGHT OUTLOOK (VISIT WWW.CPC.NOAA.GOV) ISSUED MARCH 19, 2009 NOW SUGGESTS DROUGHT CONDITIONS WILL PERSIST ACROSS VA AND MAY EVEN EXPAND NORTH AND EASTWARD DURING THE NEXT FEW MONTHS. SOIL MOISTURE AND DROUGHT RELATED DATA AND CHARTS CAN BE SEEN AT WWW.DROUGHT.GOV AND AT WWW.CPC.NCEP.NOAA.GOV/SOILMST/. GROUND WATER - VARIABLE. CURRENT GROUND WATER LEVELS ARE GENERALLY NORMAL TO ABOVE NORMAL ACROSS THE NORTHERN HALF OF THE MARFC SERVICE AREA, AND NORMAL TO BELOW NORMAL ACROSS THE SOUTHERN HALF. RESERVOIR CONDITIONS - VARIABLE. RESERVOIR CONDITIONS ARE CURRENTLY CLOSE TO AVERAGE ACROSS THE NORTHERN HALF OF THE MARFC SERVICE AREA, AND AVERAGE TO BELOW AVERAGE ESLEWHERE. FUTURE WEATHER CONDITIONS - THE NEXT SEVERAL DAYS APPEAR RATHER DRY ACROSS THE MARFC SERVICE AREA, WITH NEAR-NORMAL TEMPERATURES. AT THE PRESENT TIME THERE ARE NO STRONG INDICATIONS OF ANY WIDESPREAD HEAVY RAIN EVENTS FOR ABOUT THE NEXT WEEK. REPEATING THE LATEST NWS EXTENDED-RANGE (6-10 DAY) WEATHER FORECAST FOR THE MARFC REGION, BOTH TEMPERATURES AND PRECIPITATION ARE EXPECTED TO GRADUALLY TRANSITION FROM NORMAL/ABOVE NORMAL TO NORMAL/BELOW NORMAL DURING THE NINE-DAY PERIOD FROM MARCH 25-APRIL 02, 2009. AHPS FLOOD FORECASTS - BELOW 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. FOR THE NEXT TWO WEEKS AHPS INDICATES THAT THE LIKELIHOOD OF RIVER FLOODING IS BELOW NORMAL EVERYWHERE WITHIN THE MARFC SERVICE AREA. PLEASE VISIT WWW.WEATHER.GOV/AHPS/ FOR DETAILED AHPS INFORMATION. SUMMARY - THE SECOND HALF OF MARCH AND FIRST WEEK OF APRIL IS, ON AVERAGE, THE MOST FLOOD-PRONE TIME OF YEAR WITHIN THE MARFC SERVICE AREA. HOWEVER THIS YEAR, BASED ON CURRENT AND PREDICTED HYDROMETEOROLOGICAL CONDITIONS, THE RIVER FLOOD POTENTIAL FOR THE NEXT TWO WEEKS IS CONSIDERED BELOW AVERAGE FOR THE ENTIRE MARFC REGION FOR THIS TIME OF YEAR. WITH SNOW ESSENTIALLY ABSENT, HEAVY RAIN WOULD BE REQUIRED TO INITIATE RIVER FLOODING ANYWHERE WITHIN THE MARFC SERVICE AREA. AT THIS TIME THERE ARE NO STRONG INDICATIONS OF ANY WIDESPREAD HEAVY RAIN EVENTS FOR ABOUT THE NEXT WEEK. WATER SUPPLY OUTLOOK - ASSUMING NEAR NORMAL PRECIPITATION DURING THE NEXT FEW MONTHS, NO WATER SUPPLY SHORTAGES ARE EXPECTED ANYWHERE WITHIN THE MARFC REGION THROUGH JUNE, 2009. HOWEVER, ABNORMALLY DRY TO MODERATE DROUGHT CONDITIONS THAT CURRENTLY PERSIST ACROSS ABOUT THE SOUTHERN HALF OF THE MARFC SERVICE AREA ARE NOW OUTLOOKED TO PERSIST AND PERHAPS EVEN EXPAND NORTH AND EASTWARD DURING THE NEXT THREE MONTHS. AS SUCH, SOME WATER SUPPLY SHORTAGES MAY CERTAINLY DEVELOP THIS SUMMER IF THE DRIER-THAN-NORMAL WEATHER CONDITIONS DO PERSIST AS IS NOW BEING SUGGESTED. DROUGHT WATCHES AND EVENTUALLY WARNINGS COULD BE ISSUED FOR PORTIONS OF THE MARFC REGION THIS SPRING AND SUMMER. PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.ERH.NOAA.GOV/ER/MARFC FOR OTHER HYDROMETEOROLOGICAL INFORMATION. THIS WILL BE THE FINAL 2009 WINTER/SPRING FLOOD OUTLOOK ISSUED BY THIS OFFICE UNLESS CONDITIONS NECESSITATE OTHERWISE. SK $$ ....END MARFC.... NNNN