FGUS61 KRHA 202039 ESGRHA FLOOD POTENTIAL STATEMENT MIDDLE ATLANTIC RIVER FORECAST CENTER NATIONAL WEATHER SERVICE STATE COLLEGE PA 438 PM EDT THU MAR 20 2008 SPRING RIVER FLOOD POTENTIAL OUTLOOK MIDDLE ATLANTIC RIVER FORECAST CENTER OUTLOOK NUMBER 08-7 MARCH 20, 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 MARCH 20-APRIL 3, 2008, AND INCLUDES THE LATEST NWS EXTENDED-RANGE (6-10 AND 8-14 DAY) WEATHER FORECASTS. FOR THE MARFC SERVICE AREA, THESE FORECASTS SUGGEST THAT TEMPERATURES AVERAGED OVER THE NINE-DAY PERIOD FROM MARCH 26-APRIL 3, 2008 WILL LIKELY BE BELOW NORMAL, WHILE PRECIPITATION AVERAGED OVER THE SAME NINE DAYS WILL LIKELY BE NORMAL TO BELOW NORMAL. TO VIEW 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. CURRENT RIVER FLOOD POTENTIAL - VARIABLE. THE RIVER FLOOD POTENTIAL FOR THE NEXT TWO WEEKS IS SOMEWHAT ABOVE AVERAGE ACROSS ABOUT THE NORTHERN THIRD OF THE MARFC SERVICE AREA. THIS INCLUDES PORTIONS OF THE SUSQUEHANNA, DELAWARE AND NEW JERSEY RIVER BASINS. THE RIVER FLOOD POTENTIAL IS NEAR NORMAL ACROSS THE LOWER HALF OF THE SUSQUEHANNA AND POTOMAC RIVER BASINS, AND SOMEWHAT BELOW NORMAL ELSEWHERE. CURRENT FLOODING - VERY MINOR FLOODING IS OCCURRING ALONG A PORTION OF THE SUSQUEHANNA RIVER ALONG THE NY/PA BORDER. RECENT PRECIPITATION - VARIABLE. PRECIPITATION WITHIN THE MARFC SERVICE AREA DURING THE LAST 30 DAYS (FEBRUARY 19-MARCH 19) WAS MUCH ABOVE NORMAL ACROSS PA, NY AND THE NORTHERN THIRD OF NJ. HEADING SOUTH, PRECIPITATION WAS NORMAL TO ABOVE NORMAL ACROSS THE POTOMAC BASIN, AND NORMAL TO SOMEWHAT BELOW NORMAL ACROSS THE REMAINDER OF THE REGION. PRECIPITATION WAS GENERALLY IN THE 5-8 INCH RANGE ACROSS MOST OF PA, NY AND THE NORTHERN THIRD OF NJ. HEAVIEST AMOUNTS FELL ACROSS THE UPPER HALF OF THE DELAWARE RIVER BASIN. ELSEWHERE, PRECIPITATION WAS GENERALLY IN THE 2-5 INCH RANGE. LIGHTEST AMOUNTS WERE ACROSS CENTRAL VA AND THE SOUTHERN DELMARVA PENINSULA. PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC TO VIEW PRECIPITATION DEPARTURE MAPS. SNOW CONDITIONS - BELOW AVERAGE TO ABOUT AVERAGE. SNOW COVER IS PRESENTLY LIMITED TO JUST THE NORTHERN QUARTER OF THE MARFC SERVICE AREA. EVEN HERE, THE SNOW COVER IS QUITE PATCHY AND LIMITED TO JUST THE HIGHER ELEVATIONS OR FORESTED REGIONS. WHERE SNOW DOES EXIST, SNOW WATER EQUIVALENT VALUES ARE GENERALLY IN THE 0-1.5 INCH RANGE, WITH SOME ISOLATED HIGH-ELEVATION AMOUNTS OF GREATER THAN 2 INCHES. SNOW DEPTHS ARE GENERALLY JUST A FEW INCHES, AGAIN WITH SOME ISOLATED HIGH ELEVATION DEPTHS OF UP TO A FOOT. WHERE SNOW EXISTS, THE CURRENT SNOW CONDITIONS ARE GENERALLY CONSIDERED TO BE BELOW AVERAGE TO ABOUT AVERAGE FOR MID MARCH. ELSEWHERE, SNOW CONDITIONS ARE CONSIDERED TO BE ABOUT AVERAGE FOR MOST AREAS FOR MID MARCH. BASIN-AVERAGE WATER EQUIVALENT ESTIMATES CAN BE SEEN AT WWW.ERH.NOAA.GOV/ER/MARFC OR AT WWW.NOHRSC.NOAA.GOV. RIVER ICE - SOMEWHAT BELOW AVERAGE TO AVERAGE. NO RIVER ICE REMAINS WITHIN THE MARFC SERVICE AREA. FOR FAR UPPER PORTIONS OF THE SUSQUEHANNA AND DELAWARE RIVER BASINS IN NEW YORK, RIVER ICE CONDITIONS ARE SOMEWHAT BELOW AVERAGE FOR THIS TIME OF YEAR. ELSEWHERE, RIVER ICE CONDITIONS ARE NORMAL. STREAMFLOW CONDITIONS - VARIABLE. COMPARED TO MEDIAN FOR THIS TIME OF YEAR, STREAMFLOW REMAINS HIGH ACROSS NY, MOST OF PA AND NORTHERN NJ. HEADING SOUTHWARD, STREAMFLOW DROPS OFF QUICKLY TO ABOUT NORMAL ACROSS THE POTOMAC BASIN AND SOUTHERN NJ, THEN TO BELOW NORMAL ACROSS MUCH OF VA. STREAMFLOW IS ALSO BELOW MEDIAN ACROSS MUCH OF THE CHESAPEAKE BAY REGION AND THE DELMARVA PENINSULA, AND IN PORTIONS OF SOUTHERN NJ. 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 15, 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, PA AND THE NORTHERN HALF OF NJ. FURTHER SOUTH, UNUSUALLY MOIST CONDITIONS ARE SCATTERED ACROSS PORTIONS OF NORTHEASTERN WV, MD, AND NORTHERN DE. ELSEWHERE THE CHART INDICATES NEAR AVERAGE SOIL MOISTURE CONDITIONS FOR THIS TIME OF YEAR. ACTUAL PALMER INDEX VALUES, HOWEVER, AS WELL AS OTHER SOIL MOISTURE AND DROUGHT-RELATED DATA INDICATES PORTIONS OF VA, MD AND A SMALL PORTION OF SOUTHERN 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 ABOVE NORMAL ACROSS THE NORTH, NEAR NORMAL ACROSS THE CENTRAL REGION, AND BELOW NORMAL ACROSS THE SOUTH. RESERVOIR CONDITIONS - VARIABLE. RESERVOIR CONDITIONS ARE CURRENTLY ABOVE AVERAGE ACROSS THE FAR NORTH, AND BELOW AVERAGE ACROSS PORTIONS OF VA. FUTURE WEATHER CONDITIONS - FAIRY TYPICAL EARLY SPRING WEATHER IS ANTICIPATED FOR AT LEAST THE FIRST HALF OF THIS OUTLOOK PERIOD. QUICK-MOVING SYSTEMS WILL BE PRECEDED BY BRIEF WARMUPS, WHILE COLD FRONTAL PASSAGES WILL BRIEFLY DROP TEMPERATURES TO BELOW NORMAL. A STORM MAY FORM ALONG THE COAST EARLY NEXT WEEK, BUT ITS EFFECTS ON THE MARFC SERVICE AREA LOOK TO BE MINIMAL AT THIS TIME. THERE ARE PRESENTLY NO STRONG INDICATIONS OF ANY HEAVY RAIN EVENTS FOR AT LEAST THE NEXT WEEK AS WEATHER SYSTEMS SHOULD REMAIN RATHER PROGRESSIVE. IN SUMMARY, FAST-MOVING WEATHER SYSTEMS SHOULD PROVIDE GENERALLY LIGHT-MODERATE PRECIPITATION DURING THE NEXT WEEK, WITH TYPICAL EARLY SPRING TEMPERATURE FLUCUTATIONS. REPEATING THE LATEST NWS EXTENDED-RANGE (6-10 AND 8-14 DAY) WEATHER FORECASTS FOR THE MARFC SERVICE AREA: TEMPERATURES AVERAGED OVER THE NINE-DAY PERIOD FROM MARCH 26-APRIL 3, 2008 WILL LIKELY BE BELOW NORMAL, WHILE PRECIPITATION AVERAGED OVER THE SAME NINE DAYS WILL LIKELY BE NORMAL TO BELOW NORMAL. 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 NEAR NORMAL TO ABOVE NORMAL ACROSS ABOUT THE NORTHERN THIRD OF THE MARFC SERVICE AREA, AND SOMEWHAT BELOW NORMAL ELSEWHERE. IT SHOULD BE NOTED THAT LATE MARCH IS, ACCORDING TO HISTORY, THE MOST FLOOD-PRONE TIME OF THE YEAR ACROSS MUCH OF THE MARFC SERVICE AREA, ON AVERAGE. PUT ANOTHER WAY, HISTORY SHOWS THAT RIVER FLOODING IS A FAIRLY COMMON OCCURRENCE IN LATE MARCH SOMEWHERE WITHIN THE MARFC REGION (ESPECIALLY IN NEW YORK). VERY WET SOILS AND HIGH STREAMFLOW ARE THE AHPS FACTORS CURRENTLY FAVORING FLOODING ACROSS THE NORTH, WHILE THE LIMITED SNOW PACK IS ONE AHPS FACTOR THAT IS ACTING TO DECREASE THE RIVER FLOOD POTENTIAL. WHILE AHPS DOES TAKE INTO ACCOUNT PRECIPITATION THAT HAS OCCURRED IN HISTORY, IT DOES NOT TAKE INTO ACCOUNT FUTURE PRECIPITATION. 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. PLEASE VISIT WWW.WEATHER.GOV/AHPS/ FOR DETAILED AHPS INFORMATION. SUMMARY - THE RIVER FLOOD POTENTIAL FOR THE NEXT TWO WEEKS IS SOMEWHAT ABOVE NORMAL FOR UPPER PORTIONS OF THE SUSQUEHANNA AND DELAWARE RIVER BASINS, AS WELL AS FOR THE NORTHERN/CENTRAL NEW JERSEY BASINS. HIGH STREAMFLOW AND MUCH ABOVE-AVERAGE SOIL MOISTURE CONDITIONS ARE THE FACTORS CAUSING THE SOMEWHAT ELEVATED FLOOD RISK HERE. ELSEWHERE, THE RIVER FLOOD POTENTIAL FOR THE NEXT TWO WEEKS IS NORMAL TO SOMEWHAT BELOW NORMAL. 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 MARCH 20, 2008, DOES SUGGEST CONTINUED SLOW IMPROVEMENT ACROSS THE DROUGHT AREA DURING THE NEXT THREE MONTHS. ELSEWHERE, ASSUMING NEAR NORMAL PRECIPITATION OCCURS, NO WATER SUPPLY SHORTAGES ARE ANTICIPATED ANYWHERE WITHIN THE MARFC REGION DURING THE NEXT FIVE MONTHS. PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.ERH.NOAA.GOV/ER/MARFC FOR OTHER HYDROMETEOROLOGICAL INFORMATION. THIS IS THE FINAL REGULARLY SCHEDULED OUTLOOK OF THE 2008 SEASON. OTHER OUTLOOKS MAY BE ISSUED BY THIS OFFICE IF CONDITIONS WARRANT. SK $$ ....END MARFC.... NNNN