FGUS61 KRHA 292010 ESGRHA FLOOD POTENTIAL STATEMENT MIDDLE ATLANTIC RIVER FORECAST CENTER NATIONAL WEATHER SERVICE STATE COLLEGE PA 410 PM EDT THU MAR 29 2007 SPRING RIVER FLOOD POTENTIAL OUTLOOK MIDDLE ATLANTIC RIVER FORECAST CENTER OUTLOOK NUMBER 07-8 (FINAL) MARCH 29, 2007 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 29-APRIL 12, 2007, 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 TEMPERATURES AVERAGED OVER THE PERIOD FROM APRIL 4-12, 2007 WILL MOST LIKELY BE BELOW NORMAL, WHILE PRECIPITATION WILL MOST LIKELY RANGE FROM NORMAL TO ABOVE NORMAL. PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV/ TO VIEW MEDIUM AND LONG-RANGE WEATHER OUTLOOKS. 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 IN THE UPPER SUSQUEHANNA AND UPPER DELAWARE RIVER BASINS IN NEW YORK STATE, OTHERWISE ABOUT AVERAGE. IN NEW YORK, HIGH STREAMFLOW (INCLUDING SOME ONGOING FLOODING), WET SOILS, AND WEATHER CONDITIONS THAT ARE EXPECTED TO BE WETTER THAN NORMAL DURING THE 6-14 DAY PERIOD ARE THE MAIN FACTORS LEADING TO THE ABOVE AVERAGE RIVER FLOOD POTENTIAL THERE. CURRENT FLOODING - A FEW LOCATIONS IN THE SUSQUEHANNA RIVER BASIN IN NEW YORK STATE REMAIN ABOVE THEIR RESPECTIVE FLOOD STAGES TODAY. THIS FLOODING IS PREDICTED TO END DURING THE NEXT 24 HOURS. RECENT PRECIPITATION - MOSTLY ABOUT AVERAGE. DURING THE LAST 30 DAYS (02/27/07-03/28/07) MOST OF THE MARFC SERVICE AREA RECORDED NEAR AVERAGE PRECIPITATION (75-125 PERCENT OF NORMAL). POCKETS OF ABOVE AVERAGE PRECIPITATION (UP TO 150 PERCENT OF NORMAL) WERE OBSERVED ACROSS PORTIONS OF NEW YORK, SOUTHEASTERN PENNSYLVANIA, AND NORTHEASTERN MARYLAND. MEANWHILE, AN AREA OF BELOW NORMAL PRECIPITATION (AS MUCH 75 PRECENT BELOW NORMAL) OCCURRED ACROSS SOUTHEASTERN VIRGINIA AND THE LOWER DELMARVA PENINSULA. IN GENERAL, MOST LOCATIONS RECEIVED 3-5 INCHES OF PRECIPITATION DURING THE LAST 30-DAYS. VISIT WWW.ERH.NOAA.GOV/ER/MARFC TO VIEW PRECIPITATION DEPARTURE MAPS. SNOW CONDITIONS - SOMEWHAT ABOVE AVERAGE IN THE VERY UPPER SUSQUEHANNA AND DELAWARE BASINS IN NEW YORK, OTHERWISE AVERAGE. PORTIONS OF THE UPPER SUSQUEHANNA AND UPPER DELAWARE RIVER BASINS IN NEW YORK STATE STILL CONTAIN AN INCH OR SO OF SNOW WATER EQUIVALENT. HOWEVER SINCE THE AREAL COVERAGE IS SMALL, THIS AMOUNT OF WATER IS NOW CONSIDERED ESSENTIALLY HYDROLOGICALLY INSIGNIFICANT. SNOW DATA AND INFORMATION CAN BE FOUND AT WWW.NOHRSC.NOAA.GOV AND AT WWW.ERH.NOAA.GOV/ER/MARFC. RIVER ICE - AVERAGE. NONE REMAINING. STREAMFLOW CONDITIONS - GENERALLY NEAR MEDIAN TO ABOVE MEDIAN. STREAMFLOW IS HIGHEST IN NEW YORK STATE, WHERE IT IS CURRENTLY MUCH ABOVE MEDIAN, WITH SOME FLOODING STILL ONGOING. MEANWHILE, STREAMFLOW IS BELOW MEDIAN ACROSS SOUTHEASTERN VIRGINIA. ELSEWHERE, STEAMFLOW IS GENERALLY IN THE NEAR MEDIAN-ABOVE MEDIAN RANGE. 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 - GENERALLY ABOVE AVERAGE. THE MARCH 24, 2007, PALMER DROUGHT SEVERITY INDEX CHART IMPLIES WETTER THAN NORMAL SOIL MOISTURE CONDITIONS ACROSS MOST OF THE MARFC SERVICE AREA. ESPECIALLY WET SOILS ARE FOUND ACROSS NEW YORK STATE AND NORTHERN PENNSYLVANIA. SOIL MOISTURE-RELATED CHARTS CAN BE SEEN AT WWW.CPC.NCEP.NOAA.GOV/SOILMST/. GROUND WATER - AVERAGE TO ABOVE AVERAGE. CURRENT GROUND WATER LEVELS ARE GENERALLY IN THE RANGE OF AVERAGE TO ABOVE AVERAGE ACROSS MOST OF THE MARFC SERVICE AREA. RESERVOIR CONDITIONS - AVERAGE TO ABOVE AVERAGE. MOST WATER SUPPLY AND FLOOD CONTROL RESERVOIRS ARE HOLDING NEAR AVERAGE OR ABOVE AVERAGE STORAGES FOR THIS TIME OF YEAR. FUTURE WEATHER CONDITIONS - DRY WEATHER IS EXPECTED ACROSS MOST OF THE MARFC SERVICE AREA INTO SATURDAY. LIGHT-MODERATE RAINFALL IS EXPECTED SATURDAY NIGHT INTO MONDAY MORNING. A COLD FRONT WILL CROSS THE MARFC SERVICE AREA TUESDAY NIGHT AND WEDNESDAY, ACCOMPANIED BY MORE LIGHT-MODERATE RAINFALL. RATHER COLD, UNSETTLED WEATHER IS ANTICIPATED FOR SEVERAL DAYS FOLLOWING THE PASSAGE OF THAT COLD FRONT NEXT WEEK. AT THE PRESENT TIME, THERE ARE NO STRONG INDICATIONS OF ANY WIDESPREAD HEAVY RAIN EVENTS FOR THE NEXT WEEK OR SO. REPEATING THE EXTENDED RANGE WEATHER OUTLOOK FOR THE NINE DAY PERIOD APRIL 4-12: BELOW NORMAL TEMPERATURES, AND NORMAL-ABOVE NORMAL PRECIPITATION. AHPS FLOOD FORECASTS - SOMEWHAT ABOVE AVERAGE IN THE UPPER PORTIONS OF THE SUSQUEHANNA AND DELAWARE BASINS IN NEW YORK, OTHERWISE ABOUT AVERAGE. 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 THIS OUTLOOK PERIOD AHPS INDICATES THAT THE LIKELIHOOD OF RIVER FLOODING IS SOMEWHAT MORE LIKELY THAN HAS BEEN HISTORICALLY OBSERVED IN PORTIONS OF NEW YORK STATE, PRIMARILY DUE TO THE CURRENTLY HIGH STREAMFLOW AND VERY WET SOILS. ELSEWHERE, AHPS INDICATES A NEAR AVERAGE LIKELIHOOD OF RIVER FLOODING. PLEASE VISIT WWW.WEATHER.GOV/AHPS/ FOR DETAILED AHPS INFORMATION. SUMMARY - THE RIVER FLOOD POTENTIAL FOR THE NEXT TWO WEEKS REMAINS SOMEWHAT ABOVE AVERAGE IN PORTIONS OF NEW YORK STATE DUE TO THE HIGH STREAMFLOW, WET SOILS, AND POTENTIALLY WET WEATHER PATTERN POSSIBLE DURING THE SECOND HALF OF THIS OUTLOOK PERIOD. HOWEVER, THE SNOWPACK IS NOW NEARLY DEPLETED, AND THERE ARE NO STRONG INDICATIONS OF WIDESPREAD HEAVY RAINFALL FOR THIS REGION FOR THE NEXT WEEK OR SO. ELSEWHERE, THE RIVER FLOOD POTENTIAL IS ABOUT AVERAGE. WATER SUPPLY OUTLOOK - ASSUMING NEAR NORMAL PRECIPITATION OCCURS, NO WATER SUPPLY SHORTAGES OF ANY TYPE ARE ANTICIPATED ANYWHERE WITHIN THE MARFC REGION DURING THE NEXT SIX MONTHS. AN AREA OF RELATIVE DRYNESS STILL EXISTS ACROSS PORTIONS OF THE APPALACHIANS AND WILL NEED TO BE MONITORED 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 OUTLOOK ISSUED BY MARFC FOR THE 2007 SPRING FLOOD SEASON, UNLESS CONDITIONS CHANGE DRAMATICALLY. $$ ....END MARFC.... NNNN