FGUS61 KRHA 151756
ESGRHA

FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 156 PM EDT THU MAR 15 2007 
 
WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK
MIDDLE ATLANTIC RIVER FORECAST CENTER

OUTLOOK NUMBER 07-7  MARCH 15, 2007

NOTE: THE FLOOD POTENTIAL FOR THE NEXT SEVERAL DAYS IS VERY HIGH IN
SOUTHERN NEW YORK, CENTRAL, SOUTHERN AND EASTERN PA, AND CENTRAL AND
SOUTHERN NEW JERSEY IN RESPONSE TO THE RECENT WARM TEMPERATURES,
ASSOCIATED SNOWMELT AND HEAVY RAIN EVENT UNFOLDING AT THIS TIME.
FLOODING IS OCCURING IN PORTIONS OF THE SUQUEHANNA BASIN IN NEW YORK
STATE AT THIS TIME WHILE FLOODING IS FORECAST FOR SEVERAL DOWNSTREAM
LOCATIONS IN PA DURING THE NEXT SEVERAL DAYS.  FLOODING IS ALSO
POSSIBLE IN SE PA AND PORTIONS OF NEW JERSEY DURING THE NEXT SEVERAL
DAYS.  HIGH WATER IS ALSO POSSIBLE IN PORTIONS OF VIRGINIA AND
MARYLAND IN THE POTOMAC AND JAMES DRAINAGES AS 1.5 TO 3.5 INCHES OF
RAIN IS EXPECTED DURING THE NEXT SEVERAL DAYS.

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 15-29, 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 MARCH 21-29, 2007
WILL MOST LIKELY BE ABOVE NORMAL, WHILE PRECIPITATION WILL RANGE FROM
NORMAL TO BELOW 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 FLOODING - MULTIPLE LOCATIONS IN THE SUSQUEHANNA RIVER BASIN IN NY
STATE

RECENT PRECIPITATION - LAST 30-DAYS
JAMES BASIN - BELOW AVERAGE
POTOMAC BASIN - AVERAGE TO ABOVE AVERAGE
NEW JERSEY - AVERAGE TO ABOVE AVERAGE
SUSQUEHANNA AND DELAWARE BASINS - AVERAGE TO ABOVE AVERAGE
VISIT WWW.ERH.NOAA.GOV/ER/MARFC TO VIEW PRECIPITATION DEPARTURE MAPS.

SNOW CONDITIONS - SLIGHTLY ABOVE AVERAGE IN THE VERY UPPER SUSQUEHANNA
AND DELAWARE BASINS WITH POTENTIALLY A NEW SNOWPACK IN PA AND NJ BASED
ON CURRENT WEATHER PROJECTIONS.  THE HIGHEST ESTIMATED SNOW WATER
EQUIVALENTS ARE AROUND 2 INCHES ALONG THE PERIMETER OF THE
NORTHERNMOST SUSQUEHANNA AND DELAWARE BASINS.  ELSEWHERE IN THE MARFC
AREA SNOW IS LIMITED TO THE HIGHEST ELEVATIONS WHICH IS NORMAL FOR
THIS TIME OF YEAR.

RIVER ICE - AVERAGE.  SOME LINGERING ICE MOVEMENT IN THE NORTHERN
SUSQUEHANNA AND DELAWARE BASINS WITH THE ONGOING RAINFALL/SNOWMELT
EVENT.  ELSEWHERE, RIVER ICE IS NO LONGER PRESENT.

STREAMFLOW CONDITIONS - VARYING FROM SOUTH TO NORTH, WITH BELOW
AVERAGE IN THE SOUTHERNMOST BASINS UP TO WELL ABOVE AVERAGE IN NY
STATE WHERE SOME RIVERS ARE CURRENTLY IN FLOOD.

SOIL MOISTURE CONDITIONS - GENERALLY ABOVE AVERAGE.  
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.  HOWEVER, THERE ARE LOCALIZED AREAS WHERE
GROUND WATER CONDITIONS ARE MUCH ABOVE AVERAGE, WHILE AT THE SAME TIME
THERE ARE POCKETS OF BELOW AVERAGE GROUND WATER LEVELS.

RESERVOIR CONDITIONS - AVERAGE TO ABOVE AVERAGE.  MOST LARGE WATER
SUPPLY RESERVOIRS WITHIN THE MARFC SERVICE AREA ARE STILL HOLDING
AVERAGE OR ABOVE AVERAGE STORAGES FOR THIS TIME OF YEAR, IN FACT,
SEVERAL FLOOD CONTROL RESERVOIRS HAVE BEEN STORING WATER DURING THE
ONGOING RUNOFF EVENT WHICH WILL BE RELEASED AS ANY FLOODING AND HIGH
WATER RECEDE.

FUTURE WEATHER CONDITIONS - THE ONGOING RAIN/SNOW STORM IN THE MARFC
AREA IS THE PRIMARY WEATHER MAKER IMPACTING FLOOD POTENTIAL.  IN
ADDITION TO THE SNOWMELT AND RUNOFF CURRENTLY UNDERWAY, THIS STORM
WILL LIKELY PRODUCE A SPRING SNOWPACK WITH UP TO 1 INCH OF WATER IN
EASTERN PA AND NJ WHICH COULD BE A CONTRIBUTING FACTOR TO FLOODING
LATER IN THE PERIOD.  THE NEXT CHANCE FOR SIGNIFICANT PRECIPITATION
APPEARS TO BE NEXT WEEKEND WITH A FRONTAL PASSAGE.

AHPS FLOOD FORECASTS - ABOVE AVERAGE IN THE SUSQUEHANNA, DELAWARE AND
NEW JERSEY BASINS AND ABOUT AVERAGE IN THE POTOMAC AND JAMES RIVER
BASIS.  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 MORE LIKELY THAN HAS BEEN HISTORICALLY OBSERVED PRIMARILY
DUE TO THE HIGH FLOWS, LINGERING SNOWPACK AND WET SOILS NORTH OF THE
MASON-DIXON LINE.  IT IS RECOGNIZED THAT SOME RIVER FLOODING IS TO BE
EXPECTED (NORMAL) IN THE MARFC REGION EACH SPRING.  ALSO PLEASE VISIT
WWW.WEATHER.GOV/AHPS/ FOR DETAILED AHPS INFORMATION.

SUMMARY - THE CURRENT RIVER FLOOD POTENTIAL IS VERY HIGH IN PORTIONS
OF THE SUSQUEHANNA, DELAWARE AND NEW JERSEY BASINS BASED ON THE
ONGOING SNOWMELT/RAIN/SNOW EVENT.  THE FLOOD POTENTIAL IS NEAR AVERAGE
IN THE POTOMAC, RAPPAHANNOCK AND JAMES BASINS, CONSIDERING THE
ELEVATED FLOOD POTENTIAL ASSOCIATED WITH 1.5 TO 3.0 INCHES OF
POTENTIAL RAINFALL IN THE NEXT SEVERAL DAYS OFFSET BY OTHER HYDROLOGIC
FACTORS THAT ARE CLOSE TO NORMAL.

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 THE APPALACHIANS OF NORTHEASTERN WEST VIRGINIA AND
WESTERN MARYLAND AND WILL NEED TO BE MONITORED.  

PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.ERH.NOAA.GOV/ER/MARFC FOR
OTHER HYDROMETEOROLOGICAL INFORMATION.

THE NEXT WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK WILL BE ISSUED BY
MARFC ON THURSDAY, MARCH 22, 2007.

$$

....END MARFC....
NNNN