FGUS61 KRHA 241553
ESGRHA

FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC)
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 1053 AM EST THU JAN 24 2013 

WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK
NWS MIDDLE ATLANTIC RIVER FORECAST CENTER

OUTLOOK NUMBER 13-02 - JANUARY 24, 2013

THIS OUTLOOK IS VALID FOR THE TWO-WEEK PERIOD JANUARY 24-FEBRUARY 7,
2013.

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 AND 8-14 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.

TWO-WEEK RIVER FLOOD POTENTIAL - AVERAGE TO SOMEWHAT BELOW AVERAGE.
THE RIVER FLOOD POTENTIAL ACROSS THE MARFC SERVICE AREA FOR THE NEXT
TWO WEEKS THROUGH FEBRUARY 7, 2013 IS SOMEWHAT BELOW AVERAGE ACROSS
MOST OF THE NORTHERN HALF OF THE REGION AND CLOSER TO AVERAGE
ELSEWHERE.  NO WIDESPREAD HEAVY RAIN EVENTS ARE ANTICIPATED FOR THE
NEXT WEEK.  HOWEVER MILDER TEMPERATURES AND SNOWMELT EARLY NEXT WEEK
WILL BE ACCOMPANIED BY SOME LIGHT-MODERATE RAIN UNTIL A COLD FRONT
PASSES MIDWEEK.  THEREFORE RISING WATER LEVELS ARE LIKELY THROUGH
MIDWEEK NEXT WEEK, BUT NO FLOODING IS CURRENTLY ANTICIPATED.  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 (DECEMBER 25, 2012-JANUARY 23,
2013) RANGED FROM BELOW AVERAGE TO AVERAGE (50-125 PERCENT OF NORMAL)
ACROSS PA, NY AND NORTHERN NJ WHERE GENERALLY 1.5-3.5 INCHES (WATER
EQUIVALENT) WAS OBSERVED.  FURTHER SOUTH, PRECIPITATION RANGED FROM
AVERAGE TO ABOVE AVERAGE (80-150 PERCENT OF NORMAL) ACROSS MD, MUCH OF
NORTHERN VA, ACROSS THE NORTHERN HALF OF THE DELMARVA PENINSULA AND
ACROSS PORTIONS OF CENTRAL NJ.  IN THIS AREA GENERALLY 2.5-4.5 INCHES
FELL.  FINALLY, EVEN FURTHER SOUTH PRECIPITATION RANGED FROM ABOVE
AVERAGE TO MUCH ABOVE AVERAGE ACROSS PORTIONS OF CENTRAL/SOUTHERN VA,
THE SOUTHERN HALF OF THE DELMARVA PENINSULA AND ACROSS PORTIONS OF
CENTRAL AND SOUTHERN NJ.  THIS INCLUDES MUCH OF THE JAMES AND
APPOMATTOX RIVER BASINS IN VA.  IN THIS REGION PRECIPITATION WAS
GENERALLY 4.0-7.0 INCHES.  PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC FOR
ADDITIONAL PRECIPITATION INFORMATION.

SNOW CONDITIONS - BELOW AVERAGE TO ABOUT AVERAGE.  CURRENTLY THERE IS
A LIGHT SNOW COVER ACROSS NEARLY ALL OF THE MARFC SERVICE AREA.  WHILE
THE AREA COVERED BY SNOW IS PERHAPS A LITTLE MORE EXTENSIVE THAN IS
TYPICAL FOR THIS TIME OF YEAR, THE AMOUNT OF WATER CONTAINED IN THE
SNOW (WATER EQUIVALENT) IS GENERALLY BELOW AVERAGE TO MUCH BELOW
AVERAGE FOR THIS TIME OF YEAR, ESPECIALLY ACROSS THE NORTHERN HALF OF
THE REGION.  WATER EQUIVALENT VALUES ARE GENERALLY ONLY IN THE 0.1-1.0
INCH RANGE.  AN EXCEPTION IS ACROSS UPPER PORTIONS OF THE DELAWARE
RIVER BASIN IN NY WHERE VALUES OF 1-2 INCHES ARE FOUND, WHICH IS STILL
BELOW AVERAGE.  SNOW DEPTHS EVERYWHERE WITHIN THE MARFC SERVICE AREA
ARE PRESENTLY MOSTLY IN THE 1-6 INCH RANGE.  WHILE SOME ADDITIONAL
LIGHT SNOW MAY ACCUMULATE DURING THE NEXT FEW DAYS IN SOME AREAS, THE
SNOWPACK ACROSS THE MARFC SERVICE SHOULD REMAIN GENERALLY
HYDROLOGICALLY INSIGNIFICANT.  AGAIN THE EXCEPTION IS FOR SMALL
PORTIONS OF THE UPPER DELAWARE BASIN IN NY STATE WHERE THE SNOWPACK IS
ONLY MINIMALLY SIGNIFICANT.  WITH NO MAJOR SNOWSTORMS EXPECTED DURING
THE NEXT WEEK, AND MILD TEMPERATURES EXPECTED EARLY NEXT WEEK, SNOW
CONDITIONS WILL LIKELY TEMPORARILY DECREASE FOR MOST REGIONS BY
MIDWEEK NEXT WEEK, BUT ESPECIALLY ACROSS THE SOUTH AND EAST.  PLEASE
VISIT WWW.NOHRSC.NOAA.GOV AND WWW.ERH.NOAA.GOV/ER/MARFC FOR SPECIFICS
ON SNOW CONDITIONS.

RIVER ICE - BELOW AVERAGE TO AVERAGE.  AS OF THIS MORNING, NOT MUCH
SIGNIFICANT RIVER ICE EXISTS WITHIN THE MARFC SERVICE AREA.  HOWEVER,
RIVER ICE IS FORMING ACROSS MUCH OF THE MARFC SERVICE AREA DUE TO THE
RECENT COLD WEATHER.  WHILE RIVER ICE CONDITIONS ARE CURRENTLY BELOW
AVERAGE FOR JANUARY ACROSS PA AND NY, WITH CONTINUED COLD WEATHER
PREDICTED RIVER ICE WILL CONTINUE TO INCREASE IN THESE AREAS DURING
THE NEXT COUPLE OF DAYS.  ELSEWHERE, RIVER ICE CONDITIONS ARE CLOSER
TO AVERAGE FOR THIS TIME OF WINTER SINCE SIGNIFICANT RIVER ICE OCCURS
WITH MUCH LESS FREQUENCY ACROSS SOUTHERN AND FAR EASTERN PORTIONS OF
THE MARFC REGION.  MILDER TEMPERATURES EARLY NEXT WEEK WILL AT LEAST
TEMPORARILY HALT RIVER ICE FORMATION ACROSS THE MARFC REGION, AND MAY
EVEN LEAD TO SOME DECREASE IN RIVER ICE.

STREAMFLOW CONDITIONS - MEDIAN TO BELOW MEDIAN.  ACCORDING TO THE
U.S. GEOLOGICAL SURVEY (USGS) STREAMFLOW FOR MOST STREAMS AND RIVERS
WITHIN THE MARFC REGION CURRENTLY RANGES FROM NEAR MEDIAN TO BELOW
MEDIAN.  REAL-TIME WATER DATA CAN BE FOUND BY VISITING THE USGS WEB
PAGES AT HTTP://WATER.USGS.GOV/.

SOIL MOISTURE CONDITIONS - NORMAL TO UNUSUALLY MOIST.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS WIDELY USED TO INFER DEEP SOIL
MOISTURE CONDITIONS.  THE JANUARY 19, 2013 INDEX CHART
(WWW.CPC.NOAA.GOV/PRODUCTS WEBSITE) INDICATES SOILS ACROSS THE MARFC
SERVICE AREA CONTAIN MOISTURE THAT RANGES FROM NEAR NORMAL TO
UNUSUALLY MOIST FOR THIS TIME OF YEAR.  THE DRY SOILS IN PORTIONS OF
VA HAVE IMPROVED TO NEAR NORMAL THANKS TO LAST WEEK'S RAINS.  FOR
ADDITIONAL SOIL MOISTURE INFORMATION VISIT
WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING.

GROUND WATER - NORMAL TO BELOW NORMAL.  MOST USGS GROUND WATER
MONITORING WELLS WITHIN THE MARFC REGION ARE INDICATING NEAR NORMAL
LEVELS.  HOWEVER, MANY MONITORING WELLS LOCATED IN THE CHESAPEAKE BAY
REGION AND IN PORTIONS OF VA CONTINUE TO INDICATE BELOW NORMAL LEVELS.
PLEASE VISIT HTTP://GROUNDWATERWATCH.USGS.GOV.

RESERVOIR CONDITIONS - ABOUT AVERAGE.  IN GENERAL, MOST MAJOR
RESERVOIRS WITHIN THE MARFC REGION ARE HOLDING NEAR NORMAL STORAGES
FOR THIS TIME OF YEAR.

FUTURE WEATHER CONDITIONS - ANOTHER RATHER WEAK WEATHER SYSTEM WILL
BRING MOSTLY LIGHT SNOW TO PORTIONS OF THE MARFC REGION FRIDAY AND
FRIDAY NIGHT.  THE RECENT COLD TEMPERATURES WILL BEGIN TO MODERATE
SUNDAY AS HIGH PRESSURE MOVES EAST OFF THE COAST.  A WARM FRONT WILL
PRODUCE LIGHT MIXED PRECIPITATION MONDAY.  MILD AIR WILL SPREAD ACROSS
THE MARFC REGION BEHIND THIS FRONT, RESULTING IN SNOWMELT, ESPECIALLY
ACROSS THE SOUTH AND EAST.  A COLD FRONT WILL CROSS THE MARFC REGION
MIDWEEK NEXT WEEK ACCOMPANIED BY WHAT CURRENTLY LOOKS LIKE
LIGHT-MODERATE RAINFALL.  SEASONABLY COLDER TEMPERATURES WITH MAINLY
LIGHT PRECIPITATION RETURNS BEHIND THAT FRONT.  AT THE PRESENT TIME
THERE ARE NO STRONG INDICATIONS OF ANY WIDESPREAD HEAVY RAIN EVENTS
FOR THE MARFC SERVICE AREA FOR AT LEAST THE NEXT WEEK.  THE LATEST
(JANUARY 23, 2013) NWS 6-10 DAY AND 8-14 DAY WEATHER FORECASTS FOR THE
MARFC REGION SUGGEST NORMAL TO BELOW NORMAL TEMPERATURES WHEN AVERAGED
OVER THE NINE-DAY PERIOD JANUARY 29-FEBRUARY 6, 2013.  MEANWHILE,
PRECIPITATION WILL MOST LIKELY BE ABOVE NORMAL FOR THE SAME PERIOD.
PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV.

AHPS RIVER FORECASTS - NORMAL TO SOMEWHAT 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.  REMEMBER, AHPS RIVER
FORECASTS DO NOT TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER CONDITIONS.
FOR THE NEXT TWO WEEKS (JANUARY 24-FEBRUARY 7, 2013) AHPS RIVER
FORECASTS INDICATE THAT THE LIKELIHOOD OF RIVER FLOODING WITHIN THE
MARFC SERVICE AREA RANGES FROM A LITTLE BELOW NORMAL ACROSS THE
NORTHERN HALF TO ABOUT AVERAGE ACROSS THE SOUTHERN HALF.  PLEASE VISIT
WWW.WEATHER.GOV/AHPS/ FOR ADDITIONAL INFORMATION.

ENSEMBLE RIVER FORECASTS - NO RIVER FLOOD THREAT DURING THE NEXT WEEK.
A RELATIVELY NEW TOOL DEVELOPED BY THE NWS NOW AIDS 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 LONG-RANGE FORECASTS SHOULD BE USED WITH CAUTION AND UTILIZED AS
ANOTHER TOOL TO ASSESS RIVER FLOOD POTENTIAL FOR UP TO ONE WEEK INTO
THE FUTURE.  WITH THIS IN MIND, THE MOST RECENT RUNS (JANUARY 24,
2013) OF THE ENSEMBLE RIVER FORECASTS INDICATE NO THREAT OF RIVER
FLOODING WITHIN THE MARFC SERVICE AREA DURING THE NEXT SEVEN DAYS
(THROUGH JANUARY 31, 2013).  PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS TO
VIEW THESE ENSEMBLE RIVER FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL DURING THE NEXT TWO WEEKS THROUGH
FEBRUARY 7, 2013 SEEMS MINIMAL ACROSS THE MARFC REGION, WHICH IS
CONSIDERED ABOUT NORMAL FOR THIS TIME OF YEAR.  NO WIDESPREAD HEAVY
RAIN EVENTS ARE INDICATED FOR AT LEAST THE NEXT WEEK.  THOUGH SOME
SNOWMELT AND RAIN SEEMS LIKELY EARLY NEXT WEEK, NO FLOODING IS
CURRENTLY EXPECTED.  FAIRLY TYPICAL WEATHER CONDITIONS SEEM LIKELY
AFTER MIDWEEK NEXT WEEK INTO THE FORESEEABLE FUTURE.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (JANUARY 22, 2013)
U.S. DROUGHT MONITOR, MODERATE DROUGHT CONDITIONS PREVIOUSLY OBSERVED
ACROSS PORTIONS OF VIRGINIA HAVE DECREASED TO JUST A SMALL AREA OF
ABNORMALLY DRY CONDITIONS THANKS TO THE SIGNIFICANT RAIN THAT FELL
THERE LAST WEEK (JANUARY 14-17, 2013).  HOWEVER, A DROUGHT WATCH
ADVISORY CONTINUES FOR PORTIONS OF VIRGINIA AT THIS TIME.  ASSUMING
NEAR NORMAL PRECIPITATION DURING THE NEXT FEW MONTHS, NO WATER SUPPLY
SHORTAGES ARE EXPECTED IN VIRGINIA OR ANYWHERE ELSE WITHIN THE MARFC
REGION THROUGH AT LEAST MAY, 2013.  THE LATEST (JANUARY 17, 2013) NOAA
U.S. SEASONAL DROUGHT OUTLOOK SUGGESTS THE RESIDUAL DRY CONDITIONS
ACROSS PORTIONS OF VIRGINIA COULD SHOW ADDITIONAL IMPROVMENT DURING
THE NEXT COUPLE OF MONTHS.  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
TWO WEEKS, ON FEBRUARY 7, 2013.

SK
$$

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