FGUS61 KRHA 011847
ESGRHA

FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC)
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 147 PM EST THU MAR 01 2012 

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

OUTLOOK NUMBER 12-05 - MARCH 1, 2012

THIS OUTLOOK IS VALID FOR THE ONE-WEEK PERIOD MARCH 1-8, 2012.

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.

ONE-WEEK RIVER FLOOD POTENTIAL OUTLOOK - AVERAGE TO BELOW AVERAGE.
THE RIVER FLOOD POTENTIAL ACROS THE MARFC SERVICE AREA FOR THE NEXT
WEEK (THROUGH MARCH 8, 2012) IS CONSIDERED TO BE IN THE NORMAL TO
BELOW NORMAL RANGE FOR MOST OF THE MARFC REGION.  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 (JANUARY 31-FEBRUARY 29, 2012)
WAS GENERALLY BELOW AVEARGE (25-90 PERCENT OF NORMAL) ACROSS ABOUT THE
NORTHERN HALF OF THE REGION, AND NEAR AVERAGE (70-120 PERCENT OF
NORMAL) ACROSS ABOUT THE SOUTHERN HALF OF THE REGION.  PLEASE VISIT
WWW.ERH.NOAA.GOV/ER/MARFC FOR PRECIPITATION INFORMATION.

SNOW CONDITIONS - MUCH BELOW AVERAGE TO NEAR AVERAGE.  SOME SNOW HAS
MANAGED TO ACCUMULATE RECENTLY ACROSS PORTIONS OF NORTHERN
PENNSYLVANIA AND NEW YORK WHERE SNOW WATER EQUIVALENT VALUES CURRENTLY
RANGE AS HIGH AS ABOUT AN INCH AND A QUARTER.  SNOW DEPTHS ARE
GENERALLY ONLY A FEW INCHES IN THIS REGION.  THESE AMOUNTS ARE STILL
BELOW AVERAGE FOR THIS TIME OF YEAR, WHICH IS TYPICALLY CONSIDERED
ABOUT THE PEAK OF THE SNOW ACCUMULATION SEASON.  LITTLE OR NO SNOW
EXISTS ON THE GROUND ELSEWHERE WITHIN THE MARFC REGION WHICH,
DEPENDING ON THE AREA, RANGES FROM MUCH BELOW AVERAGE (NORTHWESTERN
REGIONS) TO ABOUT AVERAGE (SOUTHEASTERN REGIONS).  PLEASE VISIT
WWW.NOHRSC.NOAA.GOV AND WWW.ERH.NOAA.GOV/ER/MARFC FOR SPECIFICS ON
SNOW CONDITIONS.

RIVER ICE - MUCH BELOW AVERAGE TO NEAR AVERAGE.  NO HYDROLOGICALLY
SIGNIFICANT RIVER ICE EXISTS WITHIN THE MARFC SERVICE AREA.  THESE
CONDITIONS ARE MUCH BELOW AVERAGE FOR MARCH 1ST ACROSS THE
NORTHWESTERN HALF OF THE REGION, BUT CLOSER TO AVERAGE ACROSS THE FAR
SOUTH AND EAST WHERE THERE IS OFTEN LITTLE OR NO RIVER ICE DURING MANY
WINTERS.

STREAMFLOW CONDITIONS - BELOW MEDIAN TO MUCH ABOVE MEDIAN.  IN
RESPONSE TO THE SIGNIFICANT RAINFALL OF THE LAST 24-36 HOURS,
STREAMFLOW HAS INCREASED RATHER DRAMATICALLY ACROSS THE SOUTHERN HALF
OF THE MARFC REGION AND IS NOW MUCH ABOVE MEDIAN RANGE FOR THE DATE.
ELSEWHERE, ACCORDING TO THE U.S. GEOLOGICAL SURVEY (USGS) STREAMFLOW
CURRENTLY RANGES FROM BELOW MEDIAN TO MEDIAN, BUT IS ALSO INCREASING
IN THESE AREAS DUE TO THE RECENT PRECIPITATION.  REAL-TIME WATER DATA
CAN BE FOUND BY VISITING THE USGS WEB PAGES AT HTTP://WATER.USGS.GOV/.

SOIL MOISTURE CONDITIONS - NORMAL TO MUCH ABOVE NORMAL.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS WIDELY USED TO INFER DEEP SOIL
MOISTURE CONDITIONS.  THE FEBRUARY 25, 2012 INDEX CHART
(WWW.CPC.NOAA.GOV/PRODUCTS WEBSITE) INDICATES EXTREMELY MOIST SOILS
ACROSS THE NORTH, WITH NEAR NORMAL TO UNUSUALLY MOIST SOILS ACROSS THE
SOUTH.  PLEASE SEE WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING
FOR INFORMATION.

GROUND WATER - GENERALLY NORMAL TO ABOVE NORMAL.  MOST USGS GROUND
WATER MONITORING WELLS WITHIN THE MARFC REGION ARE INDICATING NEAR
NORMAL TO ABOVE NORMAL LEVELS.  HOWEVER, SOME MONITORING WELLS ACROSS
PORTIONS OF THE CHESAPEAKE BAY REGION AND SOUTHEASTERN VA CONTINUE TO
SHOW BELOW NORMAL LEVELS.  CURRENT GROUNDWATER LEVELS CAN BE SEEN AT
HTTP://GROUNDWATERWATCH.USGS.GOV/.

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

FUTURE WEATHER CONDITIONS - A COLD FRONT WILL CROSS THE MARFC REGION
THIS WEEKEND ACCOMPANIED BY MOSTLY LIGHT-MODERATE RAINFALL.  MOSTLY
DRY WEATHER WILL THEN PREVAIL FOR MUCH OF NEXT WEEK.  EARLY WEEK WILL
BE SEASONABLY CHILLY, FOLLOWED BY A WARM UP AROUND MIDWEEK.  THE
LATEST (FEBRUARY 29, 2012) NWS 6-10 DAY WEATHER FORECAST FOR THE MARFC
REGION SUGGESTS TEMPERATURES WILL MOST LIKELY BE ABOVE NORMAL WHEN
AVERAGED OVER THE FIVE-DAY PERIOD MARCH 6-10, 2012, WHILE
PRECIPITATION WILL MOST LIKELY BE IN THE NORMAL TO ABOVE NORMAL RANGE
FOR THE SAME PERIOD.  THE NWS OUTLOOK FOR THE MARFC REGION FOR THE
REST OF THE WINTER AND INTO MID-LATE SPRING (THROUGH MAY, 2012)
SUGGESTS ABOVE NORMAL TEMPERATURES AND NEAR NORMAL PRECIPITATION.
PLEASE VISIT WWW.CPC.NCEP.NOAA.GOV.

AHPS RIVER FORECASTS - GENERALLY BELOW NORMAL TO 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 (MARCH 1-14, 2012) AHPS RIVER FORECASTS
INDICATE THAT THE LIKELIHOOD OF RIVER FLOODING WITHIN THE MARFC
SERVICE AREA IS GENERALLY BELOW AVERAGE ACROSS THE SUSQUEHANNA,
DELAWARE, PASSAIC AND RARITAN BASINS.  MEANWHILE, TO THE SOUTH THE
AHPS-GENERATED FORECASTS SUGGEST A NEAR-NORMAL CHANCE OF FLOODING
DURING THE NEXT TWO WEEKS ACROSS THE POTOMAC AND JAMES BASINS.  PLEASE
VISIT WWW.WEATHER.GOV/AHPS/.

EXPERIMENTAL ENSEMBLE RIVER FORECASTS - NO RIVER FLOOD THREAT DURING
ABOUT THE NEXT WEEK ACROSS THE MARFC SERVICE AREA.  A RELATIVELY NEW
TOOL IS CURRENTLY BEING TESTED BY THE NWS TO AID 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 EXPERIMENTAL FORECASTS SHOULD BE USED WITH CAUTION AND TREATED
AS ANOTHER TOOL TO TRY TO ASSESS RIVER FLOOD POTENTIAL FOR UP TO ONE
WEEK INTO THE FUTURE.  WITH THIS IN MIND, THE MOST RECENT RUNS (MARCH
1, 2012) OF THE EXPERIMENTAL ENSEMBLE RIVER FORECASTS INDICATE VERY
LITTLE THREAT OF RIVER FLOODING WITHIN THE MARFC SERVICE AREA DURING
THE NEXT 7 DAYS (THROUGH MARCH 8, 2012).  PLEASE VISIT
WWW.ERH.NOAA.GOV/MMEFS TO VIEW THESE EXPERIMENTAL FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL DURING THE NEXT WEEK THROUGH MARCH
8, 2012 IS CONSIDERED NORMAL TO BELOW NORMAL.  IN THE ABSENCE OF HEAVY
RAIN, IT IS UNLIKELY THAT RIVER FLOODING WILL DEVELOP WITHIN THE MARFC
REGION DURING THE NEXT WEEK.  ABOUT THE ONLY CHANCE FOR HEAVY RAIN
WOULD BE IN ASSOCIATION WITH THE COLD FRONT PASSING THROUGH THE REGION
THIS WEEKEND, AND AT THIS TIME ONLY LIGHT-MODERATE RAIN IS EXPECTED TO
ACCOMPANY THE FRONT.  UP NORTH, NOT ENOUGH SNOW EXISTS ON THE GROUND
TO BE A CONCERN WITH RESPECT TO RIVER FLOODING, EVEN IF IT ALL MELTS
THIS WEEKEND.  SO WHILE RISING RIVER LEVELS ARE ANTICIPATED THROUGH
EARLY NEXT WEEK, AT THIS TIME FLOODING SEEMS UNLIKELY TO DEVELOP.

WATER SUPPLY OUTLOOK - A SMALL AREA OF MODERATE DROUGHT CONDITIONS
REMAINS OVER A PORTION OF THE DELMARVA PENINSULA, AND IT CONTINUES TO
BE ABNORMALLY DRY ACROSS A LARGER AREA THAT INCLUDES SOUTHEASTERN VA,
THE REST OF THE DELMARVA PENINSULA AND EXTREME SOUTHERN NJ.  STILL,
ASSUMING NEAR NORMAL PRECIPITATION DURING THE NEXT FEW MONTHS, NO
WATER SUPPLY SHORTAGES ARE EXPECTED ANYWHERE WITHIN THE MARFC REGION
THROUGH AT LEAST MAY, 2012.  HOWEVER, IF BELOW AVERAGE RAINFALL
CONTINUES ACROSS THE SOUTHEASTERN PORTIONS OF THE MARFC REGION DROUGHT
CONDITIONS COULD EXPAND AND/OR WORSEN IN THE NEXT COUPLE OF MONTHS
WHICH COULD EVENTUALLY LEAD TO SOME WATER SHORTAGES IN THE SUMMER
MONTHS.  THE LATEST NOAA U.S. SEASONAL DROUGHT OUTLOOK (MARCH 1) STILL
SHOWS THIS POTENTIAL FOR DROUGHT DEVELOPMENT ACROSS THE SOUTHEAST.
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
ONE WEEK ON THURSDAY, MARCH 8, 2012.

SK
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