FGUS61 KRHA 161912
ESGRHA

FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC)
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 211 PM EST THU FEB 16 2012 

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

OUTLOOK NUMBER 12-04 - FEBRUARY 16, 2012

THIS OUTLOOK IS VALID FOR THE TWO-WEEK PERIOD FEBRUARY 16-MARCH 1,
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.

TWO-WEEK RIVER FLOOD POTENTIAL OUTLOOK - GENERALLY SOMEWHAT BELOW
AVERAGE.  THE RIVER FLOOD POTENTIAL ACROS THE MARFC SERVICE AREA FOR
THE NEXT TWO WEEKS (THROUGH MARCH 1, 2012) IS CONSIDERED SOMEWHAT
BELOW AVERAGE FOR MOST OF THE MARFC REGION.  FACTORS WHICH CONTRIBUTE
TO RIVER FLOOD POTENTIAL ARE ADDRESSED INDIVIDUALLY BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - GENERALLY BELOW AVERAGE.  PRECIPITATION WITHIN
THE MARFC SERVICE AREA DURING THE LAST 30 DAYS (JANUARY 17-FEBRUARY
15, 2012) WAS BELOW AVERAGE (30-80 PERCENT OF NORMAL) ACROSS ALMOST
ALL OF THE MARFC REGION.  THE EXCEPTION WAS ACROSS A SMALL PORTION OF
WEST-CENTRAL PA, WHERE NEAR AVERAGE PRECIPITATION FELL.  PLEASE VISIT
WWW.ERH.NOAA.GOV/ER/MARFC FOR PRECIPITATION INFORMATION.

SNOW CONDITIONS - MUCH BELOW AVERAGE TO NEAR AVERAGE.  ALTHOUGH SOME
SNOW HAS FALLEN DURING THE LAST TWO WEEKS IN SOME AREAS, PRESENTLY
THERE IS AGAIN NO HYDROLOGICALLY SIGNIFICANT SNOW ON THE GROUND WITHIN
THE MARFC SERVICE AREA.  THIS IS RARE FOR THIS TIME OF YEAR ACROSS
ABOUT THE NORTHWESTERN HALF OF THE MARFC SERVICE AREA WHERE CURRENT
SNOW CONDITIONS ARE BELOW AVERAGE TO MUCH BELOW AVERAGE.  MEANWHILE,
FURTHER SOUTH AND EAST CURRENT SNOW CONDITIONS MAY BE CONSIDERED
CLOSER TO AVERAGE AS THIS AREA OFTEN HAS LITTLE OR NO SNOW ON THE
GROUND DURING MOST WINTERS.  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.  THE
CONTINUED ABSENCE OF SIGNIFICANT RIVER ICE ACROSS THE NORTHWESTERN
TWO-THIRDS OF THE MARFC SERVICE AREA IS QUITE UNUSUAL, HENCE CURRENT
RIVER ICE CONDITIONS THERE ARE BELOW AVERAGE TO MUCH BELOW AVERAGE.
FURTHER SOUTH AND EAST, CURRENT RIVER ICE CONDITIONS ARE CLOSER TO
AVERAGE AS THIS AREA OFTEN HAS LITTLE OR NO RIVER ICE DURING MOST
WINTERS.

STREAMFLOW CONDITIONS - NEAR MEDIAN TO BELOW MEDIAN.  STREAMFLOW HAS
STEADILY DECLINED FROM TWO WEEKS AGO AND IS CURRENTLY IN THE MEDIAN TO
BELOW MEDIAN RANGE ACROSS MUCH OF THE MARFC REGION.  ACCORDING TO THE
U.S. GEOLOGICAL SURVEY (USGS) MOST STREAMGAGES ACROSS THE MARFC REGION
ARE REPORTING FLOWS THAT ARE 25-130 PERCENT OF MEDIAN FOR THIS TIME OF
YEAR.  STREAMFLOW IS HIGHEST WITH RESPECT TO MEDIAN (75-130 PERCENT)
ACROSS THE NORTHWESTERN HALF OF THE MARFC SERVICE AREA, WHILE FURTHER
SOUTH AND EAST STREAMFLOW IS LOWER WITH RESPECT TO MEDIAN (25-80
PERCENT).  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 11, 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.  SOILS HAVE DRIED SLIGHTLY ACROSS ALL AREAS FROM TWO WEEKS AGO.
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.  GROUNDWATER LEVELS HAVE GENERALLY FALLEN
SLIGHTLY FROM TWO WEEKS AGO AT MOST MONITORING WELLS.  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 STORM SYSTEM THAT WILL TRACK FROM THE
DEEP SOUTH TO OFF THE CAROLINA COAST THIS WEEKEND WILL BRING MODERATE
TO HEAVY PRECIPITATION (MUCH OF IT SNOW) TO MAINLY THE SOUTHERN HALF
OF THE MARFC REGION SATURDAY NIGHT AND SUNDAY.  DETAILS CONCERNING HOW
FAR NORTH THE SNOW REACHES, AND WHERE THE AXIS OF HEAVIEST SNOW FALLS,
REMAIN UNCERTAIN AT THIS TIME.  MODERATE RAIN THEN SEEMS POSSIBLE NEXT
WEDNESDAY-THURSDAY AS TEMPERATURES WILL REMAIN GENERALLY MILDER THAN
NORMAL DURING THE NEXT TWO WEEKS.  THE LATEST (FEBRUARY 15, 2012) NWS
6-10 DAY AND 8-14 DAY WEATHER FORECASTS FOR THE MARFC REGION SUGGEST
BOTH TEMPERATURES AND PRECIPITATION WILL MOST LIKELY BE NORMAL TO
ABOVE NORMAL WHEN AVERAGED OVER THE NINE-DAY PERIOD FEBRUARY 21-29,
2012.  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.  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 (FEBRUARY 16-MARCH 1, 2012) AHPS RIVER
FORECASTS INDICATE THAT THE LIKELIHOOD OF RIVER FLOODING WITHIN THE
MARFC SERVICE AREA IS GENERALLY BELOW AVERAGE.  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
(FEBRUARY 16, 2012) OF THE EXPERIMENTAL ENSEMBLE RIVER FORECASTS
INDICATE VIRTUALLY NO THREAT OF RIVER FLOODING WITHIN THE MARFC
SERVICE AREA DURING THE NEXT 6 DAYS (THROUGH FEBRUARY 22, 2012).
PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS TO VIEW THESE EXPERIMENTAL
FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL DURING THE NEXT TWO WEEKS THROUGH
MARCH 1, 2012 IS CONSIDERED SOMEWHAT BELOW NORMAL.  ALTHOUGH SOILS IN
MANY AREAS ARE STILL WET, THERE IS STILL NO SIGNIFICANT SNOW ON THE
GROUND AT THIS TIME WITHIN THE MARFC REGION, NOR IS THERE ANY
SIGNIFICANT RIVER ICE.  ADDITIONALLY STREAMFLOWS HAVE COME DOWN DURING
THE LAST TWO WEEKS AND ARE NOW IN THE NEAR MEDIAN TO BELOW MEDIAN
RANGE.  WEATHERWISE, A SIGNIFICANT SNOWFALL IS POSSIBLE ACROSS
PORTIONS OF THE SOUTH THIS WEEKEND, FOLLOWED BY A POSSIBLE MODERATE
RAIN EVENT AROUND MIDWEEK NEXT WEEK, BUT THIS REGION HAS BEEN QUITE
DRY RECENTLY.  RISING RIVER LEVELS ARE A GOOD BET FOR LATER NEXT WEEK,
ESPECIALLY ACROSS THE SOUTH, BUT AT THIS TIME FLOODING SEEMS UNLIKELY
WITHIN THE MARFC REGION FOR AT LEAST THE FIRST WEEK OF THIS OUTLOOK
PERIOD.

WATER SUPPLY OUTLOOK - A SMALL AREA OF MODERATE DROUGHT CONDITIONS HAS
DEVELOPED OVER A PORTION OF THE DELMARVA PENINSULA, AND IT CONTINUES
TO GET INCREASINGLY DRIER ACROSS A LARGER AREA THAT INCLUDES
SOUTHEASTERN VA, THE DELMARVA PENINSULA AND 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 APRIL, 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 (FEBRUARY 16)
SHOWS THIS POTENTIAL FOR DROUGHT DEVELOPMENT.  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 ON
THURSDAY, MARCH 1, 2012.

SK
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