FGUS61 KRHA 051658
ESGRHA
FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC)
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 1158 AM EST THU JAN 05 2012 
WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK
NWS MIDDLE ATLANTIC RIVER FORECAST CENTER

OUTLOOK NUMBER 12-01 - JANUARY 5, 2012

THIS OUTLOOK IS VALID FOR THE TWO-WEEK PERIOD JANUARY 5-19, 2012.
THE FOLLOWING 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 ABOUT AVERAGE.
WHEN LOOKING AT ALL FACTORS TOGETHER, THE RIVER FLOOD POTENTIAL FOR
THE NEXT TWO WEEKS (THROUGH JANUARY 19, 2012) IS ABOUT AVERAGE FOR
EARLY-MID WINTER ACROSS THE MARFC SERVICE AREA.  FACTORS WHICH
CONTRIBUTE TO RIVER FLOOD POTENTIAL ARE ADDRESSED INDIVIDUALLY BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - GENERALLY AVERAGE TO ABOVE AVERAGE.  WHILE 2011
WAS AN EXCEPTIONALLY WET YEAR FOR NORTHERN AND EASTERN PORTIONS OF THE
MARFC REGION (WITH NUMEROUS RECORDS BROKEN), PRECIPITATION DURING THE
LAST 30 DAYS (DECEMBER 6, 2011-JANUARY 4, 2012) WAS MOSTLY IN THE
AVERAGE TO ABOVE AVERAGE RANGE (100-150 PERCENT OF NORMAL).  A NOTABLE
EXCEPTION TO THIS 30-DAY GENERALIZATION IS FOUND IN AN AREA THAT
STRETCHES FROM SOUTHWEST VA EAST-NORTHEASTWARD THROUGH THE NORTHERN
CHESAPEAKE BAY REGION, WHERE MUCH ABOVE AVERAGE PRECIPITATION HAS BEEN
OBSERVED.  HERE 30-DAY PRECIPITATION WAS 150-250 PERCENT OF NORMAL.
MEANWHILE, A SMALL REGION OF BELOW AVERAGE PRECIPITATION WAS OBSERVED
ACROSS PORTIONS OF SOUTHEAST VA AND THE LOWER DELMARVA PENINSULA.
PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC FOR PRECIPITATION INFORMATION.
SNOW CONDITIONS - MUCH BELOW AVERAGE TO AVERAGE.  PRESENTLY THERE IS
NO HYDROLOGICALLY SIGNIFICANT SNOW ON THE GROUND WITHIN THE MARFC
SERVICE AREA.  THIS IS QUITE UNUSUAL 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.  IN THIS
REGION THE MOST SIGNIFICANT SNOWFALL SO FAR THIS COLD SEASON FELL LAST
AUTUMN IN OCTOBER.  SINCE THEN, VERY LITTLE SNOW HAS FALLEN WHICH IS
VERY UNUSUAL FOR THIS AREA.  MEANWHILE, FURTHER SOUTH AND EAST CURRENT
SNOW CONDITIONS ARE CLOSER TO AVERAGE FOR THIS TIME OF YEAR SINCE THIS
AREA RECEIVES CONSIDERABLY LESS SNOW THAN NORTHERN AREAS, ON AVERAGE.
PLEASE VISIT WWW.NOHRSC.NOAA.GOV AND WWW.ERH.NOAA.GOV/ER/MARFC FOR
SPECIFICS ON SNOW CONDITIONS.

RIVER ICE - BELOW AVERAGE TO AVERAGE.  NO HYDROLOGICALLY SIGNIFICANT
RIVER ICE IS CURRENTLY FOUND WITHIN THE MARFC SERVICE AREA.  WHILE
SOME MINOR ICE EFFECTS HAVE BEEN NOTED THE LAST FEW DAYS ACROSS THE
NORTH, MILD TEMPERATURES ON FRIDAY SHOULD DECREASE OR ELIMINATE THESE
EFFECTS.  THE LACK OF RIVER ICE ACROSS THE NORTH IS AGAIN RATHER
UNUSUAL FOR THIS TIME OF YEAR, HENCE CURRENT RIVER ICE CONDITIONS ARE
BELOW AVERAGE THERE.  FURTHER SOUTH, CURRENT RIVER ICE CONDITIONS ARE
ABOUT AVERAGE AS RIVER ICE IS MUCH LESS COMMON HERE THAN ACROSS THE
NORTH.

STREAMFLOW CONDITIONS - NEAR TO ABOVE MEDIAN.  STREAMFLOW IS CURRENTLY
IN THE MEDIAN TO ABOVE MEDIAN RANGE ACROSS ALL OF THE MARFC REGION.
ACCORDING TO THE U.S. GEOLOGICAL SURVEY (USGS) MOST STREAMGAGES ACROSS
THE MARFC REGION ARE REPORTING FLOWS THAT ARE 100-400 PERCENT OF
MEDIAN FOR THIS TIME OF YEAR.  STREAMFLOW HAS DECREASED SOME FROM
EARLIER THIS WINTER WHEN MUCH ABOVE MEDIAN CONDITIONS EXISTED.
REAL-TIME WATER DATA CAN BE FOUND BY VISITING THE USGS WEB PAGES AT
HTTP://WATER.USGS.GOV/.

SOIL MOISTURE CONDITIONS - ABOVE TO MUCH ABOVE NORMAL.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS WIDELY USED TO INFER DEEP SOIL
MOISTURE CONDITIONS.  THE DECEMBER 31, 2011 INDEX CHART
(WWW.CPC.NOAA.GOV/PRODUCTS WEBSITE) INDICATES EXTREMELY MOIST SOILS
ACROSS THE NORTH, WITH UNUSUALLY MOIST TO VERY MOIST SOILS ACROSS THE
SOUTH.  THE WET SOILS REFLECT TO SOME DEGREE THE WET AUTUMN AND THE
WET YEAR THAT MUCH OF THE MARFC REGION EXPERIENCED.  PLEASE REFER TO
WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING FOR INFORMATION.

GROUND WATER - GENERALLY NORMAL TO ABOVE NORMAL.  MOST USGS GROUND
WATER MONITORING WELLS ARE INDICATING ABOVE NORMAL (IN SOME AREAS MUCH
ABOVE NORMAL) LEVELS ACROSS THE NORTHERN TWO-THIRDS OF THE MARFC
SERVICE AREA, WHILE FURTHER SOUTH GROUND WATER CONDITIONS ARE CLOSER
TO NORMAL.  HOWEVER, SOME MONITORING WELLS ACROSS PORTIONS OF THE
CHESAPEAKE BAY REGION ARE SHOWING BELOW NORMAL LEVELS.  PLEASE VISIT
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 - MILD TEMPERATURES FRIDAY WILL RETURN TO
NEAR NORMAL OVER THE WEEKEND AS A COLD FRONT CROSSES THE MARFC REGION
ACCOMPANIED BY ONLY LIGHT AND SCATTERED RAIN.  FOLLOWING THE COOL, DRY
WEEKEND, MILDER AIR WILL AGAIN OVERSPREAD THE MARFC REGION EARLY NEXT
WEEK.  A SOUTHERN STORM SYSTEM NEXT WEDNESDAY-THURSDAY COULD BRING
MODERATE-HEAVY PRECIPITATION TO MUCH OF THE REGION.  AT THIS TIME RAIN
IS INDICATED WITH THIS SYSTEM.  COLDER AND DRIER WEATHER SHOULD FOLLOW
IN THE WAKE OF THE STORM FOR AT LEAST A COUPLE OF DAYS.  THE LATEST
(JANUARY 4, 2012) NWS 6-10 DAY AND 8-14 DAY WEATHER FORECASTS FOR THE
MARFC REGION SUGGEST TEMPERATURES WILL BE NORMAL TO ABOVE NORMAL WHEN
AVERAGED OVER THE NINE-DAY PERIOD JANUARY 10-18, 2012.  MEANWHILE
PRECIPITATION WILL ALSO MOST LIKELY BE NORMAL TO ABOVE NORMAL FOR THE
SAME NINE-DAY PERIOD.  THE NWS OUTLOOK FOR THE MARFC REGION FOR THE
REST OF THE WINTER (THROUGH MARCH, 2012) SUGGESTS SOMEWHAT INCREASED
CHANCES FOR MILDER AND WETTER THAN NORMAL WEATHER.  PLEASE VISIT
WWW.CPC.NCEP.NOAA.GOV.

AHPS RIVER FORECASTS - 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 5-19, 2012) AHPS RIVER FORECASTS INDICATE THAT THE LIKELIHOOD
OF RIVER FLOODING IS NEAR AVERAGE FOR THE ENTIRE MARFC REGION.  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
(JANUARY 5, 2012) OF THE EXPERIMENTAL ENSEMBLE RIVER FORECASTS
INDICATE VIRTUALLY NO THREAT OF RIVER FLOODING WITHIN THE MARFC
SERVICE AREA DURING THE NEXT 6-7 DAYS.  TO VIEW THESE EXPERIMENTAL
FORECASTS PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS.

SUMMARY - THE RIVER FLOOD POTENTIAL DURING THE NEXT TWO WEEKS THROUGH
JANUARY 19, 2012 IS PRETTY CLOSE TO NORMAL.  ALTHOUGH THERE IS A
PROFOUND LACK OF SNOW AT THIS TIME WITHIN THE MARFC REGION, SOILS ARE
WET AND STREAMFLOW CONDITIONS ARE STILL ELEVATED.  ADDITIONALLY, A
STORM SYSTEM NEXT WEDNESDAY-THURSDAY HAS THE POTENTIAL TO PRODUCE
HEAVY RAINFALL IN SOME AREAS AND WILL NEED TO BE MONITORED.  TAKEN ALL
TOGETHER, CURRENT CONDITIONS SUGGEST ABOUT A NORMAL CHANCE OF FLOODING
DURING THE NEXT TWO WEEKS, IN SPITE OF THE FACT THAT THE WEATHER HAS
BEEN ANYTHING BUT NORMAL SO FAR THIS WINTER.

WATER SUPPLY OUTLOOK - NO DROUGHT CONDITIONS CURRENTLY EXIST WITHIN
THE MARFC REGION, AND ASSUMING NEAR NORMAL PRECIPITATION DURING THE
NEXT FEW MONTHS, NO WATER SUPPLY SHORTAGES ARE EXPECTED ANYWHERE
WITHIN THE MARFC REGION THROUGH AT LEAST MARCH, 2012.  THIS CONCLUSION
IS SUPPORTED BY THE LATEST (JANUARY 5, 2012) NOAA U.S. SEASONAL
DROUGHT OUTLOOK.  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, JANUARY 19, 2012.
SK
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