Extended Streamflow Guidance
Issued by NWS Middle Atlantic RFC

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WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK
MIDDLE ATLANTIC RIVER FORECAST CENTER
NATIONAL WEATHER SERVICE STATE COLLEGE PA
307 PM EST THU FEB 04 2016


OUTLOOK NUMBER 16-03 - FEBRUARY 4, 2016

THIS THIRD WINTER/SPRING RIVER FLOOD OUTLOOK OF 2016 IS VALID FOR THE
TWO-WEEK PERIOD FEBRUARY 04-18, 2016.

THIS OUTLOOK ESTIMATES THE POTENTIAL FOR RIVER FLOODING (NOT FLASH
FLOODING) TO DEVELOP DURING THE NEXT TWO WEEKS ACROSS THE MARFC AREA
OF RESPONSIBILITY (MID-ATLANTIC REGION) BASED ON A CURRENT ASSESSMENT
OF HYDROMETEOROLOGICAL FACTORS WHICH CAN CONTRIBUTE TO RIVER FLOODING.
ACROSS THE MARFC AREA THESE FACTORS INCLUDE FUTURE WEATHER CONDITIONS,
RECENT PRECIPITATION, SOIL MOISTURE, SNOW COVER AND SNOW WATER
EQUIVALENT, RIVER ICE, STREAMFLOW, AND OTHERS.  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 - THE RIVER FLOOD POTENTIAL IS BELOW
AVERAGE FOR ABOUT THE NORTHERN THIRD OF THE MARFC REGION, AND ABOUT
AVERAGE ELSEWHERE.  FACTORS WHICH CONTRIBUTE TO THIS ASSESSMENT OF
RIVER FLOOD POTENTIAL ARE DISCUSSED IN SOME DETAIL BELOW.

CURRENT FLOODING - GENERALLY MINOR FLOODING IS OCCURRING/PREDICTED AT
SEVERAL POINTS IN THE SOUTHERN HALF OF THE MARFC SERVICE AREA, MAINLY
IN THE POTOMAC RIVER BASIN.  FLOODING SHOULD END AT ALL LOCATIONS
DURING THE NEXT 12-36 HOURS.

RECENT PRECIPITATION - VARIABLE.  PRECIPITATION (LIQUID EQUIVALENT)
DURING THE LAST 30 DAYS (JANUARY 5-FEBRUARY 3, 2016) RANGED FROM BELOW
AVERAGE ACROSS FAR NORTHERN PORTIONS AREAS OF THE MARFC SERVICE AREA TO
MUCH-ABOVE AVERAGE ACROSS PORTIONS OF THE SOUTH.  THE WETTEST REGIONS
WITH RESPECT TO NORMAL WERE THOSE LOCATIONS AFFECTED BY THE HISTORIC
SNOWSTORM OF JANUARY 22-24, 2016.  WITHIN THE MARFC SERVICE AREA THIS
INCLUDES MUCH OF NORTHERN VA, CENTRAL MD AND SOUTHEASTERN PA WHERE 4-7
INCHES FELL WHICH IS 35-125 PERCENT ABOVE NORMAL.  OUTSIDE OF THIS CORE
OF MUCH-ABOVE NORMAL PRECIPITATION, 3.0-5.5 INCHES OF PRECIPITATION
FELL (0-60 PERCENT ABOVE AVERAGE) ACROSS MUCH OF THE REMAINDER OF THE
MARFC REGION EXCEPT IN NORTHERN PA AND NY, WHERE ONLY 1.5-3.0 INCHES
FELL (0-35 PERCENT BELOW AVEARGE). PLEASE VISIT
WWW.ERH.NOAA.GOV/ER/MARFC, THEN CLICK ON WATER SUPPLY AND THEN ON
DEPARTURES FROM AVERAGE.

SNOW CONDITIONS - VARIABLE.  THE ONLY AREA WITHIN THE MARFC SERVICE
AREA THAT PRESENTLY HAS HYDROLOGICALLY SIGNIFICANT SNOW ON THE GROUND
(AROUND AN INCH OR GREATER OF SNOW WATER EQUIVALENT) LIES IN A
RELATIVELY SMALL AREA ACROSS NORTHEASTERN WV, WESTERN AND CENTRAL MD,
EXTREME NORTHERN VA, AND IN SOUTH-CENTRAL/SOUTHEASTERN PA.  THIS
DEFINES THE CORE OF THE SNOW THAT REMAINS FROM THE HISTORICAL SNOWSTORM
OF JANUARY 22-24, 2016.  IN THIS REGION SNOW DEPTHS ARE GENERALLY 3-8
INCHES WITH SNOW WATER EQUIVALENT VALUES OF GENERALLY 0.5-1.5 INCHES
(WITH ISOLATED HIGHER VALUES OF BOTH DEPTH AND WATER EQUIVALENT).  THIS
CORE AREA IS THEN SURROUNDED BY LESSER AMOUNTS OF SNOW THAT DIMINISH TO
VIRTUALLY NO SNOW NEAR AND NORTH OF INTERSTATE 80, AND SOUTH AND EAST
OF A LINE FROM ROUGHLY LEXINGTON, VA TO WASHINGTON, D.C. TO TRENTON, NJ
TO NEW YORK, NY.  SNOW CONDITIONS ARE SOMEWHAT ABOVE AVERAGE FOR THIS
TIME OF WINTER IN THE SMALL CORE AREA OF SNOW DESCRIBED ABOVE.  OUTSIDE
OF THIS CORE AREA, SNOW CONDITIONS ARE MUCH BELOW NORMAL ACROSS ABOUT
THE NORTHERN THIRD OF THE MARFC REGION, AND ABOUT NORMAL ELSEWHERE.
SNOW INFORMATION CAN BE FOUND BY VISITING WWW.WEATHER.GOV/MARFC/SNOW
AND WWW.NOHRSC.NOAA.GOV.

RIVER ICE - BELOW AVERAGE.  RIVER ICE HAS DECREASED RECENTLY DUE TO THE
MILDER TEMPERATURES, RAINFALL, AND RISING RIVER LEVELS.  ISOLATED ICE
JAMS DID FORM DURING THE LAST WEEK, CAUSING AT LEAST ONE MINOR FLOOD
EVENT.  WHILE SOME NEW RIVER ICE MAY FORM, RIVER ICE CONDITIONS SHOULD
REMAIN RATHER LIMITED DURING THIS TWO-WEEK OUTLOOK PERIOD, WITH NO
LONG-DURATION PERIOD OF MUCH BELOW-NORMAL TEMPERATURES PRESENTLY
ANTICIPATED.

STREAMFLOW CONDITIONS - GENERALLY ABOVE TO MUCH-ABOVE NORMAL.  THE
LATEST DATA FROM THE UNITED STATES GEOLOGICAL SURVEY (USGS) INDICATE
MOST STREAMGAGES WITHIN THE MARFC SERVICE AREA ARE SHOWING STREAMFLOW
CONDITIONS THAT ARE CURRENTLY ABOVE/MUCH-ABOVE THE LONG-TERM MEDIAN FOR
THIS TIME OF YEAR.  A FEW POCKETS OF NEAR-NORMAL FLOWS ALSO EXIST,
MAINLY IN THE UPPER DELAWARE BASIN, ACROSS SOUTHERN PORTIONS OF NJ AND
ACROSS THE LOWER DELMARVA PENINSULA.  ONLY A FEW RIVER GAGES ARE BEING
AFFECTED BY ICE AFTER THE RECENT MILD TEMPERATURES AND RAIN EVENT.
PLEASE VISIT THE USGS WEB PAGES AT WWW.USGS.GOV/WATER FOR REAL-TIME
STREAMFLOW DATA.

SOIL MOISTURE CONDITIONS - NORMAL TO ABOVE NORMAL.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS USED TO INFER DEEP SOIL MOISTURE
CONDITIONS.  THE MOST RECENT (JANUARY 30, 2016) CHART, WHICH IS FOUND
AT WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/REGIONAL_
MONITORING/PALMER.GIF, SUGGESTS DEEP SOILS ACROSS MOST OF THE MARFC
SERVICE AREA CONTAIN MOISTURE THAT RANGES FROM NEAR NORMAL TO ABOVE
NORMAL FOR THIS TIME OF YEAR.  FOR ADDITIONAL SOIL MOISTURE INFORMATION
GO TO WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING AND THEN CLICK
ON U.S. MONITORING.

GROUND WATER - GENERALLY NEAR NORMAL.  MOST USGS GROUND WATER
MONITORING WELLS ACROSS THE MARFC REGION ARE CURRENTLY INDICATING
GROUND WATER LEVELS THAT ARE GENERALLY FAIRLY CLOSE TO NORMAL.  THERE
ARE SMALL POCKETS OF BOTH BELOW/ABOVE NORMAL GROUND WATER LEVELS
SCATTERED RANDOMLY ACROSS THE REGION.  PLEASE VISIT
HTTP://GROUNDWATERWATCH.USGS.GOV TO VIEW THE DATA.

RESERVOIR CONDITIONS - GENERALLY ABOUT AVERAGE.  IN GENERAL, MOST MAJOR
RESERVOIRS WITHIN THE MARFC REGION ARE HOLDING STORAGES THAT ARE CLOSE
TO AVERAGE FOR THIS TIME OF YEAR.  RESERVOIR STORAGE IN THE UPPER
DELAWARE RIVER BASIN IS CURRENTLY VERY CLOSE TO THE LONG-TERM MEDIAN.

FUTURE WEATHER CONDITIONS - OVER THE NEXT FEW DAYS THE WEATHER PATTERN
OVER THE MARFC REGION WILL BECOME MORE TYPICAL OF FEBRUARY WITH COLDER
TEMPERATURES EXPECTED.  A STORM OFF THE COAST WILL GRAZE PORTIONS OF NJ
WITH SOME MOSTLY LIGHT RAIN/SNOW DURING THE NEXT 24 HOURS.  THEN A
COMPLICATED STORM WILL MOVE INTO AND ACROSS THE REGION EARLY NEXT WEEK.
THIS STORM COULD PRODUCE SOME SIGNIFICANT SNOW FOR PORTIONS OF THE
MARFC REGION.  A STRONG COLD FRONT COULD THEN CROSS THE REGION LATE
NEXT WEEK.  AT THIS TIME NO WIDESPREAD HEAVY RAIN EVENTS ARE
ANTICIPATED FOR AT LEAST THE NEXT WEEK.  LONGER-RANGE WEATHER OUTLOOKS
SUGGEST A MILDER WEATHER PATTERN COULD DEVELOP FOR PORTIONS OF THE
MARFC REGION DURING THE LAST FEW DAYS OF THIS TWO-WEEK OUTLOOK PERIOD.
PLEASE VISIT WWW.CPC.NECP.NOAA.GOV FOR LONGER-RANGE WEATHER OUTLOOKS.

AHPS RIVER FORECASTS - VARIABLE.  THE ADVANCED HYDROLOGIC PREDICTION
SERVICE (AHPS) GENERATES LONG-TERM (30 DAYS OR GREATER) 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.  HOWEVER, NOTE THAT AHPS
RIVER FORECASTS DO NOT TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER
CONDITIONS.  FOR THIS OUTLOOK PERIOD (THROUGH FEBRUARY 18, 2016)
CURRENT AHPS RIVER FORECASTS INDICATE A NEAR OR SOMEWHAT BELOW NORMAL
CHANCE OF RIVER FLOODING FOR MOST MARFC RIVERS.  HOWEVER AHPS IS
SHOWING A SLIGHTLY ELEVATED RISK FOR RIVER FLOODING FOR PORTIONS OF THE
JAMES/APPOMATTOX/POTOMAC/SHENANDOAH/RAPPAHANNOCK RIVER BASINS DUE
MOSTLY TO THE CURRENTLY HIGH STREAMFLOW IN THOSE BASINS.

ENSEMBLE RIVER FORECASTS - AFTER THE CURRENT FLOOD/HIGH-WATER EVENT
ENDS, NO ADDITIONAL THREAT OF RIVER FLOODING.  THE MOST RECENT RUNS
(FEBRUARY 4, 2016) OF THE ENSEMBLE RIVER FORECASTS SHOW, AT SOME
LOCATIONS, THE FLOODING CURRENTLY OCCURRING.  AFTER THIS FLOODING ENDS,
THE ENSEMBLE RIVER FORECASTS DO NOT SHOW ANY ADDITIONAL THREAT OF RIVER
FLOODING DEVELOPING WITHIN THE MARFC REGION DURING THE NEXT WEEK OR SO.
PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS FOR ENSEMBLE RIVER FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL IN THE MARFC REGION DURING THE NEXT
TWO WEEKS IS BELOW AVERAGE FOR THE NORTHERN THIRD OF THE MARFC REGION.
ELSEWHERE, ONCE THE CURRENT MINOR FLOODING ENDS IN THE POTOMAC RIVER
BASIN, THE RIVER FLOOD POTENTIAL FOR THE REMAINDER OF THE MARFC SERVICE
AREA DURING THE NEXT TWO WEEKS IS ABOUT AVERAGE.  IN ALL AREAS
SIGNIFICANT RAIN WOULD BE REQUIRED TO INITIATE RIVER FLOODING AND AT
THIS TIME HEAVY RAIN IS NOT ANTICIPATED FOR AT LEAST THE NEXT WEEK.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (FEBRUARY 2, 2016) U.S.
DROUGHT MONITOR, ABNORMALLY DRY CONDITIONS EXIST ACROSS PORTIONS OF NY,
NJ, PA, MD AND WV, HOWEVER NO TRUE DROUGHT CONDITIONS EXIST.  THE
LACK OF SNOW ACROSS NORTHERN AND WESTERN PORTIONS OF THE MARFC REGION
AT THE PRESEENT TIME IS VERY UNUSUAL, AND IF IT CONTINUES FOR THE REST
THIS WINTER, MAY HAVE IMPLICATIONS ON THE WATER SUPPLY OUTLOOK FOR THIS
SPRING AND SUMMER.  NORMALLY AT THIS TIME OF YEAR ANYWHERE FROM 1-4 OR
MORE INCHES OF SNOW WATER EQUIVALENT EXISTS IN THE SNOWPACK ACROSS THE
NORTHWEST HALF OF THE REGION, AND THE MELTING OF THE SNOW IN SPRING
DOES ASSIST IN RECHARGING SOME WATER SUPPLY RESERVOIRS IN THIS REGION.
THIS BEING SAID, ASSUMING NEAR-NORMAL PRECIPITATION DURING THE NEXT FEW
MONTHS (SNOW AND RAIN), NO DROUGHT CONDITIONS OR WATER SUPPLY SHORTAGES
ARE EXPECTED TO DEVELOP ANYWHERE WITHIN THE MARFC REGION THROUGH AT
LEAST APRIL, 2016.  PLEASE VISIT WWW.DROUGHT.GOV, WWW.CPC.NCEP.NOAA.GOV
AND WWW.WEATHER.GOV/MARFC/WRO_UPDATE FOR ADDITIONAL DROUGHT AND WATER
SUPPLY INFORMATION.

PLEASE VISIT THE NWS MARFC HOMEPAGE AT WWW.WEATHER.GOV/MARFC OR FIND US
ON FACEBOOK AT WWW.FACEBOOK.COM/NWSMARFC/?REF=AYMT_HOMEPAGE_PANEL AND
ON TWITTER @NWSMARFC.

THE NEXT WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED BY THIS OFFICE IN
TWO WEEKS, ON THURSDAY, FEBRUARY 18, 2016.

$$

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