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
125 PM EDT THU MAR 15 2017

OUTLOOK NUMBER 17-06 - MARCH 15, 2017

THIS WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK IS VALID FOR THE
TWO-WEEK PERIOD MARCH 15-30, 2017.

THIS OUTLOOK ESTIMATES THE POTENTIAL FOR RIVER FLOODING (NOT FLASH
FLOODING) TO DEVELOP DURING THE NEXT TWO WEEKS ACROSS THE MIDDLE
ATLANTIC RIVER FORECAST CENTER`S (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 FOR MARFC
RIVERS DURING THE NEXT TWO WEEKS IS NEAR AVERAGE ACROSS THE NORTHERN
HALF OF THE REGION, AND BELOW AVERAGE ACROSSS THE SOUTHERN HALF.
FACTORS WHICH CONTRIBUTE TO THIS ASSESSMENT OF RIVER FLOOD POTENTIAL
ARE DISCUSSED IN SOME DETAIL BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - VARIABLE.  DURING THE LAST 30 DAYS (FEBRUARY
13-MARCH 14, 2017) PRECIPITATION (LIQUID EQUIVALENT) WAS BELOW
NORMAL TO MUCH-BELOW NORMAL ACROSS MUCH OF THE MARFC SERVICE AREA.
SOME AREAS DID RECEIVE NORMAL/ABOVE NORMAL PRECIPITATION, MAINLY IN
A ZONE FROM WESTERN MD/NORTHEASTERN WV NORTHEASTWARD THROUGH CENTRAL
AND NORTHEASTERN PA AND INTO NORTHERN NJ AND SOUTHEASTERN NY.

SNOW CONDITIONS - AVERAGE TO ABOVE AVERAGE.  DUE TO THE RECENT MAJOR
STORM, SNOW NOW COVERS APPROXIMATELY THE NORTHWESTERN THREE-QUARTERS
OF THE MARFC REGION.  SNOW DEPTHS RANGE FROM LESS THAN AN INCH NEAR
THE SOUTHERN EDGE OF THE SNOWPACK TO NEARLY THREE FEET AT A FEW
LOCATIONS IN NY.  MUCH OF THE NORTHERN HALF OF THE MARFC SERVICE
AREA HAS SNOW DEPTHS OF 8-24 INCHES.  SNOW WATER EQUIVALENT VALUES
RANGE FROM A FEW TENTHS OF AN INCH ACROSS THE SOUTHERN EDGE OF THE
SNOWPACK, TO AROUND 3 INCHES IN PORTIONS OF NY STATE AND NORTHEAST
PA.  MUCH OF THE NORTHERN HALF OF THE REGION HAS VALUES IN THE 1.0-
2.5 INCH RANGE.  SNOW CONDITIONS ARE CURRENTLY CONSIDERED AVERAGE TO
ABOVE AVERAGE FOR MID-MARCH.  SNOW INFORMATION CAN BE FOUND BY
VISITING WWW.WEATHER.GOV/MARFC/SNOW AND WWW.NOHRSC.NOAA.GOV.

RIVER ICE - ABOUT AVERAGE.  THE UNUSUALLY COLD WEATHER RECENTLY HAS
ALLOWED SOME RIVER ICE TO REFORM, MAINLY ACROSS THE NORTHERN HALF OF
THE REGION.  THIS IS RARE FOR MID MARCH.  EVEN SO, THE RIVER ICE IS
NOT PARTICULARLY THICK OR EXTENSIVE.  SOME ADDITIONAL RIVER ICE
FORMATION MAY OCCUR FOR ABOUT THE NEXT WEEK OR SO.  STILL, RIVER ICE
CONDITIONS ARE, AND SHOULD REMAIN, ABOUT AVERAGE FOR LATE WINTER.

STREAMFLOW CONDITIONS - VARIABLE.  THE LATEST DATA FROM THE UNITED
STATES GEOLOGICAL SURVEY (USGS) INDICATE ABOVE-AVERAGE STREAMFLOWS
IN AND AROUND THE DELMARVA PENINSULA/SOUTHERN NJ DUE TO RECENT
RAINFALL.  ELSEWHERE STREAMFLOWS ARE GENERALLY BELOW OR EVEN MUCH-
BELOW NORMAL FOR MID MARCH.  STREAMFLOWS ARE EXPECTED TO EVENTUALLY
RISE DURING THIS TWO-WEEK PERIOD ONCE SNOWMELT BEGINS.  PLEASE VISIT
THE USGS WEB PAGES AT WWW.USGS.GOV/WATER FOR CURRENT STREAMFLOW DATA.

SOIL MOISTURE CONDITIONS - NORMAL TO MUCH BELOW NORMAL.  THE LONG-
TERM PALMER DROUGHT SEVERITY INDEX IS USED TO INFER DEEP SOIL
MOISTURE CONDITIONS.  THE MARCH 11, 2017 CHART (FOUND AT
WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/
REGIONAL_MONITORING/PALMER.GIF) SUGGESTS DEEP SOILS ACROSS MUCH OF
THE MARFC SERVICE AREA CONTAIN MOISTURE THAT IS FAIRLY CLOSE TO
NORMAL FOR THIS TIME OF YEAR.  HOWEVER, OTHER DETAILED SOIL MOISTURE
INFORMATION (GO TO WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING
AND THEN CLICK ON U.S. MONITORING) SHOWS CONSIDERABLE SOIL MOISTURE
DEFICITS REMAIN ACROSS LARGE PORTIONS OF THE MARFC REGION,
ESPECIALLY EASTERN AND SOUTHERN REGIONS.

GROUNDWATER - VARIABLE.  MOST USGS GROUNDWATER MONITORING WELLS
ACROSS THE SOUTHEASTERN HALF OF THE MARFC REGION ARE CURRENTLY
INDICATING GROUNDWATER LEVELS THAT ARE BELOW OR MUCH-BELOW THEIR
LONG-TERM NORMALS FOR THIS TIME OF YEAR.  ELSEWHERE GROUNDWATER
LEVELS ARE CLOSER TO NORMAL.  PLEASE VISIT
HTTPS://GROUNDWATERWATCH.USGS.GOV.

RESERVOIR CONDITIONS - BELOW AVERAGE TO AVERAGE.  MOST MAJOR
RESERVOIRS WITHIN THE MARFC REGION ARE HOLDING STORAGES THAT ARE
BELOW AVERAGE/AVERAGE FOR THIS TIME OF YEAR.  RESERVOIR STORAGE IN
THE UPPER DELAWARE RIVER BASIN HAS NOW IMPROVED TO LONG-TERM MEDIAN
LEVELS, WITH SIGNIFICANT SNOWMELT STILL TO COME.

FUTURE WEATHER CONDITIONS - CONTINUED BELOW-AVERAGE TEMPERATURES AND
GENERALLY ONLY LIGHT-MODERATE PRECIPITATION EVENTS ARE EXPECTED
DURING ABOUT THE FIRST WEEK OF THIS TWO-WEEK OUTLOOK PERIOD.  AT
THIS TIME THERE ARE NO STRONG INDICATIONS OF ANY WIDESPREAD HEAVY
RAIN EVENTS, OR RAPID SNOWMELT EVENTS, FOR ABOUT THE NEXT WEEK.
LONGER-RANGE WEATHER OUTLOOKS SUGGEST TEMPERATUHES WILL GET CLOSER
TO NORMAL, WHILE PRECIPITATION MAY BE NORMAL OR ABOVE NORMAL DURING
THE SECOND WEEK OF THIS OUTLOOK PERIOD.

ENSEMBLE RIVER FORECASTS - NO THREAT OF RIVER FLOODING DEVELOPING.
THE MOST RECENT RUNS (MARCH 15, 2017) OF THE ENSEMBLE RIVER
FORECASTS SHOW NO RIVER FLOODING DEVELOPING WITHIN THE MARFC REGION
FOR ABOUT THE NEXT WEEK.  THIS IS DUE TO CURRENTLY ANTICIPATED
FUTURE WEATHER CONDITIONS WHICH DO NOT INDICATE A LOT OF SNOWMELT
NOR WIDESPREAD HEAVY RAINFALL FOR ABOUT THE NEXT WEEK.  PLEASE VISIT
WWW.WEATHER.GOV/ERH/MMEFS FOR ENSEMBLE RIVER FORECASTS.

AHPS RIVER FORECASTS - NEAR TO BELOW NORMAL.  THE ADVANCED
HYDROLOGIC PREDICTION SERVICE (AHPS) GENERATES LONG-TERM (14 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, IT IS IMPORTANT TO NOTE THAT AHPS
RIVER FORECASTS DO NOT TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER
CONDITIONS WHEREAS ENSEMBLE RIVER FORECASTS (SEE PREVIOUS SECTION)
DO.  FOR THIS OUTLOOK PERIOD (THROUGH MARCH 30, 2017) CURRENT AHPS
RIVER FORECASTS INDICATE A BELOW-NORMAL CHANCE OF RIVER FLOODING
ACROSS THE SOUTH WITH A NEAR-NORMAL CHANCE ACROSS THE NORTH.

SUMMARY - FOR THE NEXT TWO WEEKS THE RIVER FLOOD POTENTIAL FOR
RIVERS IN THE MARFC REGION IS ABOUT AVERAGE ACROSS THE NORTH, AND
BELOW AVERAGE ACROSS THE SOUTH.  AT THIS TIME NO WIDESPREAD
SIGNIFICANT RAIN OR RAPID SNOWMELT EVENTS ARE INDICATED FOR ABOUT
THE NEXT WEEK.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (MARCH 7, 2017) U.S.
DROUGHT MONITOR (HTTP://DROUGHTMONITOR.UNL.EDU), LARGE PORTIONS OF
THE MARFC SERVICE AREA CONTINUE TO SHOW CONDITIONS THAT RANGE FROM
ABNORMALLY DRY TO SEVERE DROUGHT.  DRIEST REGIONS ARE ACROSS THE
SOUTH AND EAST.  THE RECENT STORM DID PROVIDE MEANINGFUL
PRECIPITATION ACROSS EASTERN PORTIONS OF THE MARFC AREA, WHICH WILL
HELP DIMINISH THE DRYNESS SOME.  STILL ADDITIONAL ABOVE-AVERAGE
PRECIPITATION WOULD BE BENEFICIAL ACROSS THE EAST AND ESPECIALLY THE
SOUTH TO PREVENT MORE SERIOUS PROBLEMS FROM DEVELOPING THIS SPRING
AND SUMMER.  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
ON MARCH 30, 2017.

SK
$$

....END MARFC....

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