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
155 PM EST THU FEB 16, 2017

OUTLOOK NUMBER 17-04 - FEBRUARY 16, 2017

THIS FOURTH WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK IS VALID FOR
THE TWO-WEEK PERIOD FEBRUARY 16-MARCH 2, 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 IS GENERALLY BELOW AVERAGE FOR THE FIRST WEEK OF THIS OUTLOOK
PERIOD, THROUGH ABOUT FEBRUARY 23, 2017.  DURING THE SECOND WEEK OF
THIS OUTLOOK PERIOD THE RIVER FLOOD POTENTIAL INCREASES TO AVERAGE.
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 (JANUARY
16-FEBRUARY 14, 2017) PRECIPITATAION (LIQUID EQUIVALENT) WAS BELOW
TO MUCH-BELOW AVERAGE ACROSS MUCH OF VA NORTHEASTWARD THROUGH THE
CHESAPEAKE BAY REGION AND INTO SOUTHEAST PA AND SOUTHERN NJ. DRIEST
REGIONS WERE IN THE CHESAPEAKE BAY REGION. OTHERWISE IN ALL OTHER
AREAS PRECIPITATION WAS AVERAGE TO EVEN MUCH-ABOVE AVERAGE. WETTEST
AREAS INCLUDED NORTH-CENNTRAL PA AND SOUTH-CENTRAL NY.  MOST
LOCATIONS WITHIN THE MARFC SERVICE AREA RECEIVED 1.5-4.5 INCHES OF
PRECIPITATION (WATER EQUIVALENT) WHICH WAS 75 PERCENT BELOW NORMAL
IN THE CHESAPEAKE BAY REGION AND 60 PERCENT ABOVE NORMAL IN NORTH-
CENTRAL PA AND SOUTH-CENTRAL NY.  PLEASE VISIT
WWW.WEATHER.GOV/MARFC, THEN CLICK ON WATER SUPPLY AND THEN ON
DEPARTURES FROM AVERAGE.

SNOW CONDITIONS - AVERAGE TO MUCH-BELOW AVERAGE.  CURRENTLY WITHIN
THE MARFC REGION FAIRLY CONTINUOUS SNOW COVERS THE GROUND IN NY,
ACROSS NORTHERN AND NORTHEASTERN PA, AND ACROSS ABOUT THE NORTHERN
THIRD OF NJ.  THERE IS ALSO A NEGLIGIBLE SNOW COVER IN THE HIGHER
ELEVATIONS OF SOUTHWEST PA, WESTERN MD, AND NORTHEASTERN WV.  THE
ONLY REGION WHERE THE SNOW IS DEEP ENOUGH AND CONTAINS ENOUGH WATER
EQUIVALENT TO BE A FACTOR IN CONTRIBUTING TO FLOOD POTENTIAL IS
ACROSS PORTIONS OF NY, NORTHEASTERN PA AND EXTREME NORTHERN PORTIONS
OF NJ.  THIS INCLUDES UPPER PORTIONS OF THE SUSQUEHANNA BASIN, UPPER
PORTIONS OF THE DELAWARE BASIN, AND THE PASSAIC BASIN.  IN THIS
REGION SNOW DEPTHS RANGE FROM 4-15 INCHES WITH ISOLATED DEPTHS TO 20
INCHES.  CORRESPONDING WATER EQUIVALENT VALUES RANGE FROM 1-3 INCHES
WITH ISOLATED VALUES TO 3.5 INCHES.  THESE SNOW CONDITIONS ARE
SOMEWHAT BELOW AVERAGE TO AVERAGE FOR MID FEBRUARY IN THIS REGION.
OUTSIDE OF THIS REGION SNOW CONDITIONS ARE BELOW TO MUCH-BELOW
AVERAGE EXCEPT ACROSS ABOUT THE SOUTHEASTERN THIRD OF THE MARFC
REGION WHERE THE CURRENT LACK OF SNOW IS FAIRLY TYPICAL OR ABOUT
AVERAGE.  WEATHER CONDITIONS DURING THE NEXT WEEK ARE EXPECTED TO BE
WARM ENOUGH TO GRADUALLY MELT SOME OF THE SNOWPACK ACROSS NORTHERN
PA, NORTHERN NJ AND NY.  SNOW INFORMATION CAN BE FOUND BY VISITING
WWW.WEATHER.GOV/MARFC/SNOW AND WWW.NOHRSC.NOAA.GOV.

RIVER ICE - AVERAGE TO MUCH-BELOW AVERAGE.  CURRENTLY THERE IS NO
SIGNIFICANT RIVER ICE ON/IN ANY MARFC RIVERS.  THIS IS RARE FOR MID
FEBRUARY FOR MOST OF THE SUSQUEHANNA AND DELAWARE RIVER BASINS, AS
WELL AS FOR RIVERS IN NORTHERN NJ.  FOR MOST OTHER MARFC RIVERS A
LACK OF RIVER ICE DURING THE PEAK WINTER PERIOD OCCURS MORE
FREQUENTLY BUT IS STILL SOMEWHAT UNCOMMON.  BASED ON CURRENT WEATHER
PREDICTIONS FOR THE NEXT TWO WEEKS, AND THE TIME OF YEAR,
SIGNIFICANT RIVER ICE FORMATION IS UNLIKELY DURING THIS NEXT TWO-
WEEK PERIOD.

STREAMFLOW CONDITIONS - VARIABLE.  THE LATEST DATA FROM THE UNITED
STATES GEOLOGICAL SURVEY (USGS) INDICATE STREAMGAGES ACROSS ABOUT
THE NORTHWESTERN THIRD OF THE SERVICE AREA ARE SHOWING STREAMFLOWS
THAT ARE ABOVE MEDIAN FOR MID FEBRUARY.  MEANWHILE ACROSS ABOUT THE
SOUTHEASTERN TWO-THIDS OF THE AREA STREAMFLOWS ARE MOSTLY BELOW TO
MUCH-BELOW MEDIAN FOR THE DATE. PLEASE VISIT THE USGS WEB PAGES AT
WWW.USGS.GOV/WATER FOR STREAMFLOW DATA.

SOIL MOISTURE CONDITIONS - NORMAL TO BELOW NORMAL.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS USED TO INFER DEEP SOIL MOISTURE
CONDITIONS.  THE FEBRUARY 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 SOIL MOISTURE
INFORMATION (GO TO WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING
AND THEN CLICK ON U.S. MONITORING) CONTINUES TO SHOW CONSIDERABLE
SOIL MOISTURE DEFICITS REMAIN ACROSS PORTIONS OF THE MARFC REGION,
ESPECIALLY EASTERN AND SOUTHERN PORTIONS.  THIS SUPPORTS THE MOST
RECENT VERSION (FEBRUARY 14, 2017) OF THE U.S. DROUGHT MONITOR CHART
WHICH STILL SHOWS LARGE PORTIONS OF THE MARFC REGION EXPERIENCING
ABNORMALLY DRY TO SEVERE DROUGHT CONDITIONS
(HTTP://DROUGHTMONITOR.UNL.EDU).

GROUNDWATER - GENERALLY NORMAL OR BELOW NORMAL.  MANY USGS
GROUNDWATER MONITORING WELLS ACROSS ESPECIALLY EASTERN AND SOUTHERN
PORTIONS OF THE MARFC REGION ARE CURRENTLY INDICATING GROUNDWATER
LEVELS THAT ARE BELOW OR EVEN MUCH-BELOW THEIR LONG-TERM NORMALS FOR
THIS TIME OF YEAR.  STILL THERE ARE ALSO SOME WELLS SCATTERED ACROSS
THE ENTIRE REGION WITH NEAR-NORMAL OR EVEN SOMEWHAT ABOVE-NORMAL
WATER LEVELS, WITH NO REAL IDENTIFIABLE PATTERN.  VISIT
HTTPS://GROUNDWATERWATCH.USGS.GOV.

RESERVOIR CONDITIONS - ABOUT AVERAGE.  MOST MAJOR RESERVOIRS WITHIN
THE MARFC REGION ARE HOLDING STORAGES THAT ARE ABOUT AVERAGE FOR
THIS TIME OF YEAR.  RESERVOIR STORAGE IN THE UPPER DELAWARE RIVER
BASIN IS CURRENTLY STILL CONSIDERABLY BELOW THE LONG-TERM MEDIAN BUT
CONTINUES TO IMPROVE.

FUTURE WEATHER CONDITIONS - THE WEATHER DURING THE NEXT WEEK WILL
LIKELY FEATURE TEMPERATURES WARMING TO ABOVE-AVERAGE READINGS OVER
THE UPCOMING WEEKEND AND BEYOND, AND ONLY PERIODS OF MOSTLY LIGHT
PRECIPITATION.  THE SECOND WEEK OF THIS OUTLOOK PERIOD COULD PRODUCE
A MORE ACTIVE WEATHER PATTERN.  AT THIS TIME THERE ARE NO
INDICATIONS OF ANY WIDESPREAD HEAVY RAIN (OR SNOW) EVENTS FOR ABOUT
THE NEXT WEEK.

AHPS RIVER FORECASTS - NEAR NORMAL 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 NEXT SECTION) DO.
FOR THIS OUTLOOK PERIOD (THROUGH MARCH 2, 2017) CURRENT AHPS RIVER
FORECASTS INDICATE A NEAR OR BELOW-NORMAL CHANCE OF RIVER FLOODING
FOR MOST MARFC RIVERS.

ENSEMBLE RIVER FORECASTS - A MINIMAL THREAT OF RIVER FLOODING
DEVELOPING.  THE MOST RECENT RUNS (FEBRUARY 16, 2017) OF THE
ENSEMBLE RIVER FORECASTS SHOW ONLY AN ISOLATED THREAT OF RIVER
FLOODING DEVELOPING IN NY DURING THE NEXT WEEK.  THIS THREAT IS
CENTERED AROUND FEBRUARY 21-22, 2017 AND IS MAINLY ASSOCIATED WITH A
POSSIBLE PERIOD OF PROLONGED SNOWMELT ALONG WITH PERIODS OF MAINLY
LIGHT/MODERATE RAINFALL.  PLEASE VISIT WWW.WEATHER.GOV/ERH/MMEFS FOR
ENSEMBLE RIVER FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL FOR RIVERS IN THE MARFC REGION
IS GENERALLY BELOW AVERAGE DURING THE FIRST WEEK OF THIS TWO-WEEK
OUTLOOK PERIOD DUE TO EXPECTED TRANQUIL WEATHER CONDITIONS AND A
LACK OF WIDESPREAD HEAVY RAINFALL.  THE RIVER FLOOD POTENTIAL DURING
THE SECOND WEEK IS ABOUT AVERAGE AS A MORE ACTIVE WEATHER PATTERN IS
EXPECTED.  WIDESPREAD HEAVY RAINFALL WOULD BE REQUIRED TO CAUSE
RIVER FLOODING AND AT THIS TIME THERE ARE NO INDICATIONS OF ANY
WIDESPREAD HEAVY RAINFALL EVENTS FOR THE NEXT WEEK.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (FEBRUARY 14, 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.  LATEST OUTLOOKS SUGGEST
THESE DRY CONDITIONS WILL PERSIST BUT SHOULD ALSO GRADUALLY DIMINISH
OVER THE COURSE OF THE NEXT FEW WEEKS/MONTHS.  SO FAR ONLY ISOLATED
AND GENERALLY LOW-IMPACT WATER SUPPLY ISSUES HAVE BEEN NOTED WITHIN
THE MARFC SERVICE AREA IN ASSOCIATION WITH THE DRY CONDITIONS.  AT
THIS TIME, ASSUMING NEAR-NORMAL PRECIPITATION DURING THE NEXT FEW
MONTHS, WIDESPREAD WATER SUPPLY PROBLEMS ARE NOT ANTICIPATED.  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 MARCH 2, 2017.

SK
$$

....END MARFC....

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