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
1:45 PM EST WED FEB 14 2018

OUTLOOK NUMBER 18-04 - FEBRUARY 14, 2018

THIS WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK IS VALID FOR THE
TWO-WEEK PERIOD FEBRUARY 15-MARCH 1, 2018.

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 SOMEWHAT ABOVE AVERAGE.  FACTORS
WHICH CONTRIBUTE TO THIS ASSESSMENT OF RIVER FLOOD POTENTIAL ARE
DISCUSSED IN SOME DETAIL BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - VARIABLE.  PRECIPITATION HAS INCREASED
CONSIDERABLY ACROSS MUCH OF THE MARFC SERVICE AREA RECENTLY.  THANKS
TO THE RECENT STORM, SOUTHERN AND EASTERN AREAS ARE NOW, AT LEAST
FOR THE TIME BEING, RATHER WET.  OVER THE LAST 30 DAYS (JANUARY 15-
FEBRUARY 13) PRECIPITATION WAS BELOW NORMAL/NORMAL ACROSS SOUTHERN
NY, PORTIONS OF CENTRAL PA, IN WESTERN MD AND NORTHEASTERN WV.
ELSEWHERE, PRECIPITATION HAS BEEN ABOVE NORMAL/MUCH ABOVE NORMAL.
THE RECENT WET WEATHER WILL HELP REDUCE THE DRYNESS THAT HAS EXISTED
ACROSS MUCH OF THE SOUTHEASTERN HALF OF THE MARFC REGION FOR SEVERAL
MONTHS.  TOTAL PRECIPITATION DURING THE LAST 30 DAYS RANGED FROM
AROUND 1.5 INCHES IN SOUTH-CENTRAL NY TO 4-7 INCHES ACROSS MUCH OF
VA, THE DELMARVA REGION AND NJ.  PRECIPITATION DEPARTURE DATA CAN BE
VIEWED AT WWW.WEATHER.GOV/MARFC/PRECIPITATION_DEPARTURES.

SNOW CONDITIONS - BELOW AVERAGE/AVERAGE.  SNOW PRESENTLY COVERS THE
GROUND ACROSS ABOUT THE NORTHWESTERN THIRD OF THE MARFC REGION.  THE
MOST SIGNIFICANT SNOW IS FOUND ACROSS UPPER PORTIONS OF BOTH THE
SUSQUEHANNA AND DELAWARE BASINS IN NY AND NORTHERN PA.  HERE SNOW
DEPTHS RANGE FROM 3-10 INCHES WHILE SNOW WATER EQUIVALENT VALUES ARE
GENERALLY 1.0-2.0 INCHES.  ISOLATED LOCATIONS HAVE SOMEWHAT HIGHER
VALUES.  OUTSIDE OF THIS REGION SNOW DEPTHS DECREASE HEADING
SOUTHWARD TO 1-4 INCHES WHILE WATER EQUIVALENT VALUES DECREASE TO
LESS THAN AN INCH.  SNOW CONDITIONS ARE GENERALLY BELOW AVERAGE FOR
THIS TIME OF WINTER NORTHWEST OF A LINE FROM ABOUT ROANOKE VA TO
NEAR FREDERICK MD TO ABOUT POUGHKEEPSIE NY.  SOUTHEAST OF THAT LINE
SNOW CONDITIONS ARE ABOUT AVERAGE, MEANING LITTLE OR NO SNOW EXISTS
WHICH IS FAIRLY TYPICAL FOR THIS REGION.  SNOW INFORMATION CAN BE
FOUND AT WWW.WEATHER.GOV/MARFC/SNOW AND WWW.NOHRSC.NOAA.GOV.

RIVER ICE - GENERALLY BELOW AVERAGE.  RIVER ICE CONDITIONS ARE
PRESENTLY BELOW NORMAL FOR THIS TIME OF WINTER.  WHILE RIVER ICE IS
BEING OBSERVED ACROSS ABOUT THE NORTHERN THIRD OF THE MARFC REGION,
THE ICE IS NEITHER THICK NOR EXTENSIVE.  WITH A WARMER-THAN-NORMAL
WEATHER PATTERN POSSIBLE FOR MUCH OF THE NEXT TWO WEEKS, LITTLE IF
ANY NEW RIVER ICE IS EXPECTED TO FORM DURING THE NEXT TWO WEEKS.  IT
ALSO SEEMS UNLIKELY THAT TEMPERATURES WILL GET COLD ENOUGH FOR ANY
SUBSTANTIAL RIVER ICE TO REFORM FOR THE REST OF THIS WINTER.

STREAMFLOW CONDITIONS - AVERAGE/ABOVE AVERAGE.  SOME STREAMGAGES,
MAINLY IN NY, CONTINUE TO BE AFFECTED BY ICE.  THE LATEST DATA FROM
THE UNITED STATES GEOLOGICAL SURVEY (USGS) INDICATE NEAR-NORMAL TO
ABOVE-NORMAL STREAMFLOW CONDITIONS THROUGHOUT THE MARFC REGION.
PLEASE VISIT HTTPS://WATERDATA.USGS.GOV/NWIS/RT FOR CURRENT
STREAMFLOW DATA.

SOIL MOISTURE CONDITIONS - NORMAL/BELOW NORMAL.  THE LONG-TERM
PALMER DROUGHT SEVERITY INDEX IS USED TO INFER DEEP SOIL MOISTURE
CONDITIONS.  THE FEBRUARY 10, 2018 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 ABOUT 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) INDICATES SOIL MOISTURE DEFICITS
REMAIN ACROSS SOUTHERN AND EASTERN REGIONS.  THESE AREAS DID RECEIVE
2-4 INCHES OF RAIN FROM THE MOST RECENT RAIN EVENT WHICH WILL
CERTAINLY HELP TO DECREASE THE DRYNESS.

GROUNDWATER - NORMAL/BELOW NORMAL.  USGS GROUNDWATER MONITORING
WELLS ARE CURRENTLY INDICATING NEAR-NORMAL GROUNDWATER LEVELS ACROSS
ABOUT THE NORTHWESTERN TWO-THIRDS OF THE REGION, AND BELOW-NORMAL
LEVELS ELSEWHERE.  PLEASE VISIT HTTPS://GROUNDWATERWATCH.USGS.GOV.

RESERVOIR CONDITIONS - AVERAGE/BELOW AVERAGE.  MOST MAJOR RESERVOIRS
WITHIN THE MARFC REGION ARE HOLDING STORAGES THAT ARE AVERAGE/BELOW
AVERAGE FOR THIS TIME OF YEAR.  FOR EXAMPLE RESERVOIR STORAGE IN THE
UPPER DELAWARE RIVER BASIN IN NY IS SLIGHTLY BELOW THE LONG-TERM
MEDIAN BUT STILL WELL WITHIN THE NORMAL RANGE.

FUTURE WEATHER CONDITIONS - AN ACTIVE WEATHER PATTERN SEEMS LIKELY
TO CONTINUE FOR THE NEXT TWO WEEKS.  NUMEROUS WEATHER SYSTEMS SEEM
LIKELY TO PASS NEAR/THROUGH THE REGION, AND EACH HAS THE APPEARANCE
OF BEING ABLE TO PRODUCE AT LEAST MODERATE PRECIPITATION ACROSS
PORTIONS OF THE REGION.  SOME HEAVY RAINFALL SEEMS UNAVOIDABLE
DURING THIS NEXT TWO-WEEK PERIOD.  IN ADDITION, A VERY MILD PERIOD
SEEMS LIKELY FOR AT LEAST THE FIRST HALF OF NEXT WEEK, WHICH WILL
UNDOUBTEDLY CAUSE SNOWMELT WHERE SNOW STILL EXISTS.  THE COMBINATION
OF RATHER FREQUENT PERIODS OF MODERATE-HEAVY RAIN, AND SNOWMELT,
COULD EASILY PRODUCE SOME RIVER FLOODING ALMOST ANYWHERE WITHIN THE
MARFC REGION DURING THE NEXT TWO WEEKS.  THE FACT THAT STREAMFLOWS
ACROSS MOST OF THE REGION ARE NOW ELEVATED AND SOILS MORE MOIST
SUPPORTS THE IDEA OF AN INCREASED FLOOD POTENTIAL DURING THIS
PERIOD.  FINALLY, LONGER-RANGE WEATHER OUTLOOKS ALSO SUGGEST THIS
NEXT TWO-WEEK PERIOD WILL LIKELY BE MILDER AND WETTER THAN NORMAL
(VISIT WWW. CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/610DAY).

ENSEMBLE RIVER FORECASTS - A LIMITED THREAT OF RIVER FLOODING
DEVELOPING.  THE MOST RECENT RUNS (FEBRUARY 14, 2018) OF THE
ENSEMBLE RIVER FORECASTS, WHICH TAKE INTO ACCOUNT ANTICIPATED FUTURE
WEATHER CONDITIONS INCLUDING PRECIPITATION AND TEMPERATURES, DO SHOW
SOME CHANCE OF RIVER FLOODING DEVELOPING WITHIN THE MARFC REGION
DURING THE NEXT WEEK.  PLEASE VISIT WWW.WEATHER.GOV/ERH/MMEFS FOR
ENSEMBLE RIVER FORECASTS.

SUMMARY - FOR THE NEXT TWO WEEKS THE RIVER FLOOD POTENTIAL FOR
RIVERS IN THE MARFC REGION IS ABOVE AVERAGE.  HIGHER STREAMFLOWS,
WETTER SOILS, AND A POTENTIALLY ACTIVE WEATHER PATTERN CAPABLE OF
PRODUCING PERIODS OF HEAVY RAIN (AND SNOWMELT) ARE ALL FACTORS
LEADING TO THE ABOVE-AVERAGE POTENTIAL.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (FEBRUARY 6, 2018)
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 EVEN SEVERE DROUGHT.  DRIEST REGIONS ARE
ACROSS THE SOUTH AND EAST.  HOWEVER, THIS CHART DOES NOT TAKE INTO
ACCOUNT THE RECENT HEAVY RAIN EVENT THAT IMPACTED THOSE SAME
REGIONS.  A NEW CHART WILL BE RELEASED THIS WEEK, AND SOME
IMPROVEMENT IN DROUGHT CONDITIONS WITHIN THE MARFC REGION IS
ANTICIPATED.  VISIT WWW.DROUGHT.GOV, WWW.CPC.NCEP.NOAA.GOV AND
WWW.WEATHER.GOV/MARFC/WRO_NORTH 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 1, 2018.

SK
$$

....END MARFC....

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