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
1149 AM EST THU JAN 5 2017

OUTLOOK NUMBER 17-01 - JANUARY 5, 2017

THIS FIRST WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK OF 2017 IS
VALID FOR THE TWO-WEEK PERIOD JANUARY 5-19, 2017.

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 FOR MARFC
RIVERS DURING THE NEXT TWO WEEKS IS GENERALLY BELOW AVERAGE. FACTORS
WHICH CONTRIBUTE TO THIS ASSESSMENT OF RIVER FLOOD POTENTIAL ARE
DISCUSSED IN SOME DETAIL BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - GENERALLY ABOUT NORMAL. DURING THE LAST 30
DAYS (DECEMBER 6, 2016-JANUARY 4, 2017) PRECIPITATION (LIQUID
EQUIVALENT) WAS PRETTY CLOSE TO AVERAGE ACROSS MUCH OF THE MARFC
SERVICE AREA.  MOST LOCATIONS RECEIVED 2.5-4.5 INCHES OF
PRECIPITATION (WATER EQUIVALENT), WHICH WAS MOSTLY IN THE 25 PERCENT
BELOW NORMAL TO 25 PERCENT ABOVE NORMAL RANGE.  TWO AREAS WERE
SOMEWHAT DRIER.  ONE STRETCHED FROM CENTRAL PA EAST-NORTHEASTWARD
INTO NORTHERN NJ AND SOUTHEASTERN NY.  THE OTHER WAS IN A SMALL AREA
OF NORTH-CENTRAL VA.  THERE WERE ALSO SCATTERED SMALL AREAS THAT
RECEIVED SOMEWHAT ABOVE NORMAL PRECIPITATION DURING THE LAST 30
DAYS.  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 SERVICE AREA SNOW IS GENERALLY CONFINED TO NY AND ABOUT
THE NORTHERN THIRD OF PA.  EVEN HERE, THE SNOW IS PATCHY WITH LITTLE
OR NO SNOW IN THE VALLEYS.  WHERE SNOW EXISTS THE DEPTHS ARE
GENERALLY SIX INCHES OR LESS WITH ISOLATED GREATER DEPTHS IN HIGHER
ELEVATIONS.  SNOW WATER EQUIVALENT VALUES ARE GENERALLY AN INCH OR
LESS, WITH 1.5-2.5 INCHES IN SOME OF THE HIGHER ELEVATIONS IN NY.
FROM ABOUT INTERSTATE 80 AND NORTHWARD, CURRENT SNOW CONDITIONS ARE
BELOW AVERAGE TO MUCH-BELOW AVERAGE.  OTHERWISE CONDITIONS ARE
PRETTY CLOSE TO NORMAL FOR EARLY WINTER.  SNOW INFORMATION CAN BE
FOUND BY VISITING WWW.WEATHER.GOV/MARFC/SNOW AND WWW.NOHRSC.NOAA.GOV.

RIVER ICE - AVERAGE TO MUCH-BELOW AVERAGE.  ALTHOUGH THERE HAS BEEN
SOME RIVER ICE THIS WINTER, CURRENTLY LITTLE IF ANY RIVER ICE IS
FOUND ON/IN MARFC RIVERS.  THIS IS UNUSUAL FOR EARLY JANUARY FOR
UPPER PORTIONS OF THE SUSQUEHANNA AND DELAWARE RIVER BASINS, BUT IS
PRETTY MUCH NORMAL FOR MOST OTHER RIVER BASINS.  SOME RIVER ICE
FORMATION IS EXPECTED DURING THE NEXT FEW DAYS MAINLY ACROSS ABOUT
THE NORTHWESTERN THIRD OF THE MARFC REGION.  BUT MILDER TEMPERATURES
MAY ARRIVE AGAIN BY MIDWEEK NEXT WEEK WHICH COULD ACT TO DECREASE
ANY RIVER ICE AGAIN.

STREAMFLOW CONDITIONS - VARIABLE.  THE LATEST DATA FROM THE UNITED
STATES GEOLOGICAL SURVEY (USGS) INDICATE MANY STREAMGAGES WITHIN THE
MARFC SERVICE AREA ARE SHOWING STREAMFLOWS THAT RANGE FROM NEAR
MEDIAN TO ABOVE MEDIAN FOR EARLY JANUARY.  STREAMFLOWS ARE SOMEWHAT
HIGHER CURRENTLY DUE TO THE RECENT RAIN EVENT WHICH IN SOME AREAS
ALSO COMBINED WITH SOME SNOWMELT.  THERE ARE SOME SMALL AREAS WITH
NOTABLY BELOW MEDIAN FLOWS FOR THE DATE, INCLUDING PORTIONS OF PA,
NJ AND VA.  PLEASE VISIT THE USGS WEB PAGES AT WWW.USGS.GOV/WATER
FOR STREAMFLOW DATA.

SOIL MOISTURE CONDITIONS - BELOW NORMAL.  THE LONG-TERM PALMER
DROUGHT SEVERITY INDEX IS USED TO INFER DEEP SOIL MOISTURE
CONDITIONS.  THE DECEMBER 31, 2016 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 THEN CLICK ON U.S. MONITORING) SHOWS CONSIDERABLE
SOIL MOISTURE DEFICITS REMAIN ACROSS LARGE PORTIONS OF THE MARFC
REGION.  THIS SUPPORTS THE MOST RECENT VERSION (JANUARY 3, 2017) OF
THE U.S. DROUGHT MONITOR CHART WHICH SHOWS LARGE PORTIONS OF THE
MARFC REGION EXPERIENCING ABNORMALLY DRY TO SEVERE DROUGHT
CONDITIONS (HTTP://DROUGHTMONITOR.UNL.EDU).

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

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

FUTURE WEATHER CONDITIONS - TYPICAL JANUARY WEATHER WITH COLD
TEMPERATURES AND ONLY LIGHT/MODERATE PRECIPITATION IS EXPECTED FOR
THE NEXT FEW DAYS.  SOME SNOW IS EXPECTED PRETTY FAR SOUTH.  MILDER
TEMPERATURES ARE EXPECTED EARLY-MID WEEK NEXT WEEK ACCOMPANIED BY
POSSIBLY SOME MODERATE RAIN.  LONGER-RANGE WEATHER OUTLOOKS SUGGEST
ABOVE AVERAGE TEMPERATURES AND PRECIPITATION FOR MUCH OF THE MARFC
REGION WHEN AVERAGED OVER THE NINE DAY PERIOD FROM JANUARY 10-18,
2017.  LONGER-RANGE WEATHER OUTLOOKS CAN BE VIEWED AT
WWW.CPC.NCEP.NOAA.GOV.

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, NOTE THAT AHPS RIVER FORECASTS DO NOT
TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER CONDITIONS.  FOR THIS
OUTLOOK PERIOD (THROUGH JANUARY 19, 2017) CURRENT AHPS RIVER
FORECASTS INDICATE A NEAR OR BELOW-NORMAL CHANCE OF RIVER FLOODING
FOR MOST MARFC RIVERS.  THIS REINFORCES THE IDEA THAT RIVER FLOODING
WITHIN THE MARFC REGION IS RELATIVELY UNCOMMON IN JANUARY AND THAT
SIGNIFICANT WIDESPREAD RAINFALL WOULD BE NECESSARY FOR RIVER
FLOODING TO DEVELOP.

ENSEMBLE RIVER FORECASTS - A MINIMAL THREAT OF ISOLATED RIVER
FLOODING. THE MOST RECENT RUNS (JANUARY 5, 2017) OF THE ENSEMBLE
RIVER FORECASTS SHOW JUST A MINIMAL THREAT OF ISOLATED RIVER
FLOODING DEVELOPING IN THE NY BASINS DURING THE NEXT WEEK.  THIS
MINIMAL THREAT IS CENTERED AROUND 1/11-1/12 AND IS ASSOCIATED WITH A
SNOWMELT/RAIN EVENT AROUND THAT TIME PERIOD.  PLEASE VISIT
WWW.WEATHER.GOV/ERH/MMEFS FOR ENSEMBLE RIVER FORECASTS.

SUMMARY - THE RIVER FLOOD POTENTIAL FOR RIVERS IN THE MARFC REGION
DURING THE NEXT TWO WEEKS IS GENERALLY BELOW AVERAGE.  HEAVY
RAINFALL WOULD BE REQUIRED TO CAUSE RIVER FLOODING.  A
SNOWMELT/RAINFALL EVENT COULD OCCUR JANUARY 11-12 AND WILL NEED TO
BE MONITORED.  ANOTHER EVENT COULD OCCUR AROUND JANUARY 15-16.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (JANUARY 3, 2017) U.S.
DROUGHT MONITOR (HTTP://DROUGHTMONITOR.UNL.EDU), LARGE PORTIONS OF
THE MARFC SERVICE AREA ARE SHOWING CONDITIONS THAT RANGE FROM
ABNORMALLY DRY TO SEVERE DROUGHT.  LATEST OUTLOOKS SUGGEST THESE DRY
CONDITIONS MAY PERSIST AT LEAST THROUGH THE REMAINDER OF JANUARY AND
PERHAPS LONGER.  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 JANUARY 19, 2017.

SK
$$

....END MARFC....

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