Extended Streamflow Guidance
Issued by NWS Middle Atlantic RFC

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FLOOD POTENTIAL STATEMENT
MIDDLE ATLANTIC RIVER FORECAST CENTER (MARFC)
NATIONAL WEATHER SERVICE STATE COLLEGE PA
 1246 PM EST THU FEB 19 2015

WINTER/SPRING RIVER FLOOD POTENTIAL OUTLOOK
NWS MIDDLE ATLANTIC RIVER FORECAST CENTER

OUTLOOK NUMBER 15-04 - FEBRUARY 19, 2015

THIS FOURTH OUTLOOK IS VALID FOR THE TWO WEEKS FEBRUARY 19-MARCH 5,
2015.

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 - BELOW AVERAGE TO AVERAGE.  THE
POTENTIAL FOR RIVER FLOODING TO DEVELOP DURING THE NEXT TWO WEEKS IS
BELOW AVERAGE FOR ABOUT THE NORTHWESTERN HALF OF THE MARFC REGION, AND
CLOSER TO AVERAGE FOR THE SOUTHEASTERN HALF.  FACTORS WHICH CONTRIBUTE
TO RIVER FLOOD POTENTIAL ARE ADDRESSED BELOW.

CURRENT FLOODING - NONE.

RECENT PRECIPITATION - GENERALLY BELOW NORMAL.  PRECIPITATION DURING
THE LAST 30 DAYS (JANUARY 20-FEBRUARY 18, 2015) WAS MOSTLY BELOW NORMAL
ACROSS THE MARFC REGION.  MOST LOCATIONS RECEIVED 1-3 INCHES (LIQUID
EQUIVALENT) OF PRECIPITATION, WHICH IS GENERALLY 10-50 PERCENT BELOW
NORMAL.  PLEASE VISIT WWW.ERH.NOAA.GOV/ER/MARFC.

SNOW CONDITIONS - ABOVE NORMAL.  CURRENTLY SNOW COVERS NEARLY ALL OF
THE GROUND WITHIN THE MARFC SERVICE AREA, EVEN TO THE COAST.  THIS IS
FAIRLY UNUSUAL.  NY HAS SNOW DEPTHS OF 10-24 INCHES WITH LOCALLY
GREATER DEPTHS.  ACROSS NORTHERN PA AND NORTHERN NJ, DEPTHS OF 6-18
INCHES ARE COMMON.  LASTLY, ACROSS THE REMAINING PORTIONS OF THE MARFC
REGION, DEPTHS OF 3-10 INCHES PREVAIL.  WITH RESPECT TO SNOW WATER
EQUIVALENT VALUES, 2.5-5.0 INCHES WITH LOCALLY HIGHER AMOUNTS EXISTS
IN NY. HEADING SOUTH, 1-3 INCHES IS COMMON ACROSS THE NORTHERN
TWO-THIRDS OF PA AND THE NORTHERN HALF OF NJ.  THE REMAINDER OF THE
MARFC SERVICE AREA HAS SNOW WATER EQUIVALENT VALUES OF AROUND AN INCH
OR LESS.  THE SNOW CONDITIONS IN NY, AND ACROSS THE NORTHERN TWO-THIRDS
OF PA AND THE NORTHERN HALF OF NJ IS SIGNIFICANT ENOUGH TO BE A FACTOR
IN THE DEVELOPMENT OF RIVER FLOODING, ESPECIALLY IF RAPID SNOWMELT
IS COMBINED WITH SIGNIFICANT RAINFALL.  WHILE RAPID SNOWMELT AND
SIGNIFICANT RAINFALL IS CURRENTLY NOT ANTICIPATED IN THESE REGIONS
DURING THE NEXT TWO WEEKS, MILDER TEMPERATURES AND RAINFALL MAY REDUCE
OR ELIMINATE THE LESS SIGNIFICANT SNOW THAT EXISTS ACROSS SOUTHERN AND
FAR EASTERN PORITONS OF THE REGION THIS WEEKEND.  FOR DETAILED SNOW
INFORMATION PLEASE VISIT WWW.NOHRSC.NOAA.GOV AND WWW.WEATHER.GOV/MARFC.

RIVER ICE - ABOVE AVERAGE TO AVERAGE.  RIVER ICE HAS GENERALLY
INCREASED ACROSS MANY AREAS WITHIN THE MARFC REGION SINCE TWO WEEKS AGO
DUE TO THE PERSISTENT COLD WEATHER.  NORTHERN/WESTERN REGIONS CONTINUE
TO OBSERVE MORE EXTENSIVE AND THICKER RIVER ICE THAN SOUTHERN/EASTERN
AREAS.  MOST STREAMS AND RIVERS NORTH OF THE MD/PA STATE LINE HAVE
SIGNIFICANT ICE, AND MANY STREAMS AND RIVERS IN THE POTOMAC RIVER BASIN
ALSO HAVE ICE, AS DO STREAMS AND RIVERS IN CENTRAL AND NORTHERN NJ.
STILL, THE MOST EXTENSIVE AND THICKEST RIVER ICE IS FOUND WITHIN THE
SUSQUEHANNA AND DELAWARE RIVER BASINS.  SHOULD A RAPID ICE BREAKUP
OCCUR IN THESE BASINS, THE RIVER ICE IS THICK ENOUGH AND EXTENSIVE
ENOUGH THAT ICE JAMS WOULD LIKELY FORM AND SOME LOCALIZED ICE JAM
FLOODING COULD OCCUR.  HOWEVER, RIVER ICE BREAKUP IN THESE TWO BASINS
IS UNLIKELY DURING THE NEXT TWO WEEKS WITH CONTINUED COLD TEMPERATURES
PREDICTED FOR MOST OF THE OUTLOOK PERIOD.

STREAMFLOW CONDITIONS - GENERALLY BELOW MEDIAN.  LATEST DATA FROM THE
U.S. GEOLOGICAL SURVEY (USGS) INDICATES THAT STREAMFLOW ACROSS THE
MARFC REGION IS CURRENTLY GENERALLY BELOW MEDIAN.  THIS REFLECTS THE
VERY COLD TEMPERATURES EXPERIENCED DURING THE LAST 3-4 WEEKS ACROSS
MOST AREAS, AND THE FACT THAT MUCH OF THE PRECIPITATION THAT HAS FALLEN
HAS BEEN FROZEN RATHER THAN LIQUID.  ADDITIONALLY, MANY STREAM GAGES
ARE NOW AFFECTED BY RIVER ICE AND THEREFORE DO NOT REPRESENT ACTUAL
STREAMFLOW CONDITIONS.  PLEASE VISIT WWW.USGS.GOV/WATER.

SOIL MOISTURE CONDITIONS - MOSTLY ABOUT NORMAL.  THE LONG-TERM PALMER
DROUGHT SEVERITY INDEX IS WIDELY USED TO INFER DEEP SOIL MOISTURE
CONDITIONS.  THE MOST RECENT (FEBRUARY 14, 2015) INDEX CHART
(WWW.CPC.NOAA.GOV/PRODUCTS) SUGGESTS SOILS ACROSS MOST OF THE MARFC
SERVICE AREA CONTAIN MOISTURE THAT IS NEAR NORMAL FOR THIS TIME OF
YEAR.  WETTER THAN NORMAL SOILS FOR THIS TIME OF YEAR ARE STILL
INDICATED IN SMALL PORTIONS OF NY, PA, DE AND NJ.  PLEASE VISIT
WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING/US FOR ADDITIONAL
SOIL MOISTURE INFORMATION.

GROUND WATER - BELOW NORMAL TO NEAR NORMAL.  USGS GROUND WATER
MONITORING WELLS ACROSS THE MARFC REGION ARE CURRENTLY INDICATING THAT
GROUND WATER LEVELS ARE GENERALLY IN THE BELOW NORMAL TO NEAR NORMAL
RANGE.  NORTHEASTERN PA, NORTHWESTERN NJ, AND SOUTH-CENTRAL NY HAVE THE
GREATEST CONCENTRATION OF WELLS WITH BELOW-NORMAL LEVELS AT THIS TIME.
VISIT HTTP://GROUNDWATERWATCH.USGS.GOV FOR MONITORING INFORMATION.

RESERVOIR CONDITIONS - GENERALLY ABOUT AVERAGE.  IN GENERAL, MOST
MAJOR RESERVOIRS WITHIN THE MARFC REGION ARE HOLDING STORAGES THAT ARE
FAIRLY CLOSE TO AVERAGE FOR THIS TIME OF YEAR.

FUTURE WEATHER CONDITIONS - COLD HIGH PRESSURE MOVES OUT TO SEA FRIDAY
NIGHT.  A RATHER WEAK BUT FAIRLY WET LOW PRESSURE SYSTEM MOVES THROUGH
THE MARFC SERVICE AREA OVER THE WEEKEND.  MOSTLY LIGHT TO MODERATE SNOW
IS EXPECTED ACROSS THE NORTHWESTERN HALF OF THE REGION, WHILE MODERATE
TO HEAVY MIXED PRECIPITATION, INCLUDING SOME RAIN, IS LIKELY ACROSS THE
SOUTHEASTERN HALF.  COLD, DRY WEATHER FOLLOWS THIS SYSTEM THROUGH
MIDWEEK NEXT WEEK.  REINFORCING COLD AIR ARRIVES NEXT WEDNESDAY
ACCOMPANIED BY WHAT CURRENTLY LOOKS LIKE MOSTLY LIGHT TO MODERATE
PRECIPITATION FOR THE MARFC AREA, MOSTLY IN THE FORM OF SNOW.  THERE IS
A SLIGHT INDICATION OF A STRONGER COASTAL-TYPE STORM NEXT
WEDNESDAY-THURSDAY IN SOME DATA.  COLD, DRY WEATHER FINISHES OUT NEXT
WEEK, WITH PRECIPITATION POSSIBLE AGAIN DURING THE WEEKEND OF FEBRUARY
28-MARCH 1.  REGARDING THE POTENTIAL FOR WIDESPREAD HEAVY RAINFALL
AND/OR WARM TEMPERATURES THAT COULD CAUSE SIGNIFICANT SNOWMELT DURING
THIS OUTLOOK PERIOD, SOME THREAT OF THESE CONDITIONS DOES EXIST ACROSS
FAR SOUTHERN AND EASTERN PORTIONS OF THE MARFC REGION THIS WEEKEND,
FEBRUARY 21-22.  BEYOND THIS WEEKEND THERE CURRENTLY IS NO OTHER
INDICATION OF WIDESPREAD HEAVY RAINFALL AND/OR WARM TEMPERATURES
THROUGH AT LEAST SATURDAY, FEBRUARY 28.  THE LATEST (FEBRUARY 18, 2015)
6-10 AND 8-14 DAY EXTENDED WEATHER OUTLOOKS ISSUED BY THE NWS CLIMATE
PREDICTION CENTER (CPC) AND VALID FOR THE NINE-DAY PERIOD
FEBRUARY 24-MARCH 4 STRONGLY SUGGEST BELOW NORMAL TEMPERATURES WILL
CONTINUE FOR THE MARFC REGION WHEN AVERAGED OVER THE ENTIRE NINE-DAY
PERIOD.  FOR THE SAME PERIOD PRECIPITATION IS MOST LIKELY TO BE
NORMAL/BELOW-NORMAL ACROSS THE NORTHWESTERN HALF OF THE MARFC SERVICE
AREA, AND NORMAL/ABOVE-NORMAL ACROSS THE SOUTHEASTERN HALF, AGAIN WHEN
AVERAGED OVER THE ENTIRE NINE-DAY PERIOD.  PLEASE VISIT
WWW.CPC.NCEP.NOAA.GOV TO VIEW THESE OUTLOOKS.

AHPS RIVER FORECASTS - MOSTLY NEAR NORMAL.  THE ADVANCED HYDROLOGIC
PREDICTION SERVICE (AHPS) GENERATES 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.  REMEMBER, AHPS RIVER FORECASTS DO
NOT TAKE INTO ACCOUNT ACTUAL FUTURE WEATHER CONDITIONS.  FOR THE NEXT
TWO WEEKS (FEBRUARY 19-MARCH 5, 2015) AHPS RIVER FORECASTS INDICATE
THAT THE LIKELIHOOD OF RIVER FLOODING WITHIN THE MARFC SERVICE AREA IS
PRETTY CLOSE TO NORMAL FOR MOST MARFC RIVER BASINS.  PLEASE VISIT
WWW.WEATHER.GOV/AHPS/.

ENSEMBLE RIVER FORECASTS - A MINIMAL THREAT OF RIVER FLOODING
DEVELOPING FEBRUARY 22-24 ACROSS FAR SOUTHERN AND FAR EASTERN PORTIONS
OF THE MARFC REGION.  THE MOST RECENT RUNS (FEBRUARY 19, 2015) OF THE
ENSEMBLE RIVER FORECASTS SHOW A MINIMAL THREAT OF RIVER FLOODING
DEVELOPING THIS WEEKEND/EARLY NEXT WEEK ACROSS PORTIONS OF VA, EASTERN
MD, NORTHERN DE, EXTREME SOUTHEASTERN PA AND IN PORTIONS OF NJ.  THIS
THREAT IS RELATED TO A LOW PROBABILITY OF GREATER THAN AN INCH OF
RAINFALL COMBINED WITH AN EQUALLY LOW PROBABILITY OF GREATER THAN A
HALF INCH (WATER EQUIVALENT) OF SNOWMELT IN ASSOCIATION WITH THE RATHER
WEAK BUT FAIRLY WET LOW PRESSURE SYSTEM CROSSING THE MARFC REGION THIS
WEEKEND.  REMEMBER THAT ENSEMBLE RIVER FORECASTS DO NOT ACCOUNT FOR
RIVER ICE CONDITIONS AND THEREFORE DO NOT PREDICT ICE JAMS/ICE JAM
FLOODING.  PLEASE VISIT WWW.ERH.NOAA.GOV/MMEFS.

SUMMARY - THE RIVER FLOOD POTENTIAL IN THE MARFC REGION DURING THE NEXT
TWO WEEKS IS ABOUT AVERAGE FOR THE SOUTHEASTERN HALF OF THE MARFC
SERVICE AREA, INCLUDING THE JAMES, APPOMATTOX, RAPPAHANNOCK, LOWER
POTOMAC, RARITAN AND PASSAIC BASINS.  THIS INCLUDES THE SMALLER STREAMS
AND RIVERS OUTSIDE OF THESE BASINS BUT STILL LOCATED IN THE
SOUTHEASTERN HALF OF THE REGION.  ELSEWHERE, THE RIVER FLOOD POTENTIAL
IS BELOW AVERAGE FOR THE NEXT TWO WEEKS.  THE GREATEST THREAT OF RIVER
FLOODING DURING THE NEXT TWO WEEKS APPEARS TO EXIST ACROSS THE
SOUTHEASTERN PORTIONS OF THE MARFC REGION DURING THE FEBRUARY 22-24
TIME PERIOD WHEN A RATHER WEAK BUT FAIRLY WET WEATHER SYSTEM COULD
PRODUCE SOME HEAVY RAIN AND SNOWMELT.  ALSO, WEATHER CONDITIONS FOR
LATE IN THIS OUTLOOK PERIOD ARE PRESENTLY UNCLEAR, AND AS WINTER BEGINS
TO LOSE ITS GRIP THE THREAT OF SNOWMELT AND RAINFALL WILL NATURALLY
INCREASE ACROSS NORTHERN AND WESTERN REGIONS WHERE SIGNIFICANT SNOW AND
RIVER ICE EXISTS.  AS SUCH, THE LONGER-TERM RIVER FLOOD POTENTIAL FOR
THESE AREAS IS NOW CONSIDERED ABOVE AVERAGE.

WATER SUPPLY OUTLOOK - ACCORDING TO THE LATEST (FEBRUARY 17, 2015) U.S.
DROUGHT MONITOR, ABNORMALLY DRY CONDITIONS ARE STILL FOUND ACROSS
PORTIONS OF THE MARFC SERVICE AREA.  THIS INCLUDES PORTIONS OF NY, PA,
MD, WV AND VA.  HOWEVER NO TRUE DROUGHT CONDITIONS CURRENTLY EXIST
WITHIN THE MARFC SERVICE AREA, NOR ARE ANY EXPECTED TO DEVELOP DURING
THE NEXT FEW MONTHS.  LIKEWISE ASSUMING NEAR-NORMAL PRECIPITATION
DURING THE NEXT FEW MONTHS, NO WATER SUPPLY SHORTAGES ARE EXPECTED
ANYWHERE WITHIN THE MARFC REGION THROUGH AT LEAST MAY, 2015.  PLEASE
SEE WWW.DROUGHT.GOV, WWW.CPC.NCEP.NOAA.GOV AND
WWW.WEATHER.GOV/MARFC/WRO_UPDATE FOR ADDITIONAL DROUGHT AND WATER
SUPPLY INFORMATION.

FINALLY, PLEASE VISIT THE NWS MARFC HOMEPAGE AT
WWW.WEATHER.GOV/MARFC FOR OTHER HYDROMETEOROLOGICAL INFORMATION.

THE NEXT WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED BY THIS OFFICE IN
TWO WEEKS, ON THURSDAY, MARCH 5, 2015.

SK
$$

....END MARFC....
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