Flood Potential Outlook
Issued by NWS Binghamton, NY

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BINGHAMTON NY
353 PM EDT THU APR 2 2015

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK /7/...

THIS IS THE SEVENTH IN A SERIES OF REGULARLY SCHEDULED HYDROLOGIC
OUTLOOKS ISSUED DURING THE WINTER AND SPRING SEASON. THIS OUTLOOK
IS DESIGNED TO PROVIDE A GENERALIZED ASSESSMENT OF THE FLOOD
POTENTIAL ACROSS CENTRAL NEW YORK AND NORTHEAST PENNSYLVANIA AND
IS VALID ONLY FOR THE TWO WEEK PERIOD FROM APRIL 2ND TO APRIL
16TH, 2015.

THE OUTLOOK ESTIMATES THE POTENTIAL FOR RIVER AND LAKE FLOODING
BASED ON A CURRENT ASSESSMENT OF GENERALIZED HYDRO-METEOROLOGICAL
FACTORS WHICH CONTRIBUTE TO FLOODING DURING THE SPRING THAW.

IT IS IMPORTANT TO NOTE THAT SIGNIFICANT FLOODING DOES NOT OCCUR
FROM SNOW MELT ALONE. SHORT TERM HEAVY RAIN EVENTS...THE INTENSITY
OF ANY MILD SPELLS...WIND SPEED AND RAPID INCREASES IN HUMIDITY
ARE THE MOST IMPORTANT FACTORS IN DETERMINING THE OCCURRENCE AND
SEVERITY OF SPRING FLOODING. SPECIFIC FORECASTS OF HEAVY RAINFALL
AND FLASH FLOODING ARE NOT INCLUDED IN THIS OUTLOOK. OUTCOMES
BETTER...OR WORSE...THAN THIS OUTLOOK ARE POSSIBLE OVER THE NEXT
TWO WEEKS. IF CONDITIONS CHANGE RAPIDLY IN THE INTERIM...FLOOD
WATCHES OR WARNINGS WILL BE ISSUED AS NECESSARY.

...SUMMARY...
IN THE NEXT TWO WEEKS...THE FLOOD POTENTIAL IS ABOVE NORMAL FOR
THE UPPER SUSQUEHANNA AND NORTH BRANCH SUSQUEHANNA BASINS WHERE
THERE IS AN UNSEASONABLE EXCESS OF SNOW AND LIQUID WATER EQUIVALENT
FOR THE TIME OF YEAR.

THE FLOOD POTENTIAL IS NEAR NORMAL FOR THE FINGER LAKES...CHEMUNG...
UPPER DELAWARE AND OSWEGO BASINS WHERE LONG TERM PRECIPITATION AND
LOWER THAN NORMAL RESERVOIR/LAKE WATER ELEVATIONS AND STREAM FLOWS
EXIST.

...DETAILS ON CURRENT CONDITIONS...

.PRECIPITATION...BELOW NORMAL. SINCE THE BEGINNING OF THE WATER
YEAR ON OCTOBER 1ST, 2014...PRECIPITATION AMOUNTS RANGE FROM
APPROXIMATELY 5 TO 12 INCHES IN THE CHEMUNG AND MUCH OF THE FINGER
LAKES BASINS. THE REMAINDER OF THE SUSQUEHANNA...UPPER DELAWARE
AND OSWEGO BASINS WERE AVERAGING FROM 10 TO 20 INCHES. THERE ARE
ISOLATED POCKETS CLOSE TO 24 INCHES IN THE NORTHERN OSWEGO BASIN.
DESPITE WHAT APPEARS TO BE A SUFFICIENT AMOUNT OF LIQUID
PRECIPITATION...THE REALITY IS THAT MOST OF THE REGION IS
EXPERIENCING ONLY ABOUT 50 TO 75 PERCENT OF THE LONG TERM AVERAGE
PRECIPITATION FOR THE TIME PERIOD. THE HEART OF THE SUSQUEHANNA
BASIN HAS BEEN THE WETTEST WITH PRECIPITATION AMOUNTS ABOUT 90
PERCENT OF NORMAL. THESE DEFICITS HAVE BEEN ENOUGH TO PROMPT THE
U.S. DROUGHT MONITOR TO DECLARE ALL OF OUR NORTHEAST
PENNSYLVANIA...THE CHEMUNG...FINGER LAKES AND UPPER DELAWARE
BASINS IN AN ABNORMALLY DRY PERIOD (D0-DROUGHT). THE COMMONWEALTH
OF PENNSYLVANIA HAS INCLUDED ALL OF NORTHEAST PENNSYLVANIA IN A
DROUGHT WATCH ACCORDING TO CRITERIA SET BY THEIR DEPARTMENT OF
ENVIRONMENTAL PROTECTION.

.SNOW COVER AND WATER EQUIVALENT...ABOVE NORMAL. WHERE THERE IS
SNOW COVER...CONDITIONS ARE ABOVE THE LONG TERM AVERAGE FOR EARLY
APRIL. THE SNOWPACK IS NO LONGER HOMOGENEOUS ACROSS THE REGION AS
MOST VALLEY LOCATIONS HAVE LOST NEARLY ALL OF THEIR SNOW COVER...WHILE
SOME OF THE HIGHER TERRAIN AREAS STILL HAVE A CONSIDERABLE AMOUNT
OF SNOW...ESPECIALLY ON NORTH FACING ASPECTS IN THE DEEP WOODS.
ASSESSING THE SNOW DEPTH IS BECOMING A BIT MORE DIFFICULT...BUT
SPORADIC REPORTS FROM OUR OBSERVATION NETWORKS...AND NOHRSC
ANALYSIS SUGGESTS THAT VALLEY LOCATIONS UNDER 1200 FEET HAVE
GENERALLY 5 INCHES OR LESS OF SNOW...WHILE ELEVATIONS ABOVE THAT
WERE GENERALLY IN THE 6 TO 12 INCH RANGE. HIGHEST ELEVATIONS
(ABOVE 2000 FEET) OF THE CATSKILLS...POCONOS...AND THE SOUTHERN
TUG HILL IN NEW YORK MAY STILL BE APPROACHING 18 INCHES OF SNOW
COVER. THE WATER EQUIVALENT OF SNOW ALSO VARIES...BUT IN GENERAL
LIKELY FALLS IN THE 2 TO 4 INCH RANGE FOR MOST OF THE SNOWPACK
LOCATIONS. THE POCKETS OF DEEPER SNOW AT ELEVATION...AND IN
SHELTERED WOODLANDS...COULD STILL HAVE UP TO 6 INCHES OF LIQUID
EQUIVALENT YET TO MELT.

.RIVER ICE...NORMAL. MOST OF THE ICE COVER HAS FLUSHED THROUGH THE MAIN
STEM RIVERS AND TRIBUTARIES WITH ANY LINGERING REPORTS OF ICE COVER
INDICATING THAT CHANNELS ARE BETWEEN 60 TO 95 PERCENT OPEN AS OF APRIL
2ND.

.STREAMFLOW CONDITIONS...BELOW NORMAL. USGS STREAM GAUGES ACROSS
CENTRAL NY AND NORTHEAST PA ARE ANALYZED AS BEING NEAR TO BELOW
NORMAL BOTH IN SHORT TERM DAILY TRENDS...AND LONG TERM MONTHLY
AVERAGES.

.SOIL CONDITIONS...NORMAL. SHORT TERM 0-10 CM VOLUMETRIC SOIL MOISTURE
WAS ANALYZED AS WET WITH OVER 45 PERCENT MOISTURE CONTENT. THIS IS
NORMAL DURING THE SPRING MELT PERIOD. THE GROUND IS ALSO STILL FROZEN
THROUGH A FAIRLY DEEP LAYER AS INDICATED BY AN 18 INCH DEEP FROST DEPTH
MEASUREMENT AT NWS BINGHAMTON...ALTHOUGH SOME DEFROSTING IS LIKELY
TO OCCUR IN THE FIRST FEW INCHES DURING THIS UPCOMING PERIOD. LONG
TERM PALMER DROUGHT INDICES SUGGEST NORMAL SOIL CONDITIONS ACROSS
THE REGION.

.RESERVOIR AND LAKE LEVELS...BELOW NORMAL. THE ARMY CORPS FLOOD CONTROL
RESERVOIRS IN THE SUSQUEHANNA BASIN APPEAR TO BE RUNNING WITH NEAR NORMAL
POOL HEIGHTS. THE FINGER LAKES AND LAKE WALLENPAUPACK WERE ALL REPORTING
BELOW NORMAL POOL LEVELS FOR THE SEASON. THE NYC DELAWARE BASIN WATER
SUPPLY STORAGE WAS ALSO CURRENTLY WELL BELOW THE LONG TERM MEDIAN
STORAGE LEVEL.

...FORECAST OUTLOOK...

.FUTURE WEATHER CONDITIONS - THE 6 TO 14 DAY OUTLOOK CALLS FOR A
CONTINUATION OF BELOW NORMAL TEMPERATURES WITH ABOVE NORMAL PRECIPITATION.
THERE ARE SIGNALS SHOWING UP IN THE NORTHERN HEMISPHERIC PATTERN THAT
SUGGEST THE POLAR JET STREAM WILL BECOME LESS AMPLIFIED AND
GRADUALLY SHIFT TO THE NORTH OVER THE NEXT TWO WEEKS AS THE
PERSISTENT WINTER PATTERN ACROSS THE NORTHERN HEMISPHERE EVOLVES
INTO A MORE SPRING/SUMMER LIKE CONFIGURATION. THIS WILL MEAN MORE
PRECIPITATION ACTIVITY AS FAST MOVING...BUT GENERALLY WEAK SYSTEMS
MOVE ACROSS OUR REGION.

.LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS - MULTI-MODEL
ENSEMBLE FORECASTS DO SUGGEST HIGH CONFIDENCE IN INCREASING RIVER
FLOWS AND STAGES OVER THE NEXT 10-14 DAYS WITH SOME LOW TO MEDIUM
PROBABILITY OF MINOR FLOODING MAINLY IN THE SUSQUEHANNA BASIN. AT
THIS TIME...THE MAIN CONCERN SHOWS UP EARLY IN THIS OUTLOOK PERIOD
AS TWO DISTINCT...WARM WEATHER SYSTEMS MOVE THROUGH THE AREA.
WITH AN ACTIVE WEATHER PATTERN EXPECTED...THERE MAY BE OTHER TARGET
DAYS OF HEAVY RAIN AND POSSIBLE FLOOD OPPORTUNITY DOWN THE ROAD.

THE PROBABILITY GUIDANCE FROM THE ADVANCED HYDROLOGIC PREDICTION
SERVICE INDICATES THAT MOST RIVER POINTS HAVE ABOUT A 10-20 PERCENT
CHANCE OF REACHING FLOOD STAGE IN THE NEXT TWO WEEKS...WITH SOME
OF THE LOWER SET FLOOD STAGE POINTS SEEING ABOUT A 30-50 PERCENT
CHANCE OF EXCEEDING FLOOD STAGE. THESE SIGNALS SHOW UP PRIMARILY
IN THE MAIN STEM SUSQUEHANNA RIVER BASIN...WITH OTHER BASINS NOT
AS MUCH OF A CONCERN.

$$

JAB







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