Flood Potential Outlook
Issued by NWS Binghamton, NY

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NYC007-015-017-023-025-053-065-067-077-097-099-101-105-107-109-
123-PAC015-069-079-103-115-127-131-021815-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BINGHAMTON NY
207 PM EDT THU MAR 19 2015

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

THIS IS THE SIXTH 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 MARCH 19TH TO APRIL
2ND, 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...COLDER THAN NORMAL TEMPERATURES AND
GENERALLY NOMINAL PRECIPITATION SHOULD CONTINUE THE GRADUAL
SNOWMELT AND RUNOFF TREND INTO AREA RIVERS. LINGERING ICE IN THE
RIVERS POSES THE BIGGEST RISK OF FLOODING...BUT THAT SHOULD BE
TRENDING DOWN WITH TIME. WITH SEVERAL KEY ANTECEDENT CONDITIONS
ABOVE NORMAL FOR LATE MARCH...THE OVERALL RISK FOR SPRING FLOODING
REMAINS SLIGHTLY ABOVE AVERAGE FOR MOST OF OUR RIVER BASINS.

...DETAILS ON CURRENT CONDITIONS...

.PRECIPITATION...VARIABLE BY BASIN. SINCE THE BEGINNING OF THE
WATER YEAR ON OCTOBER 1ST...PRECIPITATION AMOUNTS RANGE FROM
APPROXIMATELY 5 TO 10 INCHES IN THE CHEMUNG AND MUCH OF THE FINGER
LAKES BASINS. FOR THE REMAINDER OF THE SUSQUEHANNA...UPPER
DELAWARE AND OSWEGO BASINS...AMOUNTS RANGE FROM 10 TO 20 INCHES.
LIQUID PRECIPITATION AMOUNTS ARE BASICALLY NEAR NORMAL IN THE
UPPER SUSQUEHANNA...BUT FALL SHORT BY ANYWHERE FROM 2 TO 6 INCHES
ACROSS THE REST OF THE BASINS. THIS HAS BEEN ENOUGH TO PROMPT THE
U.S. DROUGHT MONITOR TO DECLARE THESE DEFICIT AREAS AS ABNORMALLY
DRY.

.SNOW COVER AND WATER EQUIVALENT...ABOVE NORMAL. AS OF MARCH 19TH...
SNOW COVER HAD DIMINISHED SIGNIFICANTLY DURING THE PAST TWO
WEEKS...BUT THERE STILL REMAINS A SIGNIFICANT SNOW COVER FOR MUCH
OF CENTRAL NY AND NORTHEAST PA...WHICH IS ABOVE NORMAL. BARE
GROUND HAD DEVELOPED OVER MUCH OF THE CHEMUNG BASIN...FINGER LAKES
AND A GOOD PORTION OF THE UPPER MAINSTEM SUSQUEHANNA IN NORTHEAST
PENNSYLVANIA WITH POCKETS OF 4 TO 8 INCHES STILL LIKELY IN THE
WOODS AT ELEVATION. SNOW DEPTHS ELSEWHERE RANGE FROM 4 TO 16
INCHES WITH POCKETS STILL IN EXCESS OF 20 INCHES ON THE HIGHER
ELEVATIONS THROUGHOUT THE UPPER SUSQUEHANNA IN NEW YORK...THE
UPPER DELAWARE AND A GOOD PORTION OF THE WESTERN MOHAWK VALLEY.
THIS LEVEL OF SNOWPACK IS CONSIDERED NORMAL FOR THE BARE GROUND
AREAS...BUT STILL WELL ABOVE NORMAL IN THE HIGHER SNOWPACK AREAS
FOR THIS LATE IN MARCH. THE WATER EQUIVALENT OF SNOW HAD ALSO
DROPPED DOWN CONSIDERABLY DURING THE LAST TWO WEEKS. OUTSIDE OF
THE BARE GROUND AREAS...LIQUID EQUIVALENTS RANGE FROM 1 TO 4
INCHES ACROSS MOST OF THE REGION WITH SOME HIGHER ELEVATION AREAS
IN THE 6 TO 8 INCH RANGE. THIS WATER CONTENT IS ALSO ABOVE
AVERAGE.

.RIVER ICE...ABOVE NORMAL. AS OF MARCH 19TH...OUR RIVER ICE
OBSERVER NETWORK CONTINUED TO REPORT SIGNIFICANT AREAS OF RIVER
ICE COVER...BUT THERE ARE MORE OPEN CHANNELS AS COMPARED TO WHAT
WAS REPORTED EARLIER IN THE MONTH. ACTIVE ICE JAMS WERE ONGOING IN
A FEW AREAS. THOSE KNOWN AT THIS TIME WERE LOCATED ON THE SUSQUEHANNA
RIVER FROM NEAR TUNKHANNOCK TO WILKES-BARRE. SECONDARY JAMS HAD
BEEN REPORTED ON THE COHOCTON RIVER TO THE NORTHWEST OF CORNING
NY...AND A JAM NEAR ELMIRA HAD BROKEN EARLIER THIS WEEK. RIVER ICE
WILL CONTINUE TO BE A MAJOR RISK FACTOR TO FLOODING OVER THE NEXT
WEEK...AND GENERALLY LESS OF A THREAT AS WE APPROACH APRIL.

.STREAMFLOW CONDITIONS...NORMAL. ACCORDING TO THE USGS...STREAMFLOW
AT MANY OF THEIR GAUGES HAD REBOUNDED TO NEAR NORMAL GIVEN THE
SNOWMELT RUNOFF THAT HAS TAKEN PLACE OVER THE PAST COUPLE WEEKS.
SLIGHTLY ABOVE NORMAL FLOWS WERE REPORTED IN THE CHEMUNG BASIN...AND
THERE WERE STILL A FEW STREAM GAUGES AROUND THE REGION FALLING SHY
OF THE NORMAL MID MARCH FLOW.

.SOIL CONDITIONS...NORMAL. THE GROUND IS FROZEN AND THE TOPSOIL IS
GENERALLY MOIST. THE FROST LINE UNDER SNOW COVER AS INDICATED BY
THE NWS BINGHAMTON FROST DEPTH SENSOR IS 20 INCHES WHICH IS DEEP.
NON-SNOW COVERED AREAS...SUCH AS PARKING LOTS AND OTHER
STRUCTURALLY EXPOSED AREAS...MAY STILL HAVE SIGNIFICANTLY DEEPER
FROST LEVELS. THE PALMER DROUGHT INDEX SUGGESTS THAT LONG TERM
REGIONAL SOIL MOISTURE WAS GENERALLY NORMAL...WITH SOME INDICATION
OF ABNORMALLY HIGH SOIL MOISTURE STILL IN THE FINGER LAKES REGION.

.RESERVOIR AND LAKE LEVELS...VARIABLE. THE ARMY CORPS FLOOD
CONTROL RESERVOIRS IN THE SUSQUEHANNA BASIN APPEAR TO BE RUNNING
WITH NEAR NORMAL POOL HEIGHTS. THE FINGER LAKES...AND ALSO LAKE
WALLENPAUPACK...WERE ALL REPORTING BELOW NORMAL POOL LEVELS. 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
RETURN TO GENERALLY COLDER AND SLIGHTLY WETTER THAN NORMAL
CONDITIONS FOR THE NEXT TWO WEEKS. WITH AVERAGE TEMPERATURES
TYPICALLY ABOVE FREEZING THIS TIME OF YEAR...EVEN PRECIPITATION IN
A COLDER THAN NORMAL ENVIRONMENT COULD BE EITHER RAIN OR SNOW.
METEOROLOGICAL MODELS ARE HINTING AT SEVERAL MINOR SYSTEMS MOVING
THROUGH THE REGION OVER THE NEXT 10 DAYS...WITH ONE POTENTIALLY
WARM AND WET SYSTEM ON THE HORIZON ABOUT ONE WEEK FROM TODAY WHICH
WILL HAVE TO BE MONITORED CLOSELY.

.LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS -
MULTI-MODEL ENSEMBLE FORECASTS SUGGEST SIGNIFICANT...BUT GENERALLY
SLOW RESPONDING...RISES IN RIVER LEVELS OVER THE NEXT 10 TO 14
DAYS...BUT AT THIS TIME THE PROBABILITY OF EXCEEDING FLOOD STAGE
IS LOW THROUGHOUT THE SERVICE AREA. PROBABILITY GUIDANCE FROM THE
ADVANCED HYDROLOGIC PREDICTION SERVICE INDICATES THAT MOST RIVER
POINTS HAVE ABOUT A 15-30 PERCENT CHANCE OF REACHING FLOOD STAGE
IN THE NEXT TWO WEEKS. THE LONGER RANGE OUTLOOK, COVERING THE
MONTHS OF MARCH THROUGH MAY, SUGGESTS THAT SEVERAL HEADWATER RIVER
GAUGE POINTS HAVE BETWEEN A 25 TO 50 PERCENT CHANCE OF EXCEEDING
MINOR FLOOD STAGE BEFORE THE END OF THE SEASON...BUT THIS WOULD BE
HEAVILY DEPENDENT ON WHETHER OR NOT A SIGNIFICANT RAIN EVENT
DEVELOPS.

$$

JAB





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