Flood Potential Outlook
Issued by NWS Binghamton, NY

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123-PAC015-069-079-103-115-127-131-191915-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BINGHAMTON NY
206 PM EST THU MAR 5 2015

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK 5...

THIS IS THE FIFTH 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
DURING THE SPRING THAW PERIOD. THIS OUTLOOK IS VALID ONLY FOR THE
TWO WEEK PERIOD FROM MARCH 5TH THROUGH MARCH 19TH, 2015.

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 WOULD BE ISSUED AS NECESSARY.

...SUMMARY...
IN THE NEXT TWO WEEKS...THE FLOOD RISK IS CONSIDERED LOW TO
MODERATE DUE TO THE WEATHER FORECASTS SHOWING A GRADUAL RETURN OF
TEMPERATURES TOWARD SEASONAL AVERAGES AND A GENERALLY NORMAL
PRECIPITATION PATTERN. NO MAJOR STORMS...OR SIGNIFICANT MILD
SPELLS ARE IN SIGHT AT THIS TIME...BUT EVEN THE GRADUAL WARMING
SUGGESTS A CHANCE THAT ISOLATED AREAS OF RIVER ICE COULD RELEASE
AND JAM.

CONSIDERING THE LONG TERM STATE OF SOIL...SNOW AND ICE COVER
CONDITIONS IN THE REGION...THE FLOOD POTENTIAL THROUGH APRIL IS
PROJECTED TO BE ABOVE WHAT IS TYPICAL FOR THIS TIME OF YEAR.

...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 WITHIN AN INCH OF
NORMAL FOR THE SUSQUEHANNA AND OSWEGO BASINS...BUT ARE AS MUCH AS
4 TO 6 INCHES BELOW NORMAL IN THE CHEMUNG AND PORTIONS OF THE
UPPER DELAWARE REGION. 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 4TH...
SNOW COVER RANGES FROM APPROXIMATELY 8 TO 16 INCHES ACROSS NORTHEASTERN
PENNSYLVANIA AND THE CHEMUNG BASIN IN NEW YORK...WITH SPOTTY
AMOUNTS NEAR 20 INCHES OVER HIGHER TERRAIN. THE REMAINDER OF THE
UPPER SUSQUEHANNA...UPPER DELAWARE...FINGER LAKES AND OSWEGO
BASINS ARE AVERAGING 20 TO 30 INCHES OF SNOW COVER WITH SOME
AMOUNTS NEAR 3 FEET IN ELEVATIONS OF THE TULLY-HEIBERGS AND
CATSKILLS. THIS LEVEL OF SNOW PACK IS CONSIDERABLY ABOVE NORMAL
FOR THIS LATE IN THE SEASON. THE WATER EQUIVALENT OF THE SNOW PACK
RANGES FROM 2 TO 6 INCHES ACROSS MOST OF THE REGION WITH SOME
HIGHER ELEVATION AREAS IN THE 6 TO 8 INCH RANGE. THESE CONDITIONS
ARE SLIGHTLY ABOVE NORMAL.

.RIVER ICE...MUCH ABOVE NORMAL. AS OF MARCH 4TH...OUR RIVER ICE
OBSERVER NETWORK CONTINUES TO REPORT THAT MOST OF THE MAIN STEM
RIVER CHANNELS AND ASSOCIATED TRIBUTARIES HAVE SUBSTANTIAL ICE
COVER...WITH SEVERAL AREAS FROZEN SOLID. THE ACCUMULATED FREEZING
DEGREE DAY INDEX WAS RUNNING WELL ABOVE NORMAL AT ALL ASOS STATIONS.
USING THIS INDEX TO CALCULATE A THEORETICAL ICE THICKNESS SUGGESTED
THAT RIVER ICE SHOULD BE BETWEEN 12-18 INCHES THICK. THE USGS AND
OTHER SOURCES HAVE REPORTED RIVER ICE MEASUREMENTS RANGING FROM 1
TO 1.5 FEET AROUND NEW YORK. AS ICE THICKNESS EXCEEDS ONE FOOT...THE
CHANCES FOR ICE JAMMING DURING THAW EVENTS BECOMES VERY HIGH.

.STREAMFLOW CONDITIONS...BELOW NORMAL. ACCORDING TO THE USGS...AVERAGE
MONTHLY STREAMFLOW TO DATE AT GAUGES WITHIN THE SERVICE AREA WAS NEAR
TO BELOW NORMAL. MUCH OF THESE BELOW NORMAL FLOWS ARE DUE TO LOSS OF
FLOW FROM PROLONGED COLD WEATHER FREEZING RIVERS AND LIMITING RUNOFF
INTO THE HYDROLOGIC SYSTEM.

.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. ANECDOTAL
EVIDENCE FROM TOWN OFFICIALS AND DPW MANAGERS INDICATES THAT FROST
DEPTHS UNDER EXPOSED AREAS (SUCH AS ROADS AND PARKING LOTS) MAY BE
AS MUCH AS 4 TO 5 FEET DEEP WHICH IS DEEPER THAN MANY HAVE SEEN IN
DECADES. THE PALMER DROUGHT INDEX SUGGESTS THAT LONG TERM REGIONAL
SOIL MOISTURE WAS GENERALLY NORMAL...WITH SOME INDICATION OF
ABNORMALLY HIGH 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
TO SLIGHTLY ABOVE NORMAL POOL HEIGHTS. CAYUGA LAKE WAS ABOVE THE HIGH
SNOW PACK TARGET LEVEL...BUT ALL OTHER FINGER LAKES APPEARED TO HAVE
NORMAL TO BELOW NORMAL WINTER POOLS. THE LAKE WALLENPAUPACK LEVEL WAS
ON TARGET. THE NYC DELAWARE BASIN WATER SUPPLY STORAGE WAS CURRENTLY
WELL BELOW THE LONG TERM MEDIAN STORAGE LEVEL.

...FORECAST OUTLOOK...

.FUTURE WEATHER CONDITIONS - THE 6 TO 14 DAY OUTLOOK CALLS FOR A
MODERATING TREND IN TEMPERATURES BY THE MIDDLE OF THE MONTH WITH
A CHANCE FOR SLIGHTLY ABOVE NORMAL DAILY VALUES. AVERAGE DAILY
TEMPERATURES IN MARCH TYPICALLY START IN THE UPPER 20S AND WARM TO
THE UPPER 30S BY THE LAST WEEK OF THE MONTH. THE PRECIPITATION
FORECAST IS SUGGESTED TO BE ABOUT AVERAGE. THE LATEST MODEL
GUIDANCE OVER THE NEXT 10 DAYS DOES NOT SUGGEST ANY RAPID WARM UP,
OR SIGNIFICANT RAIN EVENTS. IN FACT...LATEST FORECASTS SEEM TO
INDICATE GREAT MAPLE SUGARING TYPE WEATHER WITH GRADUALLY MILDER
DAYS AND COLD NIGHTS. THIS IS ALSO A GOOD SIGN FOR A GRADUAL SNOW
MELT PERIOD.

.LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS - MULTI-MODEL
ENSEMBLE FORECASTS DO NOT SUGGEST ANY FLOODING IN THE SERVICE
AREA FOR THE NEXT 10 TO 14 DAYS. PROBABILITY GUIDANCE FROM THE
ADVANCED HYDROLOGIC PREDICTION SERVICE INDICATES THAT MOST RIVER
POINTS HAVE ONLY A 10-20 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 POINTS
WITHIN THE UPPER SUSQUEHANNA RIVER BASIN HAVE A 30 TO 50 PERCENT
CHANCE OF EXCEEDING MINOR FLOOD STAGE BEFORE THE END OF THE
SEASON.

$$

JAB







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