Flood Potential Outlook
Issued by NWS Burlington, VT

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FGUS71 KBTV 211402
ESFBTV
NYC019-031-033-089-VTC001-005-007-009-011-013-015-017-019-021-023-
027-041415-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BURLINGTON VT
1002 AM EDT THU MAR 21 2013

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

...NORMAL SPRING FLOOD POTENTIAL FOR THE NORTH COUNTRY...

THIS IS THE SEVENTH FLOOD OUTLOOK FOR THE 2013 WINTER/SPRING
SEASON. FLOOD OUTLOOKS ARE ISSUED BI-WEEKLY THROUGH THE WINTER
AND SPRING BY THE NATIONAL WEATHER SERVICE IN BURLINGTON VERMONT
TO SUMMARIZE THE FLOOD POTENTIAL DUE TO SNOW MELT AND BREAK UP OF
RIVER ICE ACROSS CENTRAL AND NORTHERN VERMONT...AND NORTHERN NEW
YORK.

...OVERVIEW...

THE SNOWMELT FLOOD THREAT IS NEAR NORMAL. RECENT ADDITIONS TO THE
SNOWPACK HAVE BROUGHT SPRING SNOW CONDITIONS TO NEAR NORMAL...AND
FROZEN GROUND WOULD SPEED RUNOFF. AN ICE JAM THREAT REMAINS ON
RIVERS NEAR THE CANADIAN BORDER IN NORTHERN VERMONT AND NEW YORK.
ELSEWHERE...THE ICE JAM THREAT HAS ENDED FOR THE YEAR.

...SNOW DEPTHS AND WATER EQUIVALENT...

RECENT SNOWFALL CONTRIBUTED UPWARDS OF TWO FEET OF NEW SNOW AND
ONE TO TWO INCHES OF WATER TO THE SNOW PACK. SNOW DEPTHS AND
WATER EQUIVALENT...OR THE AMOUNT OF LIQUID WATER LOCKED IN THE
SNOW...WAS NEAR NORMAL...AND WAS THE MAIN CONTRIBUTOR TO THE
NORMAL SPRING FLOOD THREAT.

IN NORTHERN NEW YORK...THE HIGHER TERRAIN OF THE ADIRONDACKS HAD
20 TO 30 INCHES OF SNOW...WITH 6 TO 12 INCHES IN THE VALLEYS.
HEADING NORTH INTO THE SAINT LAWRENCE VALLEY SNOW DEPTHS WERE 5
TO 10 INCHES. SNOW WATER EQUIVALENTS ACROSS NORTHERN NEW YORK
WERE 5 TO 10 INCHES IN THE HIGHER ELEVATIONS OF THE
ADIRONDACKS...AND IN THE VALLEYS THE SNOW PACK CONTAINED 1 TO 4
INCHES OF WATER. NORTH OF THE ADIRONDACKS THE SNOW HELD TWO
INCHES OR LESS.

THE CHAMPLAIN VALLEY OF NEW YORK AND VERMONT HAD 6 TO 10 INCHES
OF SNOW ON THE GROUND...AND HELD AN INCH OR LESS OF LIQUID WATER.

IN VERMONT...THE GREEN MOUNTAINS HAD TWO TO FOUR FEET OF SNOW IN
THE HIGHER TERRAIN...AND OVER A FOOT IN THE MOUNTAIN VALLEYS.
SNOW WATER EQUIVALENT WAS 4 TO 8 INCHES OVER THE HIGHER
TERRAIN...AND TWO TO FOUR INCHES IN THE VALLEYS. THE CONNECTICUT
VALLEY HAD 8 TO 12 INCHES ON THE GROUND...HOLDING AN INCH OR TWO
OF LIQUID.

THE FRESH SNOW COVER WILL HAVE TO UNDERGO A PERIOD OF WARMER
TEMPERATURES TO COMPACT AND RIPEN BEFORE IT WILL BEGIN TO MELT.

...RIVER AND SOIL MOISTURE CONDITIONS...

RIVER FLOWS WERE RUNNING ABOVE NORMAL FROM A RAIN AND SNOWMELT
EPISODE IN MID MARCH. FLOWS WILL SLOWLY DECREASE OVER THE NEXT
WEEK AS COOL TEMPERATURES LIMIT SNOWMELT RUNOFF.

RIVER ICE WAS CONFINED TO FAR NORTHERN RIVERS AND STREAMS. IN
PARTICULAR...THE MISSISQUOI AND GREAT CHAZY RIVERS TYPICALLY ARE
AMONG THE LAST TO ICE OUT...AND STILL POSE AN ICE JAM THREAT.

SOIL MOISTURE IS NEAR NORMAL ACROSS THE NORTH COUNTRY. FROST
DEPTH IS VARIABLE...AND GROUND FROST HAS RETURNED TO VALLEY
LOCATIONS THAT PREVIOUSLY THAWED DURING THE MID-MARCH WARMUP.
FROZEN GROUND CAN SPEED THE RATE OF RUNOFF WHEN SNOW MELTS OR
RAIN FALLS...AND CONTRIBUTES TO THE NORMAL SPRING FLOOD THREAT.

...WEATHER OUTLOOK...

AN UPPER LEVEL BLOCKING RIDGE OF HIGH PRESSURE TO THE EAST WILL
REMAIN IN PLACE OVER THE NEXT WEEK TO TEN DAYS. THIS WILL KEEP
THE NORTHEAST UNDER THE INFLUENCE OF LOW PRESSURE...WITH
SEASONABLY COOL TEMPERATURES AND SMALL ADDITIONS TO SNOW PACK.
WITH NO LARGE SCALE MELT OR RAIN EVENT FORECAST...IT IS LIKELY
THAT THE PRESENT SNOW PACK WILL CARRY INTO APRIL. AS THIS HAPPENS
THE REGION BECOMES MORE EXPOSED TO A PROLONGED WARM SNOWMELT AND
RAINFALL EPISODE.

...SUMMARY...

OVERALL THE WINTER/SPRING FLOOD POTENTIAL IS NEAR NORMAL. DEEP
SNOW PACK IN THE HIGHER ELEVATIONS...AND FROZEN
GROUND...CONTRIBUTE TO THE NORMAL FLOOD THREAT FOR THE LONG TERM.
ICE JAM FLOODING IS STILL A POSSIBILITY IN FAR NORTHERN
RIVERS...HOWEVER FOR MUCH OF THE ADIRONDACKS AND CENTRAL AND
SOUTHERN VERMONT THE ICE JAM THREAT HAS ENDED FOR 2013.

IT IS IMPORTANT TO NOTE THAT THE SNOW PACK AND FROZEN GROUND ARE
ONLY TWO INGREDIENTS TO FLOODING. A PERIOD OF WARM TEMPERATURES
AND HEAVY RAINFALL ARE ALSO NECESSARY TO CAUSE SPRING FLOODING...
AND THOSE CONDITIONS ARE NOT FORECAST THROUGH LATE MARCH.

THE NEXT SPRING FLOOD OUTLOOK WILL BE ISSUED THURSDAY APRIL 4.

ACCESS CURRENT WEATHER CONDITIONS AND FORECASTS ON OUR WEB SITE
AT WWW.ERH.NOAA.GOV/BTV.

$$

HANSON