Flood Potential Outlook
Issued by NWS Burlington, VT

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BURLINGTON VT
551 PM EDT THU MAR 13 2014

...SPRING FLOOD POTENTIAL OUTLOOK /6/...

THIS IS THE SIXTH FLOOD OUTLOOK FOR THE 2014 WINTER/SPRING SEASON.
THIS IS AN INTERIM, SUPPLEMENTAL OUTLOOK ISSUED IN SUPPORT OF THE
NATIONAL WINTER/SPRING FLOOD POTENTIAL OUTLOOK SCHEDULED FOR NEXT
WEEK. FLOOD OUTLOOKS ARE TYPICALLY ISSUED BI-WEEKLY THROUGH THE
WINTER AND SPRING BY THE NATIONAL WEATHER SERVICE IN BURLINGTON
VERMONT TO SUMMARIZE THE FLOOD POTENTIAL DUE TO SNOWMELT AND BREAK
UP OF RIVER ICE ACROSS CENTRAL AND NORTHERN VERMONT, AND NORTHERN
NEW YORK.

...OVERVIEW...

THERE IS A LOW PROBABILITY OF FLOODING OVER THE NEXT TWO WEEKS.
WHILE SEVERAL SHORT-LIVED INTRUSIONS OF WARMER AIR WILL AFFECT
THE REGION OVER THE NEXT FEW WEEKS, THE POLAR BRANCH OF THE UPPER
JET STREAM WILL CONTINUE TO DOMINATE THE MEAN FLOW PATTERN ACROSS
THE NORTHEAST. THUS ON AVERAGE, SEASONABLY COLD TEMPERATURES
SHOULD CONTINUE INTO LATE MARCH AND WILL ESSENTIALLY KEEP THE
MAJORITY OF THE SNOWPACK AND RIVER ICE LOCKED IN PLACE. IN THE
LONGER TERM INTO EARLY APRIL, THE FLOOD THREAT DUE TO SNOWMELT IS
ABOVE NORMAL WITH THE RECENT HEAVY ADDITION TO THE SNOWPACK THIS
WEEK. THE LONGER TERM ICE JAM POTENTIAL IS ALSO ABOVE NORMAL DUE
TO WIDESPREAD THICK RIVER ICE COVER AND MANY OLDER ICE JAMS STILL
FROZEN IN PLACE.

...SNOW DEPTHS AND WATER EQUIVALENT...

IN NEW YORK...SNOW DEPTHS RANGE FROM 1 TO 2 FEET IN THE SAINT
LAWRENCE AND CHAMPLAIN VALLEYS, AND 1.5 TO 3 FEET IN THE
ADIRONDACKS WITH LOCALLY HIGHER AMOUNTS ABOVE 3 FEET PRESENT ABOVE
1500 FEET. SNOW WATER EQUIVALENTS, THE AMOUNT OF LIQUID WATER
HELD IN THE SNOWPACK, RANGE FROM 2 TO 5 INCHES IN VALLEYS OF THE
ADIRONDACKS AND THE CHAMPLAIN VALLEY, AND 4 TO 8 INCHES AT
ELEVATIONS ABOVE 1500 FEET. AMOUNTS ABOVE 8 INCHES ARE PRESENT IN
THE HIGHEST ELEVATIONS OF THE ADIRONDACKS. VALUES IN THE SAINT
LAWRENCE VALLEY RANGE FROM 3 TO 6 INCHES WITH LOCALLY HIGHER
AMOUNTS. THESE VALUES ARE GENERALLY NEAR TO SLIGHTLY ABOVE NORMAL
FOR THE ADIRONDACKS AND THE CHAMPLAIN VALLEY...AND ABOVE NORMAL
FOR THE SAINT LAWRENCE VALLEY FOR THIS TIME OF YEAR.

IN VERMONT SNOW DEPTHS GENERALLY RANGE FROM 1 TO 2 FEET IN THE
CHAMPLAIN AND CONNECTICUT RIVER VALLEYS, AND 2 TO 3 FEET IN THE
GREEN MOUNTAINS WITH LOCALLY HIGHER AMOUNTS ABOVE 3 FEET NOTED
ABOVE 1500 FEET. SNOW WATER EQUIVALENTS VARY FROM 2 TO 5 INCHES IN
THE CHAMPLAIN AND CONNECTICUT RIVER VALLEYS...AND 4 TO 8 INCHES
ACROSS THE GREEN MOUNTAINS WITH LOCALLY HIGHER AMOUNTS ABOVE 8
INCHES NOTED ABOVE 1500 FEET. THESE VALUES ARE NEAR TO SLIGHTLY
ABOVE NORMAL FOR THE GREEN MOUNTAINS...AND ABOVE NORMAL FOR THE
CHAMPLAIN AND CONNECTICUT RIVER VALLEYS.

...RIVER AND SOIL CONDITIONS...

NEAR SURFACE SOIL MOISTURE ANOMALY MAPS SHOW VERMONT AND NORTHERN
NEW YORK WITH NEAR NORMAL SOIL MOISTURE LEVELS. HOWEVER, RIVER
FLOWS ACROSS NEW YORK AND NEW ENGLAND ARE GENERALLY AT OR BELOW
NORMAL FOR MID-MARCH DUE TO THE COLD WEATHER AND LIMITED RUNOFF
OVER THE PAST FEW MONTHS.

RIVER ICE IS STILL WIDESPREAD ACROSS THE AREA WITH THICK AND
COMPLETE COVERAGE ON MOST MAINSTEM CHANNELS. SOLID 1 TO 2 FOOT ICE
THICKNESSES ARE PRESENT ACROSS MOST OF THE REGION AND HAS STRONG
STRUCTURAL INTEGRITY DUE TO PERSISTENT COLD TEMPERATURES OVER THE
PAST FEW MONTHS. THERE ARE ALSO NUMEROUS STATIONARY ICE JAMS LEFT
IN PLACE AFTER THE JANUARY THAW, AND THOSE JAMS COULD BECOME THE
FOCUS FOR FURTHER ICE JAMMING AND/OR FLOODING CONCERNS ONCE THE
LARGE-SCALE MELT COMMENCES THIS SPRING.

...WEATHER OUTLOOK...

TEMPERATURES WILL BEGIN TO SHOW MORE VARIABILITY AS STRONGER MARCH
SUNSHINE AND RESULTANT INSOLATION ACT TO TEMPER THE SEVERITY OF
THE COLD. HOWEVER, NO SIGNIFICANT WARM-UP OR LARGE-SCALE THAWING
CONDITIONS ARE FORECAST OVER THE NEXT TWO WEEKS. SEVERAL CHANCES
FOR LIGHT SNOW OR RAIN ARE EXPECTED THROUGH THE PERIOD, BUT NO
HEAVY PRECIPITATION IS EXPECTED AT THIS TIME. THUS SIGNIFICANT
SNOWMELT OR MOVEMENT OF RIVER ICE IS NOT FORECAST.

THE OFFICIAL NATIONAL WEATHER SERVICE 6 TO 14 DAY OUTLOOK VALID
MARCH 19 TO 27 CALLS FOR BELOW NORMAL TEMPERATURES AND NEAR TO
ABOVE NORMAL PRECIPITATION.

...SUMMARY...

IN SUMMARY, FLOODING IS NOT EXPECTED OVER THE NEXT TWO WEEKS.
WHILE SOME VARIABILITY IN TEMPERATURES ARE EXPECTED, ON AVERAGE
READINGS WILL CONTINUE TO RUN SLIGHTLY BELOW NORMAL. THIS WILL
GENERALLY PREVENT SNOWMELT AND RUNOFF INTO RIVERS. LOOKING FURTHER
INTO THE SPRING, THE NEAR TO ABOVE NORMAL SNOWPACK PRESENTS A
SOMEWHAT ABOVE NORMAL FLOOD THREAT WHEN A MELT EVENTUALLY HAPPENS.
SIMILARLY, THE EXTENSIVE AND THICK ICE COVER ON RIVERS POSES AN
INCREASING RISK FOR ICE JAMS AND RESULTANT FLOODING ONCE LARGE-
SCALE THAWING CONDITIONS OCCUR.

THE NEXT WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED ON THURSDAY
MARCH 20.

FOR MORE INFORMATION, PLEASE ACCESS CURRENT WEATHER CONDITIONS AND
FORECASTS ON OUR WEB SITE AT WWW.ERH.NOAA.GOV/BTV.

$$

JMG





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