Public Information Statement
Issued by NWS Burlington, VT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

000
NOUS41 KBTV 190900
PNSBTV
NYZ026>031-034-035-087-VTZ001>012-016>019-200000-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BURLINGTON VT
500 AM EDT WED MAR 19 2014

...NATIONAL FLOOD SAFETY AWARENESS WEEK CONTINUES...



THE NATIONAL WEATHER SERVICE HAS DECLARED MARCH 17 THROUGH 21, 2014,

NATIONAL FLOOD SAFETY AWARENESS WEEK. THE NATIONAL WEATHER SERVICE

IN BURLINGTON, VERMONT WILL FEATURE A DIFFERENT EDUCATIONAL TOPIC

EACH DAY DURING THE WEEK. TODAY`S TOPIC: FLOOD HAZARDS IN THE NORTH

COUNTRY.



NORTHERN NEW YORK AND VERMONT ARE AT RISK FROM FLOODING ALL YEAR LONG.

DURING THE WINTER, THE FLOOD THREAT IS FROM ICE JAMS AND A SUDDEN SNOWMELT.

THE RISK FOR SNOWMELT FLOODING GROWS INTO THE SPRING AS TEMPERATURES WARM

AND THE SNOWPACK MELTS. SUMMERTIME THUNDERSTORMS CAN PRODUCE TORRENTIAL

DOWNPOURS AND CAUSE FLASH FLOODING. IN LATE SUMMER INTO THE FALL, TROPICAL

STORMS CAN SPREAD PROLONGED HEAVY RAIN ACROSS THE REGION.



SNOWMELT FLOODING...WHEN MELTING SNOW IS A MAJOR SOURCE OF THE WATER

INVOLVED IN A FLOOD, IT IS CONSIDERED A SNOWMELT FLOOD. UNLIKE RAINFALL,

WHICH EITHER RUNS OFF OR PERCOLATES INTO THE SOIL IMMEDIATELY, SNOWFALL

ACCUMULATES ALL WINTER LONG. WHEN SNOWMELT FINALLY OCCURS, IT CAN BE THE

EQUIVALENT OF AN ENTIRE SEASON`S PRECIPITATION RUNNING OFF ALL AT ONCE.

MOST OFTEN, SPRING MELT OF THE SNOW PACK IS A RELATIVELY SLOW PHENOMENON.

SNOWMELT RATES ARE USUALLY COMPARABLE TO LIGHT TO MODERATE RAINFALL.

HOWEVER, IF THE SNOW MELTS QUICKLY ENOUGH AND IS ACCOMPANIED BY MODERATE

TO HEAVY RAINFALL, FLOODING CAN RESULT.  SUCH WAS THE CASE ON APRIL 26-27,

2011 WHEN THUNDERSTORMS AND MELTING SNOW LED TO FLASH FLOODING ACROSS

PORTIONS OF THE NORTHERN ADIRONDACKS AND IN THE LAMOILLE RIVER BASIN OF

VERMONT.



THE NWS PROVIDES EXTENSIVE INFORMATION ABOUT SNOWPACK CONDITIONS ACROSS

THE COUNTRY. A WIDE ARRAY OF GROUND, AIRBORNE AND SATELLITE OBSERVATIONS

ARE USED TO MONITOR SNOW CONDITIONS. THE NWS IN BURLINGTON ISSUES A

BIWEEKLY WINTER/SPRING FLOOD POTENTIAL OUTLOOK WHICH SUMMARIZES THE RISK

OF SPRING FLOODING BASED ON THE DEPTH AND WATER CONTENT OF THE SNOWPACK,

RIVER FLOW AND RIVER ICE CONDITIONS, AND WEATHER FORECASTS.



ICE JAMS...ICE JAMS OCCUR WHEN THE SOLID COVER OF RIVER ICE IS BROKEN UP

BY HIGHER RIVER FLOWS, RATHER THAN SLOWLY MELTING AWAY. THE LARGE BLOCKS

OF ICE ARE CARRIED DOWNSTREAM, UNTIL THEY ARE STOPPED BY AN OBSTRUCTION

IN THE RIVER CHANNEL SUCH AS A SAND BAR OR ISLAND, BRIDGE ABUTMENT, OR

THICKER ICE COVER ON A DEEP POOL OR LAKE. THE ICE PILES UP TO FORM AN

ICE DAM, FORCING WATER LEVELS TO QUICKLY RISE.



ICE JAMS ARE UNPREDICTABLE, AND THE DEPTH AND SPEED OF RISING WATER

IMPOUNDED BY AN ICE JAM CAN VARY GREATLY. IN MARCH 1992 AN ICE JAM

DEVELOPED IN MONTPELIER VERMONT AT 7:00 AM, AND BY 8:00 A.M. THE

DOWNTOWN AREA WAS FLOODED.  DURING THE NEXT 11 HOURS, THE BUSINESS

DISTRICT WAS COVERED WITH 4 TO 5 FEET WATER.



THUNDERSTORMS WITH HEAVY RAIN...SUMMERTIME THUNDERSTORMS CAN PRODUCE

TORRENTIAL RAINFALL IN A SHORT AMOUNT OF TIME, IN ADDITION TO HAZARDS

INCLUDING STRONG WINDS, HAIL, AND DEADLY LIGHTNING. RUNOFF FROM THE

HEAVY RAIN CAN QUICKLY OVERWHELM DRAINAGE AREAS, AND CAUSE SMALL CREEKS

AND STREAMS TO BECOME RAGING RIVERS. RUNOFF CAN DAMAGE ROADS, ESPECIALLY

RURAL DIRT ROADS, BY WASHING AWAY THE ROAD SURFACE AND CARVING OUT DEEP

GULLIES. IN ORDER TO PRODUCE THE HEAVY RAINFALL, A THUNDERSTORM MAY REMAIN

STATIONARY OVER ONE LOCATION FOR AN HOUR OR MORE. OTHER TIMES, A SUCCESSION

OF SEVERAL THUNDERSTORMS MAY TRACK OVER THE SAME LOCATION, A PHENOMENON

KNOWN AS TRAINING.



TROPICAL CYCLONES AND INLAND FLOODING...WHEN IT COMES TO TROPICAL CYCLONES,

A GENERIC TERM FOR A HURRICANE, TYPHOON, OR TROPICAL STORM, WIND SPEEDS

AND SEVERITY CATEGORIES 1-5 DO NOT TELL THE WHOLE STORY. INTENSE RAINFALL,

NOT DIRECTLY RELATED TO THE WIND SPEED OF A TROPICAL CYCLONE, OFTEN CAUSES

MORE DAMAGE. SINCE THE 1970S, INLAND FLOODING HAS BEEN RESPONSIBLE FOR MORE

THAN HALF OF THE DEATHS ASSOCIATED WITH TROPICAL CYCLONES IN THE UNITED STATES.

TYPICALLY, GREATER RAINFALL AMOUNTS AND FLOODING OCCUR WHEN TROPICAL CYCLONES

HAVE A SLOW FORWARD SPEED OR ANTECEDENT SOIL MOISTURE CONDITIONS ARE HIGH.

IN VERMONT, THE TWO MOST SIGNIFICANT FLOODS IN THE STATE`S HISTORY WERE A

RESULT OF STORMS WITH TROPICAL ORIGINS, INCLUDING THE DEVASTATING IMPACTS

FROM TROPICAL STORM IRENE IN 2011.



NATIONAL FLOOD SAFETY AWARENESS WEEK CONTINUES ON THURSDAY WITH NATIONAL

WEATHER SERVICE WATER RESOURCES INFORMATION.


$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.