205  
FGUS71 KBTV 210930  
ESFBTV  
NYC019-031-033-089-VTC001-005-007-009-011-013-015-017-019-021-023-  
027-230930-  
 
WINTER/SPRING FLOOD POTENTIAL OUTLOOK  
NATIONAL WEATHER SERVICE BURLINGTON VT  
530 AM EDT THU MAR 21 2019  
   
..WINTER/SPRING FLOOD POTENTIAL OUTLOOK
 
 
THIS IS THE SIXTH FLOOD OUTLOOK FOR THE 2019 WINTER/SPRING  
SEASON. FLOOD OUTLOOKS ARE ISSUED BI-WEEKLY 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
 
 
THE THREAT OF OPEN WATER FLOODING DUE TO SNOWMELT AND RAINFALL IS  
ABOVE NORMAL ACROSS THE ADIRONDACKS AND MOST OF EASTERN, NORTH  
CENTRAL AND NORTHEASTERN VERMONT. THE THREAT IS NEAR NORMAL IN  
THE SAINT LAWRENCE AND CHAMPLAIN VALLEYS. MUCH OF THE THREAT  
EXISTS TOWARD THE LATTER HALF OF THE TWO WEEK PERIOD. THE THREAT  
OF FLOODING DUE TO ICE JAMS IS ABOVE NORMAL ACROSS NORTHEASTERN  
VERMONT, AND NEAR NORMAL ELSEWHERE.  
   
..SNOW DEPTHS AND WATER EQUIVALENT
 
 
A DECENT SNOWPACK STILL EXISTS ACROSS MOST OF THE NORTH COUNTRY.  
SNOW DEPTHS ARE GENERALLY NEAR TO ABOVE NORMAL FOR MOST OF NORTH  
CENTRAL AND NORTHEASTERN VERMONT AS WELL AS THE HIGHER TERRAIN OF  
THE ADIRONDACK AND GREEN MOUNTAINS. HERE VALUES GENERALLY RANGE  
FROM 1 TO 2 FEET IN THE VALLEYS AND MID-SLOPE AREAS, AND 2.5 TO 4  
FEET IN THE UPPER SLOPES. SUMMIT VALUES RANGE WELL IN EXCESS OF  
50 INCHES WITH THE MOST RECENT VALUE AT MOUNT MANSFIELD IN THE  
NORTHERN GREENS AT 107 INCHES. SNOW DEPTHS ARE NEAR NORMAL FOR  
LOWER ELEVATIONS OF THE SAINT LAWRENCE, CHAMPLAIN AND LOWER  
CONNECTICUT RIVER VALLEYS WHERE VALUES ARE GENERALLY LESS THAN 8  
INCHES. IN FACT, MANY AREAS OF THE CHAMPLAIN VALLEY ARE NEARLY  
DEVOID OF SNOW COVER.  
 
SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN THE  
SNOWPACK IS NEAR TO ABOVE NORMAL FOR THIS TIME OF YEAR IN  
ELEVATED TERRAIN ABOVE 1500 FEET. ELSEWHERE VALUES ARE CLOSER TO  
LATE MARCH SEASONAL LEVELS. THIS INCLUDES THE LOWER ELEVATIONS OF  
THE SAINT LAWRENCE, CHAMPLAIN AND LOWER CONNECTICUT RIVER VALLEYS  
WHERE VALUES GENERALLY RANGE FROM NEAR ZERO TO 2 INCHES. VALUES  
INCREASE MARKEDLY ACROSS THE MID-SLOPE TERRAIN FROM 1500-2500 FEET  
HOWEVER. IN THIS ZONE EQUIVALENTS RANGE FROM 4 TO 8 INCHES IN THE  
ADIRONDACKS AND FROM 5 TO 10 INCHES IN VERMONT. EVEN HIGHER  
VALUES ARE PRESENT IN THE HIGH TERRAIN OF THE ADIRONDACKS AND  
GREENS WITH ELEVATIONS ABOVE 3000 FEET LIKELY CONTAINING MORE  
THAN 10 INCHES OF WATER IN THE PACK.  
   
..RIVER AND SOIL CONDITIONS
 
 
THE PAST FEW WEEKS HAVE FEATURED SOMEWHAT LESS PRECIPITATION  
ACROSS NORTHERN NEW YORK AND VERMONT WITH NOT MUCH SNOWMELT IN  
ELEVATED TERRAIN. AS A RESULT SOIL MOISTURE STATES HAVE DRIED  
SLIGHTLY. AN OVERVIEW OF MEAN RIVER FLOWS ACROSS THE REGION SHOW  
VALUES CONTINUE TO RUN NEAR NORMAL, FALLING GENERALLY WITHIN THE  
STANDARD 25TH TO 75TH PERCENTILE RANGE AS WE ENTER THE TAIL END OF  
MARCH. THIS INCLUDES LAKE CHAMPLAIN, WHICH IS RUNNING ABOUT 0.5  
FEET ABOVE ITS NORMAL LATE MARCH LEVEL - A DECREASE FROM THE  
APPROXIMATE 1 FOOT POSITIVE DEPARTURE OBSERVED EARLIER IN THE  
MONTH. ICE COVER REMAINS VARIABLE ACROSS THE AREA WITH MORE SOLID  
COVER EXISTING ACROSS NORTHERN WATERSHEDS AND CONSIDERABLY LESS  
FURTHER SOUTH. A NUMBER OF ICE JAMS REMAIN IN PLACE IN NORTHERN  
WATERSHEDS, PARTICULARLY ACROSS NORTH CENTRAL AND NORTHEASTERN  
VERMONT. WHERE SOLID ICE COVER STILL EXISTS, IT IS ESTIMATED TO  
BE 6 TO 12 INCHES THICK. WITH AN INCREASINGLY STRONG EARLY SPRING  
SUN ANGLE, EXISTING ICE WILL CONTINUE TO SLOWLY ROT. THEREFORE,  
BARRING A HEAVY RAINFALL EVENT THE OVERALL THREAT WILL STEADILY  
LESSEN OVER THE COMING FEW WEEKS.  
   
..WEATHER OUTLOOK
 
 
A RECENT THAW FROM ROUGHLY 14 TO 16 MARCH 2019 MELTED CONSIDERABLE  
SNOW ACROSS VALLEY LOCATIONS, WHILE COOLER TEMPERATURES IN HIGHER  
ELEVATIONS LED TO LESS WATER LOSS DESPITE A GENERAL RIPENING OF  
THE PACK. FORTUNATELY THERE WAS NOT MUCH RAIN WITH THE THAW SO  
RISES ALONG RIVERS AND STREAMS REMAINED WITHIN BANK.  
 
THE UPPER LEVEL STEERING FLOW CONTINUES TO BE DOMINATED BY A  
RATHER PERSISTENT AND POSITIVE PHASE OF THE NORTH ATLANTIC  
OSCILLATION (NAO). WITH A POSITIVE PHASE OF THE NAO THERE IS  
LITTLE DOWNSTREAM BLOCKING SO SYSTEMS TEND TO BE FAIRLY  
PROGRESSIVE AND TRACK CLOSE TO OR THROUGH THE NORTHEASTERN UNITED  
STATES. ONE SUCH SYSTEM IS FORECAST TO TRACK THROUGH THE AREA OVER  
THE NEXT FEW DAYS AS ENERGY DROPPING SOUTHEAST THROUGH CANADA  
MERGES WITH A DISTURBANCE RIDING NORTH ALONG THE ATLANTIC  
SEABOARD. THE RESULT WILL LIKELY BE A FAIRLY POTENT NOR'EASTER  
BRINGING LIGHT TO MODERATE MIXED RAINS AND SNOWS TO THE VALLEYS  
AND HEAVY SNOWFALL TO HIGHER ELEVATIONS. RIGHT NOW WIDESPREAD  
FLOODING IS NO EXPECTED.  
 
AFTER THE STORM MOVES BY ANOTHER SHOT OF COLD AIR IF FORECAST TO  
MOVE INTO THE AREA THROUGH THE MIDDLE OF NEXT WEEK. AFTER THAT  
MEDIUM RANGE NUMERICAL WEATHER MODEL GUIDANCE SUGGESTS MUCH OF NEW  
ENGLAND AND NEW YORK STATE COULD SEE A MARKED WARM-UP DURING THE  
VERY END OF MARCH INTO EARLY APRIL.  
 
THE OFFICIAL NATIONAL WEATHER SERVICE 8-14 DAY OUTLOOK FOR 27  
MARCH THROUGH 2 APRIL 2019 SEEMS IN GENERAL AGREEMENT WITH THESE  
THOUGHTS AS IT CALLS FOR TEMPERATURES TO AVERAGE NEAR TO ABOVE  
NORMAL. PRECIPITATION FOR THE SAME TIME PERIOD IS FORECAST TO BE  
ABOVE NORMAL.  
 
THE BOTTOM LINE IS THAT WE LOOK TO ENTER THE LAST WEEK OF MARCH WITH  
A DEEP AND WATER LADEN SNOWPACK ACROSS THE HIGHER TERRAIN OF THE  
ADIRONDACK AND NORTHERN GREEN MOUNTAINS AND THIS WILL NEED TO BE  
MONITORED CLOSELY.  
   
..SUMMARY
 
 
BASED ON THE ABOVE INFORMATION, THE THREAT FOR OPEN WATER  
FLOODING DUE TO RUNOFF FROM SNOWMELT AND RAINFALL IS NEAR NORMAL  
IN THE CHAMPLAIN AND SAINT LAWRENCE RIVER VALLEYS. IT IS ABOVE  
NORMAL ELSEWHERE. SNOW DEPTHS AND THE WATER EQUIVALENT CONTAINED  
IN THE PACK ARE NEAR TO SLIGHTLY ABOVE NORMAL, WITH HIGHEST  
DEPARTURES ACROSS EASTERN AND NORTHEASTERN VERMONT. RIVER FLOWS  
ARE NEAR NORMAL AND ANTECEDENT SOIL MOISTURE STATES ARE NEAR TO  
SLIGHTLY ABOVE NORMAL AT MOST REPORTING SITES. WHILE THE OVERALL  
CONCERN FOR RAPID SNOWMELT AND FLOODING IS RATHER LOW OVER THE  
NEXT WEEK (THROUGH MARCH 27) IT REMAINS UNCERTAIN ON HOW THE  
THREAT WILL EVOLVE AS WE APPROACH EARLY APRIL. SHOULD NO HEAVY  
RAINFALL MATERIALIZE BEYOND THE NEXT WEEK, THEN THE THREAT WOULD  
REMAIN ON THE LOWER SIDE OF NORMAL.  
 
THE THREAT FOR FLOODING DUE TO ICE JAMS IS ABOVE NORMAL FOR MUCH  
OF NORTH CENTRAL AND NORTHEASTERN VERMONT, AND NEAR NORMAL  
ELSEWHERE WITH FOCUS ON THE LATTER HALF OF THE TWO WEEK FORECAST  
PERIOD.  
 
IT IS IMPORTANT TO NOTE THAT HEAVY RAINFALL CAN RESULT IN  
FLOODING AT ANY TIME OF THE YEAR, EVEN IN AREAS THAT HAVE LITTLE  
OR NO SNOW ON THE GROUND.  
 
THE NEXT WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED ON THURSDAY,  
APRIL 4, 2019.  
 
ACCESS CURRENT WEATHER CONDITIONS AND FORECASTS ON OUR WEB SITE  
AT WWW.WEATHER.GOV/BTV.  
 

 
 
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