Spring Flood Potential Outlook For Northern & Eastern Maine - 04/01/2021

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MEC003-009-019-021-025-029-082015-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK

NATIONAL WEATHER SERVICE CARIBOU ME

405 PM EDT THU APR 1 2021

..SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL...AND 

DOWNEAST MAINE...

THIS IS THE SEVENTH WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR 

2021, ISSUED BY THE NATIONAL WEATHER SERVICE IN CARIBOU, MAINE. 

THIS OUTLOOK IS FOR NORTHERN, CENTRAL, AND DOWNEAST MAINE FOR THE 

TWO-WEEK PERIOD OF APRIL 1ST TO APRIL 15TH 2021. 

THE FLOOD POTENTIAL FOR OPEN WATER FLOODING IS NEAR NORMAL 

ACROSS THE ENTIRE REGION. THE FLOOD POTENTIAL DUE TO ICE JAMS 

REMAINS NEAR NORMAL ACROSS THE NORTHERN MAINE RIVERS, WHILE THE

THREAT FOR ICE JAM FLOODING ACROSS THE CENTRAL AND DOWNEAST AREAS.

NO THREAT OF ICE JAM FLOODING, WHILE THE DOWNEAST REGION REMAINS 

BELOW NORMAL.

...CLIMATOLOGICAL GUIDANCE... 

PRECIPITATION WAS BELOW NORMAL ACROSS THE SOUTHERN HALF OF THE

REGION WITH NO SNOWFALL REPORTED DURING THE LAST HALF OF THE 

MONTH OF MARCH. NORTHERN AREAS REPORTED ABOVE NORMAL

PRECIPITATION DURING THE PERIOD WITH SNOWFALL BETWEEN 1 TO 3 

INCHES FALLING ON THE 27TH AND 28TH. 

TEMPERATURES AVERAGED ABOVE NORMAL DURING THE LAST HALF OF THE

MONTH OF MARCH. THIS HAS HELPED ACCELERATE THE SNOWMELT ACROSS THE

REGION AND IS RUNNING ABOUT 1 TO 2 WEEKS AHEAD OF SCHEDULE.

AN UPPER LEVEL BLOCKING RIDGE IS EXPECTED TO DEVELOP DOWNSTREAM 

OF NEW ENGLAND LEADING TO A NEGATIVE NORTH ATLANTIC 

OSCILLATION(NAO) PATTERN. THIS WILL ALLOW COLD AIR FROM CANADA TO 

BE DIRECTED SOUTHWARD AROUND THE BLOCKING UPPER LEVEL RIDGE SOUTH 

OF GREENLAND. THIS PATTERN IS EXPECTED TO HOLD RIGHT INTO THE 

SECOND WEEK OF APRIL WITH TEMPERATURES NEAR TO SLIGHTLY BELOW 

NORMAL FOR APRIL. 

THE OFFICIAL NATIONAL WEATHER SERVICE 6 TO 14 DAY OUTLOOK IS 

CALLING FOR NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES AND NEAR 

TO SLIGHTLY BELOW NORMAL PRECIPITATION. SOME OF THE NUMERICAL 

MODEL GUIDANCE IS SHOWING THAT THERE COULD BE A SHIFT IN THE 

PATTERN TOWARD THE END OF THIS TERM, WHICH COULD ALLOW FOR A MORE 

ACTIVE WEATHER PATTERN.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...

SNOW DEPTHS SAW A DRAMATIC DROP OVER THE LAST TWO WEEKS THANKS  

TO THE WARMER TEMPERATURES AND RAINFALL. AS OF 8 AM THIS MORNING, 

SNOW DEPTHS RANGED FROM 4 TO 10 INCHES ACROSS NORTHWEST MAINE, 

WHICH INCLUDES THE ALLAGASH AND NORTH WOODS REGION. FURTHER EAST 

ACROSS THE REST OF NORTHERN MAINE, SNOW DEPTHS RANGED FROM A TRACE

TO 4 INCHES WITH THE HIGHEST AMOUNTS IN THE WOODS AND ACROSS THE 

HIGHER TERRAIN. ELSEWHERE, LITTLE IF ANY SNOW WAS LEFT ON THE 

GROUND, WITH THE EXCEPTION OF SOME SNOW BANKS. 

SNOW DEPTHS ARE WELL BELOW NORMAL FOR EARLY APRIL. AS STATED 

ABOVE, THE WARMER TEMPERATURES OVER THE LAST TWO WEEKS 

ACCELERATED THE SNOWMELT, WHICH IS RUNNING ABOUT TWO WEEKS AHEAD 

OF SCHEDULE.

THE SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN 

THE SNOWPACK, DECREASED OVER THE PAST TWO WEEKS ACROSS THE REGION.

AS OF 8 AM THIS MORNING, NORTHWEST MAINE HAD 2 TO 4 INCHES, WHILE

THE REST OF NORTHERN MAINE HAD UP TO 2 INCHES IN THE WOODS AND

HIGHER TERRAIN. 

SNOW WATER EQUIVALENTS ARE WELL BELOW NORMAL ACROSS THE REGION. 

THE FROST DEPTH AT NWS CARIBOU WAS AT 5 INCHES. 

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

THE LATEST PALMER DROUGHT SEVERITY INDEX, WHICH MEASURES SOIL 

MOISTURE IN THE LONGER TERM, SHOWS NEAR NORMAL CONDITIONS FOR ALL

AREAS.

A LOOK AT THE GROUNDWATER LEVELS, COURTESY OF THE USGS, SHOWED

ABOVE NORMAL ACROSS NORTHERN AND NORTHWEST MAINE. THE CENTRAL

AREAS WERE SEEING NEAR TO SLIGHTLY ABOVE NORMAL, WHILE THE 

DOWNEAST REGION SAW GROUNDWATER LEVELS IMPROVE TO ABOVE NORMAL. 

CALAIS IN CENTRAL WASHINGTON REPORTED GROUNDWATER LEVELS WELL 

ABOVE NORMAL. 

...RIVER AND ICE CONDITIONS...

RIVER FLOWS WERE ABOVE NORMAL ACROSS NORTHERN AND CENTRAL AREAS, 

WHILE THE DOWNEAST REGION WAS SEEING RIVER FLOWS NEAR NORMAL. 

ICE COVER HAD BROKEN UP ACROSS THE RIVERS AND STREAMS THROUGHOUT

THE REGION, THANKS TO THE WARMER TEMPERATURES AND RAINFALL THAT 

TOOK PLACE DURING THE LAST WEEK OF MARCH. THERE IS STILL SOME ICE

COVER ALONG THE ST. JOHN RIVER FROM LILLE TO HAMLIN WITH AN ICE 

JAM IN PLACE JUST SOUTH OF LILLE. THE AROOSTOOK RIVER STILL HAS 

ICE COVER IN THE VICINITY OF THE CARIBOU DAM, AND FROM THE 

CARIBOU-FORT FAIRFIELD TOWN LINE ALL THE WAY TO THE INTERNATIONAL 

BORDER AT TINKER DAM. THERE IS AN ICE JAM THAT IS STILL IN PLACE 

IN FORT FAIRFIELD, FROM THE STRICKLAND ROAD TO THE FORT FAIRFIELD

BRIDGE.

...IN CONCLUSION...

THE FLOOD POTENTIAL FOR OPEN WATER FLOODING IS NEAR NORMAL ACROSS

THE ENTIRE REGION. THE FLOOD POTENTIAL DUE TO ICE JAMS REMAINS 

NEAR NORMAL FOR THE NORTHERN MAINE RIVER BASINS. THE FLOOD 

POTENTIAL FOR ICE JAM FLOODING FOR THE CENTRAL AND SOUTHERN AREAS

HAS ENDED FOR THE SEASON.

IT IS IMPORTANT TO REMEMBER THAT A HEAVY RAINFALL EVENT ALONG WITH

MILD TEMPERATURES, OR A PROLONGED WARMUP IN TEMPERATURES, CAN LEAD

TO AN INCREASED POTENTIAL FOR FLOODING WITH SNOWMELT AND RUNOFF. 

ICE BREAKING UP AND JAMMING CAN ELEVATE THE THREAT FOR FLOODING IN

A SHORT PERIOD OF TIME. 

THIS WILL BE THE LAST WINTER/SPRING FLOOD OUTLOOK ISSUED FOR THE

SEASON, UNLESS CONDITIONS WARRANT OTHERWISE.

$$

HEWITT