Flood Potential Outlook
Issued by NWS Portland, ME

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FGUS71 KGYX 191935
ESFGYX
MEC001-005-007-011-013-015-017-023-025-027-031-NHC001-003-005-007-
009-011-013-015-017-019-211945-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE GRAY ME
335 PM EDT THU MAR 19 2015

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK...

THE SHORT TERM /NEXT 2 WEEKS/ FLOOD POTENTIAL FOR WESTERN MAINE
AND NEW HAMPSHIRE IS NORMAL. THE LONGER TERM FLOOD POTENTIAL IS
ABOVE NORMAL. THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS
ABOVE NORMAL.

THIS IS THE SEVENTH IN A SERIES OF REGULARLY SCHEDULED HYDROLOGIC
OUTLOOKS ISSUED DURING THE WINTER AND SPRING SEASONS. THESE
OUTLOOKS WILL BE ISSUED EVERY TWO WEEKS UNTIL THE END OF THE SNOW
MELT SEASON... AND WILL ASSESS THE POTENTIAL FOR FLOODING BASED A
NUMBER OF FACTORS.

...CLIMATOLOGICAL GUIDANCE...

IN NORTHERN NEW ENGLAND WE HAVE SEEN SOME MODERATION IN
TEMPERATURE OVER THE LAST 7 DAYS... BUT ONCE AGAIN COLDER THAN
NORMAL ARCTIC AIR HAS FILTERED IN RESULTING IN A RETURN TO BELOW
NORMAL TEMPERATURES. THE LONGER RANGE CLIMATIC GUIDANCE SUGGEST
THAT THE COLDER AIR WILL REMAIN OVER THE NORTHEAST THROUGH MUCH OF THE
REMAINDER OF MARCH. A RIDGE WILL ONCE AGAIN SETUP IN THE WEST WITH
A TROUGH IN THE NORTHEAST. THE STORM TRACK IS EXPECTED TO BE
MOSTLY FROM NORTHWEST TO SOUTHEAST WITH QUICK MOVING CLIPPER TYPE
SYSTEMS MOVING THROUGH THE AREA WHICH WOULD LIMIT PRECIPITATION...
HOWEVER WE WILL HAVE TO WATCH TO SEE IF THE SUBTROPICAL JET AND
POLAR JET CAN PHASE WHICH WOULD LEAD TO HEAVIER PRECIPITATION
OVER MAINE AND NEW HAMPSHIRE. IT IS QUITE POSSIBLE THAT OVER THE
NEXT 2 TO 3 WEEKS THE SNOW WATER EQUIVALENT OF THE SNOWPACK IN
NORTHERN NEW HAMPSHIRE AND CENTRAL AND NORTHERN MAINE WILL
ACTUALLY INCREASE.

THE OFFICIAL NATIONAL WEATHER SERVICE 6 TO 10 DAY AND 8 TO 14 DAY
FORECAST INDICATES BELOW NORMAL TEMPERATURES WITH ABOVE NORMAL
PRECIPITATION.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENT...

...NEW HAMPSHIRE...

SNOW DEPTH ACROSS SOUTHERN NEW HAMPSHIRE IS GENERALLY 8 TO 18
INCHES. SNOW DEPTH IS A BIT LESS IN THE SOUTHERN CONNECTICUT
RIVER VALLEY ON THE ORDER OF 5 TO 10 INCHES. IN CENTRAL AND
NORTHERN NEW HAMPSHIRE SNOW DEPTH RANGE FROM 1 TO 2 FEET. AT
ELEVATIONS OF 2000 FEET OR GREATER SNOW DEPTH OF 2 TO 3 FEET ARE
COMMON.

SNOW WATER EQUIVALENT IS GENERALLY IN THE 3 TO 8 INCH RANGE
ACROSS NEW HAMPSHIRE WITH LOCALLY HIGHER AMOUNTS OF 8 TO 10 INCHES
ABOVE 2000 FEET. A SNOW SURVEY DONE NEAR CANNON MOUNTAIN AT AN
ELEVATION OF 1950 FEET INDICATED 10 INCHES OF WATER EQUIVALENT.
MOOSE FALLS IN NORTHERN NEW HAMPSHIRE REPORTED 9.5 INCHES OF WATER
EQUIVALENT ALSO AT AN ELEVATION OF 1950 FEET.

SNOW WATER EQUIVALENT ARE ABOVE NORMAL IN SOUTHERN NEW HAMPSHIRE
AND NEAR NORMAL IN NORTHERN LOCATIONS.

...WESTERN MAINE...

SNOW DEPTH IN WESTERN MAINE RANGES FROM 1 TO 3 FEET WITH LOCALLY
HIGHER AMOUNTS. LOCAL AMOUNTS OF 36 TO 42 INCHES EXIST IN
THE MOUNTAINS.

SNOW WATER EQUIVALENT GENERALLY RANGES FROM 5 TO 8 INCHES WITH
LOCAL AMOUNTS OF 8 TO 10 INCHES.

SNOW WATER EQUIVALENT IS NEAR NORMAL WITH THE EXCEPTION OF
SOUTHERN AND COASTAL LOCATIONS WHERE IT IS WELL ABOVE NORMAL.

THE DENSITY OF THE SNOWPACK IS GENERALLY BELOW 30 PERCENT WITH THE
EXCEPTION OF SOUTHERN MAINE WHERE SNOW DENSITY IS APPROACHING 35
PERCENT. A SNOWPACK IS CONSIDERED RIPE ONCE THE DENSITY REACHES
NEAR 40 PERCENT. A RIPE SNOWPACK NO LONGER HAS THE ABILITY TO
RETAIN RAINFALL AND WOULD RELEASE WATER DURING A RAIN EVENT.

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

SOIL MOISTURE ANOMALY MAPS FROM MARCH 14 INDICATE NEAR NORMAL
SOIL MOISTURE ACROSS WESTERN MAINE AND ALL OF NEW HAMPSHIRE.

THE PALMER DROUGHT SEVERITY INDEX WHICH INDICATES LONGER TERM
MOISTURE CONDITIONS SHOWS NEAR NORMAL MOISTURE FOR ALL OF NEW
HAMPSHIRE AND CENTRAL AND NORTHERN MAINE. FOR COASTAL MAINE THE
PALMER DROUGHT SEVERITY INDEX IS IN THE UNUSUALLY MOIST CATEGORY.

THE USGS REPORTS THAT GROUNDWATER LEVELS ARE MOSTLY IN THE NORMAL
RANGE FOR THE TIME OF YEAR. THERE WAS A BIT OF A BUMP UP IN GROUND
WATER LEVELS IN COASTAL MAINE AND SOUTHERN NEW HAMPSHIRE DUE TO
THE 2 TO 3 DAYS OF MILDER WEATHER LAST WEEK. RESERVOIRS IN THE
ANDROSCOGGIN RIVER BASIN ARE 40.9 PERCENT FULL WHICH IS 8.9
PERCENT ABOVE NORMAL. THE 3 MAIN RESERVOIRS IN THE KENNEBEC RIVER
BASIN ARE ALSO ABOVE NORMAL LEVELS FOR THE TIME OF YEAR.

WATER SUPPLY SHORTAGES ARE NOT ANTICIPATED.

...RIVER AND ICE CONDITIONS...

RIVER FLOWS REMAIN NEAR NORMAL FOR THE TIME OF YEAR. SOME RIVERS
IN SOUTHERN LOCATIONS SAW A BIT OF AN INCREASE DUE TO THE MILD
WEATHER THE MIDDLE OF LAST WEEK BUT THEY ARE NOW RECEDING TO
NORMAL LEVELS AGAIN.

MOST RIVERS AND STREAMS REMAIN ICE COVERED. RECENT ICE
MEASUREMENTS BY THE USGS INDICATE THAT ICE IS STILL ABOUT 12 TO 24
INCHES THICK. MUCH OF THIS ICE IS OF THE HARD BLACK ICE VARIETY.
THE ICE THICKNESS IS THE SAME AS WOULD BE EXPECTED DURING JANUARY
OR EARLY FEBRUARY. THE ICE THICKNESS IS NOT INCREASING DUE TO THE
SNOW COVER. HOWEVER IT HAS NOT YET STARTED TO DECREASE IN
THICKNESS EITHER WHICH WOULD BE THE CASE AT THIS TIME IN A YEAR
WITH NORMAL TEMPERATURES. AN ICE JAM REMAINS IN PLACE ON THE
KENNEBEC RIVER IN THE VICINITY OF MADISON. WATER LEVELS HAVE
DECREASED SIGNIFICANTLY BEHIND THIS JAM AS THE COLD WEATHER AND
LACK OF RUNOFF HAVE SEEN RIVER FLOWS LOWER. THIS JAM WILL REMAIN
IN PLACE AND MAY POSE A RISK LATER IN THE SPRING.

...IN CONCLUSION...

BASED ON THE ABOVE INFORMATION...THE WINTER/SPRING FLOOD
POTENTIAL ACROSS WESTERN MAINE AND NEW HAMPSHIRE IS NORMAL IN THE
SHORT TERM /NEXT 2 WEEKS/ BUT ABOVE NORMAL IN THE LONG TERM. THIS
IS DUE TO THE FACT THAT OVER THE NEXT 2 WEEKS PRECIPITATION IS
EXPECTED TO BE MOSTLY NEAR TO SOMEWHAT ABOVE NORMAL WITH COLDER
THAN NORMAL TEMPERATURES AND NO EXTENDED PERIODS OF WARM WEATHER
EXPECTED. HOWEVER IN THE LONGER TERM WE WILL LIKELY BE GOING INTO
APRIL WITH A SIGNIFICANT SNOWPACK AND ICE COVER. THE LATER INTO
THE SPRING SEASON WE PROGRESS WITH A SIGNIFICANT SNOWPACK THE
GREATER THE CHANCE OF A RAPID WARM UP WITH RAIN.

IT IS IMPORTANT TO NOTE THAT MAJOR FLOODING DOES NOT OCCUR
FROM SNOW MELT ALONE. RAINFALL...HOW MUCH AND IN HOW SHORT A
PERIOD OF TIME...IS THE MOST IMPORTANT FACTOR IN DETERMINING THE
SEVERITY OF FLOODING.

ANOTHER WINTER/SPRING FLOOD OUTLOOK WILL BE ISSUED BY 8 AM FRIDAY
APRIL 3.

$$

TFH



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