Flood Potential Outlook
Issued by NWS Caribou, ME

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
1256 PM EDT FRI MAR 20 2015

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN...
CENTRAL...AND DOWNEAST MAINE...

THIS IS THE SEVENTH WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR
2015...ISSUED BY THE NATIONAL WEATHER SERVICE IN CARIBOU, MAINE.
THIS OUTLOOK IS FOR NORTHERN, CENTRAL AND DOWNEAST MAINE FOR THE
TWO-WEEK PERIOD FROM MARCH 19 THROUGH APRIL 2, 2015.

THE WINTER/SPRING FLOOD POTENTIAL FOR THE CENTRAL MAINE HIGHLANDS
SOUTH TO THE COAST IS ABOVE NORMAL. FOR NORTHERN MAINE, THE FLOOD
POTENTIAL IS NEAR NORMAL, WITH FAR NORTHERN PORTIONS OF THE
COUNTY LIKELY A BIT BELOW NORMAL FOR MID TO LATE MARCH.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS SLIGHTLY ABOVE
NORMAL FOR ALL OF NORTHERN, CENTRAL, AND DOWNEAST MAINE.

...CLIMATOLOGICAL GUIDANCE...

AFTER A COLD START TO MARCH, WE HAVE SEEN A FEW DAYS HERE AND
THERE HAVE SEEN NEAR TO ABOVE NORMAL TEMPERATURES AS THE POLAR
JET STREAM BRIEFLY RETREATED FURTHER NORTH TO THE INTERNATIONAL
BORDER. THE OVERALL COLD TREND HAS CONTINUED HOWEVER; THE AVERAGE
TEMPERATURE RANGES FROM 5 TO 7 DEGREES COLDER THAN NORMAL SO FAR
THIS MONTH. IN SPITE OF THIS, THE INCREASING SUN ANGLE HAD ALLOWED
FOR SOME SNOW MELT TO OCCUR. HOWEVER, THE SNOWPACK ONCE AGAIN
INCREASED AS SNOWSTORM ON MARCH 17TH BROUGHT 12 TO 18 INCHES TO
MUCH OF THE REGION.

THIS COLDER AND SOMEWHAT ACTIVE TREND LOOKS TO CONTINUE THROUGH
THE REMAINDER OF MARCH. THE OVERALL PATTERN FAVORS WEAK RIDGING
IN THE WEST AND A DEEP DOWNSTREAM TROUGH IN THE EAST. WEAK EL NINO
HAS DEVELOPED, WHICH WILL ALLOW FOR A SOMEWHAT ACTIVE SUBTROPICAL
JET STREAM. THIS COLD AND ACTIVE PATTERN HAS BEEN VERY PERSISTENT
THROUGH THE LATTER HALF OF WINTER. SO IN SPITE OF THE
STRENGTHENING SUN, COLDER THAN NORMAL TEMPERATURES ARE EXPECTED TO
PREVAIL ACROSS MAINE OVER THE NEXT COUPLE OF WEEKS. THE PRECIPITATION
FORECAST IS A BIT MORE UNCERTAIN AS MUCH DEPENDS ON HOW THE NORTHERN
AND SOUTHERN JET STREAMS PHASE. HOWEVER, IN THE SHORT TO MID TERMS,
THERE ARE AT LEAST A FEW CHANCES OF PRECIPITATION. THE FIRST WILL
OCCUR MARCH 21ST AS A COLD FRONT CROSSES NEW ENGLAND, BRINGING
SNOW TO OUR AREA. SOME RAIN MAY MIX IN ACROSS DOWNEAST. ANOTHER
SYSTEM LOOKS TO BRING MORE SNOW, AGAIN POSSIBLY MIXED WITH RAIN,
TOWARD THE MIDDLE OF NEXT WEEK. HEADING OUT INTO THE LONGER RANGE,
THERE APPEARS TO BE YET ANOTHER SYSTEM OR TWO THREATENING OVER THE
LAST COUPLE DAYS OF THE MONTH.

THE OFFICIAL NATIONAL WEATHER SERVICE 6 TO 14 DAY OUTLOOK FOR
MARCH 25 THROUGH APRIL 2 SUPPORTS THE ABOVE THINKING WELL, CALLING
FOR BELOW NORMAL TEMPERATURES AND ABOVE NORMAL PRECIPITATION.

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

THE SNOWPACK INCREASED SIGNIFICANTLY ACROSS MUCH OF OUR REGION,
ESPECIALLY CENTRAL MAINE NORTHWARD INTO CENTRAL AND SOUTHERN
PORTIONS OF AROOSTOOK COUNTY. DEPTHS OF 2 TO 3 FEET ARE NOW
COMMON OVER NEARLY ALL OF NORTHERN, CENTRAL, AND DOWNEAST MAINE.
THESE ARE ALL NEAR TO A BIT ABOVE NORMAL FOR THIS TIME OF YEAR.
THE DEEPEST SNOW IS CURRENTLY FOUND IN THE HIGHER TERRAIN OF THE
CENTRAL HIGHLANDS AND FAR DOWNEAST MAINE, WHERE REPORTS INDICATE
AROUND 40 INCHES OF SNOW COVERS THE GROUND. THIS IS ALSO ABOVE
NORMAL. ONLY THE FAR NORTH, INCLUDING AREAS AROUND FORT KENT AND
MADAWASKA, HAS BELOW NORMAL SNOW COVER; DEPTHS ARE GENERALLY 1 TO
2 FEET IN THESE LOCATIONS.

THE SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN
THE SNOWPACK, IS STILL ABOVE NORMAL OVER THE CENTRAL HIGHLANDS
AND DOWNEAST MAINE. THESE LOCATIONS HAVE 6 TO 9 INCHES OF WATER
CONTAINED IN THE SNOW. THE SWE IS CLOSER TO NORMAL OVER
NORTHEASTERN MAINE BACK THROUGH THE SOUTHERN FRINGE OF THE NORTH
MAINE WOODS, WITH 5 TO 8 INCHES IN THE PACK. MUCH OF THE UPPER
SAINT JOHN VALLEY AND NORTH MAINE WOODS, ESPECIALLY AREAS WEST OF
ROUTE 11, HAVE 4 TO 6 INCHES OF WATER IN THE SNOW. THIS IS BELOW
NORMAL, ESPECIALLY ACROSS THE HIGHER TERRAIN.

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

NEAR SURFACE SOIL MOISTURE CONDITIONS, WHICH ARE INDICATIVE OF
NEAR TERM MOISTURE TRENDS, HAVE NOT SHOWN MUCH OF A TREND
CHANGE. ACROSS MUCH OF THE AREA, THEY ARE SLIGHTLY BELOW TO NEAR
NORMAL. THE EXCEPTION IS DOWNEAST MAINE WHERE ANTECEDENT MOISTURE
IS ABOVE NORMAL DUE TO THE COPIOUS AMOUNTS OF SNOW THEY RECEIVED
LATE JANUARY THROUGH FEBRUARY.

THE LATEST PALMER DROUGHT SEVERITY INDEX, WHICH TAKES A LOOK AT
MOISTURE STATES OVER THE LONGER RANGE OF WEEKS TO MONTHS, ALSO
REMAINS FAIRLY UNCHANGED. OUTSIDE OF DOWNEAST MAINE, WHICH IS
UNUSUALLY TO VERY MOIST, MUCH OF THE STATE IS REPORTING NEAR
NORMAL MOISTURE.

...RIVER AND ICE CONDITIONS...

RIVER FLOWS HAVE CONTINUED TO HOLD FAIRLY STEADY OVER THE PAST
SEVERAL DAYS, WITH SOME WATERWAYS SHOWING SOME MODEST RISES IN
RESPONSE TO SOME SNOWMELT THAT HAS OCCURRED ON SUNNY DAYS.
HOWEVER, A GOOD PART OF ANY SNOWMELT THAT WE`VE SEEN HAS BEEN
ABSORBED BY THE EXISTING SNOWPACK. RIVER FLOWS ARE GENERALLY NEAR
NORMAL ACROSS THE REGION, THOUGH DOWNEAST STREAMS MAY BE A BIT
BELOW NORMAL SINCE THEY NORMALLY HAVE SEEN A BIT MORE SNOWMELT IN
THEIR HEADWATERS BY THIS TIME.

ICE THICKNESSES ARE GENERALLY 1 TO 2 FEET ACROSS OUR ENTIRE AREA,
WITH THE COASTAL WATERWAYS AVERAGING CLOSE TO A FOOT. THIS IS
FAIRLY CLOSE TO NORMAL. THE STRONGER SUN ANGLE HAS LIKELY ALLOWED
FOR SOME ROT AND WEAKENING OF THE ICE WHERE IT HAS BEEN ABLE TO
GET THROUGH THE DEEP SNOWPACK. HOWEVER, RIVER ICE IS STILL LIKELY
STRONGER THAN NORMAL, ESPECIALLY IN OUR MORE SOUTHERN WATERWAYS,
DUE TO THE CONTINUED COLD WEATHER. ALTHOUGH THE SUN WILL CONTINUE
TO WORK ON THE RIVER ICE AND THE SNOW THAT LIES ATOP IT, THE
COLDER THAN NORMAL TEMPERATURES THAT WE`RE EXPECTING THROUGH THE
REST OF THE MONTH WILL LIKELY KEEP THE RIVER ICE RELATIVELY STRONG
RIGHT INTO APRIL.

WE CONTINUE TO MONITOR SEVERAL ICE JAMS THAT REMAIN LOCKED IN
PLACE ALONG MANY OF OUR RIVERS. THESE JAMS INCLUDE A 10-15 MILE
LONG JAM ON THE SAINT JOHN RIVER THROUGH SAINT FRANCIS, AS WELL AS
SEVERAL SMALLER JAMS LOCATED FURTHER DOWNSTREAM ON THE SAINT JOHN
BETWEEN FORT KENT AND VAN BUREN. THERE ARE ALSO SEVERAL KNOWN JAMS
ON THE AROOSTOOK RIVER, INCLUDING ONE IN WASHBURN THROUGH
CROUSEVILLE, ONE BETWEEN PRESQUE ISLE AND CARIBOU, AND ANOTHER
DOWNSTREAM OF FORT FAIRFIELD. FOR THE CENTRAL RIVERS, WE`VE NOTED
ICE JAMS ON THE PISCATAQUIS IN MAXFIELD, AND THE PENOBSCOT RIVER
NEAR ORONO. THESE JAMS ARE WELL FROZEN IN PLACE AND HAVE NOT MOVED
NOR CAUSED ANY FLOODING ISSUES THROUGH THE LATER WINTER MONTHS.
HOWEVER, THEY WILL BEAR WATCHING AS WE HEAD THROUGH THE SPRING AS
THEY WILL LIKELY SERVE AS A FOCUS FOR BREAK UP JAMS AND/OR WILL
PROVIDE AMPLE ICE DEBRIS AVAILABLE TO JAM DOWNSTREAM.

...IN CONCLUSION...

BASED ON THE AFOREMENTIONED INFORMATION, THE WINTER/SPRING FLOOD
POTENTIAL IS ABOVE NORMAL FOR ALL OF CENTRAL AND DOWNEAST MAINE,
INCLUDING THE PENOBSCOT, PISCATAQUIS, AND SAINT CROIX RIVER
BASINS. ALTHOUGH RIVER FLOWS ARE NEAR TO A BIT BELOW NORMAL IN
THESE AREAS, ANTECEDENT MOISTURE STATES ARE LARGELY ABOVE NORMAL,
ESPECIALLY DOWNEAST. THE SNOWPACK AND THE LIQUID WATER EQUIVALENT
CONTAINED THEREIN ARE ALSO ABOVE NORMAL. WE`VE ALREADY SEEN SOME
SLIGHT RISES IN RIVER LEVELS DUE TO THE BIT OF SNOWMELT THAT HAS
OCCURRED ON THE FEW MILD DAYS THAT WE`VE SEEN. ALTHOUGH TEMPERATURES
WILL BE BELOW NORMAL FOR THE LATTER HALF OF THE MONTH, ANY SUNSHINE
WILL ALLOW SNOWMELT TO CONTINUE. THIS WILL ALLOW THE SNOWPACK TO
CONTINUE TO RIPEN AND START CONTRIBUTING MORE MELT TO RUNOFF. THIS
WILL LEAVE THE REGION VERY VULNERABLE TO ANY MAJOR RAIN EVENTS
RIGHT INTO APRIL. EVEN IF WE DON`T GET ANY SIGNIFICANT RAIN EVENTS,
WITH SO MUCH WATER ALREADY CONTAINED IN THE SNOW, IT IS STILL MORE
LIKELY THAN NORMAL THAT WE WILL SEE FLOODING IN THESE AREAS THIS
SPRING.

ACROSS THE REMAINDER OF THE STATE, THE WINTER/SPRING FLOOD
POTENTIAL IS NEAR NORMAL TO A BIT BELOW NORMAL OVER FAR NORTHERN
MAINE. IN THESE AREAS, THE PRIMARY IMPETUS IN THE NEAR NORMAL
DESIGNATION IS THE NEAR NORMAL SNOW DEPTHS AND AMOUNTS OF WATER IN
THAT PACK. GIVEN THIS IN ADDITION TO THE NEAR NORMAL RIVER FLOWS,
NEAR NORMAL GROUNDWATER LEVELS, AND SOMEWHAT NORMAL ANTECEDENT
MOISTURE CONDITIONS, A NEAR NORMAL FLOOD THREAT SEEMS REASONABLE.
FAR NORTHERN MAINE HAS A BIT LESS SNOW AND LIQUID EQUIVALENT THAN
WHAT WE`D NORMALLY SEE IN MID TO LATE MARCH, SO THIS AREA`S FLOOD
POTENTIAL IS A BIT BELOW NORMAL.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS SLIGHTLY ABOVE
NORMAL ACROSS THE ENTIRE AREA. THE RIVER ICE IS QUITE THICK AND
ALTHOUGH IT IS NOT ABNORMALLY SO, IT IS STILL STRONG AND SOLID
WITH LITTLE ROT. THE WARMING SUN WILL HAVE A VERY HARD TIME
WORKING ON THE RIVER ICE, ESPECIALLY SINCE THE ICE IS STILL
COVERED BY AS MUCH AS 30 INCHES OF SNOW IN SOME PLACES. THEREFORE,
THE ICE WILL LIKELY STAY STRONG OVER THE NEXT FEW WEEKS, MEANING
THE ICE JAM THREAT WILL ALSO REMAIN INTO APRIL. THEREFORE ANY
LARGE SCALE RUNOFF EVENTS OVER THE NEXT 4 WEEKS OR SO WILL HAVE
THE POTENTIAL TO CAUSE ICE JAM FLOODING. THIS EASILY JUSTIFIES AN
ABOVE NORMAL THREAT.

IT IS IMPORTANT TO REMEMBER THAT VERY HEAVY RAINFALL CAN BRING
FLOODING AT ANY TIME OF THE YEAR, EVEN IN AREAS THAT DON`T HAVE A
SIGNIFICANT SNOWPACK.

THE NEXT WINTER/SPRING FLOOD POTENTIAL OUTLOOK WILL BE ISSUED BY
NWS CARIBOU ON THURSDAY APRIL 2, 2015.


$$

HASTINGS/HEWITT



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