Flood Potential Outlook
Issued by NWS Caribou, ME

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
1229 PM EST THU FEB 19 2015

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

THIS IS THE FOURTH WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR
2015...ISSUED BY THE NATIONAL WEATHER SERVICE IN CARIBOU, MAINE.
THE WINTER/SPRING FLOOD POTENTIAL IS FOR NORTHERN, CENTRAL AND
DOWNEAST MAINE FOR THE TWO-WEEK PERIOD FROM FEBRUARY 19 THROUGH
MARCH 5, 2015.

THE WINTER/SPRING FLOOD POTENTIAL FOR NORTHERN MAINE IS BELOW
NORMAL, WHILE IT IS NEAR NORMAL FOR CENTRAL AND EASTERN MAINE. FAR
DOWNEAST MAINE HAS AN ABOVE NORMAL FLOOD POTENTIAL. THE POTENTIAL
FOR FLOODING DUE TO ICE JAMS IS NEAR NORMAL ACROSS THE ENTIRE
REGION.

...CLIMATOLOGICAL GUIDANCE...

VERY COLD WEATHER HAS PREVAILED FOR THE ENTIRE MONTH OF FEBRUARY.
TEMPERATURES HAVE AVERAGED 10 TO 20 DEGREES BELOW NORMAL ACROSS
THE PINE TREE STATE. THIS IS DUE TO A PERSISTENT RIDGE POSITIONED
OVER THE WESTERN UNITED STATES, RESULTING IN A DOWNSTREAM TROUGH
OVER THE EAST. NORTHWEST FLOW AND A DEEP SNOWPACK HAVE ONLY
SERVED TO EXACERBATE THE COLD.

THE PATTERN HAS REMAINED ACTIVE AS WELL, WITH STORM SYSTEMS MOVING
ACROSS NEW ENGLAND EVERY FEW DAYS. A WEAK EL NINO HAS ALLOWED THE
SOUTHERN SUBTROPICAL JET STREAM TO PROVIDE ADDITIONAL MOISTURE AND
WARMTH NEAR THE GULF STREAM POSITIONED SOUTH OF NEW ENGLAND. THIS
PATTERN HAS RESULTED IN SEVERAL STORMS THAT HAVE STRENGTHENED
SIGNIFICANTLY AS THEY MOVED OFF THE SOUTHERN NEW ENGLAND COAST AND
OUT OVER THE GULF OF MAINE. MEANWHILE, COLD ARCTIC AIR HAS
REMAINED IN PLACE OVER NEW ENGLAND, KEEPING PRECIPITATION IN THE
FORM OF SNOW OVER THE ENTIRE REGION.

THIS COLD ACTIVE PATTERN LOOKS TO CONTINUE THROUGH AT LEAST THE
NEXT SEVERAL DAYS. GIVEN THE DEEP SNOWPACK, OVERALL TEMPERATURES
ARE EXPECTED TO REMAIN COLD, THOUGH SOME BRIEF MODERATION IS
POSSIBLE FROM TIME TO TIME. IN ADDITION TO THE SYSTEM THAT IS
CURRENTLY PRODUCING LIGHT TO MODERATE SNOW ACROSS THE REGION,
ANOTHER STORM WILL BRING MORE WINTRY PRECIPITATION THIS WEEKEND,
WITH ANOTHER POTENTIAL SYSTEM TOWARD THE MIDDLE OF NEXT WEEK. THIS
WEEKEND`S SYSTEM LOOKS TO TRACK FAR ENOUGH NORTH THAT RELATIVELY
WARM AIR WILL SPREAD INTO DOWNEAST MAINE. AS SUCH, THE
PRECIPITATION MAY ACTUALLY FALL IN THE FORM OF A SNOW/SLEET/RAIN
MIX.

THE ABOVE THINKING IS SUPPORTED BY THE OFFICIAL NATIONAL WEATHER
SERVICE 6-14 DAY OUTLOOK, WHICH CALLS FOR COLDER THAN NORMAL
TEMPERATURES. THE OUTLOOK GIVES EQUAL CHANCES OF BELOW OR ABOVE
NORMAL PRECIPITATION, BUT THIS IS UNDERSTANDABLE AS THE AMOUNT AND
PLACEMENT OF PRECIPITATION WILL DEPEND HIGHLY ON EACH STORM`S
TRACK.

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

THE SNOW DEPTH VARIES WIDELY ACROSS THE PINE TREE STATE. DOWNEAST
MAINE HAS ADDED TO THE PACK CONSIDERABLY OVER THE PAST FEW WEEKS.
MANY SPOTS ARE REPORTING 40 TO 50 INCHES OF SNOW DEPTH, WITH FAR
EASTERN LOCATIONS SUCH AS EASTPORT AND MACHIAS REPORTING MORE THAN
5 FEET OF SNOW. THIS IS OBVIOUSLY WELL ABOVE NORMAL. THE SNOW
DEPTH DECREASES SHARPLY AS ONE HEADS NORTH INTO THE CENTRAL
HIGHLANDS AND AROOSTOOK COUNTY, WHERE DEPTHS OF 12 TO 24 INCHES
ARE COMMON. FAR NORTHERN MAINE HAS MISSED OUT ON MANY OF THE
LARGER SNOW STORMS THIS MONTH AND SO THEREFORE HAS THE LEAST
AMOUNT OF SNOW ON THE GROUND. THE SAINT JOHN VALLEY LOCATIONS ONLY
HAVE 8 TO 16 INCHES OF SNOWPACK, WITH PERHAPS CLOSER TO 20 INCHES
OVER THE HIGHER ELEVATIONS OF THE UPPER VALLEY. WHILE THE CENTRAL
HIGHLANDS ARE FAIRLY CLOSE TO NORMAL FOR SNOWPACK, NORTHERN MAINE,
ESPECIALLY FROM PRESQUE ISLE NORTHWARD, HAS LESS SNOW ON THE
GROUND THAT WHAT USUALLY EXISTS IN MID TO LATE FEBRUARY.

THE SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN THE
SNOWPACK, IS CLEARLY WELL ABOVE NORMAL OVER DOWNEAST MAINE. THERE
IS 6 TO 10 INCHES OF WATER CONTAINED IN THE SNOW IN THESE
LOCATIONS. THE SWE LESSENS AS ONE HEADS NORTH, WITH MUCH OF THE
REMAINDER OF THE STATE REPORTING 4 TO 6 INCHES OF LIQUID
EQUIVALENT. THIS IS FAIRLY CLOSE TO NORMAL. AGAIN, THE EXCEPTION
IS ACROSS THE FAR NORTH WHERE THERE IS 3 TO 5 INCHES OF WATER IN
THE SNOWPACK, WHICH IS BELOW NORMAL.

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

NEAR SURFACE SOIL MOISTURE CONDITIONS, WHICH ARE INDICATIVE OF
NEAR TERM MOISTURE TRENDS, ARE MAINLY WETTER THAN NORMAL ACROSS
EASTERN NEW ENGLAND. HOWEVER, ACTUAL RUNOFF AND FILTRATION HAS
BEEN MINIMAL SINCE JANUARY DUE TO THE COLD AND WIDESPREAD SNOW
COVER. THE LATEST PALMER DROUGHT SEVERITY INDEX, WHICH TAKES A
LOOK AT MOISTURE STATES OVER THE RANGE OF WEEKS TO MONTHS, SHOWS
DOWNEAST MAINE WITH VERY MOIST ANTECEDENT CONDITIONS. THIS
INCREASES TO EXTREMELY MOIST ALONG THE COAST. CENTRAL AND NORTHERN
MAINE HAVE NEAR NORMAL LONG-TERM ANTECEDENT MOISTURE.

...RIVER AND ICE CONDITIONS...

RIVER FLOWS HAVE CONTINUED TO SUBSIDE OR HOLD FAIRLY STEADY
THROUGH THE MONTH. WITH NO SIGNIFICANT LONG-LIVED WARM UPS OR
SNOWMELT ANTICIPATED IN THE NEAR FUTURE, THIS SLOW DOWNWARD TREND
WILL CONTINUE OVER THE NEXT COUPLE OF WEEKS.

OTHER THAN THICKENING DUE TO THE VERY COLD TEMPERATURES, THE
RIVER ICE COVER HAS REMAINED FAIRLY UNCHANGED SINCE THE LAST FLOOD
POTENTIAL ISSUANCE. NORTHERN WATERWAYS ARE COVERED WITH ICE THAT
IS NOW 1 TO 2 FEET THICK. CENTRAL AND SOUTHERN RIVERS HAVE ICE
THAT IS AROUND 1 FOOT THICK. THE FAR SOUTHERN WATERWAYS LIKELY
HAVE 10 INCHES OR LESS OF ICE AT THIS TIME. THESE THICKNESSES ARE
CLOSE TO NORMAL.

ALSO UNCHANGED IS THE STATUS OF SEVERAL ICE JAMS THAT REMAIN IN
PLACE ON THE SAINT JOHN AND AROOSTOOK RIVERS. AT THIS TIME, KNOWN
JAMS INCLUDE A 10-15 MILE LONG JAM ON THE SAINT JOHN THROUGH SAINT
FRANCIS, A 5-8 MILE LONG JAM ON THE AROOSTOOK FROM CROUSEVILLE
THROUGH WASHBURN, AND A FEW SMALLER JAMS ON THE AROOSTOOK,
INCLUDING ONE JUST BELOW FORT FAIRFIELD. THERE IS ALSO AN ICE JAM
ON THE PENOBSCOT RIVER IN ORONO. THESE JAMS ARE STILL WELL FROZEN
IN PLACE AND ARE NOT CAUSING ANY FLOODING AT THIS TIME. HOWEVER,
THEY WILL BEAR WATCHING AS WE HEAD INTO SPRING AS THEY WILL LIKELY
SERVE AS A FOCUS FOR BREAK UP JAMS.

...IN CONCLUSION...

BASED ON THE AFOREMENTIONED INFORMATION, THE WINTER/SPRING FLOOD
POTENTIAL IS NEAR NORMAL FOR CENTRAL AND EASTERN MAINE, NOT
INCLUDING FAR DOWNEAST AREAS. RIVER FLOWS ARE NEAR NORMAL.
ALTHOUGH THERE IS A LOT OF SNOW ON THE GROUND AND GROUNDWATER
LEVELS ARE STILL FAIRLY HIGH, THE OVERALL WEATHER PATTERN FAVORING
COLD WEATHER MEANS IT IS UNLIKELY THAT WE WILL SEE ANY RUNOFF OR
SIGNIFICANT RISES ON THE WATERWAYS. THEREFORE, A NEAR NORMAL
POTENTIAL FOR FLOODING SEEMS REASONABLE. FOR NORTHERN MAINE, THE
THREAT FROM FLOODING IS BELOW NORMAL. SNOW WATER EQUIVALENTS ARE
BELOW NORMAL AS ARE SNOW DEPTHS, ESPECIALLY IN THE SAINT JOHN
VALLEY AND NORTHEASTERN AROOSTOOK COUNTY. GIVEN THAT WE ARE
EXPECTING BELOW NORMAL TEMPERATURES AND NEAR NORMAL PRECIPITATION
OVER THE NEXT SEVERAL DAYS, THE FLOOD THREAT IS BELOW NORMAL FOR
THIS TIME OF YEAR. IT IS IMPORTANT TO NOTE THAT IF WE ADD TO THE
SNOWPACK HOWEVER, THE LONG TERM FLOOD POTENTIAL WILL DEFINITELY BE
INCREASING.

FOR FAR DOWNEAST MAINE, THE WINTER/SPRING FLOOD POTENTIAL IS ABOVE
NORMAL. THE SNOWPACK ACROSS THIS REGION IS WELL ABOVE NORMAL, WITH
SOME LOCATIONS REPORTING NEARLY 70 INCHES ON THE GROUND. THE
AMOUNT OF WATER IN THE PACK IS CLOSE TO 10 INCHES. THIS WOULD
CONTRIBUTE A LARGE AMOUNT OF WATER DURING ANY SIGNIFICANT AND/OR
PROLONGED WARM UP. A BRIEF MELTING PERIOD IS POSSIBLE OVER THE
UPCOMING WEEKEND WITH PERHAPS SOME LIQUID PRECIPITATION TO FALL.
HOWEVER, THIS WILL LIKELY ONLY SERVE TO RIPEN THE PACK AS THE SNOW
SHOULD EASILY ABSORB ANY WATER. PEOPLE THAT HAVE INTERESTS IN FAR
DOWNEAST MAINE SHOULD STAY ABREAST OF THE LATEST FORECASTS AND
REMAIN ALERT FOR ANY RAPID WARMING, WITH OR WITHOUT SIGNIFICANT
RAINFALL.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS NEAR NORMAL FOR ALL
OF WFO CARIBOU`S FORECAST AREA. ICE COVERS NEARLY ALL WATERWAYS.
ICE THICKNESSES ARE 1 TO 2 FEET ACROSS MUCH OF THE NORTHERN
SECTION OF THE REGION, WITH AROUND 1 FOOT FOR CENTRAL AND SOUTHERN
WATERS. WHILE THERE ARE SEVERAL ICE JAMS IN PLACE, THEY ARE WELL
FROZEN AND NOT EXPECTED TO MOVE OR CAUSE ANY FLOODING IN THE NEAR
FUTURE. THAT BEING SAID, WE WILL HAVE TO MONITOR AREAS OF NORTHERN
AND CENTRAL MAINE CLOSELY AS WE HEAD TOWARD SPRING. ANY RAPID
RUNOFF EVENTS AND SIGNIFICANT INCREASES IN RIVER FLOW WOULD
CERTAINLY HAVE THE POTENTIAL TO CREATE FURTHER ICE JAMS AND
RELATED ISSUES. BUT THIS WOULD BE IN THE LONGER TERM ONLY.

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, MARCH 5, 2015.

$$

HASTINGS



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