000 FGUS71 KCAR 190951 ESFCAR MEC003-009-019-021-029-192200- WINTER/SPRING FLOOD POTENTIAL OUTLOOK NATIONAL WEATHER SERVICE CARIBOU ME 551 AM EDT FRI APR 19 2013 ...WINTER AND SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL AND DOWNEAST MAINE... THIS IS THE NINTH WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR 2013...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 APRIL 18 THROUGH MAY 2, 2013. THE WINTER/SPRING FLOOD POTENTIAL FOR FAR NORTHWEST MAINE IS SLIGHTLY ABOVE NORMAL, WHILE THE SPRING FLOOD THREAT FOR THE REMAINDER OF NORTHERN AND EASTERN MAINE IS NORMAL. THE POTENTIAL FOR FLOODING DUE TO ICE JAMS HAS GENERALLY ENDED FOR MUCH OF THE REGION. THE EXCEPTION IS ALONG THE FAR NORTHERN RIVERS INCLUDING THE ALLAGASH, BIG BLACK, AND UPPER REACHES OF THE SAINT JOHN. THERE IS STILL SOME ICE ON THESE WATERWAYS SO THE POTENTIAL FOR ICE JAM DEVELOPMENT STILL EXISTS. HOWEVER, SIGNIFICANT JAMS ARE NOT CONSIDERED LIKELY. ...CLIMATOLOGICAL GUIDANCE... THE BLOCKING RIDGE OVER GREENLAND THAT HAS DOMINATED THE WEATHER PATTERN OVER THE NORTHEASTERN UNITED STATES FOR THE PAST COUPLE OF MONTHS IS FINALLY SHOWING SIGNS OF BREAKING DOWN. THIS MEANS A TURN TOWARD MILDER CONDITIONS AS THE JET STREAM SHIFTS BACK NORTH, ESPECIALLY OVER THE NEXT WEEK. THEREAFTER, THE PATTERN BECOMES MORE CONDUCIVE FOR TROFINESS, RESULTING IN TEMPERATURES DROPPING BACK TO NORMAL. IN ADDITION, THE ACTIVE PATTERN WE HAVE BEEN EXPERIENCING LOOKS TO CONTINUE INTO LATE APRIL WITH AT LEAST TWO FRONTAL SYSTEMS EXPECTED TO MOVE ACROSS NEW ENGLAND IN THE NEXT 6-10 DAYS. THE OFFICIAL NATIONAL WEATHER SERVICE OUTLOOK CORRELATES WITH THIS THINKING AS IT CALLS FOR ABOVE NORMAL TEMPERATURES AND WETTER THAN NORMAL CONDITIONS OVER THE NEXT 1 TO 2 WEEKS. AS WE MOVE INTO EARLY MAY, THIS PATTERN EASES A BIT, WITH BOTH PRECIPITATION AND TEMPERATURES RUNNING CLOSE TO NORMAL. ...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS... COOLER-THAN-NORMAL CONDITIONS THROUGH THE FIRST HALF OF MARCH HAVE ALLOWED THE SNOWPACK ACROSS THE WOODED HIGHER TERRAIN OF NORTHERN AND CENTRAL MAINE TO REMAIN. IN THESE LOCATIONS, THERE IS STILL SOME 8 TO 18 INCHES OF SNOW ON THE GROUND. ISOLATED LOCATIONS ARE STILL REPORTING NEARLY 2 FEET OF SNOW. THIS DEEP SNOWPACK IS ABOVE NORMAL FOR MID-APRIL. ACROSS THE LOWER ELEVATIONS, SHADY AND/OR WOODED AREAS STILL HAVE 4 TO 8 INCHES OF SNOW ON THE GROUND WHILE EXPOSED REGIONS ARE NEARLY DEVOID OF SNOW COVER. THESE NUMBERS ARE BELOW NORMAL. DOWNEAST MAINE IS NOW DOWN TO BARE GROUND. THE SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN THE SNOWPACK, IS ALSO ABOVE NORMAL IN NORTHWEST MAINE. SWES HERE ARE ON THE ORDER OF 3 TO 6 INCHES, WITH OVER 9 INCHES ON NORTHEAST FACING SLOPES. ELSEWHERE, FOR THOSE AREAS THAT HAVE SNOW, THERE IS 1 TO 3 INCHES OF WATER CONTAINED IN THE PACK. ...SOIL MOISTURE AND WATER SUPPLY CONDITIONS... THE LATEST PALMER DROUGHT SEVERITY INDEX, WHICH IS A MEASURE OF LONG-TERM MOISTURE STATES, SHOWS NEAR OR WETTER THAN NORMAL CONDITIONS ACROSS NORTHERN MAINE DUE TO INCREASING SNOWMELT. FOR THE REMAINDER OF THE STATE, SOIL MOISTURE STATES ARE NEAR TO SLIGHTLY BELOW NORMAL. GROUNDWATER LEVELS ARE NEAR NORMAL ACROSS THE PINE TREE STATE. ...RIVER AND ICE CONDITIONS... RIVER FLOWS HAVE BEEN INCREASING OVER THE PAST SEVERAL DAYS AS WARMER CONDITIONS HAVE RESULTED IN SNOWMELT, THOUGH THEY ARE STILL GENERALLY NEAR NORMAL. THE FAR UPPER REACHES OF THE SAINT JOHN ARE EXPERIENCING SLIGHTLY HIGHER THAN NORMAL FLOWS DUE TO THE DEEP SNOWPACK STILL COVERING THE GROUND THERE. THE ICE JAM THREAT IS ESSENTIALLY OVER FOR NORTHERN AND EASTERN MAINE, AS THE ICE HAS FLUSHED OUT OF MOST OF THE MAINSTEM RIVERS. THIS INCLUDES THE AROOSTOOK, PISCATAQUIS, PENOBSCOT, AND MATTAWAMKEAG RIVER BASINS. HOWEVER, RIVER GAUGES ALONG THE ALLAGASH, BIG BLACK, AND UPPER SAINT JOHN RIVERS ARE STILL SHOWING SIGNS OF ICE MOVEMENT. THIS ICE IS GENERALLY THIN AND WEAK AND GENERALLY NOT CONDUCIVE TO CAUSING SIGNIFICANT ICE JAMS. THEREFORE, SUBSEQUENT JAM-RELATED FLOODING DOES NOT APPEAR TO BE LIKELY. HOWEVER, IT SHOULD BE REMEMBERED THAT ICE JAMS ARE ALWAYS A THREAT UNTIL THE ICE IS COMPLETELY GONE. IN FACT, A WEBCAM NEAR DAAQUAM, QUEBEC SHOWED SOME MINOR FLOODING DUE TO AN ICE JAM ON THURSDAY, APRIL 18. ...IN CONCLUSION... BASED ON THE AFOREMENTIONED INFORMATION, THE WINTER/SPRING FLOOD POTENTIAL IS SLIGHTLY ABOVE NORMAL ACROSS NORTHWESTERN MAINE, MAINLY ALONG AND WEST OF ROUTE 11. RIVER FLOWS AND ANTECEDENT SOIL MOISTURE STATES ARE NEAR TO SLIGHTLY ABOVE NORMAL IN THESE AREAS AND THERE IS STILL PLENTY OF WATER HELD IN THE SNOWPACK FOR MELT RUNOFF. MEANWHILE, THE REMAINDER OF NORTHERN AND CENTRAL MAINE STANDS A NORMAL FLOODING THREAT. WITH MILDER CONDITIONS EXPECTED INTO EARLY NEXT WEEK, ALONG WITH LIGHT PRECIPITATION ASSOCIATED WITH A COUPLE OF FRONTAL PASSAGES, RIVERS IN NORTHERN AND CENTRAL MAINE WILL CONTINUE TO SHOW SIGNIFICANT RISES OVER THE NEXT SEVERAL DAYS. HOWEVER, IT IS RARE FOR PURE SNOWMELT TO RESULT IN WIDESPREAD OR SIGNIFICANT FLOODING WITHOUT ADDITIONAL RUNOFF FROM HEAVY RAINFALL. THIS IS ESPECIALLY TRUE NOW THAT MOST RIVERS ARE NOW MOSTLY ICE FREE. THAT BEING SAID, THE SPRING FLOOD THREAT HAS NOT COMPLETELY PASSED IN NORTHERN AND CENTRAL MAINE. WHILE NO FLOODING IS CURRENTLY ANTICIPATED, NORTHERN AND CENTRAL WATERWAYS WILL HAVE TO BE WATCHED CLOSELY, ESPECIALLY THOSE IN THE UPPER SAINT JOHN RIVER BASIN. FOR THOSE AREAS WITH VERY LITTLE TO NO SNOW COVER, ESPECIALLY FROM BANGOR SOUTH, THE SPRING FLOOD THREAT HAS PASSED. THIS INCLUDES THE THREAT FROM ICE JAMS, AS THESE WATERWAYS ARE ICE FREE. IT IS IMPORTANT TO REMEMBER THAT VERY HEAVY RAINFALL CAN BRING FLOODING AT ANY TIME OF YEAR, EVEN IN AREAS THAT DON'T HAVE A SIGNIFICANT SNOWPACK. UNLESS CONDITIONS CHANGE DRASTICALLY, THIS WILL MOST LIKELY BE THE LAST WINTER/SPRING FLOOD POTENTIAL OUTLOOK ISSUED THIS SEASON. IF ANOTHER OUTLOOK IS DEEMED NECESSARY, IT WILL BE ISSUED BY THE NATIONAL WEATHER SERVICE CARIBOU OFFICE ON MAY 2, 2013. $$ HASTINGS