Flood Potential Outlook
Issued by NWS Boston, MA

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000 FGUS71 KBOX 191939 ESFBOX CTC003-013-015-MAC001-005-007-009-011-013-015-017-019-021-023-025- 027-RIC001-003-005-007-009-211200- WINTER/SPRING FLOOD POTENTIAL OUTLOOK NATIONAL WEATHER SERVICE TAUNTON MA 339 PM EDT THU MAR 19 2015 ...THE SPRING FLOOD POTENTIAL IS ABOVE NORMAL IN SOUTHERN NEW ENGLAND...EXCEPT NEAR NORMAL ACROSS WESTERN MASSACHUSETTS AND NORTH CENTRAL CONNECTICUT... THE SPRING FLOOD POTENTIAL FOR RIVER AND STREAM FLOODING IN SOUTHERN NEW ENGLAND IS ABOVE NORMAL...EXCEPT NEAR NORMAL IN WESTERN MASSACHUSETTS AND NORTH CENTRAL CONNECTICUT. THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS ABOVE NORMAL. THIS IS THE SEVENTH FLOOD POTENTIAL OUTLOOK OF THE 2015 WINTER/SPRING SEASON. FLOOD OUTLOOKS ARE ISSUED EVERY ONE TO TWO WEEKS INTO THE SPRING TO ASSESS THE POTENTIAL FOR FLOODING. THE OUTLOOKS ARE BASED ON CURRENT AND FORECAST HYDROMETEOROLOGICAL CONDITIONS. THIS INCLUDES SNOW COVER AND SNOW WATER EQUIVALENT...STREAM AND RIVER LEVELS AND THE AMOUNT OF ICE COVERAGE...ALONG WITH EXPECTED TEMPERATURES AND PRECIPITATION OVER THE NEXT TWO WEEKS. ...RECENT PRECIPITATION AND TEMPERATURES... FROM LATE JANUARY INTO EARLY MARCH...SOUTHERN NEW ENGLAND WAS BOMBARDED WITH A SERIES OF SNOWSTORMS COUPLED WITH WELL BELOW NORMAL TEMPERATURES. DURING THE FIRST HALF OF MARCH...THE ACTIVE WEATHER PATTERN WAS QUIETER BUT REMAINED COLDER THAN NORMAL OVERALL. PRECIPITATION WAS AVERAGING NEAR OR BELOW NORMAL...ON THE ORDER OF 1 TO 3 INCHES OF LIQUID EQUIVALENT. TEMPERATURES WERE UP SEVERAL DEGREES BELOW NORMAL. ...OBSERVED SNOW DEPTHS AND WATER EQUIVALENTS... DURING THE PAST 2 WEEKS SNOW DEPTHS HAD DECREASED ACROSS MUCH OF SOUTHERN NEW ENGLAND...BUT A ROBUST SNOW PACK REMAINED ACROSS MUCH OF THE AREA. ACROSS MASSACHUSETTS...WITH THE EXCEPTION OF THE PIONEER VALLEY AND SOUTHEAST PORTION OF THE STATE...SNOW DEPTHS RANGED MOSTLY FROM 10 TO 20 INCHES. CORRESPONDING SNOW WATER EQUIVALENT RANGED FROM 3 TO 7 INCHES. THIS WAS SLIGHTLY ABOVE NORMAL IN WESTERN MASSACHUSETTS...BUT ABOVE NORMAL TO ANOMALOUSLY HIGH FOR MID MARCH ACROSS CENTRAL AND EASTERN MASSACHUSETTS. ACROSS THE LOWER ELEVATIONS OF THE PIONEER VALLEY...SNOW DEPTHS HAD DIMINISHED TO JUST A FEW INCHES WITH UP TO AN INCH OR SO OF WATER EQUIVALENT. SNOW DEPTHS IN NORTHERN CONNECTICUT...NORTHERN RHODE ISLAND AND SOUTHEAST MASSACHUSETTS NORTH OF I-195 RANGED FROM SEVERAL INCHES TO JUST OVER A FOOT. SNOW WATER EQUIVALENTS VARIED...BUT MOSTLY RANGED FROM 2 TO 5 INCHES. THESE VALUES WERE WELL ABOVE NORMAL IN NORTHERN RHODE ISLAND AND SOUTHEAST MASSACHUSETTS...ANOMALOUSLY HIGH FOR MID MARCH...EXCEPT SLIGHTLY ABOVE NORMAL FOR THIS TIME OF YEAR IN NORTH CENTRAL CONNECTICUT. ALONG SOUTHERN RHODE ISLAND...THE IMMEDIATE SOUTH COAST OF MASSACHUSETTS...AND THE CAPE AND ISLANDS...SNOW DEPTH VARIED. CONDITIONS RANGED FROM BARE GROUND TO UP TO 4 TO 8 INCHES. SNOW WATER EQUIVALENT RANGED FROM ZERO TO ABOUT 3 INCHES. THIS WAS ABOVE NORMAL FOR THIS TIME OF YEAR. ...RIVER AND ICE CONDITIONS... RIVER FLOWS INCREASED SUBSTANTIALLY ACROSS SOUTHERN NEW ENGLAND DURING THE PAST WEEK...REFLECTING RECENT RAINFALL AS WELL AS SNOWMELT. RIVER FLOWS HAD INCREASED TO NORMAL FOR THIS TIME OF YEAR ACROSS MOST OF THE REGION...WITH A FEW GAGES RUNNING ABOVE NORMAL IN SOUTHEAST MASSACHUSETTS AND RHODE ISLAND. A COMBINATION OF RAINFALL AND SNOWMELT BROUGHT THE PAWCATUCK RIVER AT WESTERLY ABOVE ACTION STAGE. AS OF MARCH 19 MANY RIVERS AND STREAMS HAD EXPERIENCED A NOTEABLE DECREASE IN RIVER ICE. HOWEVER AS GENERAL RULE THERE WAS MUCH STILL MORE ICE THAN IS TYPICAL FOR MID MARCH WITHIN SOUTHERN NEW ENGLAND. THE LOWER CONNECTICUT RIVER CONTINUED TO HAVE CONSIDERABLE ICE COVERAGE...BUT ICE MELT WAS NOTICEABLE AND STARTING TO OPEN UP AREAS OF THE RIVER THAT WERE PREVIOUSLY COMPLETELY OR NEARLY COMPLETELY FROZEN OVER. RECENT OBSERVATIONS OF THIS TREND INCLUDED THE NORTHAMPTON AND SPRINGFIELD AREAS. ON THE NORTH NASHUA RIVER IN FITCHBURG ICE COVERAGE AS OF MARCH 12 WAS NEAR 66 PERCENT WITH 6 TO 9 INCH THICKNESS OBSERVED THIS WEEK. DOWNSTREAM IN LEOMINSTER...AS OF MARCH 18 THE RIVER WAS ICE FREE. ICE FREE CONDITIONS WERE ALSO NOTED FURTHER DOWNSTREAM ON THE NASHUA RIVER IN BOLTON. RIVER ICE WILL CONTINUE TO DIMINISH DURING THE SECOND HALF OF MARCH DUE TO THE INCREASINGLY HIGH SUN ANGLE. ICE COULD REMAIN INTACT A BIT LONGER FARTHER INLAND DUE TO THE COLDER THAN NORMAL TEMPERATURES. GIVEN THE CURRENT EXTENT OF RIVER ICE ON SOME AREA WATERWAYS...THE RIVER ICE JAM FLOOD THREAT IS ABOVE NORMAL FOR THIS TIME OF YEAR. ANY RAIN OR RAINFALL/SNOW MELT THAT PRODUCES A RISE OF 3 TO 4 FEET ON RIVERS AND STREAMS COULD CAUSE BREAKUP AND MOVEMENT OF RIVER ICE...AND BRING THE POTENTIAL FOR BREAK UP ICE JAMS. ...SOIL MOISTURE CONDITIONS AND WATER SUPPLY... OVER THE PAST WEEK...THE HIGHER SUN ANGLE...ACCOMPANIED BY SOME DAYS WITH TEMPERATURES CLOSE TO NORMAL...HAVE ENABLED MORE RIPENING OF THE SNOWPACK. SNOWMELT HAD PRODUCED RUNOFF AND PERCOLATION/ INFILTRATION OF MOISTURE. SOIL MOISTURE IS NOW CLOSE TO NORMAL. EXAMINING GROUNDWATER MONITORING WELLS ACROSS THE REGION COURTESY OF THE UNITED STATES GEOLOGICAL SURVEY ( USGS ) MOST AREAS HAVE NORMAL TO BELOW NORMAL GROUNDWATER LEVELS. WATER SUPPLY RESERVOIRS ARE GENERALLY AT NORMAL LEVELS FOR THIS TIME OF YEAR. THE SCITUATE RHODE ISLAND RESERVOIR HAD INCREASED TO 91.7 PERCENT OF CAPACITY AS OF MARCH 19. AS OF MARCH 1 QUABBIN RESERVOIR WAS AT 95.4 PERCENT CAPACITY AND WACHUSETT RESERVOIR WAS AT 84.5 PERCENT CAPACITY. ...TEMPERATURE AND PRECIPITATION OUTLOOK... DURING FRIDAY INTO FRIDAY NIGHT...A QUICK MOVING SYSTEM WILL BRING SOME SNOW TO SOUTHERN NEW ENGLAND. MAINLY LIGHT ACCUMULATIONS ARE EXPECTED. SOME SCATTERED RAIN AND SNOW SHOWERS ARE POSSIBLE ON SATURDAY...THEN MAINLY DRY CONDITIONS ARE FORECAST FOR SUNDAY THROUGH NEXT TUESDAY. ANOTHER LOW PRESSURE SYSTEM MAY BRING ANOTHER CHANCE FOR PRECIPITATION DURING THE MIDDLE OF NEXT WEEK. TEMPERATURES ARE EXPECTED TO BE MAINLY BELOW NORMAL FOR MUCH OF THE NEXT 7 DAYS...WITH TEMPERATURES MODERATING TOWARDS NORMAL AROUND THE MIDDLE OF NEXT WEEK. THIS IS EXPECTED TO BRING CONTINUED GRADUAL SNOWMELT. THE OFFICIAL NATIONAL WEATHER SERVICE OUTLOOK FOR MARCH 26 TO APRIL 1 CALLS FOR TEMPERATURES TO AVERAGE BELOW NORMAL. DURING THE SAME PERIOD PRECIPITATION IS FORECAST TO AVERAGE ABOVE NORMAL. ...SUMMARY... BASED ON THE INFORMATION AVAILABLE AT THIS TIME...THE SPRING FLOOD POTENTIAL IS ABOVE NORMAL ACROSS CENTRAL AND EASTERN PORTIONS OF SOUTHERN NEW ENGLAND. THE SPRING FLOOD POTENTIAL IS NEAR NORMAL ACROSS WESTERN MASSACHUSETTS AND NORTH CENTRAL CONNECTICUT. RIVER FLOWS HAVE INCREASED TO NEAR NORMAL. SNOW DEPTHS AND WATER EQUIVALENTS ARE ABOVE TO MUCH ABOVE NORMAL FOR THIS TIME OF YEAR ACROSS MUCH OF THE AREA...IN PARTICULAR ACROSS CENTRAL AND EASTERN MASSACHUSETTS...RHODE ISLAND...AND NORTHEAST CONNECTICUT. MELTING SNOW WILL RAISE RIVER LEVELS AND THAT WILL LEAVE THE REGION VERY VULNERABLE TO ANY MAJOR RAIN EVENTS RIGHT INTO APRIL. EVEN WITH NO LARGE RUNOFF EVENTS IN SIGHT...WITH SEVERAL INCHES OF WATER IN THE SNOWPACK...IT IS STILL POSSIBLE THAT WE WILL SEE FLOODING ACROSS PARTS OF THE AREA THIS SPRING. THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS ABOVE NORMAL ACROSS SOUTHERN NEW ENGLAND. MANY RIVERS AND STREAMS HAVE LOST SUBSTANTIAL RIVER ICE...BUT AS A GENERAL RULE THERE SOME AREAS STILL HAD MUCH MORE ICE THAN IS TYPICAL FOR MID MARCH. RIVER ICE HAS BEEN ON THE DECLINE ACROSS SOUTHERN NEW ENGLAND...BUT SOME AREA WATERWAYS STILL HAVE CONSIDERABLE ICE COVERAGE. OVER THE NEXT 2 WEEKS RIVER ICE WILL CONTINUE TO ROT AND DECAY. HOWEVER... UNTIL THE ICE CLEARS OUT...RIVERS AND STREAMS ARE VULNERABLE TO ICE JAMS IF SUBSTANTIAL RUNOFF OCCURS. KEEP IN MIND THAT HEAVY RAIN CAN CAUSE FLOODING ANY TIME OF THE YEAR...EVEN WITHOUT A SNOWPACK. THOSE WITH INTERESTS ALONG RIVERS AND STREAMS SHOULD CHECK THE HAZARDOUS WEATHER OUTLOOK...WHICH HIGHLIGHTS ANY POTENTIAL FLOOD EVENTS OVER THE NEXT 7 DAYS. GO TO WEATHER.GOV/BOSTON AND CLICK ON THE OPTION CURRENT HAZARDS...THEN CLICK ON LOCAL OUTLOOK. THE NEXT SPRING FLOOD POTENTIAL OUTLOOK WILL BE ISSUED ON THURSDAY APRIL 2. $$ NMB FOR THE LATEST UPDATES...PLEASE VISIT OUR WEBPAGE AT WWW.WEATHER.GOV/BOSTON YOU CAN FOLLOW US ON FACEBOOK AT WWW.FACEBOOK.COM/NWSBOSTON YOU CAN FOLLOW US ON TWITTER AT @NWSBOSTON

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