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Extended Streamflow Guidance
Issued by NWS Northeast RFC
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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE
NORTHEAST RIVER FORECAST CENTER...TAUNTON MA
1005 AM EDT THU APR 18 2013

...FOR OFFICIAL NATIONAL WEATHER SERVICE USE ONLY...

SPRING FLOOD POTENTIAL FOR THE NORTHEASTERN U.S. /9/

THE SPRING FLOOD POTENTIAL FOR THE NORTHEAST UNITED STATES IS
SLIGHTLY ABOVE NORMAL ACROSS NORTHWESTERN MAINE...NORTHERN NEW
HAMPSHIRE...PORTIONS OF THE NORTHERN GREEN MOUNTAINS IN VERMONT AND
PORTIONS OF THE ADIRONDACKS.

THE SPRING FLOOD POTENTIAL IS NEAR NORMAL ACROSS WESTERN AND CENTRAL
NEW YORK AND THE MID CONNECTICUT RIVER VALLEY REGION OF VERMONT AND
NEW HAMPSHIRE.

ELSEWHERE ACROSS THE NERFC SERVICE AREA...THE WINTER SPRING FLOOD
POTENTIAL IS BELOW NORMAL.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS BELOW NORMAL ACROSS
NORTHERN MAINE AND NORTHERN NEW HAMPSHIRE...GREEN MOUNTAINS AND THE
ADIRONDACKS WHERE ICE HAS THINNED OUT OR BECOME SPARSE IN COVERAGE.
ELSEWHERE THE ICE JAM FLOOD POTENTIAL IS BELOW NORMAL AS THE THREAT
HAS WELL PASSED FOR THE SEASON.

...CLIMATE GUIDANCE...

THE NORTHEASTERN UNITED STATES HAS EXPERIENCED A NEGATIVE NORTHERN
ATLANTIC OSCILLATION (NAO) OR BLOCKING PATTERN THE PAST COUPLE OF
MONTHS DATING BACK TO MID FEBRUARY. THE BLOCKING PATTERN ASSOCIATED
WITH THE NEGATIVE NAO HAS WEAKENED THE PAST COUPLE OF WEEKS CAUSING
THE GREENLAND RIDGE TO BREAK DOWN WITH TIME. THIS HAS HELPED ALLOW
TEMPERATURES TO MODERATE WITH TIME ACROSS THE NORTHEAST AS THE JET
STREAM HAS GRADUALLY LIFTED NORTH.

AVERAGE TEMPERATURES OVER THE PAST COUPLE OF WEEKS HAVE GENERALLY
BEEN RUNNING SLIGHTLY BELOW NORMAL ACROSS NORTHERN NEW YORK STATE
AND NORTHERN NEW ENGLAND. AVERAGE TEMPERATURES HAVE BEEN SLIGHTLY
ABOVE NORMAL OVER WESTERN NEW YORK AND SOUTHEASTERN NEW YORK STATE
EXTENDING ACROSS MOST OF SOUTHERN NEW ENGLAND.

THE PACIFIC NORTH AMERICAN (PNA) TELECONNECTION HAS REMAINED
SLIGHTLY NEGATIVE OVER THE PAST COUPLE OF WEEKS. A DEEP TROUGH
ACROSS THE ROCKIES HAS BEEN PREVALENT WITH DISTURBANCES EJECTING
EAST FROM THE PLAINS STATES INTO THE NORTHEAST.

THE DEVELOPMENT OF POSITIVE NAO AND POSITIVE PNA TELECONNECTION
PATTERNS OVER THE NEXT COUPLE OF WEEKS WILL FAVOR MORE TRANSIENT
WEATHER CONDITIONS DURING THE INTERIM. THIS PATTERN WILL EVENTUALLY
FAVOR SOME TROUGH DEVELOPMENT ACROSS THE EASTERN UNITED STATES
DURING THE LAST WEEK OF APRIL. WE GENERALLY EXPECT MILDER THAN
NORMAL AVERAGE TEMPERATURES TO OCCUR AT LEAST UNTIL THAT TIME. THE
JET STREAM PATTERN WILL BECOME ACTIVE AGAIN WITH SEVERAL
DISTURBANCES TRACKING FROM THE PACIFIC NORTHWEST INTO THE OHIO
VALLEY. THIS SHOULD TRANSLATE INTO AN INCREASED THREAT FOR
PRECIPITATION ACROSS THE NORTHEAST NEARING THE END OF APRIL.

THE OFFICIAL NATIONAL WEATHER SERVICE 8 TO 14 DAY OUTLOOK GENERALLY
REFLECTS THIS SCENARIO WITH NEAR NORMAL TEMPERATURES FORECAST ACROSS
MOST OF THE NORTHEAST EXCEPT BELOW NORMAL TEMPERATURES OVER WESTERN
NEW YORK. ABOVE NORMAL PRECIPITATION IS FORECAST ACROSS THE
NORTHEAST DURING THIS TIMEFRAME.

NUMERICAL WEATHER GUIDANCE IS CONCURRING ON A PRECIPITATION EVENT
LATE THIS FRIDAY INTO SATURDAY THE 19TH/20TH WITH AN ASSOCIATED COLD
FRONTAL PASSAGE BUT THIS WILL BE PROGRESSIVE. A COLD FRONT MAY ALSO
APPROACH BY WEDNESDAY THE 24TH OR THURSDAY THE 25TH. BEYOND THAT
WILL HAVE TO MONITOR WHETHER CUTOFF LOW PRESSURE FORMS ACROSS THE
EASTERN UNITED STATES SOMETIME AROUND THE 26-28TH TO SEE IF A MORE
SIGNIFICANT PRECIPITATION THREAT OCCURS.

...OBSERVED SNOW DEPTHS AND WATER EQUIVALENTS...

COOLER THAN NORMAL TEMPERATURES AND ADDITIONAL SNOWFALL DURING THE
PAST COUPLE OF WEEKS HAVE ALLOWED ABUNDANT SNOWPACK TO REMAIN AND
ACROSS THE MOUNTAINS OF NORTHERN NEW ENGLAND AND NORTHERN NEW YORK
STATE.

MOST OF SOUTHERN NEW ENGLAND AND ALL OF THE SOUTHERN HALF OF NEW
YORK STATE CONTINUES TO BE SNOW FREE.

...NEW YORK STATE...

SNOW IS GONE SOUTH AND WEST OF THE MOHAWK RIVER. HOWEVER ACROSS THE
TUG HILL PLATEAU AND THE ADIRONDACKS...2 TO 8 INCH SNOW DEPTHS REMAIN
PARTICULARLY ACROSS ELEVATIONS ABOVE 1000 FT. SNOW WATER EQUIVALENTS
RANGE FROM 1 TO 5 INCHES ACROSS THESE AREAS.

...VERMONT...

SIGNIFICANT SNOW COVER IS GENERALLY CONFINED ACROSS THE CENTRAL AND
NORTHERN HIGH TERRAIN OF THE GREEN MOUNTAINS FROM 1000 TO 1500 FEET
AND ABOVE. MOST OF THE LOWER ELEVATIONS ARE BARE. LIGHTER AMOUNTS
ARE NOTED ACROSS THE SOUTHERN GREEN MOUNTAINS EXTENDING INTO THE FAR
NORTHERN BERKSHIRES. SNOW DEPTHS ACROSS THESE AREAS GENERALLY RANGE
FROM 2 TO 12 INCHES WHICH IS ABOVE NORMAL FOR THIS TIME OF YEAR.
LOCALLY HIGHER AMOUNTS ARE NOTED ABOVE 1500 FEET. SNOW WATER
EQUIVALENTS RANGE FROM 2 TO 8 INCHES ACROSS THESE AREAS WITH LOCALLY
HIGHER AMOUNTS. THE GROUND IS BARE ACROSS MOST OF THE LOWER
ELEVATIONS OF VERMONT.

...NEW HAMPSHIRE...
SIGNIFICANT SNOW COVER IS CONFINED ACROSS THE HIGH TERRAIN OF
CENTRAL AND NORTHERN WHITE MOUNTAINS PARTICULARLY AT ELEVATIONS
ABOVE 1000 TO 1500 FEET. SNOW DEPTHS VARY FROM 2 TO 12 INCHES ACROSS
THESE AREAS EXCEPT UP TO 18 INCHES AT MOUNT WASHINGTON AS OF THIS
THURSDAY MORNING. THIS IS ABOVE NORMAL FOR THIS TIME OF YEAR. SNOW
WATER EQUIVALENTS RANGE FROM 2 TO 8 INCHES. THE GROUND IS BARE
ACROSS THE LOWER ELEVATIONS OF CENTRAL AND SOUTHERN NEW HAMPSHIRE.

...MAINE...
SIGNIFICANT SNOW COVER REMAINS ACROSS THE HIGH TERRAIN OF WESTERN
AND NORTHERN MAINE ABOVE 1000 FEET AS WELL AS THE FORESTED AREAS.
SNOW DEPTHS RANGE FROM 2 TO 15 INCHES ACROSS THESE AREAS. HOWEVER
THERE ARE STILL SOME SPOT LOCATIONS ACROSS THE NORTH WOODS WHICH
HAVE MUCH MORE...22 INCHES AT WINTERVILLE AND 31 INCHES AT PARLIN
POND AS OF 17 APRIL 2013. THIS IS GREATER THAN NORMAL FOR THIS TIME
OF YEAR. SNOW WATER EQUIVALENTS GENERALLY RANGE FROM 2 TO 8 INCHES
ACROSS THESE AREAS... BUT LOCALIZED 10 TO 14 INCH SNOW WATER
EQUIVALENTS WERE FOUND AT LOCATIONS WITH THE DEEPEST SNOW
COVER...WHICH IS GREATER THAN NORMAL FOR THIS TIME OF YEAR. THE
GROUND IS BARE ALONG THE COASTAL PLAIN.

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

THE PALMER DROUGHT SEVERITY INDEX LOOKS AT THE ANTECEDENT SOIL
MOISTURE OVER THE PAST SEVERAL MONTHS. THE LATEST DROUGHT UPDATE
ISSUED ON 13 APRIL 2013 SHOWS MOST OF NEW ENGLAND AND NEW YORK STATE
WITH NEAR NORMAL ANTECEDENT SOIL MOISTURE CONDITIONS. THE EXCEPTION
WAS ACROSS WESTERN NEW YORK WETTER THAN NORMAL SOIL STATES HAVE
PREVAILED. SOIL MOISTURE STATES REMAIN NEAR OR ABOVE NORMAL ACROSS
MOST OF NORTHERN NEW YORK STATE...VERMONT...NEW HAMPSHIRE AND
WESTERN MAINE AS SNOWMELT CONTINUES ACROSS THESE AREAS.

NEAR TERM SOIL MOISTURE CONDITIONS ARE NOW RUNNING BELOW NORMAL
ACROSS SOUTHEASTERN NEW YORK AND SOUTHERN NEW ENGLAND.

GROUNDWATER LEVELS COURTESY OF THE USGS ARE NEAR NORMAL ACROSS
NORTHERN NEW YORK STATE...VERMONT...NEW HAMPSHIRE AND MAINE. BELOW
NORMAL TO NEAR NORMAL GROUNDWATER LEVELS ARE CURRENTLY OBSERVED
ACROSS EXTREME SOUTHEASTERN NEW YORK STATE AND CONNECTICUT...WITH
NEAR TO ABOVE NORMAL GROUNDWATER LEVELS INDICATED ACROSS WESTERN
NEW YORK AND PORTIONS OF CENTRAL NEW YORK.

NEW YORK CITY AREA RESERVOIR LEVELS REMAIN SLIGHTLY BELOW NORMAL FOR
THIS TIME OF YEAR AT 92.9 PERCENT. THE NORMAL RESERVOIR LEVEL FOR
APRIL 12TH IS 96.9 PERCENT.

SCITUATE RESERVOIR IN RHODE ISLAND IS STILL REPORTING OVER 100
PERCENT CAPACITY...SPILLING OVER ONTO THE FLASHBOARDS.

KENNEBEC RIVER BASIN RESERVOIRS IN MAINE ARE 43.4 PERCENT FULL.
NORMAL IS 50.8 PERCENT FULL.

ANDROSCOGGIN BASIN RESERVOIRS IN MAINE AND NEW HAMPSHIRE ARE 45.9
PERCENT FULL. NORMAL IS 45 PERCENT FULL.

...RIVER AND ICE CONDITIONS...

RIVER FLOWS ARE RUNNING WELL BELOW NORMAL ACROSS SOUTHEASTERN NEW
YORK STATE...CONNECTICUT AND RHODE ISLAND...AND NEAR NORMAL ACROSS
MOST OF MASSACHUSETTS...NORTHERN NEW YORK STATE...VERMONT AND
MOST OF NEW HAMPSHIRE.

RIVER FLOWS ARE RUNNING BELOW NORMAL ALONG THE MAINE COASTAL
PLAIN...BUT FLOWS ARE RUNNING NEAR OR ABOVE NORMAL ACROSS THE
INTERIOR BASINS WHERE MELTING SNOW COVER PROVIDES SOME RECHARGE FOR
THE RIVERS AND STREAMS. RIVER FLOWS ARE ALSO RUNNING AT OR ABOVE
NORMAL LEVELS ACROSS CENTRAL AND WESTERN NEW YORK STATE DUE TO
SIGNIFICANT RAINFALL DURING THE PAST COUPLE OF WEEKS.

THERE ARE LOCATIONS WHICH REMAIN AT LEAST PARTIALLY ICE AFFECTED IN
NORTHERN MAINE...NEAR JACKMAN AND MOOSEHEAD LAKE. THE AROOSTOOK
RIVER IS GENERALLY ICE FREE. MOST OF THIS ICE HAS EITHER MOVED
OUT...THINNED OUT OR BECOME ROTTEN AND WEAK AT THIS TIME.

SOME FROZEN GROUND STILL EXISTS OVER PORTIONS OF THIS REGION WITH
RECORDED FROST DEPTH AT CARIBOU AT 19 INCHES BUT THIS IS CONTINUING
TO THAW OUT.

...IN CONCLUSION...

BASED ON THE INFORMATION AVAILABLE AT THIS TIME...THE WINTER SPRING
FLOOD POTENTIAL IS SLIGHTLY ABOVE NORMAL ACROSS AREAS OF WESTERN AND
NORTHWESTERN MAINE AND NORTHERN NEW HAMPSHIRE BASINS WHERE RIVER
FLOWS ARE AROUND OR SLIGHTLY ABOVE NORMAL LEVELS FOR THIS TIME OF
YEAR. THERE IS STILL DECENT COVERAGE AND SIGNIFICANT WATER LEFT IN
THE SNOWPACK TO CONTRIBUTE TO RUNOFF. NUMERICAL WEATHER GUIDANCE IS
INDICATING A WARMUP WITH A COUPLE OF ROUNDS OF PRECIPITATION
ANTICIPATED FRIDAY NIGHT INTO SATURDAY AND AGAIN DURING THE MID TO
LATTER PORTION OF NEXT WEEK WHICH MIGHT BE ENOUGH TO PRODUCE SOME
FLOODING. THE SAINT JOHNS...ANDROSCOGGIN...PEMIGEWASSET AND SACO
RIVER BASINS MAY BE OF PARTICULAR HIGHER CONCERN.

THE WINTER/SPRING FLOOD POTENTIAL IS SLIGHTLY ABOVE NORMAL OVER
PORTIONS OF THE NORTHERN GREEN MOUNTAINS...AND NORTHEASTERN
ADIRONDACKS WHERE SIGNIFICANT SNOW COVER RESIDES BUT PARTICULARLY
ABOVE 1000-1500 FEET. A CONTINUED WARMUP IS ANTICIPATED WITH AT
LEAST A COUPLE ROUNDS OF PRECIPITATION EXPECTED FRIDAY AND AGAIN
NEXT WEEK. HOWEVER THE THREAT MAY BE MORE LOCALIZED. THE MISSISQUOI
RIVER NEAR NORTH TROY IN VERMONT...GREAT CHAZY RIVER NEAR PERRY
MILLS AND AUSABLE FORKS IN NEW YORK STATE MAY BE OF PARTICULAR
HIGHER RISK. ELSEWHERE ACROSS THIS REGION THE SPRING FLOOD POTENTIAL
IS NEAR NORMAL.

THE SPRING FLOOD POTENTIAL ACROSS WESTERN NEW YORK STATE IS NEAR
NORMAL...WHERE STREAM FLOWS AND SOIL MOISTURE LEVELS REMAIN HIGH
BUT SNOW COVER HAS COMPLETELY BEEN LOST.

ELSEWHERE ACROSS THE REMAINDER OF THE NERFC SERVICE AREA...THE
SPRING FLOOD OUTLOOK CALLS FOR BELOW NORMAL POTENTIAL ACROSS
SOUTHEASTERN NEW YORK AND MUCH OF SOUTHERN NEW ENGLAND...WHERE
STREAMFLOWS AND SOIL MOISTURE LEVELS ARE GENERALLY RUNNING BELOW
NORMAL AND THIS AREA IS ALSO REMAINS SNOW FREE. IN ADDITION GREENUP
IS BEGINNING TO OCCUR ACROSS THESE AREAS.

IT IS IMPORTANT TO REMEMBER THAT HEAVY RAINFALL CAN CAUSE FLOODING
AT ANY TIME OF YEAR...EVEN IN AREAS WITHOUT A SIGNIFICANT SNOW PACK.

A GRAPHIC DEPICTING THE FLOOD POTENTIAL ON A BASIN BY BASIN BASIS IS
AVAILABLE ON THE NERFC WEB SITE AT

***WWW.ERH.NOAA.GOV/NERFC/SFPOG.HTML***

ALL IN LOWER CASE.

THE NEXT SPRING FLOOD POTENTIAL OUTLOOK MAY BE ISSUED 2 MAY
2013...PENDING FURTHER SPRING FLOOD ASSESSMENT AND FEEDBACK.
OTHERWISE THIS WILL BE THE LAST ISSUANCE OF THE SEASON.

END/STRAUSS
$$
National Weather Service Weather Forecast Office
