Flash Flood in New Hampshire, September 18, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
334 AM EDT SAT SEP 18 2004

...FLOOD WATCH FOR MUCH OF INTERIOR SOUTHERN NEW ENGLAND TODAY...

.SHORT TERM (TODAY AND TONIGHT)...
COLD FRONT IS SLOWLY PUSHING S THROUGH NEW ENGLAND AND WAS LOCATED
FROM NORTHWEST CT INTO CENTRAL AND NORTHEAST MA. ETA/GFS ARE SIMILAR
IN BRINGING IT INTO CT...RI AND SE MA THIS MORNING BEFORE DROPPING
IT FARTHER S THIS AFTERNOON.

REGIONAL RADAR LOOP SHOWS AN IMPRESSIVE BAND OF RAIN ON THE COLD
SIDE OF THE BOUNDARY...WHERE VERY STRONG LOW LEVEL FRONTOGENESIS IS
COMBINING WITH DEEP MOISTURE AND DIVERGENCE ALOFT.  THIS SYSTEM HAS
A HISTORY OF PRODUCING EXCESSIVE RAINFALL TO OUR W IN PA AND UPSTATE
NY...AND GIVEN FACT THAT THESE DYNAMICS SHIFT INTO SOUTHERN NEW
ENGLAND THIS MORNING...WE STILL THINK MANY LOCATIONS WILL RECEIVE
BETWEEN 2 AND 4 INCHES OF RAIN WITH THE POTENTIAL FOR 5 INCHES IN A
FEW SPOTS.

A FLOOD WATCH IS BEING ISSUED FOR TODAY AND WILL INCLUDE SOUTHWEST
NH...WESTERN AND CENTRAL MA...AND NORTHERN CT.  RAINFALL OF 2 TO 4
INCHES WITH LOCALLY AS MUCH AS 5 INCHES MAY CAUSE FLOODING OF SMALLER
RIVERS AND STREAMS IN THESE AREAS PER GUIDANCE VALUES...THOUGH WE
HAVE A BIT MORE BREATHING ROOM IN NORTHERN CT. A PORTION OF THIS AREA
ALREADY RECEIVED UP TO AN INCH OF RAIN FRIDAY...AND WE ARE ALREADY
SEEING EXCESSIVE RAINS UPSTREAM WHICH WILL SHIFT INTO OUR WESTERN AND
NORTHERN ZONES EARLY THIS MORNING.

THIS AMOUNT OF RAIN SHOULD NOT BE A PROBLEM FOR RI AND EASTERN MA
WHERE VALUES ARE HIGHER...SO WE WILL UPDATE THE FLOOD STATEMENT FOR
THESE LOCATIONS. MAINSTEM RIVERS ARE EXPECTED TO REMAIN WITHIN THEIR
BANKS.

TREND OF CURRENT FORECAST REMAINS INTACT...WITH SHOWERS PERHAPS
LINGERING IN SOUTHEAST MA EARLY THIS EVENING BEFORE CLEARING SETS
IN FROM N TO S TONIGHT.

.LONG TERM (SUNDAY THROUGH FRIDAY)...
HIGH PRESSURE ACROSS SOUTHEAST CANADA AND THE GREAT LAKES HEADS
TOWARD SOUTHERN NEW ENGLAND SUNDAY.  THIS HIGH PRESSURE IS EXPECTED
TO SETTLE OVER THE MID ATLANTIC AND OHIO VALLEY BY TUESDAY.  WHILE
NOT DIRECTLY OVERHEAD...THIS SYSTEM WILL BE CLOSE ENOUGH TO DOMINATE
OUR WEATHER ANY WAY FOR MOST OF THE UPCOMING WEEK.

A BACKDOOR COLD FRONT IS FORECAST TO APPROACH SOUTHERN NEW ENGLAND
FROM THE NORTHEAST THURSDAY INTO FRIDAY...PROVIDING AN INCREASE IN
CLOUDS AT LEAST.

TEMPERATURE WISE...IT WILL BE LESS HUMID AND COOLER THAN IT HAS
BEEN RECENTLY.  STRONG COLD AIR ADVECTION SUNDAY SHOULD ENSURE THIS
IS THE COLDEST DAY DURING THIS PERIOD.  EVEN AS WE APPROACH AUTUMN
NEXT WEEK...THE SUN IS STILL STRONG ENOUGH TO REBOUND TEMPERATURES
MONDAY INTO WEDNESDAY.  GUIDANCE TEMPERATURES LOOK REASONABLE...SO
WILL NOT STRAY TOO FAR.

&&

.AVIATION...
IFR/LIFR CONDITIONS WILL PREVAIL TODAY WITH THE HEAVIER RAINFALL
EXPECTED INTO EARLY AFTERNOON. CONDITIONS SHOULD IMPROVE TO MVFR AT
ALL TERMINALS LATE THIS AFTERNOON...WITH RAPID IMPROVEMENT TO VFR
THIS EVENING.

&&

.MARINE...
SMALL CRAFT ADVISORIES WILL BE HEADLINED FOR ALL WATERS TODAY AS N
TO NE WINDS INCREASE RAPIDLY BEHIND THE COLD FRONT THIS MORNING...
THEN ANOTHER SURGE OF 20 TO 30KT GUSTS ARE EXPECTED TONIGHT AS COLD
ADVECTION GETS UNDERWAY AND LAPSE RATES STEEPEN DRAMATICALLY OVER
THE WARMER WATER. MODEL SOUNDINGS LOOK MARGINAL TO REACH GALE
WARNING CRITERIA ON THE OUTER WATERS.

IN THE LONGER TERM SUNDAY THROUGH WEDNESDAY...SOUTH SWELLS FROM
TROPICAL STORM JEANNE SHOULD IMPACT THE SOUTH COASTAL AND OUTER
WATERS SUNDAY AND MONDAY.  THESE SWELLS SHOULD SUBSIDE TUESDAY INTO
WEDNESDAY. WINDS COULD APPROACH 25 KT SUNDAY INTO MONDAY...THE
DECREASE TO LESS THAN 15 KT TUESDAY AND WEDNESDAY.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...FLOOD WATCH TODAY CTZ002>004.
MA...FLOOD WATCH TODAY MAZ002>005-008>012-026.
NH...FLOOD WATCH TODAY NHZ011-012-015.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR ALL WATERS.

SHORT TERM...JWD
LONG TERM...BELK