-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 230549
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1249 AM EST FRI JAN 23 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO BUILD OVER THROUGH TOMORROW. A
COASTAL STORM WILL IMPACT MUCH OF THE REGION SATURDAY INTO
SATURDAY NIGHT WITH THE POTENTIAL FOR HEAVY SNOW ACROSS PARTS OF
THE AREA. MORE SNOW IS POSSIBLE MONDAY IF LOW PRESSURE TRACKS
CLOSE ENOUGH TO THE COAST...BUT EITHER WAY VERY COLD WEATHER
FOLLOWS NEXT WEEK.

&&

.NEAR TERM /THROUGH TODAY/...

-- Changed Discussion --
100 AM UPDATE...

SCT CLOUD COVER IS STARTING TO MOVE INTO WESTERN MASS TONIGHT.
THIS COMBINED WITH A WEAK PRESSURE GRADIENT IS STALLING TEMPS FROM
RADIATING OUT OVERNIGHT. HAVE ADJUSTED TEMPS TO ACCOUNT FOR THESE
TRENDS. OTHERWISE FORECAST REMAINS ON TRACK.

PREVIOUS DISCUSSION...

LOOKS LIKE JUST ENOUGH OF A LOW LVL PRES GRADIENT TO MAINTAIN
SOME W-NW FLOW THROUGH THE OVERNIGHT AND GIVEN THAT CLOUDS MAY
TAKE SOME TIME TO ERODE...WILL MITIGATE RADIATIONAL COOLING
POTENTIAL. ALSO NOTE THAT GUIDANCE WHICH INITIALIZED DWPTS
WELL...ARE A BIT HIGHER THIS ROUND THAN PREVIOUS SUGGESTING LESS
ROOM FOR COOLING. THEREFORE...FEEL THAT WHILE THE MOS MINS MAY BE
A BIT TOO WARM GIVEN THE CLEARING...MINS LEFTOVER FROM PREVIOUS
SHIFT LOOK RIGHT IN LINE...SO NO MAJOR CHANGES TO OVERNIGHT MINS
FROM PREVIOUS FORECAST.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/...
TOMORROW...
RIDGE OF HIGH PRES WILL CREST ACROSS THE REGION DURING THE
AFTERNOON TOMORROW.  THEREFORE...DRY WX CONTINUES TO PREVAIL.
A SLIGHT UPTICK IN MID LVL WARM ADVECTION SHOULD FOLLOW THE RIDGE
PASSAGE UNDER VERY WEAK RETURN FLOW. THEREFORE...WITH A FAIR
AMOUNT OF AFTERNOON SUN...SUSPECT HIGHS WILL BE A BIT WARMER
TOMORROW THAN THEY WERE TODAY...WITH MAINLY MID 30S TO EVEN A FEW
SPOTS NEAR 40 BY LATE AFTERNOON.

TOMORROW NIGHT...
INCREASING CLOUDS AND MODEST WARM ADVECTION EXPECTED AHEAD OF
DEVELOPING LOW PRES IN THE MID ATLANTIC. THEREFORE...ALTHOUGH MINS
ARE LIKELY TO FALL BACK BELOW FREEZING...SUSPECT THEY WILL BE
WARMER TOMORROW NIGHT THAN THE LAST FEW. WITH MORE WIDESPREAD
UPPER TEENS TO MID 20S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
HIGHLIGHTS...

* FAST MOVING COASTAL STORM SAT INTO SAT NIGHT
* MORE SNOW POSSIBLE MON IF LOW TRACKS CLOSE ENOUGH TO OUR REGION
* VERY COLD AIR FOLLOWS NEXT WEEK

DETAILS...

SAT AND SAT NIGHT...

RAPIDLY DEEPENING MID LEVEL SHORT WAVE WILL CAUSE SURFACE LOW TO
BOMB OUT AS IT PASSES BY SAT EVENING. 12Z MODELS HAVE COME INTO
BETTER AGREEMENT WITH TRACK OF COASTAL LOW...TAKING IT OVER OR JUST
INSIDE 40/70 BENCHMARK. DESPITE GOOD MODEL AGREEMENT...FORECAST
REMAINS VERY DIFFICULT AND CONFIDENCE IS LOWER THAN WE WOULD LIKE AT
THIS TIME FRAME SINCE ANY WOBBLES IN TRACK HAS HUGE INFLUENCE IN
PRECIPITATION TYPE AND SNOWFALL AMOUNTS.

ON LARGER SCALE...PATTERN IS NOT FAVORABLE FOR WIDESPREAD
SIGNIFICANT SNOWS IN SOUTHERN NEW ENGLAND. IN ADDITION THERMAL
PROFILES ARE MARGINAL WITH LACK OF STRONG SURFACE HIGH TO
NORTH...AND WITHOUT STRONG THERMAL GRADIENT PRECIPITATION SHIELD ON
ITS NW SIDE WILL BE MORE LIMITED THAN THAT WE NORMALLY EXPECT WITH
WINTER STORMS. BUT RAPID DEEPENING SHOULD HELP TO COMPENSATE
SOMEWHAT...ESPECIALLY ON BACKSIDE OF STORM SAT AFTERNOON/EVENING
WHEN WE COULD SEE BURST OF ACCUMULATING SNOW.

1) PRECIPITATION TYPE AND HEAVY SNOW...

PRECIPITATION LOOKS TO BEGIN SAT MORNING FROM S TO N...STARTING AS
SNOW ACROSS MUCH OF AREA EXCEPT FOR RAIN ON CAPE COD AND ISLANDS.

STILL LOOKING AT POTENTIAL FOR NARROW BAND OF HEAVY WET SNOW...MOST
LIKELY FROM N CENTRAL CT INTO WORCESTER HILLS...NW RI AND INTERIOR
NE MA. DESPITE WARMING ALOFT...FORECAST SOUNDINGS IN THIS REGION ARE
NEARLY ISOTHERMAL...SO POTENTIAL EXISTS FOR ACCUMULATING SNOW WHERE
IT COMES DOWN HEAVY AND ACROSS HIGHER ELEVATIONS.

WE ISSUED A WINTER STORM WATCH FOR THESE AREAS WHERE WE HAVE 50
PERCENT CONFIDENCE ON REACHING WARNING CRITERIA...ALBEIT THE LOWER
END /6 OR 7 INCHES/. ALSO HAVE TO BE CONCERNED WITH POSSIBILITY OF
DOWNED TREE LIMBS AND WIRES WHERE SNOWFALL EXCEEDS 5 INCHES DUE TO
WET NATURE OF SNOW.

FARTHER S AND E...THERE SHOULD BE CHANGE TO RAIN AS MILDER AIR
ARRIVES WITH LITTLE IF ANY ACCUMULATION. HOWEVER WE DO EXPECT ALL
AREAS TO CHANGE TO SNOW LATER SAT AFTERNOON AND SAT EVENING...
EVEN DOWN TO CAPE COD AND ISLANDS...AS STORM RAPIDLY DEEPENS AND
DRAWS COLDER AIR INTO REGION.

OUR THINKING IS WE MAY NEED TO ISSUE WINTER WEATHER ADVISORIES
ACROSS REST OF RI AND E MA IN LATER FORECASTS...EITHER FOR 2-4"
TOTALS OR A BRIEF PERIOD OF HEAVY SNOW AND GUSTY WINDS RESULTING IN
DANGEROUS TRAVEL...OR BOTH!

2) STRONG WINDS ACROSS THE CAPE/ISLANDS...

RAPID DEEPENING OF LOW AS IT PASSES 40/70 SHOULD BRING PERIOD OF
STRONG N/NW WINDS SAT NIGHT TO CAPE COD AND ISLANDS. FORECAST
SOUNDINGS SHOW POTENTIAL 40-45KT...BUT IF MODELS ARE UNDERDOING
STRENGTH OF LOW WINDS COULD BE HIGHER. WE WILL PROBABLY NEED TO
ISSUE WIND ADVISORIES IN LATER FORECASTS...BUT CONFIDENCE IS NOT YET
HIGH ENOUGH TO DO SO NOW.

3) COASTAL FLOODING...

REFER TO COASTAL FLOOD SECTION BELOW FOR DETAILS.

SUNDAY AND MONDAY...

12Z GFS SHOWS POTENTIAL FOR A SIGNIFICANT WINTER STORM SUN NIGHT AND
MON AS UPPER LOW CLOSES OFF S OF NEW ENGLAND AND DEVELOPS POTENT
SURFACE LOW WHICH PASSES S OF US AS WELL. ON OTHER HAND WE HAVE 12Z
ECMWF WHICH DOES NOT CARVE OUT AS DEEP OF UPPER TROUGH AND HAS MORE
SUPPRESSED/WEAKER SOLUTION...BUT ITS TREND HAS BEEN TO COME A LITTLE
FARTHER N ON THIS RUN. WHILE UNCERTAINTY IS HIGH THIS FAR OUT...GFS
LOOKS TO BE OUTLIER BUT WE DO THINK WE STAND CHANCE AT SOME
ACCUMULATING SNOW.

TUESDAY THROUGH THURSDAY...

GENERALLY DRY...BLUSTERY AND VERY COLD WEATHER PREVAILS WITH
POTENTIAL FOR SOME OCEAN EFFECT SNOWS MAINLY FOCUSED OFFSHORE. AS
MENTIONED BEFORE COLD AIR IS FAIRLY SHALLOW SO NEED TO KEY ON
TEMPERATURES BELOW 850 MB WHICH ARE A BIT MISLEADING.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE.

BEFORE 00Z...HIGH CONFIDENCE VFR. LOW PROB OF MVFR SCT DECK IN
WESTERN MASS.

TODAY AND TONIGHT...HIGH CONFIDENCE VFR.

KBOS TAF...HIGH CONFIDENCE IN TAF.

KBDL TAF...HIGH CONFIDENCE IN TAF.

OUTLOOK /SATURDAY THROUGH TUESDAY/...

SATURDAY AND SATURDAY NIGHT...MODERATE CONFIDENCE. MVFR/IFR IN RAIN
AND WET SNOW...MAINLY RAIN ON CAPE COD AND ISLANDS BEFORE CHANGE TO
SNOW SAT EVENING WHEN N/NW WINDS COULD GUST TO 45KT.

SUNDAY...HIGH CONFIDENCE. VFR. NW WINDS GUSTING TO 30 KT.

MONDAY...LOW CONFIDENCE. MVFR/IFR POSSIBLE IN SNOW.

TUESDAY...MODERATE CONFIDENCE. VFR.
-- End Changed Discussion --

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH TOMORROW NIGHT/...HIGH CONFIDENCE.

LOW PRES CONTINUES TO DEEPEN AND MOVE OFFSHORE THROUGH THE
OVERNIGHT HOURS. THIS WILL YIELD A FEW MORE LIGHT OCEAN EFFECT
SHOWERS THROUGH THE EVENING. OTHERWISE...EXPECT A BUILDING SWELL
ON THE E OUTER WATERS TO REACH ABOUT 5-6 FT LATE TONIGHT...SO WILL
BE HOISTING A SMALL CRAFT ADVISORY BEGINNING AFTER MIDNIGHT AND
CONTINUING INTO TOMORROW.

A PERIOD OF CONDITIONS BELOW SCA IS EXPECTED LATE TOMORROW INTO
TOMORROW NIGHT.

OUTLOOK /SATURDAY THROUGH TUESDAY/...

SATURDAY AND SATURDAY NIGHT...MODERATE TO HIGH CONFIDENCE.  LOW
PRESSURE BOMBS OUT AS IT RAPIDLY MOVES NORTHEAST AND CROSSES NEAR
40/70 BENCHMARK SAT EVENING. STRONGEST WINDS EXPECTED SAT AFTERNOON
AND SAT NIGHT WITH N/NW GALES ON MOST OF WATERS. GALE WATCHES HAVE
BEEN POSTED. RAIN SAT SHOULD CHANGE TO SNOW SAT EVENING.

SUNDAY...HIGH CONFIDENCE. DIMINISHING WINDS AND SEAS...BUT PROBABLY
STAYING IN SCA ON OUTER WATERS.

MONDAY AND TUESDAY...LOW CONFIDENCE. LOW PRESSURE TRACKS S OF NEW
ENGLAND...BUT SHOULD COME CLOSE ENOUGH TO BRING INCREASING N/NE
WINDS AND BUILDING SEAS. GALE FORCE WINDS POSSIBLE LATE MON INTO
EARLY TUE.

&&

.TIDES/COASTAL FLOODING...
MINOR IMPACTS ARE POSSIBLE WITH THE WEEKEND SYSTEM ALONG PORTIONS OF
THE MASSACHUSETTS EAST COAST. THERE ARE COUNTERACTING FACTORS.
FACTORS THAT COULD LEAD TO SOME EROSION AND COASTAL FLOODING WILL BE
THE RAPID DEEPENING OF THE SYSTEM WHICH LEADS TO ISALLOBARIC FORCING
AND THE FACT THE ASTRO TIDE IS RELATIVELY HIGH STILL THIS WEEKEND.
HOWEVER...FACTORS MITIGATING EROSION AND INUNDATION INCLUDE A VERY
PROGRESSIVE SYSTEM THAT WILL LIMIT DURATION OF ANY SIGNIFICANT
ONSHORE FETCH. AND AS LUCK HAS IT...THE SHORT PERIOD OF ANY
CONSEQUENTIAL STORM SURGE WILL LIKELY OCCUR AROUND THE SATURDAY
EVENING LOW TIDE. THE SURGE WILL BE JUST STARTING TO BUILD FOR THE
SATURDAY AFTERNOON HIGH TIDE...POSSIBLY .5 TO 1.0 FEET...AND A
DIMINISHING SURGE...PROBABLY NO MORE THAN 1 TO 1.5 FEET...WILL OCCUR
AT THE TIME OF THE VERY EARLY SUNDAY MORNING HIGH TIDE WHEN SURFACE
WINDS WILL HAVE BACKED AROUND TO NW. NEARSHORE SEAS ALONG THE OPEN
COASTLINE WILL LIKELY BE ONLY ABOUT 5 TO 7 FEET EARLY SATURDAY
AFTERNOON AND BETWEEN 10 AND 15 FEET EARLY SUNDAY MORNING...LIKELY
NOT LARGE ENOUGH TO POSE A SIGNIFICANT OVERWASH RISK.

CONSIDERING THE VARIOUS FACTORS...WE ANTICIPATE A POTENTIAL FOR
MINOR COASTAL FLOODING ALONG VULNERABLE EAST FACING SHORELINES FROM
BOSTON SOUTH AT THE TIME OF THE SATURDAY EARLY AFTERNOON HIGH
TIDE...GENERALLY 2 TO 230 PM. THERE IS ALSO A CHANCE OF SOME MINOR
COASTAL FLOODING AND BEACH EROSION ALONG NE AND N FACING SHORELINES
AT THE TIME OF THE EARLY SUNDAY MORNING HIGH TIDE...GENERALLY 230 AM
TO 3 AM. SHOULD THE SYSTEM APPROACH SOONER...THEN THE IMPACT COULD
BE SOMEWHAT MORE FOR THE SATURDAY AFTERNOON HIGH TIDE. IF THE SYSTEM
SHOULD SLOW DOWN SOME...WHICH HAS NOT BEEN THE MODEL TREND OF
LATE...THEN THERE COULD BE A LITTLE MORE IMPACT FOR EARLY SUNDAY
MORNING HIGH TIDE.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SATURDAY
     EVENING FOR CTZ002>004.
MA...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SATURDAY
     EVENING FOR MAZ004>006-011>014-026.
RI...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SATURDAY
     EVENING FOR RIZ001.
MARINE...GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR
     ANZ231>235-237-250-254>256.
     SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ250-
     254.
     SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR ANZ255.
-- End Changed Discussion --

&&

$$
SYNOPSIS...DOODY/JWD
NEAR TERM...DOODY/DUNTEN
SHORT TERM...DOODY
LONG TERM...JWD
AVIATION...DUNTEN/JWD
MARINE...DOODY/JWD
TIDES/COASTAL FLOODING...STAFF