-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 091153
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
653 AM EST MON DEC 9 2013

.SYNOPSIS...
LOW PRESSURE LIFTING NORTH FROM THE MID ATLANTIC WILL BRING MIXED
PRECIP TODAY. ANOTHER DISTURBANCE MAY BRING ACCUMULATING SNOW
TUESDAY...MAINLY SOUTH OF THE MASSACHUSETTS TURNPIKE. MAINLY
DRY...BUT UNSEASONABLY COLD AND BLUSTERY WEATHER IS EXPECTED FOR
THE REST OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
7 AM UPDATE...
A SQUEEZE PLAY THIS MORNING BETWEEN TWO BATCHES OF HEAVIER
PRECIP...ONE WHICH IS MOVING THROUGH CT CLOSELY ASSOCIATED WITH
THE LOW PRES WAVE TO THE S WHILE THE OTHER IS RIDING THE MA/NH
BORDER AND HAS DEVELOPED ALONG A WEAK CONVERGENT BOUNDARY BETWEEN
THE DRAINAGE FLOW AND EASTERLY MARINE LAYER. IN THE NRN HEAVIER
BAND...A PERIOD OF MORE ACCUMULATING SNOW IS EXPECTED THANKS TO
ENHANCED DYNAMIC COOLING WHILE THE SRN BANDS ARE MORE RAIN THANKS
TO WARM LAYER STARTING TO ON THE SRN COAST. BETWEEN
THESE...WIDESPREAD FREEZING DRIZZLE AND SNIZZLE CONTINUES TO LEAD
TO LIGHT ICE/SNOW ACCUMULATIONS WHICH WILL CONTINUE AS LONG AS THE
SFC-H7 MOISTURE LAYER HOLDS. SOUNDINGS STILL SHOW RAPID DRYING
ABOVE H7...SO LIKELY SEE MAINLY DRIZZLE ALTHOUGH ACCUMS ARE STILL
LIKELY. GIVEN THE LATEST TEMP/DWPT TRENDS...CURRENT TIMING OF THE
ADVISORIES STILL SEEMS GOOD. THE EARLIEST TO DROP /THE SE COASTAL
PLAIN AT 15Z/ MAY BE ABLE TO GO A LITTLE EARLIER AS DWPTS CONTINUE
TO CLIMB AND SEVERAL LOCALES ARE NEAR TO SLIGHTLY ABOVE FREEZING.
AM NOTING STRONGER DRAINAGE FLOW IN THE CT VALLEY HOWEVER...SO
THEY LIKELY HOLD TO FREEZING PRECIP MUCH OF THE MORNING.

PREVIOUS DISCUSSION...

VERY LIGHT SNOW OCCURRING IN SNE EARLY THIS MORNING WITH NORTHERN
EXTENT OF WARMER AIR ALOFT AND CHANGEOVER TO FZRA LIFTING N/NE
FROM THE SOUTHERN CT. PRECIP ON RADAR IS QUITE DISORGANIZED AS THE
COLUMN IS NOT SATURATED THROUGH A DEEP LAYER AND MUCH OF THE SNOW
GROWTH REGION ABOVE 700 MB IS DRY. ICE IN THE CLOUD LAYER ACTUALLY
BEING INTRODUCED BELOW 850 MB.

HEAVIER PRECIP SOUTH OF NEW ENG IS ASSOCD WITH DEEPER MOISTURE
AND OMEGA INTO THE SNOW GROWTH REGION...BUT GUIDANCE INDICATES
THE NORTHERN EXTENT OF THIS MOISTURE AND LIFT WILL JUST CLIP THE S
COAST THIS MORNING. FURTHER INTO THE INTERIOR...THE MID LEVELS
NEVER SATURATE AND ACTUALLY DRY DURING THE DAY. THIS COMBINED WITH
WEAK OMEGA WILL RESULT IN A LIGHT QPF EVENT TODAY. SNOW ACCUM
WILL BE LIMITED TO A COATING TO AN INCH FOR MOST OF THE
REGION...WITH LOCALLY UP TO 2 INCHES POSSIBLE ACROSS NORTHERN
HIGHER TERRAIN. BUT THERE REMAINS A CONCERN FOR LIGHT ICING
ACROSS MUCH OF THE REGION...ESPECIALLY INTERIOR.

SNOW WILL CHANGE TO FREEZING RAIN/DRIZZLE THROUGH 12Z SOUTH OF
THE MASS PIKE...WITH CHANGEOVER OCCURRING TO THE NORTH LATER THIS
MORNING THROUGH MIDDAY. CURRENT TEMPS REMAIN BELOW FREEZING ACROSS
MOST OF THE REGION SO EVEN PORTIONS OF THE COAST WILL LIKELY SEE A
BRIEF PERIOD OF FZRA. A CHANGE TO PLAIN RAIN/DRIZZLE WILL OCCUR IN
THE COASTAL PLAIN DURING THE MORNING AS EASTERLY WINDS WARM THE
BOUNDARY LAYER WITH HIGH TEMPS REACHING THE LOW TO MID 40S S/E OF
I95 CORRIDOR IN RI AND SE MA.

HOWEVER...LOW LEVEL COLD AIR WILL BE SLOW TO ERODE IN THE
INTERIOR AS GUIDANCE SIGNALING GOOD COLD AIR DAMMING SIGNATURE.
WITH OPEN WAVE LIFTING ACROSS SE NEW ENG...LIGHT N WINDS IN THE
INTERIOR AND CT VALLEY WILL HELP TO LOCK IN THE COLD AIR WITH
PARTS OF THE DISTANT INTERIOR STRUGGLING TO REACH 32 DEGREES
WHICH WILL RESULT IN AN EXTENDED PERIOD OF FREEZING RAIN/DRIZZLE.

DURING THE AFTERNOON PRECIP WILL LIKELY TAPER OFF AND BECOME
DRIZZLE/FREEZING DRIZZLE AS SOUNDINGS SHOW NO ICE IN THE CLOUD
LAYER.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
WAVE LIFTS TO THE NORTH THIS EVENING WITH DRIER WESTERLY FLOW
DEVELOPING. EXPECT MAINLY DRY CONDITIONS WITH LOW CLOUDS
ERODING...ALTHOUGH MID/HIGH CLOUDS WILL BE MOVING IN OVERNIGHT.
LOW TEMPS WILL BE MOSTLY IN THE 20S...EXCEPT LOWER 30S NEAR THE
COAST.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
HIGHLIGHTS...

* PERIOD OF SNOW POSSIBLE SOUTH OF MA PIKE ON TUE
* MAINLY DRY AND UNSEASONABLY COLD WED THROUGH FRI
* LOW CONFIDENCE FORECAST NEXT WEEKEND

OVERVIEW AND MODEL PREFERENCES...
09/00Z MODEL LONG RANGE GUIDANCE SHOWS GOOD AGREEMENT IN SYNOPTIC
PATTERN THROUGH MUCH OF THE LONG TERM UNTIL THE WEEKEND...AT WHICH
POINT DIFFERENCES IN PHASING OF BOTH THE SRN AND NRN STREAM
CONTINUE SHOW. THEREFORE...HAVE GENERALLY MODERATE TO HIGH
CONFIDENCE THROUGH MUCH OF THE WORK WEEK...AND IN THE ARCTIC
AIRMASS SETTLING OVER THE REGION. WITH THIS AGREEMENT WILL
CONTINUE TO BASELINE WITH A CONSENSUS BLEND OF DETERMINISTIC
GUIDANCE...WPC...AND PERSISTENCE.

THE MAIN CAVEAT IN THE MID TERM WILL BE A FAST MOVING WAVE ON TUE
INITIATING A WEAK SFC FRONTAL WAVE ON A STALLED FRONTAL BOUNDARY
TO THE S. THIS LOOKS TO INITIATE SOME SNOWFALL ACROSS THE SRN HALF
OF THE REGION PER LATEST SOUNDINGS. THE KEY WILL BE THE BEST MID
LVL F-GEN BAND AND HOW FAR N IT IS ABLE TO TRAVEL. LATEST NAM IS
MUCH FURTHER N...WHILE THE ECMWF CONTINUES TO BE THE FARTHEST
OFFSHORE. GFS SEEMS LIKE A GOOD MIDDLE GROUND AS IT IS LESS ROBUST
WITH PRECIP THAN THE NAM...BUT A BIT HIGHER THAN THE CURRENT ECMWF
/WHICH HAS COME FURTHER N THAN PREVIOUS RUNS/ THEREFORE...WILL
LEAN CLOSER TO THE GFS FOR TUE...THE ONLY BREAK FROM THE BLEND
PROPOSED ABOVE FOR THIS UPDATE.

DETAILS...

TUE...MODERATE CONFIDENCE.
WILL BE MONITORING FOR A PERIOD OF SNOW PARTICULARLY S OF THE
MASS PIKE FROM ABOUT MID MORNING INTO THE AFTERNOON HOURS AS A
WEAK SFC FRONTAL WAVE INITIATES SOME MODEST MID LVL F-GEN BANDING
TO ITS N. WHILE THE EXACT PLACEMENT OF THIS BAND IS A LITTLE
UNCERTAIN...HAVE AT LEAST ENOUGH CONFIDENCE TO ERR TOWARD HIGH
CHANCE-LOW LIKELY POPS FOR THIS POTENTIAL. INTERESTINGLY...THE
LIFT PROVIDED BY THE F-GEN BAND IS LOCATED ALMOST PERFECTLY IN THE
-10C TO -20C LAYER WHICH IS ICE-SATURATED...SOMETHING THIS
MORNING/S STORM WAS LACKING. GIVEN THAT THIS WAVE LOOKS TO HAVE
GULF ORIGINS...QPF VALUES WITHIN THE BAND RANGE FROM 0.1-0.4
INCHES DEPENDING ON ITS TRACK. RATIOS MAY BE A BIT HIGHER DUE TO
WEAKER WINDS AND BETTER SNOW GROWTH EFFICIENCY COULD YIELD NEAR
ADVISORY LEVEL SNOWFALL FOR SOME AREAS IN CT/RI/SE MA...BUT THERE
IS ALSO A FAIR AMOUNT OF NEAR SFC DRY AIR TO OVERCOME. NOT
CONFIDENT IN THE BAND SETUP TO PULL THE TRIGGER...BUT SOMETHING
WORTH WATCHING. FURTHER N...MAY BE A SHARP CUTOFF ACROSS NRN MA
AND SRN NH WHERE LITTLE TO NO SNOW MAY BE OBSERVED. TEMPS MAY ALSO
BE AN ISSUE AS SOME MAY JUST INCH ABOVE FREEZING AS SNOWS TAPER
OFF...SO HAVE TO WATCH OUT FOR DYNAMIC COOLING WHICH COULD PROMOTE
SNOW ACCUM DESPITE TEMPS WARMING TO THE MID 30S.

TUE NIGHT INTO FRI...
PERIOD OF ANOMALOUS COLD AND MAINLY DRY WX PREVAILS AS 1040 HIGH
PRES SLIDES IN. ONLY FLY IN THE OINTMENT HERE IS A DRY PASSAGE OF
AN ARCTIC COLD FRONT ON WED NIGHT-THU INTRODUCING THE COLDER
TEMPS. THIS MAY LEAD TO A PERIOD OF OCEAN EFFECT SNOWS POSSIBLE
FOR THE CAPE/NANTUCKET AS V-COMPONENT TO THE WIND SHIFTS MORE
NORTHERLY BEHIND THE FRONT. AM NOTING H85 TEMPS DIPPING AS LOW AS
-18C TO -20C...SO SUSPECT HIGHS PARTICULARLY THU AND FRI MAY
STRUGGLE TO BREAK INTO THE 30S WHILE LOWS DIP BACK INTO THE SINGLE
DIGITS ACROSS MANY LOCATIONS. IN ESSENCE AVG TEMPS ABOUT 10-15
DEGREES BELOW NORMAL.

THIS COMING WEEKEND-EARLY NEXT WEEK...
AS MENTIONED ABOVE...GUIDANCE CONTINUES TO SHOW SIGNIFICANT
STRUGGLES REGARDING THE PHASING OF A NORTHERN AND SOUTHERN STREAM
SHORTWAVES WHICH ARE YET TO BE SAMPLED. LATEST DETERMINISTIC RUNS
ARE MORE SIMILAR TO PREVIOUS 00Z ITERATIONS...WITH THE ECMWF
PHASING THE TWO AND THE GFS NOT. ENSEMBLES SUPPORT BOTH NEARLY
EQUALLY AT THIS POINT. THE ECMWF/S PHASING SUPPORTS A COASTAL
STORM WHILE THE GFS IS AN INSIDE RUNNER BECAUSE IT TRANSITIONS THE
NRN WAVE INTO QUEBEC. WILL CONTINUE TO HIGHLIGHT SOME POPS FOR
MORE UNSETTLED WX FOR SUN...BUT BLEND THE WARM/COLD SOLUTIONS FOR
THE TIME BEING UNTIL THE WAVES ARE BETTER SAMPLED AND CONFIDENCE
BECOMES HIGHER IN ANY ATTENDANT LOW TRACK.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

NEAR-TERM /THROUGH TONIGHT/...

GENERALLY HIGH CONFIDENCE IN TRENDS TODAY...BUT LOWER CONFIDENCE
OF TIMING OF PRECIP TYPE CHANGES AND THE PRECIP/FOG ENDING THIS
EVENING-OVERNIGHT.

MAINLY IFR/MVFR TODAY. WIDESPREAD LIGHT MIXED PRECIP IS EXPECTED
TO CONTINUE THROUGH THE MORNING. THIS WILL INCLUDE A PERIOD OF
LIGHT SNOW AND FREEZING RAIN WITH LIGHT SNOW/ICE ACCUMULATIONS. IT
MAY ACTUALLY BE THAT FREEZING RAIN IS MORE OF A FREEZING DRIZZLE
MUCH OF THE DAY. THERE WILL BE A SLOW CHANGE FROM S TO N TO ALL
RAIN OVER THE NEXT SEVERAL HOURS BUT TIMING IN TAFS MAY BE OFF BY
A COUPLE OF HOURS. EXPECT THROUGH THE LATE AFTERNOON AND EVENING
FOR THE PRECIP TO GRADUALLY END AND FOG TO LIFT THROUGH THE
EVENING HOURS...LEADING TO VFR CONDTIONS OVERNIGHT.

KBOS TAF...HIGH CONFIDENCE IN MVFR/IFR CONTINUING. WITH WINDS OUT
OF THE E...MAINLY RAIN EXPECTED THROUGH THE MORNING VERY SOON.

KBDL TAF...HIGH CONFIDENCE IN MVFR/IFR CONTINUING. LOW CONFIDENCE
IN TIMING OF PTYPE TRANSITIONS. FREEZING PRECIP LIKELY LINGERS FOR
AT LEAST A FEW MORE HOURS YET.

OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...

TUE...MODERATE CONFIDENCE.
A PERIOD OF SNOWFALL MAY LEAD TO IFR/MVFR CIGS/VSBYS AT TERMINALS
ESPECIALLY S OF THE MASS PIKE. SOME TERMINALS N MAY REMAIN VFR
MOST OF THE DAY /ESPECIALLY IN SRN NH/ CONDITIONS IMPROVE
EVERYWHERE DURING THE EVENING HOURS.

TUE NIGHT INTO FRI...HIGH CONFIDENCE.
MAINLY VFR THRUT. ONLY CAVEAT WILL BE THE POSSIBILITY OF
LOCALIZED MVFR CONDITIONS IN SOME OCEAN EFFECTS -SHSN/SHRA FOR
CAPE/ISLAND TERMINALS WITH THE BEST CHANCES WED NIGHT AND THU.
STRONG NW WIND GUSTS ALSO POSSIBLE LATE TUE NIGHT INTO WED NIGHT.
-- End Changed Discussion --

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

NEAR-TERM /THROUGH TONIGHT/...HIGH CONFIDENCE.

A PERIOD OF EASTERLY WIND GUSTS TO 25-30 KT EXPECTED OVER THE
OPEN WATERS THROUGH THE MORNING...ESPECIALLY SOUTH OF THE COAST.
WINDS DIMINISH AND VEER TO THE S AND SE LATER TODAY.

ANOTHER PULSE OF G25 KT POSSIBLE THIS EVENING OVER THE OUTER
WATERS AS WINDS SHIFT TO THE WEST.

SMALL CRAFT ADVISORIES CONTINUE. AREAS OF RAIN/DRIZZLE AND FOG
WILL LIMIT VSBYS AT TIMES TODAY.

OUTLOOK...TUESDAY THROUGH FRIDAY...HIGH CONFIDENCE.

TUE...MODERATE CONFIDENCE.
SEAS GRADUALLY SLACKEN THROUGH THE DAY BUT MAY REMAIN ABOVE 5 FT
ON THE ERN OCEAN WATERS. WINDS GENERALLY BELOW 20 KT SAVE FOR A
FEW STRONGER GUSTS ON NRN WATERS. SOME SMALL CRAFT ADVISORIES MAY
REMAIN FOR SEAS ALONE.

TUE NIGHT INTO FRI...HIGH CONFIDENCE IN TRENDS BUT LOWER
CONFIDENCE IN EXACT TIMING OF ANY HEADLINES.
A PROLONGED PERIOD OF AT LEAST SMALL CRAFT ADVISORY CONDITIONS
LOOKS LIKELY THROUGH THIS PERIOD AS W-NW WINDS WILL OFTEN REMAIN
25 KT OR HIGHER THROUGH THE PERIOD WITH SEAS 5-8FT ON THE OUTER
WATERS. THERE IS ALSO THE LOW PROBABILITY THAT OCCASIONAL GALE
FORCE WIND GUSTS OCCUR LATE TUE NIGHT AND AGAIN THU NIGHT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR CTZ002.
     WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
     CTZ003-004.
MA...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
     MAZ002>004-008>011-026.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
     MAZ017-018-020-021.
     WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
     MAZ005-006-012>014.
NH...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NHZ011-
     012-015.
RI...WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
     RIZ002>007.
     WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
     RIZ001.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
     ANZ231>234.
     SMALL CRAFT ADVISORY UNTIL 7 AM EST TUESDAY FOR ANZ235-237-
     254>256.
     SMALL CRAFT ADVISORY UNTIL 7 AM EST TUESDAY FOR ANZ250.
     SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ251.

&&

$$
SYNOPSIS...KJC/DOODY
NEAR TERM...KJC/DOODY
SHORT TERM...KJC
LONG TERM...DOODY
AVIATION...KJC/DOODY
MARINE...KJC/DOODY