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000
FXUS61 KBOX 060913
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
413 AM EST FRI DEC 6 2013

.SYNOPSIS...
A COLD FRONT WILL STALL SOUTH OF NEW ENGLAND TODAY AS A WAVE OF
LOW PRESSURE TRACKS ALONG THE FRONT TONIGHT. RAIN WILL CHANGE TO
SNOW AND SLEET TONIGHT WITH ACCUMULATING SNOW LIKELY IN THE
INTERIOR. ARCTIC HIGH PRESSURE BUILDS INTO NEW ENGLAND THIS
WEEKEND BRINGING MUCH COLDER TEMPS BUT DRY WEATHER. THE HIGH
SHIFTS TO THE MARITIMES SUNDAY NIGHT AS A COMPLEX STORM SYSTEM
MOVES FROM THE PLAINS AND GULF OF MEXICO. THIS WILL SPREAD A MIX
OF PRECIPITATION INTO OUR AREA LATE SUNDAY NIGHT WHICH WILL CHANGE
TO RAIN DURING MONDAY. ANOTHER COLD HIGH PRESSURE AREA BRINGS DRY
WEATHER FOR TUESDAY THROUGH THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
330 AM UPDATE...
SHALLOW COOL AIR STILL HANGING ON ACROSS THE MERRIMACK VALLEY IN
S NH WITH READINGS IN THE UPPER 30S...WHILE TEMPS ARE WELL INTO
THE 50S ELSEWHERE. COLD FRONT ENTERING THE BERKSHIRES WILL REACH
THE COAST AROUND 12Z. IT WILL TAKE UNTIL THE WIND SHIFT BEHIND
THE FROPA TO MIX OUT THIS LOW LEVEL COOL AIR IN NH WITH TEMPS
RISING SHARPLY BEFORE COOLING TOWARD SUNRISE. AREAS OF
FOG...LOCALLY DENSE IN SPOTS WILL PERSIST EARLY THIS MORNING.

POST FRONTAL SHOWERS ACROSS UPSTATE NEW YORK WILL MOVE ACROSS SNE
THROUGH MID MORNING BRINGING A PERIOD OF RAIN AS AREA OF LOW
LEVEL FRONTOGENESIS MOVES THROUGH. WE EXPECT A LULL IN THE PRECIP
FOR A FEW HOURS AROUND MIDDAY INTO THIS AFTERNOON...BUT NEXT BATCH
OF PRECIP ASSOCD WITH FRONTAL WAVE WILL BE MOVING IN FROM THE SW
BY LATE AFTERNOON. PTYPE STILL MAINLY RAIN THROUGH TODAY.

MAX TEMPS WILL OCCUR THIS MORNING WITH READINGS IN THE 40S AND 50S
THEN COOLING INTO THE 30S NW AND 40S ELSEWHERE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MODELS SIMILAR WITH TRACK OF SFC WAVE OFF THE MID ATLC COAST
TONIGHT TO NEAR THE 40/70 BENCHMARK. DEEP MOISTURE AND STRONG MID
LEVEL LIFT ASSOCD WITH FRONTOGENETICAL FORCING WILL RESULT IN A
PERIOD OF MOD TO HEAVY PRECIP TONIGHT. PTYPE WILL BE AN ISSUE AS
COLDER AIR WILL BE DRAINING SOUTH ACROSS THE REGION AS THE HEAVIER
PRECIP MOVES IN.

MODELS SOUNDINGS SHOW RAPID COOLING OF THE COLUMN THIS EVENING IN
THE DISTANT INTERIOR WITH ISOTHERMAL PROFILE NEAR 0C FOR SEVERAL
HOURS BEFORE COOLING FURTHER. ECMWF IS MOST AGGRESSIVE WITH THE
COLD AIR BUT WE USED A BLEND OF GFS/ECMWF THERMAL PROFILES AND
QPF TO DERIVE PTYPE AND SNOW AMOUNTS. EXPECT RAIN TO QUICKLY
CHANGE TO SLEET THEN SNOW NORTH OF THE PIKE THIS EVENING...WITH A
CHANGEOVER AFT MIDNIGHT FOR BOS AND AREAS S OF THE PIKE. A BRIEF
PERIOD OF FREEZING RAIN IS POSSIBLE IN THE INTERIOR DURING THE
TRANSITION...BUT SOUNDINGS SUGGEST MORE OF A CHANGOVER TO SLEET
THEN SNOW.

SNOWFALL TRICKY AS MAX QPF WILL BE SOUTH OF THE COLDER AIR.
CURRENT THINKING IS AN AREA OF 2-4" ACCUM NORTH OF THE MASS PIKE
AND WEST OF I495 WITH LOCALLY 5-6" POSSIBLE IN THE BERKSHIRES.
THIS FITS WELL WITH SREF PROBS WHICH HAVE HIGHEST PROBS OF >4" IN
THE BERKSHIRES. AMOUNTS MAY BE SLIGHTLY LESS INTO S NH WHICH WILL
BE ON THE NORTHERN FRINGE OF THE STORM. WE WILL GO WITH WINTER
WEATHER ADVISORIES FOR WESTERN AND NORTH CENTRAL MA.
ELSEWHERE...WE HAVE COATING TO 2 INCHES EXCEPT FOR THE S COAST
WHERE RAIN WILL END AS A BRIEF PERIOD OF SNOW/SLEET WITH LITTLE TO
NO ACCUM EXPECTED.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
OVERVIEW AND MODEL PREFERENCES...
WITH 06/00Z MODEL GUIDANCE CONTINUING TO SHOW REASONABLY GOOD
AGREEMENT IN THE SYNOPTIC SCALE PATTERN THROUGH THE LONG
TERM...WILL CONTINUE TO BASELINE THE FORECAST WITH CONSENSUS BLEND
OF OPERATIONAL AND ENSEMBLE GUIDANCE ALONG WITH THE PREVIOUS
FORECAST AND WPC DATA. THERE ARE STILL SOME MESOSCALE ISSUES
/PARTICULARLY REGARDING THE THERMAL PROFILE/ FOR A STORM EARLY
THIS COMING WEEK WHICH WILL NEED TO BE REFINED...BUT THE BLEND
TAKES INTO ACCOUNT THE FULL SPECTRUM. IN ESSENCE...THE ECMWF AND
SEVERAL OF BOTH THE GEFS AND ECENS MEMBERS CONTINUE TO BE ON THE
MORE AMPLIFIED END OF THE ENVELOPE...SLOWER WITH THE TIMING OF THE
FRONTS AND KEEPS THE DEEP NEAR SFC COLD LAYER IN PLACE LONGER. THE
GFS REMAINS ON THE FASTER...AND OVERALL WARMER SIDE OF THE
GUIDANCE.

IN TERMS OF THE BROAD SCALE. BROAD SW FLOW WILL DEVELOP THROUGH
THE WEEKEND AND EARLY NEXT WEEK BETWEEN SUBTROPICAL RIDGING FROM
THE SE AND DEEP LONGWAVE TROF SLIDING FROM THE PLAINS INTO ERN
CANADA. THE KICKER WAVE IS THE WAVE WHICH WILL BRING ABOUT THE SUN
NIGHT-MON STORM...WHICH WILL YIELD A PERIOD OF ARCTIC DRY AIR FOR
MUCH OF NEXT WEEK AS THE LONGWAVE SHIFTS INTO ERN CANADA AND MORE
W FLOW DEVELOPS.

DETAILS...

SAT AND SUN...
1040+ HPA HIGH PRES WILL BE SLOWLY SLIDING OVER SRN CANADA AND
NRN NEW ENGLAND THROUGH THE PERIOD. AFTER REMNANT SNOW AND RAIN
SHOWERS DISSIPATE ACROSS THE SOUTHEAST EARLY SAT...A PERIOD OF
COOLER AND DRY WX WILL PREVAIL THROUGH THE PERIOD. EXPECT
BLUSTERY AND COOL CONDITIONS DUE TO 20+ MPH WIND GUSTS WITH HIGHS
IN THE MID 30S TO LOW 40S AND LOWS DIPPING INTO THE TEENS AND LOW
20S. SUN...BUILDING CLOUD COVER AND A COOLER START WILL LEAD TO
HIGHS SLIGHTLY COOLER THAN SAT BUT WITH LIGHTER WINDS.

SUN NIGHT INTO MON...
ALTHOUGH THERE IS FAIRLY HIGH CONFIDENCE IN THE TRACK OF LOW PRES
THROUGH THE GREAT LAKES...WITH A CONNECTION TO GULF MOISTURE AND
HIGH PWATS ALMOST 3 STANDARD DEVIATIONS ABOVE NORMAL /AROUND 1.5
INCHES/...THE TRICKINESS TO THIS STORM WILL BE MAINLY IN HOW DEEP
AND HOW LONG COLD AIR DAMMING HOLDS IN THE ISENTROPIC LIFT REGIME
SUN NIGHT INTO EARLY MON. THIS COLD AIR WILL ALSO BE DRY...WHICH
MAY LIMIT PRECIP EFFICIENCY INITIALLY AND THEREFORE LIMIT SNOW
ACCUMS. ECMWF KEEPS H92 TEMPS AS LOW AS -4C TO -6C ALL THE WAY
UNTIL 12Z MON...AND CONTINUES /ALONG WITH OTHER GUIDANCE TO SOME
EXTENT/ TO COOL FURTHER EACH RUN. IN ANY CASE...CONFIDENCE IS
MODERATE THAT THERE WILL BE SOME ACCUMULATING SNOW ALL THE WAY TO
THE S COAST SUN NIGHT. EXACTLY HOW MUCH WILL BE DEPENDENT ON THE
DEPTH OF THE COLD AIR DAMMING AND STRENGTH OF THE ISALLOBARIC
NORTHERLY FLOW. ASSUMING AVERAGE SNOW RATIOS AND A MEAN OF THE
AVAILABLE QPF...THIS SUGGESTS AT LEAST ADVISORY LEVEL /3+ INCHES/
OF SNOWFALL FOR MUCH OF SRN NEW ENGLAND BY DAYBREAK MON...WITH
HIGHER ACCUMS POSSIBLE PARTICULARLY N OF THE MASS PIKE.

THE OTHER ISSUE WILL BE DURING THE MORNING AND MID DAY PERIOD
MON. COLD AIR MAY ACTUALLY BE TRAPPED BY A WEAK COASTAL LOW PRES
SLIDING N AND WHETHER IT REMAINS OFFSHORE OR MOVES INLAND. SHOULD
THE FORMER BE THE CASE IT MAY TAKE SOME TIME /IF IT DOES AT ALL/
FOR A CHANGE TO SLEET/FZRA IN EXTREME NRN MA AND SRN NH.
ELSEWHERE...THE COMBINATION OF SOME ACCUMULATED SNOW...WARM AIR
ALOFT AND COLD AIR DAMMING MAY LEAD TO A TRANSITION TO FZRA AND
SLEET WITH SOME LIGHT ICE ACCUMULATIONS. GIVEN THIS...ASIDE FROM
THE SNOWFALL POTENTIAL...A WINTRY MIX MAY BE AFFECTING THE MON
MORNING COMMUTE IN SOME PLACES. THERMAL PROFILES WILL BE GRADUALLY
REFINED THROUGH TIME AS CONFIDENCE IN THE TRACK/TIMING OF THE
COASTAL LOW...HIGH PRES AND MID LVL WARM AIR RISES. STAY TUNED TO
UPDATES.

MON NIGHT INTO TUE...
WITH A STRONGER SHORTWAVE STILL UPSTREAM THE SW FLOW ALOFT
CONTINUES...ALLOWING THE COLD FRONT ASSOCIATED WITH THE SUN NIGHT
AND MON STORM TO SLOW JUST OFFSHORE. A SECONDARY FRONTAL WAVE
ASSOCIATED WITH THE STRONGER SHORTWAVE ALOFT MAY LEAD TO AN
INCREASE IN PRECIP CHANCES ACROSS THE SRN PERIPHERY OF THE REGION
DURING THE DAY TUE. WITH COLD AIR ALREADY SLIDING IN FROM THE
NW...THIS MAY WELL BE ANOTHER PERIOD OF ACCUMULATING SNOWFALL FOR
PORTIONS OF S COASTAL CT/RI AND SE MA. OTHERWISE...BLUSTERY NW
FLOW DEVELOPS AS A NOSE OF ARCTIC HIGH PRES SLIDES OVER FROM THE
W. EXPECT TEMPERATURES TO BEGIN DIPPING WELL BELOW NORMAL.

THE LATTER HALF OF NEXT WEEK...
LONGWAVE TROF AND ATTENDANT ARCTIC HIGH PRES WILL BE BUILDING
ACROSS THE REGION THROUGH THE PERIOD. THIS WILL LEAD TO
TEMPERATURES WELL BELOW NORMAL THROUGH LATE IN THE WEEK. WED MAY
FEEL THE COLDEST THANKS TO WHAT APPEARS TO BE A BRISK NW
WIND...WHILE THE PRES GRADIENT SLACKENS THU AND FRI. EITHER WAY
EXPECT HIGHS AND LOWS TO BE AT LEAST 10-15F BELOW NORMAL. MAINLY
DRY WX IS LIKELY AS LONG AS HIGH PRES REMAINS IN PLACE. ONLY
CAVEAT WILL BE THE POSSIBILITY OF SOME OCEAN EFFECT SNOWS WED AND
THU WITH SST-H85 TEMP DIFFERENCES ALMOST 15C AND N-NW FLOW.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...

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

MODERATE CONFIDENCE OVERALL.

WIDESPREAD IFR/LIFR CONDITIONS WILL GRADUALLY IMPROVE TO MVFR
LATE THIS MORNING INTO THE AFTERNOON...WITH A BRIEF PERIOD OF
VFR POSSIBLE THIS AFTERNOON IN THE INTERIOR. AREA OF SHOWERS
WILL MOVE INTO THE REGION...EXITING 12-15Z. WIND SHIFT TO NW/N
THIS MORNING.

LATE TODAY THROUGH TONIGHT...CONDITIONS LOWER TO MVFR/IFR AS NEXT
BATCH OF PRECIP MOVES INTO THE REGION. PTYPE INITIALLY RAIN...BUT
CHANGING TO SNOW/SLEET THIS EVENING ACROSS N MA AND S NH WITH
CHANGEOVER OCCURRING AFTER MIDNIGHT BDL-BOS CORRIDOR. PTYPE SHOULD
REMAIN MOSTLY RAIN PVD TO CAPE/ISLANDS BUT ENDING AS A BRIEF
PERIOD OF SNOW/SLEET 09-12Z. RUNWAYS WILL BECOME SNOW COVERED
NORTHERN MA AND S NH.

KBOS TAF...MODERATE CONFIDENCE IN TAF. TEMPORARY IMPROVEMENT LATE
THIS MORNING INTO THE AFTERNOON BEFORE LOWERING CONDITIONS
TONIGHT. RAIN CHANGES TO SLEET/SNOW AFT 06Z.

KBDL TAF...MODERATE CONFIDENCE IN TAF. TEMPORARY IMPROVEMENT LATE
THIS MORNING INTO THE AFTERNOON BEFORE LOWERING CONDITIONS
TONIGHT. RAIN CHANGES TO SLEET/SNOW NEAR 06Z.

OUTLOOK...SATURDAY THROUGH MONDAY...

SAT AND SUN...HIGH CONFIDENCE.
MAINLY VFR AFTER SOME SNOW/RAIN SHOWERS DISSIPATE SAT MORNING. NW
WIND GUSTS AROUND 20 KT POSSIBLE SAT...LIGHTER WINDS SUN.

SUN NIGHT THROUGH MON NIGHT...MODERATE CONFIDENCE.
MIX OF IFR/MVFR AS STORM CENTER CROSSES THE REGION. EXACT TIMING
IS UNCERTAIN...BUT PRECIP LOOKS TO START AS SNOW SUN NIGHT...THEN
CHANGE TO A WINTRY MIX MON MORNING BEFORE SOME LOCATIONS TURN TO
ALL RAIN. CONDITIONS IMPROVE SOMEWHAT MON NIGHT.

TUE...MODERATE CONFIDENCE.
MAINLY VFR AWAY FROM THE S COAST...WHERE SOME SNOW SHOWERS MAY
LEAST TO IFR/MVFR CONDITIONS DURING EARLY HALF OF THE DAY. GUSTY
NW WINDS EXPECTED.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

THROUGH TONIGHT...HIGH CONFIDENCE.

PREFRONTAL SW GUSTS TO 20 KT WILL SHIFT TO N BY MIDDAY. LIGHT N
WINDS THIS EVENING INCREASING LATE WITH 20 KT GUSTS POSSIBLE. LOW
PROB FOR A FEW G25 KT. WE HAVE SCA FOR SOUTHERN WATERS AS SEAS
WILL BE BUILDING TO 4-6 FT.

OUTLOOK...SATURDAY THROUGH TUESDAY...

SAT AND SAT NIGHT...HIGH CONFIDENCE.
SMALL CRAFT ADVISORIES LIKELY LINGER AS 5-7FT SEAS CONTINUE ON
OCEAN WATERS WITH SOME NW WIND GUSTS APPROACHING 25 KT LATE IN THE
DAY AND DURING THE EVENING HOURS.

SUN AND SUN NIGHT...HIGH CONFIDENCE.
WINDS AND SEAS GENERALLY REMAIN BELOW SMALL CRAFT ADVISORY
THRESHOLDS THROUGH THE PERIOD...ALTHOUGH SOME RAIN/SNOWS MAY BEGIN
TO REDUCE VSBYS SUN NIGHT.

MON INTO TUE...MODERATE CONFIDENCE.
A PERIOD OF RAIN WILL BE ACCOMPANIED BY GUSTY EAST TO NORTHEAST
WINDS ON MON. IT/S POSSIBLE SOME OF THESE WINDS REACH GALE
FORCE...BUT AT LEAST SMALL CRAFT ADVISORIES ARE LIKELY. SEAS WILL
ALSO RISE TO 5-9 FT. WINDS WILL THEN SHIFT TO THE W ON TUE...BUT
CONTINUE TO GUST TO AT LEAST SMALL CRAFT ADVISORY LEVELS WITH SEAS
REMAINING ELEVATED.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     SATURDAY FOR MAZ002>004-008>010-026.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM EST THIS
     EVENING FOR ANZ235-237.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EST
     SATURDAY FOR ANZ254>256.

&&

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