-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 071735
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1235 PM EST SAT DEC 7 2013

.SYNOPSIS...

LOW PRES MOVES OFFSHORE TODAY AS HIGH PRES BUILDS IN FROM THE
WEST. THE HIGH WILL SETTLE OVER NEW ENGLAND TONIGHT AND SUNDAY.
ANOTHER LOW PRES MOVING UP FROM THE SOUTH WILL BRING A WINTRY MIX
OF PRECIPITATION LATE SUN NIGHT INTO MON. MAINLY DRY BUT COLD
WEATHER WILL FOLLOW FOR THE MIDDLE AND END OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

-- Changed Discussion --
1 PM UPDATE...

REVIEWING THE 12Z SOUNDING FROM ALBANY...LOW-LEVEL MOISTURE
TRAPPED BENEATH THE INVERSION AROUND H8 COUPLED WITH BUILDING DRY
AIR AND SUBSIDENCE ASSOCIATED WITH ARCTIC HIGH PRESSURE BUILDING
FROM THE WEST IS LENDING TO SCATTERED-BROKEN LOW-LEVEL CLOUDS.
THIS IS LIMITING TEMPERATURES IN PART...WHILE ALLOWING OTHER
LOCATIONS TO WARM WITH ABUNDANT SUNSHINE. ALREADY SEEING LOCATIONS
ACROSS SOUTHEAST MASSACHUSETTS /INCLUDING THE TAUNTON WFO/ WARM
INTO THE LOWER 40S. WILL CONTINUE WITH THE HIGH TEMPERATURE
FORECAST WITH VALUES AROUND THE MID- TO UPPER-30S WITH LOCATIONS
OVER THE SOUTHEAST COASTAL PLAIN INTO THE LOW 40S.

SEEING SOME GUSTY NORTHWESTERLY WINDS AROUND 15 TO 20 MPH AS A
CONSEQUENCE OF BOUNDARY-LAYER MIXING OF FASTER MOMENTUM TO THE
SURFACE. ALSO SEEING THE GRADUAL DROP-DOWN OF DEWPOINTS.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...

ARCTIC HIGH PRES BUILDS OVER NEW ENG TONIGHT INTO SUNDAY BRINGING
DRY AND COLD CONDITIONS. CLEAR SKIES AND DIMINISHING WIND TONIGHT
WILL LEAD TO GOOD RADIATIONAL COOLING AND MINS MOSTLY IN THE
TEENS...EXCEPT LOWER 20S NEAR THE COAST. ON SUNDAY...SUNSHINE WILL
GIVE WAY TO INCREASING MID/HIGH CLOUDS DURING THE DAY AS MID LEVEL
WAA DEVELOPS WITH INCREASING MOISTURE FROM THE SOUTH. MAX TEMPS
UPPER 20S TO MID 30S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...

HIGHLIGHTS...

*  WINTRY MIX WITH STORM SUN NIGHT AND MON
*  HIGH PRES BUILDS IN TUE THRU THU BRINGING COLD DRY WEATHER

OVERVIEW AND MODEL PREFERENCES...
WITH THE LATEST /07.00Z/ MODEL GUIDANCE CONTINUING TO SHOW FAIRLY
GOOD AGREEMENT WITH THE OVERALL SYNOPTIC FLOW PATTERN ACROSS THE
REGION THROUGH MUCH OF NEXT WEEK...THE FOCUS WILL BE ON THE /STILL
UNCERTAIN/ MESOSCALE DIFFERENCES REGARDING A WINTRY MIX SITUATION
FOR SUN NIGHT INTO MON. ECMWF CONTINUES TO BE ON THE COLDER SIDE
OF THE ENVELOPE OF SOLUTIONS AND CONTINUES TO HAVE SUPPORT FROM
MANY GEFS AND ECENS MEMBERS WHILE THE OPERATION GFS IS STILL ON
THE WARMER AND MORE PROGRESSIVE SIDE. WITH THIS UPDATE...WILL
BEGIN ERRING ON THE SLIGHTLY COLDER SOLUTION AS THIS SEEMS TO BE
BOTH THE MOST CONSISTENT AS WELL AS THE MORE LIKELY SCENARIO GIVEN
COLD AIR DAMMING FROM 1040 HPA HIGH PRES OVER THE CANADIAN
MARITIMES. FEEL THAT THE COLDER AIR WILL STRUGGLE TO GIVE UNDER
WHAT WILL LIKELY BE STRONG WARM ADVECTION ALOFT. THEREFORE...WHILE
A CONSENSUS BLEND WILL STILL BE USED...IT WILL HAVE MORE WEIGHT
TOWARD THE LATEST ECMWF PARTICULARLY FOR THE THERMAL FIELDS.

IN REGARDS TO THE PATTERN FOR MUCH OF THE WEEK...AS SUBTROPICAL
RIDGING SLIDES FURTHER OFFSHORE OF THE SE CONUS...THE SW FLOW WILL
GIVE WAY TO MAINLY W FLOW IN CONJUNCTION WITH LONGWAVE TROF
SETTING UP ACROSS ERN CANADA AND NRN NEW ENGLAND. THIS MEANS
FOLLOWING THE STORM FOR SUN NIGHT-MON NIGHT...A TRANSITION TOWARD
AN ARCTIC AND BLUSTERY AIRMASS WILL YIELD TEMPERATURES BELOW
NORMAL WITH MAINLY DRY WX RIGHT THROUGH THE END OF THE WORK WEEK.

DETAILS...

SUN NIGHT INTO MON NIGHT...MOST OF THE FOCUS IS ON THIS SYSTEM
FOR THIS UPDATE.

TIMING...
A PERIOD OF SNOW LOOKS LIKELY PARTICULARLY AFTER MIDNIGHT SUN
NIGHT IN THE STRONG ISENTROPIC REGIME AHEAD OF AN APPROACHING WARM
FRONT. COLD AIR ENTRENCHED ACROSS THE REGION ESPECIALLY BELOW H8
WILL KEEP THE P-TYPE SNOW ACROSS MOST OF SRN NEW ENGLAND
INITIALLY. THE SNOW THEN LOOKS TO CHANGE TO A WINTRY MIX WHICH MAY
INCLUDE A PERIOD OF FZRA WITH ICE ACCUMULATIONS SOMETIME DURING
THE MORNING COMMUTE INTO MID MORNING MON. THEN...BY MID MORNING
SOME AREAS /PARTICULARLY CT/RI/SRN MA ARE LIKELY TO CHANGE TO ALL
RAIN...ALLOWING FOR SOME MELTING OF THE ICE/SNOWPACK FROM THE
PREVIOUS NIGHT...WHILE NORTHERN LOCATIONS MAY REMAIN A WINTRY MIX.

SNOW/ICE...
SEE THE UNCERTAINTY SECTION BELOW...BECAUSE THE THERMAL
STRUCTURES WILL ALSO AFFECT HOW MUCH OF EITHER SNOW/ICE FALLS.
LATEST INDICATIONS SUGGEST THAT WITH PRECIP NOT REALLY FORMING
UNTIL AFTER MIDNIGHT...AND WITH COLD DRY AIR IN PLACE FROM
STRONG/COLD HIGH PRES TO THE NE...THAT TOTAL QPF VALUES MAY BE
LIMITED INITIALLY AS EVAP OCCURS. HOWEVER...IT DOES APPEAR THAT IT
WILL START AS ALL SNOW EVERYWHERE WITH A GUIDANCE AVERAGE AROUND
0.1-0.2 INCHES OF LIQUID. ASSUMING AVERAGE 10 TO 1 RATIOS THERE
MAYBE AN INCH TO 3 OR SO INCHES POSSIBLE BY THE TIME THE MORNING
COMMUTE BEGINS/SUNRISE. IF A TRANSITION TO SLEET/FZRA OCCURS...ICE
ACCUMULATIONS MAY ACTUALLY INCREASE AS QPF OUTPUT INCREASES AFTER
12Z...EXACERBATED IN THOSE AREAS WHERE A SNOWPACK HAS FORMED.
THEREFORE...NOT OUT OF THE QUESTION THAT OVER A TENTH OF AN INCH
OF ICE IS POSSIBLE IN SOME LOCALES...BUT THIS WILL NEED TO BE
BETTER REFINED.

IMPACTS...
THE MAIN ISSUE IS THAT THERE IS A MODERATE TO HIGH POTENTIAL FOR
SNOW...AND POSSIBLY EVEN ICE TO BE OCCURRING DURING THE MONDAY
MORNING COMMUTE. ANY UNTREATED ROADS MAY ALREADY BE OR BECOME
SLIPPERY...AND ANY AREAS THAT ARE STILL SNOWING MAY SEE REDUCED
VISIBILITIES.

UNCERTAINTY...
ALTHOUGH THERE IS GOOD AGREEMENT THAT STRONG LOW PRES WILL MOVE
FROM THE SOUTHEAST THROUGH THE GREAT LAKES AT THIS TIME...THERE IS
STILL SOME UNCERTAINTY REGARDING THE TRACK OF WEAK COASTAL LOW
PRES AT THE WARM/COLD FRONT TRIPLE POINT. LATEST GUIDANCE
CONTINUES TO ERR ON KEEPING THIS JUST OFFSHORE BUT WITHIN THE
40/70 BENCHMARK MON MORNING. THE ISSUE HERE IS THAT THIS TRACK
WILL LIMIT THE ABILITY OF WARM AIR TO MOVE IN ACROSS THE
AREA...MAINTAINING STRONG NORTHERLY ISALLOBARIC FLOW AND KEEPING
COLD AIR ENTRENCHED. THIS TRACK WILL NEED TO BE MONITORED AS IT
WILL HAVE A SIGNIFICANT IMPACT ON THERMAL PROFILES AND WHEN/IF A
CHANGE FROM SNOW TO A WINTRY MIX IS EXPECTED. SOME
AREAS...PARTICULARLY ACROSS NORTHERN MA AND SRN NH...MAY NEVER
FULLY CHANGE TO RAIN WITH SFC MELTING. THE COLDER SOLUTION
PREFERRED WITH THIS UPDATE...SUGGESTS THAT THIS MAY WELL BE THE
CASE. SFC TEMPERATURES WILL HAVE TO BE WATCHED CLOSELY DURING THE
EVENT.

IN ANY OF THE POTENTIAL CASES HERE...PRECIP /IN WHATEVER FORM/
WILL BE GRADUALLY COMING TO AN END BY THE EVENING MON...WITH WHAT
APPEARS TO BE AN AVERAGE OF ABOUT 0.5+ INCHES OF LIQUID TOTAL BY
THE TIME IT WRAPS UP. STILL SOME ISSUES TO REFINE
HERE...PARTICULARLY WITH THE LOWERING OF QPF AND THE THERMAL
PROFILES. THEREFORE...SNOW/ICE TOTALS ARE LIKELY TO CHANGE OVER
THE NEXT 24-36 HOURS. STAY TUNED TO FORECAST UPDATES.

TUE INTO LATE WEEK...
ALTHOUGH THERE IS STILL SOME UNCERTAINTY REGARDING A SECONDARY
FRONTAL WAVE WHICH MAY DELIVER SOME SNOWS TO S COASTAL LOCATIONS
TUE...THE PERIOD WILL BE MARKED BY A STRONG ARCTIC HIGH PRES WHICH
WILL BE MOVING OVER THE REGION. THIS WILL YIELD A PERIOD OF MAINLY DRY
WX WITH TEMPERATURES WELL BELOW NORMAL FOR MID DECEMBER. SOME
STRONG BLUSTERY NW WINDS /PARTICULARLY ON WED/ MAY MAKE IT FEEL
QUITE COLD.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...

-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

NEAR-TERM /THROUGH MONDAY/...MODERATE CONFIDENCE.

SCT-BKN 025-035 WITH NW WINDS GUSTING AROUND 15 KTS INTO THIS
EVENING. CLEARING OVERNIGHT AS WINDS BECOME LIGHT AND VARIABLE
SWINGING E-SE THROUGH THE DAY SUNDAY TOWARDS SUNDAY NIGHT.
INCREASING MID- TO UPPER-LEVEL CLOUDS LATE SUNDAY. GOING DOWNHILL
SUNDAY NIGHT INTO MONDAY WITH CIGS LOWERING TO IFR WITH A WINTRY
MIX OF MAINLY SLEET-FREEZING RAIN...ESPECIALLY MONDAY MORNING.
CHANGEOVER TO RAIN THROUGH THE DAY MONDAY ANTICIPATED...ESP SOUTH
OF THE MASS-PIKE.

KBOS TAF...HIGH CONFIDENCE IN TAF THROUGH SUNDAY.

KBDL TAF...HIGH CONFIDENCE IN TAF THROUGH SUNDAY.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

SUN NIGHT INTO MON NIGHT...MODERATE TO HIGH CONFIDENCE.
MAINLY IFR/MVFR THROUGH THE PERIOD. A PERIOD OF SNOW STARTING
LATE SUN NIGHT WILL TRANSITION TO A WINTRY MIX...THEN TO ALL RAIN
MON MORNING INTO MON AFTERNOON...ALTHOUGH SOME TERMINALS MAY STAY
AS A WINTRY MIX THROUGH THE PERIOD PARTICULARLY IN NRN MA AND SRN
NH. SOME ACCUMULATING SNOW...AND SOME LIGHT ICE ACCUMULATIONS ON
RUNWAYS POSSIBLE.

TUE INTO WED...HIGH CONFIDENCE.
MAINLY VFR ALTHOUGH A FEW SNOW SHOWERS POSSIBLE ALONG THE S
COAST/CAPE/ISLANDS AT TIMES WITH LOCALIZED MVFR/IFR VSBYS AND
CIGS. BLUSTERY NW WINDS ESPECIALLY ON WED.
-- End Changed Discussion --

&&

.MARINE...

FORECASTER CONFIDENCE LEVELS...

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

THROUGH SUNDAY...HIGH CONFIDENCE.

NORTHWEST WINDS TO WHICH AN INFREQUENT GUST EXCEEDING 25 KTS WILL
BE POSSIBLE AROUND MIDDAY INTO AFTERNOON. WINDS DIMINISHING INTO
TONIGHT WITH HIGH PRESSURE BUILDING OUT OF THE WEST. SMALL-CRAFT
ADVISORIES OVER THE OUTER WATERS MAINLY FOR SEAS...BUT WILL KEEP
WITH GENERIC HEADLINES WITH THE THREAT OF WINDS HIGHLIGHTED ABOVE.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

SUN NIGHT...HIGH CONFIDENCE.

WINDS AND SEAS GENERALLY REMAIN BELOW SMALL CRAFT THRESHOLDS
THROUGH THE OVERNIGHT HOURS...ALTHOUGH WINDS SEAS PICK UP TOWARD
DAYBREAK. SOME RAIN/SNOW SHOWERS AND POSSIBLE FOG WILL REDUCE
VSBYS ESPECIALLY AFTER MIDNIGHT.

MONDAY NIGHT INTO TUESDAY NIGHT...MODERATE CONFIDENCE.

EXPECT A PROLONGED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS
THROUGH THE PERIOD. SEAS BUILD TO 5-7 FT UNDER 20-30 KT E TO NE
WINDS INTO THE DAY MON. THE WINDS SHIFT TO THE W MON NIGHT INTO
TUE BUT REMAIN ELEVATED. SEAS DO AS WELL. ESPECIALLY ON THE OCEAN
WATERS. PERIODS OF RAIN AND FOG /ESPECIALLY MON/ REDUCE VSBYS.

WEDNESDAY...MODERATE CONFIDENCE.

AT LEAST SMALL CRAFT ADVISORY LEVEL NW WINDS EXPECTED WED...
ALTHOUGH THERE IS THE POSSIBILITY OF GALE FORCE WIND GUSTS. SEAS
AFTER A SLIGHT DIMINISHING TUE NIGHT...ONCE AGAIN BUILD
PARTICULARLY ON THE OCEAN WATERS...REACHING 6-8 FT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST SUNDAY FOR ANZ250-254>256.

&&

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