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Area Forecast Discussion
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000
FXUS61 KBOX 180300
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1000 PM EST WED DEC 17 2014

.SYNOPSIS...

SCATTERED RAIN OR SNOW SHOWERS ARE POSSIBLE TONIGHT AS AN UPPER
LEVEL DISTURBANCE CROSSES NEW ENGLAND. HIGH PRESSURE WILL SLOWLY
PASS ACROSS NORTHERN NEW ENGLAND LATE THIS WEEK...BRINGING DRY AND
SEASONABLE CONDITIONS. LOW PRESSURE WILL PASS WELL SOUTH OF THE
REGION...BRINGING A PERIOD OF SCT RAIN AND/OR SNOW SHOWERS THIS
WEEKEND INTO EARLY NEXT WEEK. STRONGER LOW PRESSURE WELL WEST OF
NEW ENGLAND LOOKS TO BRING RAIN AND GUSTY ONSHORE WINDS THE MIDDLE
OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

10 PM UPDATE...

A FEW RETURNS SHOWING UP ON RADAR THIS EVENING.  MAINLY JUST A FEW 
RAIN SHOWERS GIVEN MILD BOUNDARY LAYER TEMPS...BUT A FEW WET SNOW 
FLAKES PROBABLY OCCURRING ACROSS THE HIGHER TERRAIN.

MAIN SHORTWAVE SWEEPS ACROSS THE REGION BETWEEN 6Z AND 12Z THU.  THE 
BEST MOISTURE/FORCING WILL BE ACROSS OUR NORTHERN ZONES...SO WILL 
HAVE THE HIGHEST POPS NORTH OF MA TURNPIKE.  HOWEVER...ENOUGH 
FORCING FOR A FEW RAIN/SHOWERS ACROSS NORTHERN CT/RI/SOUTHERN MA.  

AS FOR PTYPE...MAINLY SCATTERED SNOW SHOWERS ACROSS THE HIGHER 
TERRAIN.  IN THE LOWER ELEVATIONS AND COASTAL PLAIN...BOUNDARY LAYER 
WILL BE MILD ENOUGH FOR RAIN SHOWERS INITIALLY.  MAY SEE THESE AREAS 
MIX WITH OR CHANGE TO A FEW SNOW SHOWERS TOWARD DAYBREAK AS TEMPS 
COOL A BIT.

SNOW ACCUMULATIONS OF A COATING TO LESS THAN 1 INCH ARE POSSIBLE 
ACROSS PORTIONS OF THE HIGHER TERRAIN...BUT DO NOT SEE MUCH MORE 
THAN THAT.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
EXPECT TO SEE FEW LINGERING SNOW SHOWERS THU MORNING ACROSS NE MA
AS SYSTEM DEPARTS. OTHERWISE DRY WEATHER WILL PREVAIL THU AND THU
NIGHT.

GUSTY W/NW WINDS /30-35 MPH/ ANTICIPATED AS A RESULT OF LOW
PRESSURE DEEPENING OVER MARITIMES. THIS SHOULD HELP TO SCOUR OUT
CLOUDINESS A BIT...BUT DO NOT EXPECT TOTAL CLEARING AS UPPER
TROUGH STILL HANGS BACK FROM NEW ENGLAND TO GREAT LAKES...EVEN
THROUGH THU NIGHT.

STAYED CLOSE TO BLEND OF MODEL GUIDANCE WHICH RESULTS IN HIGHS
FROM UPPER 30S NW TO MID 40S SE THU...AND LOWS MAINLY IN 20S THU
NIGHT.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
HIGHLIGHTS...

* DRY WEATHER AND NEAR OR SLIGHTLY BELOW TEMPS FOR FRIDAY AND SAT
* LOW PRESSURE WILL PASS S OF NEW ENGLAND THIS WEEKEND...BUT WILL 
  STILL SEE SCT LIGHT RAIN AND/OR SNOW SHOWERS
* STRONGER LOW PRESSURE DEVELOPING WELL WEST OF THE REGION LOOKS TO 
  BRING PERIODS OF HEAVY RAIN AND GUSTY WINDS BY CHRISTMAS EVE 

OVERVIEW AND MODEL PREFERENCES...
12Z MEDIUM RANGE MODEL SUITE WAS IN GENERALLY GOOD AGREEMENT...
THOUGH TIMING AND TRACK ISSUES DID COME INTO PLAY FOR WEAK LOW
PRES PASSING WELL S OF THE REGION SUN NIGHT/MON...THEN WITH THE
STRENGTHENING LOW PRES CENTER ACROSS THE GREAT LAKES ASSOCIATED
WITH A LONG WAVE NEG TILT TROUGH WHICH WILL WRAP IN MOISTURE BY
AROUND CHRISTMAS EVE DAY.

MID AND UPPER LEVEL STEERING CURRENTS REMAIN IN A SPLIT FLOW
ACROSS NORTH AMERICA EARLY IN THIS FORECAST CYCLE. MODELS IN VERY
GOOD AGREEMENT THAT THIS PATTERN EVOLVES INTO AN AMPLIFIED
TROUGH/RIDGE SET UP...WITH LONG WAVE TROUGH DIGGING THROUGH THE
CENTRAL U.S. TO THE WESTERN GULF OF MEXICO COAST BY EARLY NEXT
WEEK. 12Z ECMWF AND GFS BOTH CONTINUE TO EVOLVE CUTOFF H5 LOW
PRES...WHICH WILL CAUSE THE LONG WAVE TROUGH TO BECOME NEGATIVELY
TILTED ACROSS THE SE U.S. WHILE BOTH MODELS DID SIGNAL THIS
EVOLUTION...TIMING IS IN QUESTION...ESPECIALLY WITH THE
DEVELOPMENT OF LOW PRES AND A SLUG OF HEAVY RAINFALL MOVING UP
THE EASTERN SEABOARD WITH THE POSSIBILITY OF SOME MIXED PRECIP TO
START WELL INLAND AROUND TUESDAY THAT WILL CHANGE TO RAIN WITH
GUSTY EAST TO SOUTHEAST WINDS BRINGING MILDER AIR BY CHRISTMAS EVE
DAY.

ONE THING TO NOTE ON THIS PATTERN EVOLUTION...CONSIDERING WE ARE
TALKING ABOUT A SYSTEM ABOUT A WEEK AWAY...THE 12Z GFS/EC OP RUNS
WERE RATHER CLOSE WITH THE STRENGTH OF THE PARENT LOW OVER THE
OHIO VALLEY MOVING INTO THE GREAT LAKES EARLY NEXT WEEK.
HOWEVER...THERE ARE TIMING AND TRACK ISSUES FOR THE LATE MON-WED
TIMEFRAME OF THE LOW AND SHORT WAVE WRAPPING AROUND IT WHICH LOOKS
TO AFFECT THE REGION...WHICH LENDS TO SOMEWHAT LOWERED CONFIDENCE.
DO FEEL THERE IS A GOOD SHOT FOR PRECIP...IT IS A MATTER OF THE
ONSET AND ENDING OF THIS PRECIP. SO...LEANED TOWARD THE WPC
GUIDANCE AS WELL AS BLEND OF THE GFS/EC ENSEMBLES ALONG WITH A BIT
OF THE GFS/EC OP RUNS.

DETAILS...
 
FRIDAY AND SATURDAY...HIGH CONFIDENCE.
AS UPPER LOW MOVES INTO THE MARITIMES EARLY FRIDAY...UPPER LEVEL
RIDGE AND BUBBLE CUTOFF HIGH OVER CENTRAL CANADA WILL SHIFT ACROSS
QUEBEC DURING THIS TIMEFRAME. ASSOCIATED SURFACE HIGH WILL SLOWLY
SHIFT E AS WELL...BRINGING MAINLY DRY CONDITIONS FRIDAY INTO EARLY
SATURDAY. EXPECT TEMPS TO RUN CLOSE TO OR SLIGHTLY BELOW SEASONAL
NORMS.

DURING MID TO LATE SATURDAY...AS THE AXIS OF THE HIGH PASSES OVER
SOUTHERN QUEBEC...WINDS SHIFT TO E-NE. ALL MEDIUM RANGE MODELS
BRING LIGHT PRECIP TOWARD THE COAST BY SATURDAY EVENING AND...WITH
MARGINAL TEMPS AWAY FROM THE COAST...HAVE INCLUDED SLIGHT CHANCE
TO LOW CHANCE POPS FOR RAIN AND/OR SNOW SHOWERS WITH THE BEST SHOT
RIGHT ALONG THE COAST. MAY ALSO SEE PATCHY DRIZZLE AND FOG
DEVELOP.

LOW PRES WILL APPROACH THE MID ATLC COAST LATE SAT NIGHT...SO
APPEARS SOME MOISTURE FROM THIS SYSTEM WILL WORK N INTO CT/S RI
DURING THE PRE-DAWN HOURS...SO COULD SEE SOME SCT RAIN/SNOW
SHOWERS THERE.

SUNDAY AND MONDAY...LOW TO MODERATE CONFIDENCE. 
THIS WAS A TOUGH PORTION OF THE FORECAST AS PATTERN BEGINS TO
UNDERGO CHANGE TO THE WEST. A RATHER FLAT SHORT WAVE WORKS OFF THE
MID ATLC COAST WITH ASSOCIATED SURFACE REFLECTION. THIS SYSTEM OUT
OF THE SOUTHERN STREAM DOES NOT LOOK TO PHASE UP WITH ANYTHING IN
THE NORTHERN STREAM. HOWEVER...WILL STILL SEE PERIODS OF SCT RAIN
AND/OR SNOW SHOWERS WITH THE CONTINUED ONSHORE FLOW AS THIS
SOUTHERN LOW SLOWLY SHIFTS OFFSHORE WHILE THE HIGH TO THE N SLOWLY
MOVES E AS THE OVERALL STEERING PATTERN SLOWS DOWN AND BECOMES
MORE AMPLIFIED WITH THE DIGGING LONG WAVE TROUGH OVER THE CENTRAL
U.S.

WITH THE ONSHORE WINDS...EXPECT ANY MIXED RAIN/SNOW TO CHANGE TO 
RAIN ACROSS EASTERN MA/RI/PORTIONS OF N CT...WHILE SCT LIGHT SNOW 
SHOWERS CONTINUE INLAND. NOT MUCH IN THE WAY OF QPF...SO NOT 
EXPECTING TOO MUCH SNOW ACCUMULATIONS MAINLY ACROSS THE HIGHER 
INLAND TERRAIN. EXPECT HIGHS BOTH DAYS IN THE MID-UPPER 30S WELL 
INLAND TO THE MID 40S ALONG THE COAST.

TUESDAY AND WEDNESDAY...LOW CONFIDENCE...MAINLY FOR TIMING. 
ANOTHER LOW THAT DEVELOPS ACROSS THE EASTERN GULF OF MEXICO WILL
PASS WELL S OF THE REGION DURING TUESDAY...BUT WILL KEEP EASTERLY
WINDS IN PLACE. THIS WILL ALSO KEEP THE CHANCE FOR LIGHT PRECIP
ACROSS THE REGION. NOTING SOME PLACEMENT ISSUES FOR THE AXIS OF
THIS MOISTURE AND HOW FAR N IT WILL SHIFT FROM THE SECOND PASSING
LOW. WITH CONTINUED ONSHORE FLOW...TEMPS WILL BE A LITTLE BIT
MILDER WITH HIGHS FROM THE UPPER 30S OVER THE HIGHEST INLAND
TERRAIN TO THE MID AND UPPER 40S ALONG THE S COAST.

IN THE MEANTIME...THE UPPER LEVEL PATTERN WILL TAKE SHAPE BY
TUESDAY ACROSS THE CENTRAL U.S...WITH LONG WAVE TROUGH DIGGING TO
THE GULF OF MEXICO. H5 CUTOFF LOW FORMS ACROSS THE UPPER MID WEST
/THOUGH PLACEMENT ISSUES IN PLAY/...WHILE SURFACE LOW PRES FORMS
ACROSS THE MISSISSIPPI VALLEY. THE UPPER TROUGH BECOMES NEGATIVELY
TILTED BY 12Z WED...WHICH WILL ALLOW THE SURFACE SYSTEM TO DEEPEN
AS IT ROTATES ACROSS WESTERN PA/CENTRAL VA. A SLUG OF QPF...TAPPED
FROM THE TROPICS...WILL SHIFT UP THE EASTERN SEABOARD DURING WED.
NOTED PWATS ON ORDER OF 1.3 TO 1.4 INCHES...WHICH IS ABOUT +2 SD
ABOVE SEASONAL NORMALS FOR MID TO LATE DECEMBER. WILL ALSO SEE
E-SE WINDS INCREASE WITH STRONG LOW LEVEL JET WORKING UP THE COAST
/H85 WINDS BRIEFLY INCREASE TO 60-70 KT AS JET CROSSES DURING
WED/.

HAVE PRETTY GOOD CONFIDENCE IN PRECIP MOVING IN DURING WEDNESDAY
INTO CHRISTMAS EVE AS MODELS CONTINUE TO SIGNAL THIS...BUT BIG
QUESTION WILL BE THE ONSET AND ENDING OF THIS SLUG OF PRECIP.
ALSO...SINCE TEMPS WILL BE CHILLY TO START WELL INLAND...WILL SEE
PERIOD OF MIXED PRECIP THERE TO START BEFORE CHANGING OVER TO
RAIN. HAVE CARRIED LIKELY POPS FOR THIS TIMEFRAME...THOUGH STILL
QUESTIONS ON EXACT TIMING. TEMPS WILL RISE WITH THE INCREASING
ONSHORE FLOW... LIKELY TO AS MUCH AS 10 DEGREES ABOVE SEASONAL
NORMS.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
FORECASTER CONFIDENCE LEVELS...

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

10 PM UPDATE...

SHORT TERM /THROUGH THURSDAY NIGHT/...MODERATE CONFIDENCE.

TONIGHT...MAINLY VFR CIGS OVERNIGHT.  PERIOD OF MVFR CONDITIONS 
POSSIBLE IN SCATTERED RAIN/SNOW SHOWERS...WITH THE BEST CHANCE 
NORTH OF THE MA TURNPIKE.

THURSDAY...VFR CIGS DOMINATE AFTER LEFTOVER MVFR CIGS DURING
MORNING...PERHAPS SCATTERED RAIN/SNOW SHOWERS ACROSS NE MA. NW
WINDS GUST AS HIGH AS 25-30 KT.

THURSDAY NIGHT...VFR. NW WIND GUSTS TO 25 KT ACROSS CAPE COD AND
ISLANDS EARLY.

KBOS TERMINAL...MODERATE CONFIDENCE.  A BRIEF PERIOD OF MVFR 
CONDITIONS ARE POSSIBLE IN A FEW RAIN/SNOW SHOWERS BETWEEN 8Z AND 
12Z.

KBDL TERMINAL...HIGH CONFIDENCE. 

OUTLOOK...FRIDAY THROUGH MONDAY...

FRIDAY...HIGH CONFIDENCE. VFR.

SATURDAY...LOW TO MODERATE CONFIDENCE. VFR TO START...THEN 
DEVELOPING MVFR CONDITIONS ESPECIALLY ACROSS THE COAST MAINLY SAT 
AFTERNOON/NIGHT.

SUNDAY AND MONDAY...LOW CONFIDENCE. LOW END VFR TO MVFR CIGS. PATCHY 
MVFR TO LOCAL IFR VSBYS IN SCT RAIN AND/OR SNOW SHOWERS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...MODERATE CONFIDENCE.

SCA REMAINS POSTED FOR ALL WATERS THROUGH THU...AND FOR OUTER
WATERS THROUGH THU NIGHT. LOW PRESSURE DEEPENING OVER MARITIMES
WILL RESULT IN STRONG W/NW WINDS ACROSS WATERS...SOLIDLY 25-30KT
GUSTS WITH OUTSIDE CHANCE OF SOME 35KT GUSTS ON OUTER WATERS. HOWEVER
WE ARE NOT CONFIDENT ENOUGH TO UPGRADE TO GALE WARNINGS AT THIS
TIME. PEAK GUSTS SHOULD OCCUR LATE TONIGHT THROUGH THU AFTERNOON.
WINDS GRADUALLY SUBSIDE THU NIGHT BUT SEAS WILL TAKE A BIT LONGER
TO DIMINISH.

MAY SEE SCATTERED RAIN/SNOW SHOWERS ON E MA WATERS LATE TONIGHT
INTO THU MORNING...ESPECIALLY NEAR CAPE ANN AND MERRIMACK RIVER.

OUTLOOK...FRIDAY THROUGH MONDAY...

MODERATE TO HIGH CONFIDENCE THROUGH SUNDAY...THEN LOW CONFIDENCE 
MONDAY.

FRIDAY...NW WIND GUSTING UP TO 20 KT. SEAS START OFF AROUND 5 FT 
ACROSS THE OUTER WATERS EARLY FRI...BUT SHOULD SUBSIDE BY FRI 
EVENING.

SATURDAY AND SUNDAY...WINDS AND SEAS BELOW SMALL CRAFT CRITERIA. 
WIND SHIFT TO E-NE DURING SUN AND SEAS BUILD UP TO 4 FT ON THE OUTER 
WATERS. 
 
MONDAY...EXPECT NE WINDS GUSTING UP TO 20 KT. LOW PROB OF 25 KT 
GUSTS AS WELL AS 5 FT SEAS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THURSDAY FOR ANZ230-
     232>237.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ231-250-251-
     254>256.

&&

$$
SYNOPSIS...EVT/JWD
NEAR TERM...FRANK
SHORT TERM...JWD
LONG TERM...EVT
AVIATION...FRANK/EVT/JWD
MARINE...EVT/JWD



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