Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 282330
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
630 PM EST WED JAN 28 2015

.SYNOPSIS...

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL BUILD OVER NEW
ENGLAND TONIGHT AND THURSDAY...THEN MOVE EAST THURSDAY EVENING.
THIS WILL BRING VERY COLD AIR FOR TONIGHT AND THEN MODERATION ON
THURSDAY. AN ALBERTA CLIPPER WILL MOVE EAST FROM THE PLAINS AND
BRING A CHANCE OF SNOW THURSDAY NIGHT THROUGH FRIDAY NIGHT. VERY
COLD CONDITIONS LINGER THROUGH THE WEEKEND. ANOTHER STORM MAY
BRING SNOW TO THE REGION SUNDAY NIGHT AND MONDAY.

&&

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

630 PM UPDATE...

TEMPERATURE CHANGES MADE ACCORDINGLY FOR THE EXPECTATION THAT AS
WINDS BECOME LIGHT OVERNIGHT AND HIGH PRESSURE BUILDS FROM THE W
THAT IN AREAS OF DEEP SNOWPACK THE TEMPERATURE SHOULD QUICKLY
DROP WITH RADIATIONAL COOLING. EXPECTING LOWS DOWN TO AROUND ZERO
WITH LOCATIONS FALLING A FEW TO SEVERAL DEGREES BELOW-ZERO.

TEMPERATURES ALREADY ON THE DOWNTREND QUICKLY. WITH THE DEEP 20+
INCH SNOWPACK AT OUR OFFICE...IN A LITTLE LESS THAN AN HOUR...THE
TEMPERATURE AT OUR FORECAST OFFICE HAS DROPPED NEARLY 5-DEGREES!

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...

THURSDAY...HIGH PRESSURE OVERHEAD AND LOW DEWPOINTS SHOULD RESULT
IN A DRY WEATHER DAY. AS THE HIGH MOVES OFFSHORE...MOISTURE FROM
THE NEXT SYSTEM WILL START STREAMING IN AT HIGH LEVELS. THE
AFTERNOON SHOULD FEATURE INCREASING/THICKENING HIGH CLOUDS WHICH
MAY DIM THE SUN. TEMPERATURES AT 950 MB WILL BE AROUND -5C AND
WOULD SUPPORT SURFACE MAX TEMPS EITHER SIDE OF 30F. CAPE COD AND
ISLANDS MAY INCH A TAD HIGHER TO THE MID 30S.

THURSDAY NIGHT AND FRIDAY...

WE CONTINUE TO WATCH DISTURBANCES IN BOTH THE NORTHERN AND
SOUTHERN STREAMS WHICH ARE EXPECTED TO PHASE BY THURSDAY AND
EVOLVE INTO AN ELONGATED TROUGH OVER THE EASTERN USA BY FRIDAY.
THE PRIMARY LOW ACTUALLY RACES TOWARD THE GREAT LAKES THURSDAY
NIGHT. BUT THE SOUTHERN UPPER JET CURLS AROUND THE ELONGATED
TROUGH AND EXTENDS ITS LEFT EXIT REGION EITHER OVER OR JUST SOUTH
OF SOUTHERN NEW ENGLAND. THIS SHOULD SUPPORT A COASTAL DEVELOPMENT
OFF OUR COAST ON FRIDAY. A MORE NORTHERLY DEVELOPMENT WOULD FOCUS
LOW LEVEL LIFT AND PRECIPITATION FARTHER NORTH...A MORE SOUTHERLY
DEVELOPMENT WOULD BRING THINGS FARTHER SOUTH. THE GFS SUGGESTS THE
NORTHERN SOLUTION...THE ECMWF AND GGEM DEVELOP THE SECONDARY
SOUTHEAST OF NANTUCKET.

WE HAVE OPTED MORE TOWARD THE SOUTHERN DEVELOPMENT. THIS WOULD
SUPPORT ROUGHLY 0.20 TO 0.30 INCHES OF PCPN DURING THURSDAY NIGHT
AND FRIDAY. THERMAL PROFILES MOSTLY FAVOR SNOW...BUT WITH SOME
POTENTIAL FOR RAIN MIXING IN MIDDAY BEFORE THE SECONDARY DEVELOPS
AND PULLS COLDER AIR IN. THIS SUGGESTS SNOW ACCUMULATIONS OF 2-5
INCHES WITH THE THE EVENTUAL NEED FOR A WINTER WEATHER ADVISORY
WHEN THE STORM GETS CLOSER.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

* SNOW EASTERN AREAS FRI NIGHT DIMINISHES AS LOW EXITS THE AREA
* ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BRISK NW WINDS
* COASTAL STORM POSSIBLE SUN NIGHT-MON, BUT LOW CONFIDENCE

OVERVIEW...LOW PRESSURE CENTER IS EXPECTED TO BE OFF THE MAINE COAST
FRI NIGHT. SNOW IS MOST LIKELY EASTERN AREAS...ESPECIALLY COASTAL
AREAS CLOSER TO THIS LOW SUCH AS BOSTON AND POINTS NORTH. THE
SNOW IS FORECAST TO GRADUALLY WIND DOWN DURING THE NIGHT FRI NIGHT
AS THE LOW PULLS AWAY.

ARCTIC AIR WILL USHER INTO NEW ENGLAND BEHIND THIS DEPARTING LOW FOR
THE WEEKEND WITH BLUSTERY NW WINDS AND FRIGID WIND CHILLS. WINDS
CHILL ADVISORIES MAY BE NEEDED FRI NIGHT.

A MORE VIGOROUS SHORTWAVE DIVES INTO THE EASTERN STATES SUN NIGHT
AND MONDAY. MODELS CONTINUE TO STRUGGLE WITH REGARDS TO THE
AMPLITUDE OF THE TROUGH AND THE CORRESPONDING SURFACE LOW AND TRACK.
THE LATEST 28.12Z OPERATIONAL RUNS OF THE GFS AND ECMWF NOW ARE MORE
PROGRESSIVE AND SHOW A WEAKER SURFACE LOW AND WELL EAST OF THE
BENCHMARK. HOWEVER BOTH MODELS DID JUST THE SAME SEVERAL DAYS
BEFORE OUR RECENT BLIZZARD...SO WE CANNOT HAVE ANY DEGREE OF
CONFIDENCE WITH EITHER A HIT OR A MISS THIS FAR OUT IN TIME. WE
WILL CONTINUE TO USE A MODEL BLEND INCLUDING THEIR ENSEMBLES AS
THERE IS A HIGH DEGREE OF SPREAD AMONGST THEM.

HIGH PRESSURE WILL BUILD INTO THE REGION TUE-WED AS THE
SHORTWAVE/LOW MOVES EAST WITH HIGH PRESSURE TAKING OVER...BRINGING
QUIET WEATHER MID WEEK. YET ANOTHER CHANCE OF SNOW OR A WINTRY
MIX ENTERS THE PICTURE BY THU. AN ACTIVE WINTERTIME PATTERN
INDEED!

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...

FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM...THROUGH TONIGHT...HIGH CONFIDENCE.

0Z UPDATE...NO MAJOR CHANGES MADE.

TONIGHT...VFR. SKC. LIGHT WIND.

THURSDAY...VFR. INCREASING CLOUDS ABOVE 10 THOUSAND FEET. LIGHT
WIND.

THURSDAY NIGHT AND FRIDAY...
CIGS LOWER OVERNIGHT TO MVFR/IFR IN SNOW. SOME RAIN MAY MIX WITH
THE SNOW AT ACK AND HYA. PRECIPITATION STARTS AFTER MIDNIGHT AND
CONTINUES UNTIL FRIDAY AFTERNOON. WINDS SHIFT TO NORTHWEST EARLY
AFTERNOON WITH GUSTS OF 20 TO 25 KNOTS POSSIBLE. SKY CONDITIONS
IMPROVE TO VFR IN THE CT VALLEY AFTER THE WIND SHIFT TO
NORTHWEST...MVFR/IFR SHOULD LINGER IN THE EAST THROUGH EVENING.

KBOS TAF...HIGH CONFIDENCE IN TAF.

KBDL TAF...HIGH CONFIDENCE IN TAF.

OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...

FRIDAY NIGHT...LOW CONFIDENCE. VFR WEST. POSSIBLE IFR TO START
FOR EASTERN LOCALES...BUT WITH IMPROVEMENT EXPECTED OVERNIGHT.

SATURDAY-SUNDAY...HIGH CONFIDENCE. VFR. GUSTY NORTHWEST WINDS
25-35 KNOTS SATURDAY...LIGHTER WINDS SUNDAY.

SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. COASTAL LOW TRACK HIGHLY
UNCERTAIN. JUST WAY TOO EARLY TO HAVE ANY CONFIDENCE ON VFR OR IFR
THIS PERIOD.

&&

.MARINE...

FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM/TONIGHT THROUGH FRIDAY/...HIGH CONFIDENCE TONIGHT AND
THURSDAY...MODERATE CONFIDENCE THURSDAY NIGHT AND FRIDAY.

630 PM UPDATE...NO MAJOR CHANGES.

TONIGHT...DIMINISHING NORTHWEST WIND. DIMINISHING FREEZING SPRAY
POTENTIAL. GUSTS AT LAND STATIONS ARE BELOW 25 KNOTS. BUOY 013
EAST OF BOSTON HAD GUSTS TO 23 KNOTS AT 3 PM. STILL ROUGH SEAS
WITH 5-8 FEET ON THE OUTER WATERS AS WELL AS PARTS OF CAPE COD BAY
AND MASSACHUSETTS BAY. WE WILL KEEP THE SMALL CRAFT ADVISORY IN
EFFECT FOR THESE WATERS THROUGH THE PART OR ALL OF THE NIGHT.

THURSDAY...HIGH PRESSURE BUILDS OVER THE WATERS. THIS SHOULD BRING
LIGHT WIND WHICH WILL ALLOW SEAS TO SUBSIDE. A SMALL CRAFT
ADVISORY WILL LINGER INTO THE MORNING ON THE OUTER WATERS EAST OF
MASSACHUSETTS.

THURSDAY NIGHT-FRIDAY...LOW PRESSURE FROM THE MIDWEST WILL
REDEVELOP OVER THE COASTAL WATERS FRIDAY. SNOW WILL MOVE IN AFTER
MIDNIGHT AND THROUGH THE MORNING FRIDAY WITH REDUCED VISIBILITY.
SOUTH WINDS WILL SLOWLY INCREASE WITH GUSTS TO 20 KNOTS BY FRIDAY
MORNING. WINDS WILL THEN SHIFT TO NORTHWEST FRIDAY AFTERNOON WITH
POTENTIAL FOR 30 KNOT GUSTS BY EVENING.

OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE FRI-
SAT...LOW CONFIDENCE SUN-MON.

FRIDAY...LOW PRES WILL CROSS THE WATERS. EXPECT REDUCED VSBYS IN
SNOW. EXPECT WINDS TO SHIFT TO NW AND INCREASE FRI NIGHT...WITH
GALES POSSIBLE OVER THE WATERS. FREEZING SPRAY WILL LIKELY DEVELOP
FRI NIGHT.

SATURDAY...NW GALES EXPECTED WITH POTENTIAL FOR FREEZING SPRAY. HIGH
SEAS FORECAST...10-12 FT OFFSHORE WATERS. WINDS WILL BEGIN TO
DIMINISH SAT NIGHT WITH A CORRESPONDING LOWERING OF SEAS.

SUNDAY...WINDS AND SEAS AT SMALL CRAFT ADVISORY LEVELS EARLY
SUNDAY...BUT WILL DIMINISH THROUGH THE DAY.

SUNDAY NIGHT-MONDAY...MUCH WILL DEPEND ON STRENGTH AND TRACK OF A
POSSIBLE COASTAL LOW SO TAKE THE OFFICIAL FORECAST OF WINDS/SEAS
DURING THIS PERIOD WITH A GRAIN OF SALT. A LOW CLOSER TO THE COAST
WOULD SPELL A SIGNIFICANT IMPACT TO MARINERS...WHILE AN
OFFSHORE/WEAKER TRACK WOULD HAVE MUCH LESS IMPACT. TOO EARLY TO
SAY EITHER WAY...SO WENT WITH A MODEL BLEND.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR ANZ231-251.
     SMALL CRAFT ADVISORY UNTIL NOON EST THURSDAY FOR ANZ250-254.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ255-256.

&&

$$

SYNOPSIS...WTB/SIPPRELL/GREGORIA
NEAR TERM...WTB/SIPPRELL/GREGORIA
SHORT TERM...WTB
LONG TERM...GREGORIA
AVIATION...WTB/SIPPRELL/GREGORIA
MARINE...WTB/GREGORIA



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