Area Forecast Discussion
Issued by NWS Boston, MA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KBOX 021500
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1000 AM EST MON MAR 2 2015

.SYNOPSIS...
DRY AND BLUSTERY WEATHER FOLLOWS BEHIND THE PASSAGE OF A COLD FRONT
EARLY THIS MORNING. LOW PRESSURE FROM NORTHERN CANADA AND
ASSOCIATED LOW FORMING OVER THE PLAINS MONDAY WILL MERGE...THEN
PASS WEST AND NORTH OF NEW ENGLAND. THIS WILL BRING ABOUT A WINTRY
MIX...CHANGING TO RAIN LATE TUESDAY INTO WEDNESDAY. DRY AND COLD
WEATHER RETURNS FOR THE END OF THE WEEK.

&&

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

1000 AM UPDATE...

COLD FRONT HAS BEGUN TO MOVE INTO SOUTHERN NEW ENGLAND PER VWP
PROFILES. THIS FRONT IS FAIRLY ROBUST SO EXPECT ANOTHER SURGE OF
COLD AIR BEHIND IT. AS THE FRONT MOVES THROUGH...SOME LIGHT SNOW
SHOWERS AND/OR FLURRIES WILL SKIRT ACROSS THE REGION. OVERALL IT
WILL GENERALLY BE DRY AS TEMP/DEWPOINT DEPRESSION WILL RISE AS
HIGH MARCH SUN ANGLE WILL WARM THE REGION UP INTO THE MID TO UPPER
30S. HOWEVER IT WILL FEEL COOLER AS WIND WILL INCREASE THROUGHOUT
THE DAY. 925 MB JET OF 30-40 KTS WILL MOVE THROUGH ALLOWING FOR
ABOUT 30-40 MPH GUSTS TODAY. THIS WILL KEEP WIND CHILL VALUES
AROUND 20-28F. FINALLY WE SHOULD SEE PARTIAL SUNSHINE...BUT ALSO
A LOT OF STRATO-CUMULUS CLOUDS ESPECIALLY ACROSS THE INTERIOR.

MADE ONLY MINOR TWEAKS TO THE ONGOING FORECAST TO ACCOUNT FOR
FLURRIES/LIGHT SNOW POTENTIAL. OTHERWISE FORECAST REMAINS ON TRACK
FOR TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
TONIGHT...

A LARGE HIGH PRESSURE SYSTEM BUILDS IN FROM THE WEST.  DIURNAL
CUMULUS CLOUDS WILL DISSIPATE THIS EVENING...RESULTING IN MAINLY
CLEAR SKIES.  WINDS WILL ALSO GRADUALLY DIMINISH AND EVENTUALLY
DECOUPLE IN THE TYPICAL LOCATIONS.  THIS SHOULD ALLOW LOW TEMPS TO
FALL WELL DOWN INTO THE SINGLE DIGITS TO EVEN BELOW ZERO IN THE
NORMALLY COLDEST OUTLYING LOCATIONS.  MEANWHILE...URBAN CENTERS OF
DOWNTOWN BOSTON/PROVIDENCE WILL SEE LOW TEMPS IN THE MIDDLE TEENS.

TUESDAY...

HIGH PRESSURE WILL MOVE EAST OF THE REGION AS LOW PRESSURE TRACKS
TOWARDS THE GREAT LAKES.  PLENTY OF SUNSHINE IN THE MORNING WILL
GIVE WAY TO MOSTLY CLOUDY SKIES TUE AFTERNOON.  DRY WEATHER SHOULD
PREVAIL EVERYWHERE THROUGH MID AFTERNOON...BUT WARM ADVECTION OVER
THE COLD DOME SHOULD ALLOW LIGHT SNOW TO DEVELOP BY LATE AFTERNOON
OR EARLY EVENING ACROSS WESTERN MA/NORTHERN CT.  HIGH TEMPS AROUND
30 TO THE LOWER 30S...BUT WITH MUCH LESS WIND THEN TODAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
OVERVIEW AND MODEL PREFERENCES...
LONGWAVE E CANADIAN TROF REMAINS THE DOMINANT FEATURE DEFINING
THE DAILY SENSIBLE WX ACROSS THE NORTHEAST. GIVEN AO/NAO REMAIN
MOSTLY NEGATIVE AND PNA SHIFTS FROM NEGATIVE TO NEAR
NEUTRAL..SUSPECT LITTLE CHANGE WITH THIS FEATURE AT LEAST THROUGH
THE LONG TERM. THEREFORE...EXCEPT WHERE THE SRN STREAM DOMINATES
COMING OUT OF A SPLIT ROW REGIME UPSTREAM..EXPECT MAINLY BELOW
NORMAL TEMPERATURES THROUGH AT LEAST THIS COMING WEEKEND. THE ONE
CAVEAT...A PHASING OF STREAMS AS NRN AND SRN STREAM WAVES MERGE IN
THE MIDDLE OF THE WEEK IS A TRICKY FORECAST...AS THE MID LVL
WARMING IS LIKELY TO OCCUR MUCH FASTER THAN LOW LVL WARMING THANKS
TO ENTRENCHED COLD AIR AND A DEEP SNOWPACK ACROSS THE REGION ARE
LIKELY TO SLOW WARM ADVECTION NEAR THE SFC. A MIXED PRECIP EVENT
IS LIKELY...BUT NAM/GFS REMAIN COLDER WHILE ECMWF REMAINS THE MORE
AMPLIFIED /STARTING COLDER...BUT ENDING WARMER/ THAN THE REST OF
THE GUIDANCE. ECMWF HAS COOLED A BIT THOUGH...LENDING SOME
CONFIDENCE TO THE FACT THAT A BLEND OF THE ENSEMBLES /COOLER THAN
THE ECMWF BUT WITH SOME WEIGHT TOWARD A WARMER SOLUTION/ WOULD BE
THE BEST STARTING POINT FOR THIS PARTICULAR FORECAST. THIS
ENSEMBLE BLEND WORKS WELL FOR THE REMAINDER OF THE FORECAST AS
WELL.

DETAILS...

TUE NIGHT INTO WED...
OVERVIEW...
WITH A MERGER OF THE NRN STREAM /COLD AIR/ AND THE SRN STREAM
/MORE MOISTURE AND WARMER AIR/ AS WELL AS A ROBUST 50+ KT H92 LLJ
WILL LEAD TO STRONG ISENTROPIC LIFT AND OVERRUNNING AS ATTENDANT
LOW PRES PASSES N OF THE REGION. MOISTURE THROUGH THE COLUMN IS
RATHER HIGH...PWATS 2+ STD DEVIATIONS ABOVE NORMAL ARE LIKELY
GIVEN THE SRN STREAM CONNECTION. WITH COLD AIR TO START...H92
TEMPS START ABOUT -6C AND H85 TEMPS START ABOUT-8C TUE
EVENING...WARM ADVECTIVE OVERRUNNING WILL START AS SHIELD OF
MODERATE SNOWFALL..SLR/S WILL BE GRADUALLY BECOMING LOWER HOWEVER
AS WARM AIR MOVES LIFTS THE DENDRITE ZONE OUT OF PEAK OMEGA. THE
ONLY FIGHTING CHANCE THE SNOW WILL HAVE INITIALLY IS UPPER LVL
INSTABILITY WHERE H7-H4 LAPSE RATES INCREASE. THIS MAY AID THE
LIFT SOMEWHAT AND PRODUCE ENOUGH DYNAMIC COOLING TO OVERCOME THE
WARMING INITIALLY...BUT IT APPEARS THE MID LVL WARM AIR WILL WIN
EVENTUALLY. WHAT THIS ALL MEANS IS THAT MODERATE TO HEAVY PRECIP
WILL START AS SNOW...AND GRADUALLY TRANSITION TO A WINTRY MIX OF
SLEET AND FREEZING RAIN...FOLLOWED BY ALL RAIN INTO THE DAY ON WED
AS MID LVL TEMPS WARM INTO THE POSITIVE DIGITS.

TIMING...
SNOW WILL BEGIN LATE TUE IN WRN MA AND CT...THEN SPREAD E THROUGH
THE LATE AFTERNOON AND EVENING HOURS. NOT OUT OF THE QUESTION A
PERIOD OF 1+ INCH/HOUR RATES ARE OBSERVED GIVEN THE LIFT. THE SNOW
WILL BECOME HEAVIER AND WETTER AS TIME PROGRESSES THROUGH THE
OVERNIGHT. IT APPEARS...EVEN IN THE COLDER SOLUTIONS THAT A
GRADUAL TRANSITION TO SLEET THEN FREEZING RAIN OCCURS MAINLY 10PM
TO 4AM WED. HOWEVER...WITH DEEP SNOW...ANY RAIN COULD FREEZE ON
CONTACT AS SFC TEMPS ARE LIKELY TO STAY A BIT COLDER THAN 2M
TEMPS. THEREFORE...COULD SEE ICE ACCRETION EVEN AS OBSERVED TEMPS
SHIFT INTO THE MID-UPPER 30S...AND LINGER INTO MORNING HOURS WED.
HOWEVER...DRIER AND COOLER AIR WILL BE ATTEMPTING TO SHIFT IN
DURING THE DAY AS A TRANSITION TO STRAIGHT RAIN OCCURS...SUCH THAT
A LULL IN PRECIP IS POSSIBLE BY AFTERNOON. OTHERWISE...EXPECT
MAINLY RAIN DURING THE MORNING WED.

PRECIP TYPE/TOTALS...
THE INITIAL SNOWFALL IS LIKELY TO BE MAINLY MODERATE...WITH
PERIODS APPROACHING AN INCH/HOUR AND WELL END FIRST ALONG THE S
COAST AND LAST AT THE MA/NH BORDER IN THE EARLY MORNING HOURS WED.
SUSPECT THAT HIGHEST TOTALS WILL BE IN NW MA WHERE OROGRAPHIC LIFT
ENHANCES SNOWFALL RATES. ACCUMS OF ADVISORY LVL LOOK LIKELY AS
0.25-0.5 INCHES OF QPF ARE LIKELY BEFORE THE CHANGE. INITIALLY A
CHANGE TO SLEET IS EXPECTED IN HIGHER RETURNS...WITH A GRADUAL
SHIFT TO FREEZING RAIN. ICE AMOUNTS ARE TRICKY...AS 2M TEMPS ARE
LIKELY TO SKEW DATA. WITH DEEP SNOWPACK IN PLACE...WILL LIKELY SEE
SOME ICE ACCRETION APPROACHING T-0.1 INCHES IN SPOTS...ESPECIALLY
ON TOP OF THE AREA SNOWS. GRADUALLY...THE WARMING WILL LIKELY
SHIFT INTO THE 40S /ESPECIALLY AFTER DAYLIGHT WED/ AND FURTHER
ACCRETION WILL BECOME LIMITED.

OTHER IMPACTS TO CONSIDER...
THE LOWER SLR /HEAVIER-WETTER/ NATURE OF THE SNOW WILL EXACERBATE
ROOF LOADING...AND IT ONLY GET/S WORSE WITH THE POTENTIAL FOR SOME
HEAVY ICE ON TOP AND SOME LIQUID WATER GETTING INTO THE SNOWPACK.
THEREFORE...THERE IS THE RISK FOR FURTHER ROOF COLLAPSES IF NOT
TAKEN CARE OF. ALSO...AS A TRANSITION TO RAIN OCCURS...WILL LIKELY
SEE A FAIR AMOUNT OF ROADWAY PONDING AND NUISANCE POOR DRAINAGE
FLOODING ESPECIALLY DURING THE MORNING WED AS SOME SNOWMELT
OCCURS AND DRAINS CLOG. NOT EXPECT MUCH IN THE WAY OF RIVERINE OR
STREAM FLOODING AS THE SNOWPACK SHOULD EASILY HANDLE THE 1.00
INCHES OF TOTAL QPF EXPECTED. STAY TUNED FOR FURTHER DETAILS AS WE
APPROACH.

WED NIGHT INTO THU...
ANOTHER PERIOD TO WATCH. THE LEFTOVER COLD FRONTAL BOUNDARY
SHIFTS OFFSHORE LEADING TO A LULL WED AFTERNOON INTO WED EVENING.
HOWEVER...MODELS CONTINUE TO HINT AT REASONABLY ROBUST ANAFRONTAL
LOW PRES WAVE TRAVERSING THE FRONT LATE WED NIGHT INTO THU. THIS
IS SOMEWHAT ATYPICAL TO SEE ONE OF THIS STRENGTH...BUT GIVEN THE
UPPER LVL SHORTWAVE WILL BE ROTATING OVER FROM THE W AND
DEEPENING SOME...IT CAN/T BE RULED OUT. THE BIG QUESTION HERE IS
WHAT THE TEMPS WILL BE BY THIS TIME. WED COULD BE VERY WARM
ESPECIALLY IF ANY SUNNY BREAKS ARE OBSERVED AND W WINDS ARE
EXPECTED BY THE AFTERNOON. HOWEVER...BY THE OVERNIGHT
PERIOD...COLD ADVECTION WILL HAVE BEGUN ALOFT...LOWERING THE
DENDRITE ZONE. THEREFORE...YET ANOTHER ROUND OF LIGHT TO MODERATE
SNOW IS POSSIBLE...WITH ACCUMS POSSIBLY REACHING ADVISORY LVL ON
TOP OF THE SNOW AND ICE FROM THE PREVIOUS 24 HOURS. QPF VALUES OF
0.3-0.5 ARE PROGGED...WHICH WOULD SUGGEST EASY ACCUMS TO ADVISORY
LVL. IT APPEARS THE PEAK WOULD BE MAINLY ALONG THE S COAST...AT
LEAST THAT/S WHERE F-GEN AND MOISTURE SEEM TO BE MOST COINCIDENT.

THU NIGHT INTO FRI...
STRONG ARCTIC HIGH PRES MAKES A TRIUMPHANT RETURN TO THE REGION
AS 1040+HPA IN THE MASS FIELDS COMBINE WITH -20C H85 TEMPS. EXPECT
ANOTHER PERIOD OF COLD WITH POTENTIAL FOR SUB-ZERO NIGHTS AND
HIGHS WELL BELOW NORMAL. IN FACT...CAN/T RULE OUT THE POTENTIAL
NEED FOR WIND CHILL HEADLINES THU NIGHT AS THIS IS WHEN PRES
GRADIENT APPEARS STRONG ENOUGH TO SUPPORT IT.

NEXT WEEKEND...
LOOKS MAINLY DRY AS HIGH PRES REMAINS IN CONTROL COULD SEE A WEAK
UPPER DISTURBANCE AND ATTENDANT COLD FRONT ATTEMPT TO MAKE A
PASSAGE. HOWEVER...VERY DRY AIRMASS IN PLACE COULD PREEMPT ANY
PRECIPITATION ATTEMPTS.

EARLY NEXT WEEK...
HINTS AT ANOTHER POTENTIAL MODERATE LOW PRES WITH PRECIP IN
TOW...HOWEVER LOTS OF UNCERTAINTY AS TO TIMING OR P-TYPES AT THIS
TIME.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY THROUGH TUESDAY/...

TODAY...HIGH CONFIDENCE.
LAST OF THE IFR CONDITIONS ON CAPE/ISLANDS DISSIPATES BY 13-14Z.
VFR...PATCHY MVFR OTHERWISE. WIND GUSTS PICK UP LATER THIS
MORNING WITH GUSTS 25-35 KT EXPECTED THIS AFTERNOON AND EVENING
OUT OF THE W.

TONIGHT...HIGH CONFIDENCE.  WINDS GRADUALLY DIMINISH THIS EVENING
WITH VFR CONDITIONS CONTINUING.

TUESDAY...MODERATE TO HIGH CONFIDENCE.  VFR CONDITIONS
THROUGH AT LEAST MID AFTERNOON.  MVFR-IFR CONDITIONS MAY DEVELOP BY
LATE TUE AFTERNOON OR EARLY TUE EARLY EVENING ACROSS WESTERN
MA/NORTHERN CT AS LIGHT SNOW DEVELOPS.

KBOS TAF...HIGH CONFIDENCE.  NORTHWEST WIND GUSTS OF 25 TO 35 KNOTS
DEVELOP LATER THIS MORNING AND CONTINUE INTO THE AFTERNOON.

KBDL TAF...HIGH CONFIDENCE.  NORTHWEST WIND GUSTS OF 25 TO 35 KNOTS
DEVELOP LATER THIS MORNING AND CONTINUE INTO THE AFTERNOON.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...

TUE NIGHT INTO WED...HIGH CONFIDENCE.
PERIODS OF IFR AND OCCASIONAL IFR POSSIBLE. SNOW TO
START...TRANSITIONING TO SLEET THEN FREEZING RAIN...THEN STRAIGHT
RAIN THROUGH THE OVERNIGHT AND EARLY MORNING HOURS. SNOW ACCUMS
GENERALLY 1-4 INCHES...ICE ACCUMS A TRACE TO A TENTH OF AN INCH
POSSIBLE. SOUTHERLY WINDS WITH LLWS LIKELY.

WED NIGHT INTO THU...MODERATE CONFIDENCE.
AFTER A LULL IN PRECIP EARLY WED...A PERIOD OF RAIN TRANSITIONING
TO SNOW IS POSSIBLE...ESPECIALLY TOWARD THE SOUTH COAST. VFR
LIKELY NORTH...IFR LIKELY IN SNOWFALL.

FRI...HIGH CONFIDENCE.
CONDITIONS IMPROVE. VFR LIKELY.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY THROUGH TUESDAY/...

TODAY AND TONIGHT...HIGH CONFIDENCE.  A COLD FRONT CROSSES THE
REGION EARLY THIS MORNING AND WINDS WILL PICKUP QUICKLY AFTER
SUNRISE.  NORTHWEST WIND GUSTS OF 35 TO 40 KNOTS WILL DEVELOP BY
LATE MORNING AND CONTINUE INTO THE EVENING IN THE COLD AIR ADVECTION
PATTERN.  GALE WARNINGS POSTED FOR ALL WATERS.  WINDS WILL BEGIN TO
DIMINISH FOR THE SECOND HALF OF THE NIGHT AS HIGH PRESSURE BEGINS TO
BUILD IN FROM THE WEST.  IN ADDITION...WIDESPREAD LIGHT FREEZING
SPRAY EXPECTED TONIGHT.

TUESDAY...HIGH CONFIDENCE.  WINDS WILL HAVE DROPPED BELOW SMALL
CRAFT ADVISORY THRESHOLDS BY EARLY MORNING AS HIGH PRESSURE BUILDS
ACROSS THE WATERS. HOWEVER...LEFT OVER SWELL WILL KEEP SMALL CRAFT
SEAS GOING ACROSS THE OUTER-WATERS UNTIL AROUND NOON.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY..MODERATE CONFIDENCE.

TUE NIGHT INTO WED...
LOW PRES MOVES WELL INLAND...WITH A PERIOD OF SNOW RAPIDLY
CHANGING TO SLEET THEN RAIN ACROSS THE WATERS OVERNIGHT TUE NIGHT.
LOW VSBYS EXPECTED. SLY WINDS GUST TO AROUND 25 KT AT TIMES WITH
SEAS INCREASING 5-8 FT BY WED MORNING ON THE OCEAN WATERS. SMALL
CRAFT ADVISORIES LIKELY.

WED NIGHT INTO THU NIGHT...
ANOTHER WAVE OF LOW PRES MOVES ALONG A STALLED FRONTAL BOUNDARY
OVER THE WATERS. PRECIP CONTINUES. NW WINDS CONTINUE TO GUST 25
KT. ALSO...SEAS REMAIN ELEVATED 5-8FT. SMALL CRAFT ADVISORIES
LIKELY CONTINUE.

FRI...
CONDITIONS IMPROVE...SMALL CRAFT ADVISORIES MAY BE ABLE TO BE
TAKEN DOWN.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...GALE WARNING UNTIL 1 AM EST TUESDAY FOR ANZ231-232-250-251-254-
     255.
     GALE WARNING UNTIL 11 PM EST THIS EVENING FOR ANZ233>235-237-
     256.
     GALE WARNING UNTIL 8 PM EST THIS EVENING FOR ANZ230-236.

&&

$$
SYNOPSIS...FRANK/DOODY
NEAR TERM...FRANK/DUNTEN
SHORT TERM...FRANK
LONG TERM...DOODY
AVIATION...FRANK/DOODY
MARINE...FRANK/DOODY



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.