Area Forecast Discussion
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000
FXUS61 KBOX 012106
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
406 PM EST SUN MAR 1 2015

.SYNOPSIS...
A FAST MOVING LOW PRESSURE SYSTEM WILL BRING ACCUMULATING SNOW
LATER TODAY AND ESPECIALLY TONIGHT WITH THE HIGHEST AMOUNTS
EXPECTED SOUTH OF THE MASSACHUSETTS TURNPIKE. HIGH PRESSURE
BRINGS DRY COLD AIR FOR THE EARLY WEEK. 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 SWING A
COLD FRONT ACROSS THE REGION ON WEDNESDAY. DRY AND COLD WEATHER
RETURNS FOR THE END OF THE WEEK. ANOTHER COLD FRONT MOVES THROUGH
ON SATURDAY.

&&

.NEAR TERM /UNTIL 5 PM THIS AFTERNOON/...
1 PM UPDATE...

LIGHT SNOW IS WORKING ITS WAY INTO SOUTHERN NEW ENGLAND...BASED ON
18Z OBS LIGHT SNOW HAS MADE IT INTO THE SPRINGFIELD AREA AND LIGHT
SNOW HAS EVEN STARTED AT PVD. THE SNOW WILL CONTINUE TO GRADUALLY
OVERSPREAD THE REMAINDER OF OUR AREA AS THE AFTERNOON
PROGRESSES...LIKELY REACHING BOSTON AROUND 20Z. AGAIN ONLY MINOR CHANGES
MADE TO HOURLY TEMPS TO REFLECT LATEST OBS...FORECAST HIGHS
CONTINUE TO LOOK ON TRACK.

EARLY MORNING DISCUSSION...

MID LEVEL CLOUDINESS WILL STREAM INTO SOUTHERN NEW ENGLAND AND
THICKEN DURING THE MORNING HOURS IN ADVANCE OF APPROACHING LOW
PRESSURE.  SOUTHWEST FLOW ALOFT OVERRUNING THE COLD DOME AT THE
SURFACE MAY ALLOW FOR SOME LIGHT SNOW/FLURRIES TO BREAK
OUT ACROSS THE INTERIOR LATE THIS MORNING/EARLY AFTERNOON AND THEN
FIND THEIR WAY TO THE COAST BY MID TO LATE AFTERNOON.  THE LIFT
THROUGH MID AFTERNOON IS FAIRLY WEAK...SO THE AREAS OF SNOW SHOULD
BE RATHER LIGHT. ANY ACCUMULATIONS THAT OCCUR WILL PROBABLY BE
A DUSTING TO LESS THAN 1 INCH THROUGH THAT THAT TIME.  HIGH TEMPS
WILL MAINLY BE IN THE UPPER 20S TO AROUND 30.

&&

.SHORT TERM /5 PM THIS AFTERNOON THROUGH MONDAY NIGHT/...
*** BULK OF THE ACCUMULATING SNOW OCCURS BETWEEN 3 PM AND 1 AM WITH
  THE HEAVIEST AMOUNTS SOUTH OF THE MA TURNPIKE ***

1) OVERVIEW AND TIMING:

THE BULK OF THE ACCUMULATING SNOW WILL OCCUR BETWEEN 3 PM AND
1 AM ACROSS THE REGION.  THE SNOW SHOULD TAPER OFF TO FLURRIES
TOWARD DAYBREAK MONDAY.  THE MODELS DO AGREE THAT THE BETTER FORCING
WILL OCCUR TO THE SOUTH OF THE MA TURNPIKE.  THIS A RESULT
OF SECONDARY LOW PRESSURE NEAR THE SOUTH COAST...ALLOWING FOR
SOME SURFACE CONVERGENCE AS WELL AS THE INTENSIFICATION OF THE LOW
LEVEL JET.

THE BIGGEST ISSUE IS THE MODELS ARE NOT IN AGREEMENT IN HOW
INTENSE THE FORCING WILL BE ACROSS THE REGION THIS EVENING.  THE
RGEM/NAM ARE THE MOST ROBUST WITH QPF SOUTH OF THE MA TURNPIKE.  THE
NAM SHOWS A PERIOD OF FAIRLY STRONG LIFT OF 15 TO 20 MICROBARS PER
SECOND WITHIN THE BEST SNOWGROWTH REGION THIS EVENING.  THIS WOULD
TRANSLATE TO A PERIOD OF 1+ INCH PER HOUR SNOWFALL RATES NEAR AND
SOUTH OF THE MA PIKE.  ON THE OTHER HAND...THE GFS ALSO HAS FAIRLY
STRONG LIFT...BUT KEEPS IT SOUTHEAST OF OUR REGION OUT OVER THE
OCEAN.  THE SECONDARY LOW PRESSURE SYSTEM ON THE GFS IS WEAKER AND
FURTHER SOUTHEAST...RESULTING IN THE LOW LEVEL JET BEING DISPLACED
FURTHER EAST.  THE ECMWF/UKMET SOLUTIONS SEEM TO BE THE MIDDLE
GROUND WHICH WE WILL LEAN TOWARDS.

2) WINTER WEATHER HEADLINES AND SNOW ACCUMS:

WITH THAT SAID...THE OTHER DILEMMA IS WHAT TO DO WITH THE CURRENT
HEADLINES.  THIS DOES NOT APPEAR TO BE THE TYPE OF SETUP WHERE WE
ARE GOING TO RECEIVE WIDESPREAD WARNING SNOWFALL AMOUNTS.  THE
WINDOW FOR THE VERY STRONG LIFT/FORCING IS SHORT-LIVED AND REALLY
WOULD LIKE TO SEE THE LOW LEVEL JET A BIT MORE BACKED TO TRANSPORT
DEEPER MOISTURE NORTHWARD.  THEREFORE...FEEL THAT FOR MOST OF THE
REGION WINTER WEATHER ADVISORY/S FOR 3 TO 6 INCHES OF SNOW WILL
COVER IT.  HOWEVER...GIVEN THERE IS NICE OMEGA IN THE SNOW GROWTH
REGION...WE MIGHT BE LOOKING AT SOME DECENT RATIOS.  SO WE STILL CAN
NOT RULE OUT THE LOW RISK OF REACHING WARNING AMOUNTS AND LATER
SHIFTS WILL HAVE TO MONITOR CLOSELY...ESPECIALLY ACROSS NORTHERN CT
AND NORTHWEST RI.

WE DID UPGRADE A SMALL AREA FROM CENTRAL AND SOUTHERN RHODE ISLAND
INTO SOUTHEAST MA INCLUDING THE SOUTH COAST TO A WINTER
STORM WARNING.  THE NOSE OF THE LOW LEVEL JET LOOKS TO TRANSPORT
SOME DEEPER MOISTURE INTO THIS REGION.  THERE ALSO COULD BE SOME
ENHANCEMENT ALONG THE LAND/SEA INTERFACE AND A WEAK SURFACE
BOUNDARY SO WENT WITH 4 TO 8 INCHES IN THIS REGION.

3) PTYPE AND IMPACTS:

THE MODELS HAVE TRENDED COLDER OVER THE PAST 24 HOURS.
THEREFORE...EXPECT THIS BE PRETTY MUCH A SNOW EVENT.  IT DOES BECOME
A VERY CLOSE CALL NEAR THE SOUTH COAST...BUT WERE LEANING TOWARDS IT
STAYING MAINLY WET SNOW.  IF PRECIPITATION LIGHTENS UP THAT MAY
INCREASE THIS RISK WE SEE A BRIEF CHANGE OVER TO RAIN.
MEANWHILE...WE WENT WITH A HIGH END WINTER WEATHER ADVISORY FOR THE
CAPE BECAUSE THEY MAY CHANGE TO RAIN FOR A TIME...ESPECIALLY EAST OF
HYANNIS.  IF THE CHANGE OVER DOES NOT OCCUR...WE MAY NEED TO UPGRADE
THEM TO A WINTER STORM WARNING ESPECIALLY NEAR THE CAPE COD CANAL
GIVEN EXPECTED QPF.

THE ONE THING WILL ALSO HAVE TO WATCH IS AREAS NEAR THE SOUTH COAST
AND CAPE COD.  LOOKS TO BE A WET SNOW DOWN THAT WAY AND ON GOING
ROOF ISSUES MAY BE EXACERBATED...ESPECIALLY IF ANY AREAS THAT ARE
ABLE TO EXCEED 6 INCHES OF WET SNOW.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

BIG PICTURE... THE BROAD UPPER FLOW CONTINUES TO FEATURE A TROUGH
TRANSITING EAST ACROSS THE COUNTRY...REACHING THE EASTERN USA DURING
THE LATE WEEK AND LINGERING THROUGH THE WEEKEND. MEANWHILE AN UPPER
RIDGE SHIFTS FROM THE PACIFIC OCEAN BACK ASHORE ONTO THE WEST COAST.
CONTOUR HEIGHTS IN THE TROUGH ARE LOWEST THURSDAY-FRIDAY AND NEAR
NORMAL OVER THE WEEKEND. THIS MEANS A TREND TO COLDER TEMPS THURSDAY-
FRIDAY FOLLOWED BY A TREND CLOSER TO NORMAL OVER THE WEEKEND.

DAILIES...

TUESDAY... HIGH PRESSURE OVER THE REGION MOVES OFFSHORE BY AFTERNOON
WITH AIRFLOW SWINGING FROM NORTHWEST TO SOUTHWEST. THE SURFACE
AIRMASS STARTS OUT QUITE DRY WITH DEW POINTS IN THE SINGLE NUMBERS
BELOW ZERO TO START...CLIMBING TO 5-10 ABOVE BY EVENING. MODEL CROSS
SECTIONS SHOW INCREASING MOISTURE MORNING AND AFTERNOON ABOVE 700
MB. THIS SUGGESTS INCREASING MID AND HIGH CLOUDS WHILE DRY BENEATH.
LOW LEVEL JETS FROM THE CAROLINAS AND MIDWEST AND THE SURFACE
PRESSURE GRADIENT ALL SUGGEST THE INFLOW AND ISENTROPIC LIFT WILL
REMAIN TO OUR WEST THROUGH THE DAY...POSSIBLY ENTERING WESTERN MA/CT
AT OR AFTER 21Z. SO WE EXPECT INCREASING CLOUDS TUESDAY BUT
OTHERWISE DRY WEATHER THROUGH THE DAY. POSSIBLE LIGHT SNOW AROUND
THE EVENING RUSH HOUR IN THE CT RIVER VALLEY. TEMPS SHOULD REACH THE
MID 20S TO AROUND 30.

TUESDAY NIGHT-WEDNESDAY... NORTHERN AND SOUTHERN STREAM SHORTWAVES
MERGE OVER THE GREAT LAKES AND TRACK INTO CANADA. THIS BRINGS A MILD
FLOW OF AIR UP OVER NEW ENGLAND. THE LEADING EDGE OF THIS AIR
REACHES WESTERN SECTIONS TUESDAY EVENING AND EASTERN SECTIONS
TUESDAY NIGHT. TEMPERATURE PROFILES SUPPORT AN INITIAL PERIOD OF
SNOW CHANGING TO RAIN OR FREEZING RAIN OVERNIGHT. ACTUALLY...THE
MODELS MAY NOT BE HANDLING WELL THE CHILLING MASS OF SNOW AND COLD
GROUND /A.K.A. THE GIANT ICECUBE/ WHICH WOULD MEAN THE ACTUAL MAX
SFC TEMPS WILL BE COOLER THAN MODEL FORECASTS. TEMPERATURES AT 925
AND 950 MB WILL BE IN THE 30S...SO EXPECT SURFACE TEMPS NO HIGHER
THAN THE LOWER 40S.

THE SURFACE LOW PRESSURE AREA PASSES WELL NORTH OF NEW ENGLAND
WEDNESDAY AND SWINGS A COLD FRONT THROUGH THE REGION DURING THE
AFTERNOON OR EVENING. MOISTURE CROSS SECTIONS SHOW DECREASING RH IN
THE LIFT AND NUCLEATION ZONES ALOFT WEDNESDAY MORNING...SO THE TREND
THROUGH THE DAY SHOULD BE TO DIMINISHING POPS.

THURSDAY-FRIDAY... THE WEDNESDAY COLD FRONT WILL ALIGN WITH THE
UPPER FLOW AS IT MOVES SOUTH OF NEW ENGLAND...SLOWING ITS OFFSHORE
PROGRESS TO A CRAWL. MEANWHILE WE WILL BE UNDER THE RIGHT ENTRANCE
REGION OF THE SUPPORTING UPPER JET...A SOURCE OF UPPER VENTING. THIS
SHOULD SUPPORT LINGERING CLOUDS AND A CHANCE OF PCPN...WITH TEMPS
SUPPORTIVE OF SNOW. BEST CHANCE SOUTH COAST...LESSER CHANCE FARTHER
NORTH. THE JET AND SURFACE FRONT SWEEP OFFSHORE THURSDAY NIGHT. HIGH
PRESSURE THEN MOVES OVER THE EASTERN USA FOR FRIDAY. TEMPS ALOFT
SUPPORT MAX SFC TEMPS IN THE 20S.

SATURDAY-SUNDAY... ANOTHER NORTHERN STREAM SHORTWAVE AND COLD FRONT
SWINGS THROUGH THE FLOW SATURDAY. CROSS SECTIONS SHOW SOME MOISTURE
ALOFT BUT MOST OF IT IS CONCENTRATED TO OUR NORTH.  ALSO JUST
LIMITED LIFT TO WORK ON THAT MOISTURE. WE WILL HAVE 25-50 PCT SKY
COVER AND NIL POPS. HIGH PRESSURE THEN BUILDS FOR SUNDAY.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY AND TONIGHT/...

18Z UPDATE...MODERATE CONFIDENCE.

THIS AFTERNOON...MVFR CIGS/VSBYS IN LIGHT SNOW AT BAF-BDL BUT MAINLY
VFR TO THE EAST TO START...WITH CIGS AND/OR VSBYS LOWERING TO MVFR
ACROSS THE REMAINDER OF SOUTHERN NEW ENGLAND TERMINALS BETWEEN
18Z AND 21Z IN LIGHT SNOW.

TONIGHT...MODERATE CONFIDENCE. THE BULK OF THE MODERATE TO EVEN
BRIEFLY HEAVY SNOW WILL OCCUR THIS EVENING WHEN WIDESPREAD IFR TO
LIFR CONDITIONS OCCUR. THE LOWEST CONDITIONS WILL MOST LIKELY BE
SOUTH OF THE MA TURNPIKE. PTYPE PRETTY MUCH ALL SNOW...EXCEPT FOR
THE VERY IMMEDIATE SOUTH COAST/CAPE WHERE SNOW MAY MIX WITH OR
CHANGE TO RAIN FOR A TIME. WHETHER OR NOT THAT HAPPENS IS
UNCERTAIN...BUT WE DO THINK THAT AT LEAST THE ISLANDS WILL MIX OR CHANGE
TO RAIN.

BULK OF SNOW ENDS BY 8Z TO 9Z TONIGHT AND MUCH OF THE THE REGION
SHOULD IMPROVE TO VFR CONDITIONS BY 12-13Z MONDAY.

KBOS TAF...CONFIDENT IN OVERALL TRENDS BUT THERE IS UNCERTAINTY ON
TIMING. SOME LIGHT SNOW IS EXPECTED DURING MID TO LATE
AFTERNOON...BUT THE BULK OF ACCUMULATING SNOW WITH IFR TO LIFR
CONDITIONS EXPECTED MAINLY THIS EVENING.

KBDL TAF...CONFIDENT IN OVERALL TRENDS BUT THERE IS UNCERTAINTY ON
TIMING. BULK OF ACCUMULATING SNOW WITH IFR TO LIFR CONDITIONS
EXPECTED AFTER 3 OR 4 PM.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...MODERATE CONFIDENCE. VFR DURING THE DAY WITH INCREASING
SKY COVER. MVFR CIGS/VSBYS POSSIBLE LATE IN THE DAY CT RIVER VALLEY.

TUESDAY NIGHT-WEDNESDAY...MODERATE CONFIDENCE. CONDITIONS LOWERING
TO IFR/LIFR. INITIALLY SNOW BUT CHANGING TO SLEET/FREEZING RAIN
DURING THE NIGHT AND RAIN IN THE COASTAL PLAIN OVERNIGHT. PCPN
CHANGES TO RAIN ALL AREAS WEDNESDAY...BUT COLD SURFACES COULD
MAINTAIN A FREEZING RAIN ELEMENT WEDNESDAY MORNING. COLDER AIR MOVES
IN WEDNESDAY NIGHT CHANGING ANY RAIN TO SNOW.

THURSDAY...LOW CONFIDENCE. VFR NORTH OF A HFD-BOS LINE. MVFR CIGS
AND AREAS OF MVFR/IFR VSBYS IN SNOW...DIMINISHING BY EVENING.
NORTHWEST WINDS GUSTING TO 20 KNOTS.

FRIDAY...MODERATE CONFIDENCE. VFR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY AND TONIGHT/...HIGH CONFIDENCE.

A WEAK WAVE OF LOW PRESSURE MOVES ACROSS THE WATERS LATER
TODAY AND TONIGHT.  WEAK PRESSURE GRADIENT SHOULD KEEP
WINDS/SEAS BELOW SMALL CRAFT THRESHOLDS TODAY AND TONIGHT.  THE
SYSTEM REALLY INTENSIFIES AS IT MOVES INTO THE CANADIAN MARITIMES
NEAR DAYBREAK MONDAY...SO WESTERLY WIND GUSTS MAY REACH 20 TO 25
KNOTS NEAR 12Z MONDAY.  OTHERWISE...RAIN AND SNOW LATE TODAY AND
ESPECIALLY TONIGHT WILL REDUCE VISIBILITIES AT TIMES FOR MARINERS.

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

TUESDAY... LINGERING 5 FOOT SEAS SOUTH AND EAST OF NANTUCKET IN THE
MORNING BUT DIMINISHING. NORTHWEST WINDS DIMINISHING FROM 20 KNOTS.
ANY SMALL CRAFT ADVISORY SHOULD END IN THE MORNING.

TUESDAY NIGHT-WEDNESDAY...SOUTH TO SOUTHWEST WINDS WILL INCREASE TO
20-25 KNOTS. SEAS WILL BUILD 6 TO 10 FEET ON THE OUTER WATERS AND ON
RI SOUND. REDUCED VSBYS...INITIALLY SNOW BUT CHANGING TO RAIN. A
SMALL CRAFT ADVISORY MAY BE NEEDED.

THURSDAY...NORTHWEST WIND GUSTING TO 25 KNOTS. SEAS 5 TO 8 FEET
MAINLY ON THE OUTER WATERS...DIMINISHING LATE. A SMALL CRAFT
ADVISORY MAY BE NEEDED.

FRIDAY... SHIFTING WINDS LESS THAN 20 KNOTS. SEAS LESS THAN 5 FEET.
QUIET WEATHER.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR CTZ002>004.
MA...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR MAZ017>021.
     WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR MAZ002>016-
     022>024-026.
RI...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR RIZ002>008.
     WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR RIZ001.
MARINE...GALE WARNING FROM 11 AM MONDAY TO 4 AM EST TUESDAY FOR ANZ231-
     232-250-251-254-255.
     GALE WARNING FROM 11 AM TO 11 PM EST MONDAY FOR ANZ233>235-237-
     256.
     GALE WARNING FROM 11 AM TO 8 PM EST MONDAY FOR ANZ230-236.

&&

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



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