Snow Advisory 6, NWS Boston/Norton, MA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
422 AM EST FRI FEB 29 2008

.SYNOPSIS...
COLD HIGH PRESSURE WILL BUILD INTO THE REGION TONIGHT AND FRI...THEN
MOVING OFFSHORE FRI EVENING. LOW PRESSURE WILL EXIT THE GREAT LAKES
FRI NIGHT AND MOVE ACROSS NEW ENGLAND SAT...BRINGING A PLOWABLE SNOW
TO MUCH OF INTERIOR SOUTHERN NEW ENGLAND. THIS STORM WILL MOVE TO
THE MARITIMES SUN WITH GUSTY NW WINDS...THEN HIGH PRESSURE WILL
BUILD INTO THE REGION SUN NIGHT. A WARMING TREND IS LIKELY NEXT
WEEK...BUT A SIGNIFICANT STORM MAY AFFECT SOUTHERN NEW ENGLAND
SOMETIME TUE OR WED.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATED DISC COMING SOON.

A VERY COLD START FRI AM...ALTHOUGH NOT MUCH OF A WIND CHILL AS
WINDS WILL BE VERY LIGHT. SUNSHINE WILL GIVE WAY TO INCREASING FRI
AFTERNOON CLOUDS AS ANTICYCLONIC FLOW BECOMES CYCLONIC DURING THE
AFTERNOON IN RESPONSE TO CLIPPER TYPE LOW APPROACHING THE GREAT
LAKES.

APPEARS MOST IF NOT ALL OF THE DAYLIGHT HOURS /ESPECIALLY RI AND
EASTERN MA/ WILL REMAIN DRY...AS MODELS CONTINUE TO TREND SLOWER
WITH ONSET OF PRECIP. THEREFORE...WE DELAYED THE ARRIVE OF THE SNOW
TIL AFTER DARK.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
UPDATED DISCUSSION COMING SOON

FRI NIGHT AND SATURDAY...

WARM ADVECTION SNOWS AHEAD OF CLIPPER SYSTEM WILL OVERSPREAD THE
REGION FRI EVENING FROM WEST TO EAST.  AIRMASS IS QUITE COLD TO
START SO EVEN SOUTH COAST WILL BEGIN AS SNOW.  HOWEVER...WITH LOW
TRACKING ACROSS CENTRAL NEW ENGLAND...INCREASING SOUTHERLY LOW LEVEL
JET/INFLOW WILL WARM BOUNDARY LAYER ALONG THE SOUTH COAST YIELDING
SNOW MIXING WITH AND CHANGING TO RAIN. AROUND AN INCH OF
ACCUMULATION BY DAYBREAK SAT IS EXPECTED ALONG THE SOUTH COAST.

NOW THE TRICKY PART OF THE FORECAST. TYPICALLY SOUTHEAST INFLOW IS A
GIVEN FOR SNOW TO RAIN ACROSS MUCH OF THE AREA. HOWEVER...GIVEN THE
MAGNITUDE OF THE COLD AIRMASS IN PLACE ACROSS THE REGION COMBINED
WITH OCEAN TEMPS AT THEIR CLIMATOLOGICAL MINIMUM...BOUNDARY LAYER
WARMING WILL BE SLOW TO PENETRATE INLAND AND DEPTH OF WARM LAYER WILL
LIKELY BE SHALLOW.

IN ADDITION...ALL MODEL GUIDANCE INDICATES TEMPS ALOFT WILL BE COLD
DURING THE EVENT ALONG WITH STRONG HEIGHT FALLS OVER THE REGION LATE
FRI NIGHT INTO SAT. THIS SUGGEST POTENTIAL DYNAMICAL COOLING
/COOLING THE COLUMN FROM TOP-DOWN/ ATTEMPTING TO OFFSET BOUNDARY
LAYER WARMING. IN ADDITION...STRONG PRES FALLS OF 12 MBS OVER 6 HRS
ENDING 12Z SAT IS LOCATED ACROSS NORTHEAST RI. THIS WOULD LIKELY
BACK SURFACE WINDS FROM SOUTHEAST TO EAST SAT...RESULTING IN LESS
BOUNDARY LAYER WARMING. IN ADDITION...THIS WOULD ALSO SUGGEST
SECONDARY LOW PRES DEVELOPING FARTHER SOUTH /THAN GFS/ INTO MASS BAY
OR CAPE COD BAY PER 12Z GGEM. FURTHERMORE...HEAVIEST QPF OCCURRING
LATE AT NIGHT AND EARLY SAT AM FAVORS SIGNIFICANT SNOWFALL FARTHER
SOUTHEAST.

ALL OF THESE FACTORS WOULD SUGGEST A LOW PROBABILITY OF A
SIGNIFICANT /4-7 INCHES/ SNOWFALL AS FAR EAST AS THE RT-128 CORRIDOR
AND SOUTH TO I295 IN NORTHERN RI. THE MORE LIKELY SCENARIO IS FOR
SIGNIFICANT SNOWS ACROSS MUCH OF THE INTERIOR EASTWARD TO I495
CORRIDOR IN EASTERN MA...AND SOUTHWARD TO THE CT/MA BORDER EASTWARD
TO JUST NORTH OF THE RI BORDER. LATER SHIFTS WILL HAVE TO MONITOR MODEL
TRENDS FOR POSSIBLE WINTER STORM WATCH EXPANSION EASTWARD TO BOSTON
AND ITS NORTH SHORE AND SOUTHWARD TO I295 IN NORTHERN RI.

SNOW WILL BECOME HEAVY AT TIMES LATE FRI NIGHT THROUGH SAT MORNING
AS SIGNIFICANT TROF AMPLIFICATION TAKES PLACE AS TROF BECOMES
NEGATIVELY TILTED AND EVENTUALLY A CLOSED MID LEVEL CIRCULATION OVER
NEW ENGLAND LATER SAT.  LOW LEVEL SOUTHERLY JET CRANKS UP TO 55 KT
DURING THIS TIME ALONG WITH LFQ OF 110 KT JET STREAK MOVING ACROSS
THE AREA. THIS WILL YIELD A DEEP COLUMN OF LIFT FROM ABOUT 09Z-15Z
SAT.

MODEL QPF IS IN GOOD AGREEMENT WITH LIQUID STORM TOTALS OF 0.60 TO
0.70. SNOW GROWTH IS FAVORABLE OVER NORTHERN MA AND NEARBY NH. THIS
COMBINED WITH COLDER THERMAL PROFILES HERE MAY YIELD GREATER THAN
10-1 SNOW RATIOS.  FOR NOW OUR PRELIMINARY SNOW TOTALS ARE AS
FOLLOWS:

BOSTON-PROVIDENCE CORRIDOR: 2-4
SOUTH COAST AND SOUTH SHORE: 1-2
NORTHERN CT-NORTHERN RI: 3-6
INTERIOR MA AND SOUTHERN NH: 4-8

SNOW WILL END FROM WEST TO EAST LATER SAT MORNING AS DRY SLOT MOVES
ACROSS THE REGION.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
SFC LOW WILL BE IN THE GULF OF MAINE SAT EVENING AND MODELS INDICATE
DEEPER MOISTURE WRAPPING AROUND 700 MB LOW...AND AFFECTING SNE.
THIS MOISTURE COMBINED WITH CLOSED UPPER MOVING ACROSS NEW ENG WILL
LIKELY BRING RESULT IN LINGERING SNOW SHOWERS SAT EVENING...
ESPECIALLY FROM S NH INTO N CENTRAL AND E MA WHERE BEST QG FORCING
IS LOCATED.  ANY SNOW SHOWERS WILL MOVE OUT LATE SAT NIGHT WITH
CLEARING MOVING IN FROM SW TO NE LATE SAT NIGHT INTO SUN...LEADING
TO INCREASING SUNSHINE DURING SUN.

WIND WILL BE A BIG FACTOR LATE SAT NIGHT INTO SUN AS VERY STRONG
PRESSURE GRADIENT DEVELOPS BEHIND DEPARTING LOW.  GFS SOUNDINGS SHOW
POTENTIAL FOR GUSTS TO 50 MPH WHILE NAM WIND FIELD IS A BIT LESS.
WE TOOK A CONSERVATIVE APPROACH AND BLENDED NAM/GFS TO ARRIVE AT
GUSTS TO 40-45 MPH SUN MORNING.  WIND ADVISORIES MAY EVENTUALLY BE
NEEDED.  WE UNDERCUT MOS TEMPS A BIT ON SUN TO REFLECT COOLER 2M
TEMPS.

WINDS DIMINISH LATE SUN AND ESPECIALLY SUN NIGHT AS SFC RIDGE MOVES
INTO THE REGION.

MILDER AIR MOVES IN MON AS SW FLOW DEVELOPS...BUT IT SHOULD REMAIN
DRY.  TEMPS WELL INTO 40S.

MED RANGE GUIDANCE NOW IN BETTER AGREEMENT WITH SPLIT FLOW PATTERN
AND STRONG SOUTHERN STREAM SYSTEM FOR TUE/WED.  NORTHERN STREAM WILL
BRING A COLD FRONT INTO NEW ENG ON TUE WHICH WILL LIKELY STALL
ACROSS THE REGION AS SOUTHERN STREAM LOW APPROACHES FROM THE SW.
SOME SHOWERS PSBL WITH THIS BOUNDARY MON NGT/TUE...BUT IT APPEARS
BULK OF PRECIP WILL BE TUE NIGHT INTO WED AS LOW TRACKS TO THE
WEST.  THERE WILL BE A FAIRLY STRONG SFC HIGH TO THE NE LEFT BY
NORTHERN STREAM WHICH MAY PROVIDE ENOUGH LOW LEVEL COLD AIR FOR SOME
FZRA TUE NIGHT WELL INTO THE INTERIOR...BUT THIS WILL BE MAINLY A
RAIN EVENT WITH HEAVY RAFL POSSIBLE.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
TONIGHT...VFR.

FRIDAY...VFR.

FRI NIGHT...MVFR QUICKLY LOWERING TO IFR DURING THE EVENING FROM
WEST EAST. LOCAL LIFR AFTER 06Z. SNOW...LIKELY CHANGING TO RAIN LATE
ALONG THE SOUTH COAST.

SAT...IFR IN THE MORNING WITH MVFR SOUTH COAST...IMPROVING TO MVFR DURING
THE AFTERNOON.

OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY...
SAT NIGHT...MAINLY VFR BUT AREAS OF MVFR POSSIBLE SAT EVENING.
INCREASING NW WINDS LATE SAT NIGHT.

SUN AND MON...VFR. STRONG NW WINDS SUN WITH GUSTS TO 35-40 KTS
POSSIBLE.

TUE...CONDITIONS POSSIBLY LOWERING TO MVFR.

&&

.MARINE...
TONIGHT...
SMALL CRAFT ADVISORY IN EFFECT TONIGHT FOR THE SOUTH OCEAN
WATERS FOR LEFTOVER SEAS WHICH IS A COMBINATION OF WESTERLY WIND
WAVES AND SOUTHERLY SWELLS. OTHERWISE DIMINISHING WINDS WITH GOOD
VSBY. COULD BE SOME LIGHT FREEZING SPRAY DURING THE EVENING.

FRIDAY...
LIGHT WINDS BECOMING SOUTHEAST AS HIGH PRES DRIFTS OFFSHORE.

FRI NIGHT...
SOUTHEAST WINDS INCREASE TO 20-30 KT AS LOW PRES TRACKS ACROSS
CENTRAL NEW ENGLAND.

SAT...E TO SE WINDS OF 20-30 KT MAY GUST TO GALE FORCE DEPENDING ON
THE STRENGTH OF THE SECONDARY LOW AND ITS LOCATION. WINDS BECOME
WEST DURING AFTN AS STORM EXITS INTO THE GULF OF MAINE.

OUTLOOK...SAT NIGHT THROUGH TUESDAY...
WEST TO NORTHWEST GALES DEVELOPING SAT NIGHT WITH GUSTS POSSIBLY
REACHING 40 KTS LATE SAT NIGHT INTO SUN AS STRONG PRESSURE GRADIENT
DEVELOPS IN THE WAKE OF INTENSIFYING LOW. WINDS GRADUALLY DIMINISH
THROUGH SUN NIGHT AS HIGH PRES MOVES INTO THE REGION.

WINDS BECOME SW MON AS HIGH PRESSURE MOVES OFFSHORE...INCREASING MON
NGT WITH GUSTS NEAR 25 KTS POSSIBLE AHEAD OF COLD FRONT.  SOUTHERLY
WINDS PERSIST TUE AS COLD FRONT STALLS NORTH OF THE WATERS WITH
APPROACHING STORM FROM THE OHIO VALLEY.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...HEAVY SNOW WARNING FROM 10 PM THIS EVENING TO 12 PM EST
     SATURDAY FOR CTZ002-003.
     SNOW ADVISORY FROM 10 PM THIS EVENING TO 12 PM EST SATURDAY
     FOR CTZ004.
MA...HEAVY SNOW WARNING FROM 10 PM THIS EVENING TO 12 PM EST
     SATURDAY FOR MAZ002>006-008>012-026.
     SNOW ADVISORY FROM 10 PM THIS EVENING TO 12 PM EST SATURDAY
     FOR MAZ007-013>016.
NH...HEAVY SNOW WARNING FROM 10 PM THIS EVENING TO 12 PM EST
     SATURDAY FOR NHZ011-012-015.
RI...SNOW ADVISORY FROM 10 PM THIS EVENING TO 12 PM EST SATURDAY
     FOR RIZ001-003.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 5 PM EST
     SATURDAY FOR ANZ230>237-250-254-255.

&&

SYNOPSIS...KJC
NEAR TERM...EVT
SHORT TERM...EVT
LONG TERM...KJC
AVIATION...KJC/EVT
MARINE...KJC/EVT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TAUNTON MA
407 PM EST THU FEB 28 2008

MAZ002>006-008>012-026-NHZ011-012-015-292115-
WESTERN FRANKLIN MA-EASTERN FRANKLIN MA-NORTHERN WORCESTER MA-
CENTRAL MIDDLESEX MA-WESTERN ESSEX MA-WESTERN HAMPSHIRE MA-
WESTERN HAMPDEN MA-EASTERN HAMPSHIRE MA-EASTERN HAMPDEN MA-
SOUTHERN WORCESTER MA-NORTHERN MIDDLESEX MA-CHESHIRE NH-
EASTERN HILLSBOROUGH NH-WESTERN AND CENTRAL HILLSBOROUGH NH-
407 PM EST THU FEB 28 2008

...WINTER STORM WATCH IN EFFECT FROM FRIDAY EVENING THROUGH SATURDAY
MORNING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL
MASSACHUSETTS...EASTERN MASSACHUSETTS...NORTHEASTERN
MASSACHUSETTS...WESTERN MASSACHUSETTS AND SOUTHERN NEW HAMPSHIRE.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   WINTER STORM WATCH.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

CTZ002>004-MAZ007-013>024-RIZ001>008-292115-
HARTFORD CT-TOLLAND CT-WINDHAM CT-EASTERN ESSEX MA-
WESTERN NORFOLK MA-SOUTHEAST MIDDLESEX MA-SUFFOLK MA-
EASTERN NORFOLK MA-NORTHERN BRISTOL MA-WESTERN PLYMOUTH MA-
EASTERN PLYMOUTH MA-SOUTHERN BRISTOL MA-SOUTHERN PLYMOUTH MA-
BARNSTABLE MA-DUKES MA-NANTUCKET MA-NORTHWEST PROVIDENCE RI-
SOUTHEAST PROVIDENCE RI-WESTERN KENT RI-EASTERN KENT RI-BRISTOL RI-
WASHINGTON RI-NEWPORT RI-BLOCK ISLAND RI-
407 PM EST THU FEB 28 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN
CONNECTICUT...EASTERN MASSACHUSETTS...NORTHEASTERN
MASSACHUSETTS...SOUTHEASTERN MASSACHUSETTS...NORTHERN RHODE ISLAND
AND SOUTHERN RHODE ISLAND.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A CLIPPER SYSTEM WILL BRING THE POSSIBILITY OF SNOW CHANGING OVER TO
A WINTRY MIX LATE FRIDAY NIGHT INTO EARLY SATURDAY MORNING TO
NORTHERN CONNECTICUT...RHODE ISLAND...AND EASTERN MASSACHUSETTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

ANZ230>237-250-254-255-292115-
BOSTON HARBOR-CAPE COD BAY-NANTUCKET SOUND-VINEYARD SOUND-
BUZZARDS BAY-RHODE ISLAND SOUND-NARRAGANSETT BAY-BLOCK ISLAND SOUND-
COASTAL WATERS FROM MERRIMACK RIVER MA OUT 25 NM TO PLYMOUTH MA OUT
40 NM...INCLUDING THE STELLWAGEN BANK NATIONAL MARINE SANCTUARY-
COASTAL WATERS FROM PROVINCETOWN MA TO CHATHAM MA TO NANTUCKET MA
OUT 20 NM-
COASTAL WATERS FROM MONTAUK NY TO BLOCK ISLAND RI TO MARTHAS
VINEYARD MA TO NANTUCKET MA SOUTHEAST TO 20 NM-
407 PM EST THU FEB 28 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MASSACHUSETTS COASTAL WATERS
AND RHODE ISLAND COASTAL WATERS.

.DAY ONE...TONIGHT

AREAS OF LIGHT FREEZING SPRAY ARE POSSIBLE TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

GALE FORCE WEST TO NORTHWEST WINDS ARE LIKELY SATURDAY NIGHT INTO
SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.