Snow Squall Warning 12, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
435 PM EST Wed Dec 18 2019

.SYNOPSIS...
A strong Arctic cold front will progress across Southern New
England tonight. Periods of scattered snow showers and possible
snow squalls through early this evening, then a period of well
below normal temperatures and low wind chills tonight into
Thursday. This coupled with the winds will bring very low wind
chill values. Dry and cold conditions continue into Friday. Dry
weather likely lingers through the weekend into early next week
and will be accompanied by moderating temperatures.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A strong Arctic cold front, with a shot of the coldest air thus
experienced in this winter season awaiting behind it, is currently
progressing across the Adirondacks into central NY. Regional radar
shows two clusters of snow showers with embedded snow squalls: the
first is now extending from west-central MA through the Hartford
area on towards the northwest NYC suburbs. Snow squall parameter
values according to SPC's mesoanalysis have been between 1-3 units
across a good part of Southern New England, capturing favorable
conditions for snow squalls. Observations at 312 PM at Bradley Intl
Airport indicate visbys down to less than a mile. Lacking
particularly robust low-level frontogenesis, in spite of favorable
snow squall parameter values, snow showers/snow squalls should be
more scattered, versus a true snow squall line as is seen in some of
the more dangerous and high impact snow squall episodes which have
occurred in the past. The 12 and 18z NAM-3km and the HRRR short-
range guidance appear to be handing this cluster/broken band the
best, which brings scattered snow showers into the Boston/Providence
area by 4-6 PM. The second area of more active snow squalls is back
across central NY and up into the Champlain Valley in VT, and while
models are simulating more organized snow squalls there, there's no
indication in guidance that these will make it this far south. With
the snow squall threat being greatest during the PM commute,
motorists should be prepared to encounter rapidly changing
visibility and road conditions in snow squalls, even if such
features are brief. Short-fused SPSs, or a snow squall warning could
be issued in a particularly robust situation with visbys less than a
quarter-mile, could be issued this afternoon to address these
threats.

The Arctic front progresses into the coastal waters by early
tonight. Winds will then shift and become NWly and advect in
increasingly cold low-level air (850 mb temps -20 to -22C, generally
even colder than prior guidance runs by a couple degrees C). This
frigid low-level air mass will steepen lapse rates and lead to gusty
and strong winds late tonight and overnight, and also lead to sub-
zero wind chills across most of northern CT, RI into a large part of
MA.

On the winds and gusts, sustained winds increase this evening into
overnight to around 15-25 mph inland with gusts 35-38 mph. On the
Cape and Islands, still looking at 25-35 mph sustained winds, with a
contined potential for Advisory-level wind gusts based on strong
mixed-layer winds progged across Cape Cod, the Islands and Block
Island. A Wind Advisory remains valid for these areas.

By tonight, the bigger story will be the very cold temperatures and
wind chills. Temperatures are expected to sharply fall through the
teens by midnight and into the single digits to low teens by
daybreak. Wind chills between 15 to 20 below zero appear possible
across the eastern slopes of the Berkshires, and as low as 15 below
in the hills of northern Worcester County. Have opted to expand the
Wind Chill Advisory into northern Worcester County based on the
updated wind chill forecast. But it will also be frigid overnight
for many, even outside of the Wind Chill Advisory areas. Lowest wind
chills between -5 to -10F should be common across the remainder of
interior MA, CT into RI, around -5 below in the coastal plain, and 0
to -5 towards the Cape and Islands. These low wind chills will tend
to be the coldest by early morning. With temperatures this cold, we
could see any areas of wet pavement or slush freeze up, though it
will be quite windy and exceedingly dry which may help dry
things out to some extent through evaporation.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Blustery, very cold and dry will be the story for Thursday. Models
show sharp northwesterly gradient flow continuing, though we
shouldn't mix as deep leading to less gustiness. We are still
looking at daytime wind chills between -5F and 10F above zero by
afternoon given the blustery northwest winds. With the thermal
trough overhead during the day on Thursday, this will offset heating
from full sunshine. Only looking at highs in the teens to low 20s
for many areas, some 15 to 20 degrees below normal for this time of
year.

Good radiational cooling likely on Thursday night with clear skies
and a very dry air mass. Lingering northwest winds will continue
around 10 mph with lowest wind chills between -5 and 5F. Low
temperatures upper single digits to the teens, though near 20F
towards the Outer Cape.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights...

* Prolonged period of dry weather expected during this time

* Well below normal temperatures expected into this weekend, then
  becoming more normal for late December into early next week.

Large high pressure should extend from central Canada into the
central Appalachians by late this week. This will maintain a
prolonged period of dry weather into early next week across
southern New England.

Our region will be on the cold side of this high pressure through
late this week. Modified arctic air will overspread southern New
England, leading to well below normal temperatures. Once the core of
this high pressure is focused more from the central Appalachians
into the Mid Atlantic states this weekend, wind direction should
shift to more of a westerly direction, which should mean a warming
trend this weekend into early next week.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Thursday Night/...

21z TAF Update:

Rest of Today...Moderate to high confidence.

Band of scattered snow showers and embedded snow squalls now
moving through central MA southwestward toward northern CT.
Most immediate threat for low-visibility snow is at PVD, with
bands of snow showers now over northern MA potentially
threatening BOS between 23-00z.

Tonight...High confidence.

VFR. Low prob of flurries/light snow showers early tonight at
BAF and BDL from a lake-effect bands but too unlikely to include
mention in the TAFs. Biggest concern is the NW wind gusts, with
winds 15-25 kts gusts 35-40 kts, strongest at BOS and on the
Cape.

Thursday into Thursday Night...High confidence.

VFR. Strong NW winds with local gusts up to 30 kt during the
day on Thursday, with NW winds 5-10 kts gusts 18-20 kts Thursday
night.

KBOS Terminal...High confidence in TAF trends, moderate on snow
squall potential. Scattered snow showers, possible snow squalls
22-00z. Best chance N/W of Logan, but may need to TEMPO in snow
squalls with future amendments.

KBDL Terminal...High confidence in TAF. Flurries/light snow
showers possible 00-03z, though low prob.

Outlook /Friday through Monday/...

Friday: VFR. Breezy.

Friday Night through Monday: VFR.

&&

.MARINE...
Short Term /through Thursday Night/...

Gale warnings remain in effect for the waters with the
expectation of strong NW winds behind an Arctic front. NW gusts
35-45 kts tonight into the first part of Thursday. Eventually
replaced with SCAs as winds subside into Thursday night. Seas
will be becoming rough and increasing to 6-12 ft, highest
offshore waters, with around 2 ft in the bays.

With the colder air moving in and cooler ocean temperatures
expect freezing spray across the eastern nearshore waters. A
Freezing Spray Advisory remains valid and will be in effect
tonight into Thursday morning.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt. Local rough seas.

Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.

Saturday Night through Monday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 10 AM EST Thursday for MAZ022>024.
     Wind Chill Advisory from midnight tonight to 10 AM EST
     Thursday for MAZ002-004-008-009.
RI...Wind Advisory until 7 AM EST Thursday for RIZ008.
MARINE...Freezing Spray Advisory from 1 AM to 10 AM EST Thursday for
     ANZ231-232-251.
     Gale Warning until noon EST Thursday for ANZ231>235-237-251-
     255-256.
     Gale Warning until 7 AM EST Thursday for ANZ230-236.
     Gale Warning until 10 PM EST Thursday for ANZ250-254.

&&

SYNOPSIS...Belk/Loconto
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Belk
AVIATION...Belk/Loconto
MARINE...Belk/Loconto

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
404 AM EST Wed Dec 18 2019

CTZ002>004-MAZ003>007-010>021-026-RIZ001>007-190915-
Hartford CT-Tolland CT-Windham CT-Eastern Franklin MA-
Northern Worcester MA-Central Middlesex MA-Western Essex MA-
Eastern Essex MA-Eastern Hampshire MA-Eastern Hampden MA-
Southern Worcester 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-Northern Middlesex MA-Northwest Providence RI-
Southeast Providence RI-Western Kent RI-Eastern Kent RI-Bristol RI-
Washington RI-Newport RI-
404 AM EST Wed Dec 18 2019

This Hazardous Weather Outlook is for northern Connecticut, central
Massachusetts, eastern Massachusetts, northeastern Massachusetts,
southeastern Massachusetts, western Massachusetts, northern Rhode
Island and southern Rhode Island.

.DAY ONE...Today and tonight.

Scattered snow squalls are possible this afternoon and evening which
could briefly drop visibility to near zero with heavy snow and gusty
winds.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MAZ002-008-009-190915-
Western Franklin MA-Western Hampshire MA-Western Hampden MA-
404 AM EST Wed Dec 18 2019

...WIND CHILL ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 10 AM EST
THURSDAY...

This Hazardous Weather Outlook is for western Massachusetts.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Chill Advisory.

Scattered snow squalls are possible this afternoon and evening which
could briefly drop visibility to near zero with heavy snow and gusty
winds.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Chill Advisory.

Wind Advisories may be needed for a time Wednesday night into
Thursday. Wind Chill Advisories may be needed Wednesday night in
the east slopes of the Berkshires.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

MAZ022>024-190915-
Barnstable MA-Dukes MA-Nantucket MA-
404 AM EST Wed Dec 18 2019

...WIND ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO 10 AM EST
THURSDAY...

This Hazardous Weather Outlook is for southeastern Massachusetts.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Advisory.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

RIZ008-190915-
Block Island RI-
404 AM EST Wed Dec 18 2019

...WIND ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO 7 AM EST
THURSDAY...

This Hazardous Weather Outlook is for southern Rhode Island.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Advisory.

Brief period snow and sleet late tonight into early Tuesday morning
before turning over to all rain.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

ANZ233>235-237-255-256-190915-
Vineyard Sound-Buzzards Bay-Rhode Island Sound-Block Island Sound-
Coastal Waters extending out to 25 nm South of Marthas Vineyard and
Nantucket-
Coastal Waters from Montauk NY to Marthas Vineyard extending out to
20 nm South of Block Island-
404 AM EST Wed Dec 18 2019

...GALE WARNING IN EFFECT FROM 6 PM THIS EVENING TO NOON EST
THURSDAY...

This Hazardous Weather Outlook is for Massachusetts coastal waters
and Rhode Island coastal waters.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ250-254-190915-
Coastal waters east of Ipswich Bay and the Stellwagen Bank National
Marine Sanctuary-
Coastal waters from Provincetown MA to Chatham MA to Nantucket MA
out 20 nm-
404 AM EST Wed Dec 18 2019

...GALE WARNING IN EFFECT FROM 6 PM THIS EVENING TO 10 PM EST
THURSDAY...

This Hazardous Weather Outlook is for Massachusetts coastal waters.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ231-232-251-190915-
Cape Cod Bay-Nantucket Sound-Massachusetts Bay and Ipswich Bay-
404 AM EST Wed Dec 18 2019

...GALE WARNING IN EFFECT FROM 6 PM THIS EVENING TO NOON EST
THURSDAY...
...FREEZING SPRAY ADVISORY IN EFFECT FROM 1 AM TO 10 AM EST
THURSDAY...

This Hazardous Weather Outlook is for Massachusetts coastal waters.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.
   Freezing Spray Advisory.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.
   Freezing Spray Advisory.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230-236-190915-
Boston Harbor-Narragansett Bay-
404 AM EST Wed Dec 18 2019

...GALE WARNING IN EFFECT FROM 6 PM THIS EVENING TO 7 AM EST
THURSDAY...

This Hazardous Weather Outlook is for Massachusetts coastal waters
and Rhode Island coastal waters.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

For the latest updates...please visit our webpage at
www.weather.gov/boston

You can follow us on Facebook at
www.facebook.com/us.nationalweatherservice.boston.gov

You can follow us on Twitter at
@NWSBoston

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Boston/Norton MA
434 PM EST Wed Dec 18 2019

MAZ017-018-020-021-RIZ001-002-182230-
Northern Bristol-Southern Bristol-Southern Plymouth-Western
Plymouth-Northwest Providence-Southeast Providence-
434 PM EST Wed Dec 18 2019

...A SNOW SQUALL WILL AFFECT EASTERN PROVIDENCE COUNTY AND MUCH OF
BRISTOL COUNTY MASSACHUSETTS...

At 431 PM EST...A snow squall was over Central Falls, or over
Pawtucket, moving east at 20 mph.

Locations impacted include...
Providence, New Bedford, Fall River, Pawtucket, Taunton, East
Providence, Dartmouth, Cumberland, North Providence, Johnston, North
Attleborough, Bridgewater, Attleboro, Mansfield, Middleborough,
Smithfield, Lincoln, Central Falls, Norton and Somerset.

Drivers need to remain alert. These conditions often lead to
accidents, especially on highways, since road conditions can change
rapidly. Avoid braking suddenly. Consider delaying travel until the
squalls pass.

&&

LAT...LON 4174 7113 4176 7112 4177 7111 4179 7112
      4177 7112 4174 7114 4184 7150 4201 7144
      4200 7138 4199 7138 4200 7134 4193 7079
      4167 7088
TIME...MOT...LOC 2131Z 284DEG 19KT 4191 7138

Belk

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Boston/Norton MA
447 PM EST Wed Dec 18 2019

CTZ004-MAZ017-020-RIZ001>007-182245-
Windham-Northern Bristol-Southern Bristol-Northwest
Providence-Bristol-Washington-Eastern Kent-Western
Kent-Newport-Southeast Providence-
447 PM EST Wed Dec 18 2019

...A SNOW SQUALL WILL AFFECT NORTHERN AND CENTRAL RHODE ISLAND AND
MUCH OF BRISTOL COUNTY MASSACHUSETTS THIS AFTERNOON...

At 444 PM EST...A snow squall was over Foster, or 9 miles northwest
of Coventry, moving southeast at 25 mph. Visibility around 1 mile is
expected, but could be less across northern Rhode Island.

Locations impacted include...
Providence, Fall River, Warwick, Cranston, Pawtucket, East
Providence, Coventry, North Providence, South Kingstown, West
Warwick, Johnston, North Kingstown, Newport, Bristol, Plainfield,
Smithfield, Lincoln, Somerset, Portsmouth and Killingly.

Drivers need to remain alert. These conditions often lead to
accidents, especially on highways, since road conditions can change
rapidly. Avoid braking suddenly. Consider delaying travel until the
squalls pass.

&&

LAT...LON 4171 7207 4201 7170 4175 7112 4165 7121
      4172 7116 4172 7126 4164 7121 4150 7133
      4167 7128 4168 7128 4158 7133 4171 7129
      4179 7137 4178 7139 4165 7136 4166 7137
      4169 7145 4154 7143 4153 7134 4145 7140
TIME...MOT...LOC 2144Z 294DEG 21KT 4182 7175

Belk

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Boston/Norton MA
502 PM EST Wed Dec 18 2019

MAZ005>007-026-182300-
Northwest Middlesex County-Eastern Essex-Central Middlesex
County-Western Essex-
502 PM EST Wed Dec 18 2019

...A snow squall will affect Northwest Middlesex County...Eastern
Essex...Central Middlesex County...Western Essex...

At 501 PM EST...A snow squall was over Pepperell, or 8 miles
southwest of Nashua, moving east at 30 mph.

Locations impacted include...
Lowell, Lynn, Nashua, Lawrence, Peabody, Methuen, Salem, Billerica,
Beverly, Woburn, Chelmsford, Andover, Dracut, Tewksbury, North
Andover, Danvers, Reading, Burlington, Wilmington and Westford.

Drivers need to remain alert. These conditions often lead to
accidents, especially on highways, since road conditions can change
rapidly. Avoid braking suddenly. Consider delaying travel until the
squalls pass.

&&

LAT...LON 4270 7087 4249 7091 4251 7104 4253 7104
      4253 7108 4252 7109 4252 7113 4253 7113
      4252 7115 4260 7166 4262 7168 4271 7167
      4270 7129 4273 7127
TIME...MOT...LOC 2201Z 278DEG 25KT 4265 7159

Belk

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Boston/Norton MA
505 PM EST Wed Dec 18 2019

MAZ004-005-007-014-015-026-182300-
Northwest Middlesex County-Eastern Essex-Suffolk-Central Middlesex
County-Northern Worcester-Southeast Middlesex-
505 PM EST Wed Dec 18 2019

...A snow squall will affect portions of northern
Worcester...central Middlesex and Suffolk Counties this evening...

At 503 PM EST...A snow squall was over Leominster, moving east at
30 mph.

Locations impacted include...
Boston, Cambridge, Lynn, Newton, Somerville, Waltham, Malden,
Brookline, Medford, Revere, Peabody, Arlington, Everett, Leominster,
Fitchburg, Billerica, Woburn, Chelsea, Chelmsford and Watertown.

Drivers need to remain alert. These conditions often lead to
accidents, especially on highways, since road conditions can change
rapidly. Avoid braking suddenly. Consider delaying travel until the
squalls pass.

&&

LAT...LON 4250 7095 4238 7100 4238 7101 4237 7100
      4235 7101 4237 7104 4238 7105 4237 7105
      4234 7101 4233 7102 4232 7105 4231 7103
      4231 7106 4247 7186 4262 7178
TIME...MOT...LOC 2203Z 281DEG 28KT 4254 7174

Belk

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