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000 
FXUS61 KBOX 151216
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
716 AM EST Sun Dec 15 2019

.SYNOPSIS...
Mainly dry but windy weather is on tap for the region today. 
Low pressure moves out of the mid Mississippi and Ohio River 
valleys Monday. This low will push south of the region Monday 
night and Tuesday, bringing light snow, ice and rain. An arctic 
front moves across Wednesday with patchy light snow across 
western areas as well as Cape Cod and the islands. Dry 
conditions move in for late this week, with very cold 
temperatures on Thursday, then readings may moderate a little 
on Friday.

&&

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

7 AM Update...

Noting generally cloudy skies across the interior with a mix of
cloud and brightening skies most of the coastline as seen on 
latest GOES-East Nighttime Microphysics RGB satellite imagery. 
Cloud cover trend over the last couple of hours has seen 
increasing cloud cover thanks to large area of clouds across 
most of NY state and PA which have been shifting E. May see 
some brief breaks in the cloud deck through mid morning, but 
overall expect mostly cloudy skies with some breaks through mid
afternoon, then should improve late in the day.

The big story for today's weather will be the strong winds.
Continue to see excellent mixing through the mid and lower
levels with strong cold air advection from H925 to H85 as well
as strong winds aloft, up to 40-50 kt at H85. Some of these
strong winds could very well mix down during the day, with
potential wind gusts up 30-40 kt and possibly a bit higher 
along the immediate coast and across the higher terrain. 

Will see temps only top off in the mid-upper 30s across the
higher inland terrain ranging to the mid 40s along the immediate
coast. However, this will feel quite a bit colder thanks to the
gusty winds, with wind chill values in the 20s to mid 30s. 

* Westerly wind gusts of 40 to 50 mph today.

Powerful low pressure dropping below 970 mb will continue to 
lift northward through eastern Canada today. The resultant 
pressure gradient along with steepening lapse rates with the 
cold pool aloft will result in windy conditions today. Bufkit 
soundings continue to support 40 to 50 mph wind gusts across 
much of the region. Therefore, Wind Advisories will continue for
most areas north of the CT/RI and MA border. We will come close
to meeting criteria across CT/RI too, but not confident enough 
to extend southward at this time. Regardless, 40 to 50 mph wind 
gusts expected today with the strongest across the high terrain 
as well as as portions of the Cape/Islands.

Impressive cold pool aloft will result in a scattered to broken
deck of cloudiness, but still expect peeks of sunshine. 
Westerly flow coupled with steep lapse rates and lake moisture 
will result in scattered snow showers in the Berks. Across the 
rest of our region, dry weather will dominate but a few passing 
sprinkles/flurries can not be ruled out given the steep lapse 
rates. 

High temps will range from the upper 30s in the high terrain, 
to the lower to middle 40s elsewhere. Although it will feel 
colder given the windy conditions.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...

Tonight...

The powerful low pressure system will lift further into 
northern Canada and the pressure gradient begins to relax. 
Westerly wind gusts of 35 to 45 mph are still possible into the
first half of the evening, but should see a downward trend 
especially after midnight as a ridge of high pressure gradually
builds in from the west. Low temps are expected to drop into 
the upper teens to middle 20s in most locations by daybreak 
Monday in the cold air advection pattern.

Monday...

A ridge of high pressure over our region will keep us dry 
during the day on Monday. We will see some mid level cloudiness 
overspread the region in advance of low pressure lifting 
northeast across the mid Atlantic. High temps will be colder 
than today, remaining in the 30s but with much less wind than 
today.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...

Highlights... 

* Confidence moderate to high for a plowable snow as well as icy 
  roads, Monday night through Tuesday, with the best chance across 
  interior MA/CT into northern RI. Impact to the Tuesday AM commute 
  from snow, sleet and/or freezing rain. Details remain uncertain on 
  snow and ice accumulations which will depend upon the thermal 
  structure and precipitation type changes. 
  
* Scattered snow showers from midday Wednesday into early evening 
  ahead of Arctic cold front, with some snow squalls possible.

* Temperatures fall to between 10 and 20 degrees below normal late 
  Wednesday night and Thursday with Wind Chill values from zero to 
  around -10 possible. 

* Some gradual temperature moderation on Friday, but readings 
  remain below normal. 
  
Details...

After a period of light snow and/or rain showers today as a
couple of fronts push across, a high pressure ridge builds
across tonight as temperatures fall close to seasonal levels.
Low pressure will shift east out of the central Mississippi into
the Ohio River valleys. High pressure will linger to the north
and, as the low approaches late Monday, clouds will increase. 
The cold air will remain Monday night, so light snow will 
develop. However, milder air will slide above the cold dome, so
will see a change over to a wintry mix mainly across southern 
areas after midnight, then will slide north through Tuesday 
while enough milder air works in mainly near and S of the Mass 
Pike that the precip should change to rain. the low will pass
close to or south of the S coast late Tue, so will see the 
precip change back to snow as colder air returns then will taper
off during Tuesday night. 

A shot of Arctic air will push out of central Canada with
another high pressure center. So, will see dry conditions but
the coldest air so far this season on Thursday. The arctic dome
will shift slowly east Thursday night into Friday so
temperatures will moderate somewhat but it will remain cold to
end the work week. 

Monday Night Through Tuesday Night: 

** Low to Moderate Confidence for Winter Weather conditions 
 Monday Night through Tuesday ** 

Light west winds will linger across the region Monday night as
low pressure moves slowly E out of the Ohio and central
Appalachians. With a generally flat mid level flow, which will
start to tilt SW as a long wave trough digs across the central
and western Plains, will see leading edge of light snow will
push S-N across CT/RI Monday evening. 

Noting a classic cold dome of air lingering across the region
Mon night, while milder air will ride above it. This will allow
for mixed precip to start to work in late Monday night as the
precip lifts N-NE. Temps will start off in the mid 20s to mid
30s, coldest across the interior and higher terrain, then
transitions into a non-diurnal temp trend as readings slowly
rise overnight into Tuesday morning. 

Still some uncertainty on the snow accumulations and especially
how much icing will be realized leadings into the Tuesday
morning commute. Looks like the best chances for freezing rain
and/or sleet will occur away from the immediate coast to start
the commute, then should change to rain by around mid to late
morning from around the Boston-Providence corridor southward to
the S coast. A wintry mix should continue through the afternoon
well inland, which could be the biggest impact especially across
untreated roadways and other outdoor surfaces. 

As the low pushes S and E of Cape Cod and the islands late in
the day, should see a change back over to snow toward Tuesday
evening except across the S coast, Cape Cod and the islands.
Should see the precip taper off Tuesday evening, though snow
showers may linger across the E slopes of the Berkshires from
time to time overnight. 

Current forecast suggests snow amounts on the order of less than
an inch along the S coast to around 2-4 inches from around the
Mass Pike northward, but still quite a bit of uncertainty on the
timing of the mixing and/or changeover to rain and how far that
will lift northward. Another issue will be the icing and its
impacts. Could see about 0.1 to 0.2 inches across portions of N
CT, N RI into most areas of Massachusetts. 

Headlines for at least Advisory level conditions across the
interior remain possible (at least), but still questions on
placement of the PTYPES and how long they will last overnight
into Tuesday. 

Pretty confident for impacts across most roadways for the
Tuesday morning commute, especially areas near/north of Route 6
in CT and RI and near/NW of I-95, and especially across from
Hartford to NW of Providence to Boston and the interior SE Mass
areas. Coastal MA/RI into part of SE MA should see a shorter 
period of winter weather before changing to a cold rain.

Wednesday... 

Will see mainly dry conditions except for some spotty snow
showers across the higher terrain and possibly across Cape Cod
and the islands. Another weak trough moves across which may
enhance some light snow showers elsewhere, but will be tough
with lack of moisture away from the higher terrain and near the
coastline. Something to keep an eye on, though. 

Wednesday Night into Thursday Night... 

Arctic airmass dives SE across the region after the front passes
during early Wed night. Models continue to signal H85 temps
diving to -14C to -18C through the night. Light snow lingers
across outer Cape Cod and the island through around midnight
then should push offshore.

The coldest air of the season arrives Wed night and Thu. Lows
Wed night will bottom out in the single digits and teens, except
around 20s across outer Cape Cod and the islands. However, with
W-NW winds at 10-20 mph, maybe a bit higher along the immediate
coast, could see wind chill values bottom out from -5 to -10 
well inland and especially across the higher terrain to zero to
5 above along the coast by daybreak Thursday. May see some
dangerous wind chills especially for the children waiting for
buses out of doors. Bundle up!

As high pressure approaches Thursday, winds will diminish but
the cold air will remain in place. While temperatures moderate
some, it will remain cold though the wind chills will not be
quite as cold. Highs will be in the mid teens to around 20
inland and in the 20s across the coastal plain. 

Friday and Saturday... 

Large high pressure will dominate across the mid Atlc and
northeast both Friday and Saturday. It will remain cold on
Friday with highs in the 20s to around 30, though NW winds 
will be in the 5-10 mph range. Winds shift to N-NE but remain
light on Saturday with temps in the mid 20s and 30s with winds
veering to NE.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

Short Term /through Monday/...

Today...High confidence.  
Mainly VFR conditions despite a scattered to broken deck of mid
level cloudiness. May see brief MVFR CIGS across the inland high
terrain such as at KORH. Can not rule out a brief sprinkle or 
flurry at times. Strong W winds will continue through the 
day with gusts up to 30 to 40 knots in most locations, with some
gusts up to 40-45 knot across the high terrain, as well as 
portions of the Cape/Islands. 

Tonight...High confidence. 
VFR conditions. W winds gusts diminish a bit, but still expect 
many locations to gust between 25 and 35 knots through around
03Z-05Z.

Monday...High confidence. 
VFR conditions despite some mid level cloudiness, especially 
south of the Mass Turnpike. W winds of 5 to 15 knots.

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night: MVFR/IFR conditions possible. FZRA, chance SN,
chance PL.

Tuesday: Mainly IFR, with areas MVFR possible. Breezy. RA, SN,
PL, FZRA.

Tuesday Night: Mainly VFR, with local IFR possible. Breezy.
Slight chance SN.

Wednesday: VFR. Breezy. 

Wednesday Night through Thursday: VFR. Windy with gusts up to
35 kt.

&&

.MARINE...
Short Term /through Monday/...

Today and tonight...High confidence.  
Powerful storm across eastern Canada will continue to lift 
north with the pressure dropping below 970 mb. The result will 
be strong westerly gales. Gusts of 40 to 45 knots today and a 
good portion of tonight. High pressure will begin to build in 
from the southwest after midnight, which should allow winds to 
gradually trend downward after that time. Seas 8 to 15 feet 
across the outer waters today, gradually subsiding tonight.

Monday...High confidence.  Lingering SCA wind gusts across the 
eastern waters in the morning will diminish by afternoon as high 
pressure builds over the waters. Seas will also subside, but 
some 5 foot seas may linger across the eastern outer waters into
Mon afternoon.

Outlook /Monday Night through Thursday/...

Monday Night: Winds less than 25 kt. Rain likely, freezing rain
likely, chance of snow. Local visibility 1 to 3 nm.

Tuesday: Winds less than 25 kt. Local rough seas. Rain. 

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 9 ft. Chance of rain. Local
visibility 1 to 3 nm.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 9 ft. Slight chance of snow.
Areas of visibility 1 to 3 nm.

Wednesday Night: Strong winds with gusts up to 35 kt. Rough
seas up to 11 ft. Slight chance of snow. Visibility 1 to 3 nm.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 11 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 9 PM EST this evening for MAZ023-024.
     Wind Advisory until 7 PM EST this evening for MAZ002>016-018-
     019-021-022-026.
RI...Wind Advisory until 9 PM EST this evening for RIZ008.
MARINE...Gale Warning until 1 AM EST Monday for ANZ231>234-251-255-256.
     Gale Warning until 10 PM EST this evening for ANZ230.
     Gale Warning until 7 PM EST this evening for ANZ236.
     Gale Warning until 11 PM EST this evening for ANZ235-237.
     Gale Warning until 4 AM EST Monday for ANZ250-254.

&&

$$
SYNOPSIS...Frank/EVT
NEAR TERM...Frank/EVT

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