Special Weather Statement, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
146 PM EDT Tue Oct 23 2018

.SYNOPSIS...

Low pressure moving through New England will bring showers today,
especially to northern Massachusetts, before it heads offshore
tonight. Another surge of unseasonably chilly air moves into the
region Thursday and Friday. A significant coastal storm may impact
the region this weekend with heavy rainfall and strong coastal
winds, with some wet snow or mixed precipitation possible in the
interior.

&&

.NEAR TERM /THROUGH TONIGHT/...

2 pm update...

Scattered showers with embedded heavier downpours erupting over
S/SE areas of CT and RI. Latest RAP mesoanalysis illustrating
steep low level lapse rates and elevated instability. Undergoing
forcing in association with lead shortwave energy to parent closed
low-mid level low, beneath the left front quadrant of the upper
level jet, deep moist plume being captured as illustrated per
precipitable waters in RAP mesoanalysis is easily lofted.

As alluded to earlier, convective indices exceeding thresholds,
especially with respect to total totals. Couple hundred J/kg CAPE.
Plenty of SW uni-directional shear with both the 0-6 km mean wind
and bulk shear SW parallel. Anywhere surface SE wind, can't rule
out some 0-1 km turning / helicity which requires watching. Also
can't rule out graupel given low freezing levels and ascent of
an unstable column per RAP model soundings through said freezing
layer.

Isolated thunder prevailing with heavy rain / gusty wind wording.
Mainly focused E of aforementioned low and potent shortwave in
regions of better instability and low level forcing.

Outcomes entirely possible along and N of the attendant warm front
beginning to show up around the N MA border parent to the surface
low to the sweeping vortmax sweeps through. Elevated convection
possible above the shallow surface inversion with the focus over
NE MA.

First batch of rain ongoing, should be through by the end of the
PM commute, possibly a second sweeping batch of showers into eve
along the sweeping cold front as the surface low ejects out over
the Gulf of ME.

Continued consensus of high-res model guidance with latest near-
term forecast.

Tonight...

Showers lifting out however lingering mainly over N/NE MA. The
surface low traversing through the region. Continued ascent
upon an inflow moist-axis. The warm front lifting N as the cold
front sweeps through, mechanisms that'll keep the shower
activity going but advect it more towards the N/NE. Winds
backing out of the NW becoming blustery beneath the continued
rotating vortmax and mid-level closed low / trof axis. Will see
the low deepen as it becomes more vertically stacked, the
cyclonic trowaling axis beginning to emerge out of the E,
pushing W into interior N New England. Lows mainly subsequent of
cold air advection, lean with consensus of forecast guidance
around the upper 30s.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...

Wednesday...

Lingering showers over N/NE Massachusetts, especially the high
terrain, otherwise a chilly, raw day. Trowal axis and cyclonic
rearward ascent behind the closed mid-level low. Deformation
back across N New England, roughly SW-NE, associated lift with
the trowaling moist-axis. Otherwise blustery NW winds with cold
air advection allowing for steep lapse rates, mix-down of fast
winds to the surface. Gusts up around 35 mph will be possible.
Broken ceilings, prefer to actually lean towards the cooler side
of guidance with most areas seeing highs in the 40s, can't rule
out upper 30s for the high terrain if precipitation maintains a
long duration, subsequent lower column cooling.

Wednesday night...

Higher confidence of clearing out, winds diminishing. Consensus
of model forecast guidance has the mid-upper level disturbance
exiting resulting in prevailing subsidence. Drier air working in
rearward, cold air advection still continuing and lapse rates
remaining steep. However pressure gradient relaxing, winds should
diminish. Perhaps some lingering clouds and sprinkles along the
high terrain. With the winds still on the breezy side, will stray
from coldest forecast guidance. Still lean with lows well into
the 30s, high terrain in the 20s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...

Highlights...

* Dry weather with below normal temps Thu/Fri
* Rain and coastal wind Sat with some mixed precip possible interior
* Unsettled with showers at times Sun/Mon

Wednesday night into Friday...

Blustery and colder weather Wed night and Thu as deep mid level
trough east of New Eng slowly lift north, then diminishing wind by
Fri as high pres builds over New Eng. Dry weather through the period
with below normal temps.

Saturday through Monday...

Mid level trough undergoes significant amplification over the
eastern US as series of shortwaves dive into the mean trough. Models
signaling a coastal storm emerging off the mid Atlc coast and
tracking NE. Lots of moving parts with several shortwaves rotating
through the trough so still uncertainty regarding timing, intensity
and track of this storm. Ensemble guidance from GEFS and EPS
indicate wet period Sat into Sun, with potential for some heavy
rainfall Sat. However, if GFS is correct there is enough cold air in
the column for some snow accumulation in parts of the interior on
Sat, while ECMWF is mostly rain with just a bit of snow/sleet at the
onset. GFS and ECMWF both indicate 50-60 kt easterly low level jet
so also the potential for strong winds along the coast. Timing is
uncertain but latest guidance is highlighting Sat for the strongest
winds. Astronomical tides are a bit elevated this weekend so if the
easterly jet verifies, some minor coastal flood issues would be
possible.

Lots of spread with respect to low position on Sun but unsettled
weather expected Sun/Mon as mid level trough axis remains west of
New Eng with multiple shortwaves moving into the region.

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...

Forecaster Confidence Levels...

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

Short Term /through Wednesday Night/...High confidence.

Rest of today...
RA becoming widespread, lifting NE. Embedded +RA, possible TSRA.
Can't rule out associated gusty SW winds, upwards around 30 kt.
Low-end VFR / MVFR, lower with RA. S winds mainly along and S of
PSF-BOS, N winds otherwise. Higher confidence RA mainly N/E of
PSF-IJD-BID and associated lower conditions.

Tonight...
Winds reverting NW, becoming blustery. Associated -RA chances
that lingering mainly N of PSF-GHG. With RA, low-end VFR / MVFR
lingers. Gusts with NW winds up around 20 kts, highest over the
high terrain.

Wednesday...
Continued blustery NW winds, increasing gusts through the day up
as high as around 30 to 35 kts. RA continued to linger N/NE of
PSF-GHG, mainly over NE MA and points N/E. BKN CIGs mostly,
low-end VFR / MVFR, especially lower for high terrain.

Wednesday night...
Blustery NW winds diminishing as do CIGs. SCT low-end VFR / MVFR
more likely for high terrain with the possibility of a sprinkle.

KBOS Terminal...
Most RA activity around 18-20z, watching closely for +RA and SW
wind gust threat along with the possibility of graupel / small
hail. TEMPO for lower conditions. Monitoring for VCTS in the
first 6-hours. Lower conditions and showery weather likely to
linger all the way through much of Wednesday.

KBDL Terminal...
Mainly VCSH with SW winds today, low-end VFR CIGs with some MVFR
CIGs. Bigger story starting tonight going into Wednesday will be
the blustery NW winds, up around 30 kts possible during Wednesday.

Outlook /Thursday through Sunday/...

Thursday through Friday: VFR. Breezy.

Friday Night: Mainly VFR, with local IFR possible. Windy with
local gusts to 30 kt. Chance FZRA, slight chance RA.

Saturday: Mainly MVFR, with local VFR possible. Strong winds
with local gusts to 40 kt. Chance RA, FZRA likely.

Saturday Night: MVFR. Windy with gusts to 35 kt. Chance RA.

Sunday: Windy with gusts to 35 kt. Chance RA, slight chance
SHRA.

&&

.MARINE...

Forecaster Confidence Levels...

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

Short Term /through Wednesday Night/... High confidence.

Increasing S/SE winds today and building seas as warm front lifts
into CT, RI, and SE MA. Small Craft Advisories posted for all but
Boston Harbor and Narragansett Bay into tonight, before winds and
seas subside briefly. Low pressure heads to Gulf of Maine tonight,
followed by high pressure Wednesday. Winds shift to W/NW tonight and
increase on Wednesday, with 25-30kt gusts expected on all
waters.

Outlook /Thursday through Sunday/...

Thursday through Thursday Night: Low risk for Small Craft
Advisory winds with gusts up to 25 kt. Local rough seas.

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

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Chance of rain.

Saturday: Moderate risk for gale force winds with gusts up to
40 kt. Areas of rough seas. Rain likely.

Saturday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 17 ft. Chance of rain.

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 17 ft. Chance of rain, chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 5 PM this afternoon to midnight EDT
     tonight for ANZ232-233.
     Small Craft Advisory until 8 PM EDT this evening for ANZ231.
     Small Craft Advisory until midnight EDT tonight for ANZ235-237-
     251.
     Small Craft Advisory until 8 AM EDT Wednesday for ANZ250-
     254>256.

&&

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

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
342 AM EDT Tue Oct 23 2018

CTZ002>004-MAZ002>024-026-RIZ001>008-240745-
Hartford CT-Tolland CT-Windham CT-Western Franklin MA-
Eastern Franklin MA-Northern Worcester MA-Central Middlesex MA-
Western Essex MA-Eastern Essex MA-Western Hampshire MA-
Western Hampden 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-Barnstable MA-Dukes MA-Nantucket MA-
Northern Middlesex MA-Northwest Providence RI-
Southeast Providence RI-Western Kent RI-Eastern Kent RI-Bristol RI-
Washington RI-Newport RI-Block Island RI-
342 AM EDT Tue Oct 23 2018

This Hazardous Weather Outlook is for northern Connecticut, all of
Massachusetts east of Berkshire County, and Rhode Island.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

A significant coastal storm may bring strong winds along the coast on
Saturday, with some mixed precipitation possible in the interior. In
addition, there is a low risk of splashover this weekend along the
east coast of Massachusetts.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230>237-250-251-254>256-240745-
Boston Harbor-Cape Cod Bay-Nantucket Sound-Vineyard Sound-
Buzzards Bay-Rhode Island Sound-Narragansett Bay-Block Island Sound-
Coastal waters east of Ipswich Bay and the Stellwagen Bank National
Marine Sanctuary-Massachusetts Bay and Ipswich Bay-
Coastal waters from Provincetown MA to Chatham MA to Nantucket MA
out 20 nm-
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-
342 AM EDT Tue Oct 23 2018

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

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.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/NWSBoston

You can follow us on Twitter at
@NWSBoston

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Special Weather Statement
National Weather Service Boston/Norton MA
301 PM EDT TUE OCT 23 2018

MAZ018>022-231930-
Eastern Plymouth MA-Southern Bristol MA-Southern Plymouth MA-
Western Plymouth MA-Barnstable MA-
301 PM EDT TUE OCT 23 2018

...STRONG THUNDERSTORMS MOVING INTO THE CAPE COD CANAL REGION...

At 301 PM EDT, Doppler radar was tracking a strong thunderstorm over
Mattapoisett, or near Marion, moving northeast at 20 mph.

Pea size hail and winds in excess of 30 mph will accompany this
storm.

Locations impacted include...
Plymouth, Marion, Middleborough, Wareham, Sandwich, Bourne, Carver,
Acushnet, Mattapoisett and Rochester.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

These storms may intensify and become capable of producing damage.
Stay tuned for updated statements and possible warnings.

&&

LAT...LON 4176 7049 4171 7068 4172 7070 4170 7070
      4166 7084 4174 7091 4191 7071
TIME...MOT...LOC 1901Z 227DEG 18KT 4170 7082

SIPPRELL

Special Weather Statement
National Weather Service Boston/Norton MA
306 PM EDT TUE OCT 23 2018

RIZ001-002-231930-
Northwest Providence RI-Southeast Providence RI-
306 PM EDT TUE OCT 23 2018

...STRONG THUNDERSTORMS OVER NORTHERN RHODE ISLAND...

At 305 PM EDT, Doppler radar was tracking a strong thunderstorm over
Scituate, or near Johnston, moving northeast at 20 mph.

Pea size hail and winds in excess of 30 mph will accompany this
storm.

Locations impacted include...
Providence, Cranston, Pawtucket, East Providence, Woonsocket, North
Providence, Johnston, Smithfield, Lincoln, Central Falls, North
Smithfield, Scituate, Glocester and Foster.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

These storms may intensify and become capable of producing damage.
Stay tuned for updated statements and possible warnings.

&&

LAT...LON 4182 7170 4200 7153 4185 7134 4184 7134
      4176 7163
TIME...MOT...LOC 1905Z 230DEG 19KT 4181 7162

SIPPRELL

Special Weather Statement
National Weather Service Boston/Norton MA
318 PM EDT TUE OCT 23 2018

MAZ022-231945-
Barnstable MA-
318 PM EDT TUE OCT 23 2018

...STRONG THUNDERSTORM...

At 318 PM EDT, Doppler radar was tracking a strong thunderstorm near
Provincetown, moving northeast at 30 mph.

Winds in excess of 40 mph will accompany this storm.

Locations impacted include...
Provincetown and Truro.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

&&

LAT...LON 4203 7013 4204 7015 4203 7018 4202 7017
      4202 7021 4206 7026 4209 7024 4210 7019
      4206 7007
TIME...MOT...LOC 1918Z 220DEG 28KT 4199 7029

BW

Special Weather Statement
National Weather Service Boston/Norton MA
320 PM EDT TUE OCT 23 2018

CTZ002-003-MAZ004-010-011-231945-
Hartford CT-Tolland CT-Eastern Hampden MA-Northern Worcester MA-
Eastern Hampshire MA-
320 PM EDT TUE OCT 23 2018

...STRONG THUNDERSTORMS DEVELOPING ACROSS THE CONNECTICUT RIVER
VALLEY...

At 320 PM EDT, Doppler radar was tracking a strong thunderstorm over
Springfield, moving northeast at 20 mph.

Pea size hail and winds in excess of 30 mph will accompany this
storm.

Locations impacted include...
Springfield, Chicopee, Enfield, Amherst, Agawam, West Springfield,
Ludlow, Longmeadow, East Longmeadow, Belchertown, Wilbraham, Palmer,
Somers, Ware, Monson, Granby, Hampden, Warren and Brimfield.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

These storms may intensify and become capable of producing damage.
Stay tuned for updated statements and possible warnings.

&&

LAT...LON 4201 7254 4207 7263 4235 7247 4218 7214
TIME...MOT...LOC 1920Z 220DEG 19KT 4211 7252

SIPPRELL