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Area forecast discussion 
National Weather Service Taunton Massachusetts
1115 PM EST Wednesday Nov 26 2014

Synopsis...
strong low pressure just south of Nantucket will continue to
deepen as it moves toward Nova Scotia overnight. The variety of
weather impacts from this storm will diminish overnight...with
conditions improving for Thanksgiving day. High pressure builds
over New England Friday...then shifts offshore over the weekend.
A warm front moves across the region Saturday night. A cold front
then swings through New England late Sunday night or Monday.
Another warm front approaches next Wednesday.

&&

Near term /until 6 am Thursday morning/...

1045 PM update...

Continue to track surface low pressure as it passed S of Marthas
Vineyard and Nantucket over the last couple of hours. Noting the
low tending to elongate SW-NE with pressure down to 997 hpa at 03z as
it shifts east of Nantucket. NE regional 88d radar signatures showing
precipitation tapering off except for band of precipitation moving east out of the
Hudson Valley into the Berkshires through NE New Jersey...likely
associated with the middle level low pressure. 00z NAM indicating this 700 mb
low should shift NE overnight...taking the remaining precipitation with
it. Strongest winds continue along the immediate East Coast from
around Plymouth to Cape Cod and the islands.

Temperatures have been falling as surface winds back to north and diminish
across central and western areas with precipitation tending to change
back to light snow...but still see -fzra at kash. Should continue
to see this trend through the remainder of the overnight.

Continued to trend precipitation ending from SW-NE through the overnight
as previously forecast...though might linger across S New Hampshire/NE Massachusetts
into daybreak.

Have updated near term forecast to bring conditions current.

&&

Short term /6 am Thursday through 6 am Thursday/...
see long term section.

&&

Long term /Thursday through Wednesday/...
big picture... Thanksgiving starts with a two-stream trough over the
eastern USA and a ridge over the west. Shortwave in the southern
stream moves over New England Thursday...quickly followed by a
northern stream shortwave on Friday. The flow GOES zonal over the
weekend. A shortwave in the northern stream drops south from
northern Canada and moves along the border early next week. A second
northern shortwave will deepen over the Great Lakes midweek drawing
milder air north over New England.

Model upper contours are similar through the weekend. The ggem edges
faster early next week. The European model (ecmwf) becomes sharper with the Great
Lakes shortwave next midweek but has a similar axis location as the
GFS. We favored a blend of the model data.

The dailies...

Thursday-Friday.... southern and northern stream shortwaves move
across New England. This maintains some weak lift in an airmass that
maintains deep moisture through Friday morning before drying. With
this combination we held on to chance probability of precipitation Thursday across much of
mass and New Hampshire. The airmass dries Friday so land areas should see a
clearing trend. Over water there will be an 18c air-water temperature
difference...an equilibrium level of 6400 feet...and a 12-14 knot
northwest wind. This should support ocean effect rain/snow showers.
The northwest fetch will favor mainly offshore showers although
Provincetown and Truro might get clipped.

Saturday-Sunday... high pressure axis shifts offshore. Clouds
increase in the warm advection...but lift is rather weak. We
indicated slight chance probability of precipitation Saturday as a warm front lifts
northeast through the region. Decreasing clouds and probability of precipitation Sunday as
the warm front shifts north of US.

Monday...Great Lakes shortwave/surface low swings a cold front
through New England. There is uncertainty as to timing of the
front...but limited support for lift and showers from the right
entrance region of a trailing upper jet. We indicated chance probability of precipitation
and stretched the time from early morning through the evening.

Tuesday-Wednesday... high pressure moves across the region Tuesday
and brings cooler temperatures. The next shortwave approaches Wednesday
with warm advection running over the top of those cooler temperatures. We
used chance probability of precipitation from early morning through the day. Temperature
profiles suggest a mix of precipitation at the start especially north/west of
Boston...but temperatures warm enough on Wednesday for rain.

&&

Aviation /04z Thursday through Monday/...
forecaster confidence levels...

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

Short term /through tonight/...moderate confidence.

Tonight...precipitation winds down starting 01z along the South Coast
and 06z in southwest New Hampshire. Visibilities 1/2 mile to 1 mile in heavy snow
from western mass into southern New Hampshire...2-3 miles in northern
CT...and 3-5 miles in rain in Rhode Island and southeast mass. These will
improve to p6sm from south to north 01z to 06z. Most ceilings
500-1000 feet which should improve to 1500-2000 feet overnight.

Strong north-northeast winds linger in Rhode Island and southeast mass early
tonight...then diminish as directions shift to northwest
overnight.

Kbos terminal...high confidence in trends but lower confidence in
exact timing. Heaviest precipitation through 03z

Kbdl terminal...high confidence in trends but lower confidence in
exact timing especially ptype.

Outlook...Thursday through Monday...moderate confidence

Thursday...mixed VFR and MVFR with scattered rain/snow showers.
Diminishing northwest winds.

Friday...VFR with northwest winds gusting 15-20 knots.

Saturday-Sunday...increasing sky cover but mainly VFR. Low potential
for MVFR ceilings moving north off the ocean into Cape Cod and islands.
Increasing southwest winds at 2000 feet above ground level...reaching 35-40
knots...with lighter southwest winds at surface. This would mean
potential for low level wind shear Sunday.

Monday...cold front moves across New England with scattered showers.
Brief MVFR ceilings/visibilities in any showers. Continued southwest winds
ahead of the front with 35-40 knots at 2000 feet above ground level and potential
low level wind shear.

&&

Marine...
forecaster confidence levels...

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

Short term /through tonight/...

Tonight...high confidence.
Gale center tracks just south of Nantucket and east of Outer Cape
cod by midnight. NE gale force winds will push NE between 05z-07z
then will back to north-northwest through the remainder of the night as they
diminish. Seas appear to have maxed out at 10-15 feet on the open
waters including mass and Ipswich bays and up to 6 feet on the
southern open sounds...which should slowly subside through the
remainder of the night. Low visibilities in rain early...then will slowly
improve as precipitation weakens. Precipitation will mix with or change to snow
showers before ending across the southern waters by around 08z-
09z...but could linger on the eastern waters through sunrise.

Outlook...Thursday through Monday...moderate confidence.

Thursday...northwest winds gust near 25 knots early but diminish
through the day. Seas start the day rough...with heights 8 to 12
feet on the exposed waters...then diminish through the day. Small
Craft Advisory will be needed on most waters.

Friday... lingering 5 to 6 foot seas on the outer waters. Northwest
winds will gust near 20 knots. A Small Craft Advisory may be needed
on some of the waters.

Saturday-Sunday... southwest winds gusting to 20 to 25 knots
Saturday and around 25 knots Sunday. Seas will be less than 5 feet
Saturday and then build to 5 to 6 feet on the exposed waters Sunday.
A Small Craft Advisory may be needed Sunday.

Monday...southwest winds gusting 20 to 25 knots until the cold front
moves through. Winds then shift to west-northwest behind the front
with similar gusts. Seas on the exposed waters will be 5 to 8 feet.
A Small Craft Advisory may be needed.

&&

Tides/coastal flooding...
high tide of concern is shortly after midnight tonight. Strongest
winds and pressure falls occur during low tide this evening with
winds and surge easing toward high tide. Thus impacts will be
limited with very minor erosion and tidal flooding.

&&

Box watches/warnings/advisories...
CT...Winter Storm Warning until 7 am EST Thursday for ctz002>004.
Massachusetts...Winter Storm Warning until 7 am EST Thursday for maz002>006-
008>012-026.
Wind Advisory until 3 am EST Thursday for maz019-022>024.
Winter Weather Advisory until 7 am EST Thursday for maz007-
013>017.
New Hampshire...Winter Storm Warning until 7 am EST Thursday for nhz011-012-
015.
Rhode Island...Winter Weather Advisory until 7 am EST Thursday for riz001>003.
Marine...Gale Warning until 5 am EST Thursday for anz230>237.
Gale Warning until 7 am EST Thursday for anz250-251-254>256.

&&

$$
Synopsis...wtb/rlg
near term...evt
short term...rlg
long term...wtb
aviation...wtb/rlg
marine...wtb/rlg/evt
tides/coastal flooding...staff

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