Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 300613

Area Forecast Discussion
National Weather Service Taunton MA
113 AM EST Wed Nov 30 2016

Dry and mild overnight into Wednesday morning along with areas of
dense fog especially across valley locations. Another soaking
rain affects the region late Wednesday afternoon and night. Near
seasonable conditions with breezy NW flow follows for the late
week period into the weekend. Early next week, another wet-
weather disturbance is possible with a potential wintry-mix with
onset changing over to all rain.



1 am update...

*** Dense fog CT River Valley/I-91 corridor this morning ***

Dense Fog...

Winds have decoupled in the CT river valley and coupled with low
level moisture /dew pts in the upper 40s to lower 50s/ has
resulted in dense fog to form. Thus have issued a dense fog
advisory for this region until 14z/9am...with slow improvement
thereafter. Elsewhere areas of dense fog may form as winds drop
off during the predawn hours. This coupled with low level moisture
in the form of dew pts in the 50s across RI and eastern MA may be
sufficient for additional areas of dense fog to develop later this
morning. Will monitor as the morning progresses.


low level jet moving offshore however pres rises approaching from
the west yielding sw winds to gusts up to 25-30 kt across Cape Cod
and the islands. However the trend will be for winds to continue
to diminish during the predawn hours.


Mild early this morning with post frontal airmass dew pts in the
40s and 50s.



* Another soaking rain later Wednesday into Wednesday night

Wednesday and Wednesday night...

Areas of fog should burn off by mid morning on Wednesday. While
it will start off dry, another shortwave will approach from the
SW. Easterly winds at the surface coupled with moist SW flow
aloft will increase the forcing for ascent. Light rain will
develop later into the morning into the afternoon from west to
east. The heavier rain will probably not arrive until late
Wednesday afternoon/evening when another impressive low level jet
of 45 to 55 knots joins with PWATS that remain 2+ standard
deviations above normal. There will be pockets of impressive
frontogenesis/omega that should lead to bands of locally heavy
rainfall. We also can not rule out an isolated t-storm or two
S of the MA Pike with some marginal elevated instability. High
temps on Wednesday should be in the upper 40s to the middle 50s,
with the mildest readings found south of the MA Turnpike.

In a nutshell...rainfall amounts from this second system should
average between 0.50 and 1.50 inches. The rain should come to an
end toward daybreak on Thursday as shortwave energy moves east of
the region. Low temps will be in the 40s.



*/ Highlights...

 - Near seasonable, dry pattern with breezy NW winds late week into
   the weekend

 - Initial wintry mix changing over to all rain possible early next

*/ Overview...

Perhaps an over-running onset of mixed wintry precipitation events,
but otherwise a warm-wetter pattern continues. La Nina is seemingly
the dominant influence upon the N Hemisphere as all other atmospheric
teleconnections are near-neutral, relatively flat. A more buckled
pattern than idealized across N America, with strong C CONUS cyclo-
genesis drawing down colder air W beneath a favorable region of
troughing while latching into tropical maritime air S. Would appear
with prevailing E CONUS downstream ridging, deepening and occluding
storm centers out of the C CONUS are stretched N/W of S New England,
inside-runners, placing S New England in the warmer and wetter
region of outcomes. A progressive pattern of initial over-running
followed by a sweeping cold front before high pressure and colder
air settles back in. Can not rule out a continuation of mixed
wintry precipitation events with the onset of storm systems noting
the potential for cold air damming and triple point lows. Will
note in the details below.

Would appear Arctic air presently is locked up round the polar low.
Indications though that as we go towards mid-December the polar low
and associated energy becomes displaced. Associated jet stream round
the maritimes becomes buckled and more amplified. Potentially thus
we could see shots of Arctic air being introduced as we go deeper
into Winter. No doubt if the pattern continues we would see such air
slide S across the Rockies into the C CONUS before sliding E, likely
moderating. It`s early but worth noting of potential trends down the
road, something to watch.

*/ Details...

Thursday through the Weekend...

NW flow and cold air advection initially through which mid-level
energy and moisture continue to rotate round a dying low pressure
center over the N/E Great Lakes Region. A reinforcing cold front
inbetween around Saturday morning. Usual pattern: colder NW flow
over the Lakes invokes broken to overcast cloud decks along with
showery precipitation, downsloping over the high terrain N/W of our
region, only scattered to broken decks remain with a slight chance
of a shower, the greatest chance being over the Berkshires. Well-
mixed lapse rates with diurnal heating, will see the mix-down of
drier air and faster winds, but nothing that would appear to reach
advisory level criteria. Cooler air over warmer waters, ocean-effect
processes proceed, and depending on the direction of the wind, will
more than likely impact the Outer Cape and Islands, especially on
Saturday behind the reinforcing cold front. Will go with chance of
showers at times for the aforementioned locales. Conditions overall
will feel cooler given the breezy NW winds, but in actuality remain
near-seasonable for this time of year. High pressure across the
region over the weekend from the SW, will see a return S flow.

Early next week...

Consensus indications of wet-weather though the exact evolution and
timing remains uncertain. With onset it is possible to see wintry
mixed precipitation associated with over-running ahead of an area of
low pressure emerging out of the S CONUS, especially if high pressure
sets up over E Canada as some of the solutions indicate. Leaning
towards an inside runner solution occluding into the E Great Lakes
as a secondary low develops at the triple point and rapidly deepening
offshore. Going with ensemble means but advertising low confidence.
Chance PoPs for now through the remainder of the week.


Forecaster Confidence Levels...

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

Short Term /through Thursday/...

115 am update...

Thru 12z...

Low confidence forecast. Trends for cigs and vsbys is upward as
west winds mix out low level moisture. However as winds diminish
toward sunrise ground fog may develop especially with dew pts in
the 40s and 50s. This already taking place in the CT river valley
where winds have diminished and dense fog as formed. Not
expecting any improvement here until 14z/15z. Elsewhere trend
upward to MVFR-VFR but have to watch ground fog to develop 09z-12z
which may lower conditions back to IFR-MVFR. Worst conditions will
likely be in the interior valleys and low lying locations near the

After 12z...

MVFR-VFR however local LIFR-IFR in dense fog CT river valley and
low lying sections elsewhere will improve to MVFR-VFR toward
midday. Then conditions lower back to MVFR-IFR in rain 18z-21z
with rain becoming steady and heavy at times from BDL-ORH-ASH and
pts westward. Confidence is low on exact timing but higher on


Widespread IFR with embedded LIFR in rain...heavy at times inland
from BDL-ORH-ASH and points westward. LLWS possible south coast.
vsbys and cigs may improve to MVFR-VFR beginning 09z-12z Wed along
with a drying trend and a wind shift to the west.


Any early MVFR cigs quickly lift to VFR along with dry conditions.
Diurnal clouds yield VFR cigs for the afternoon. West winds 15 to
25 kt along with dry runways. High forecast confidence.

KBOS TAF...MVFR-VFR this morning lowers to MVFR-IFR 21Z-24Z today
as rain overspreads the terminal. Not expecting any dense fog this
morning at Logan.

KBDL TAF...LIFR in dense fog this morning likely lingers until
14z-15z then slow improvement thereafter.

Outlook /Thursday Night through Sunday/...

SCT-BKN low-end VFR. NW winds, blustery at times, especially along
the coast with gusts initially Thursday and Friday up to 30 kts,
tapering downward with time. MVFR possible over the Outer Cape with
chance -RA and a breezy N wind.


Forecaster Confidence Levels.

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

Short Term /through Thursday/...

7 pm update...

Tonight...Moderate to high confidence.

S gusts up to 40 kts expected with moderate to heavy rain which
will push E of the waters later tonight prior to midnight. With
gales, will see waves build 7 to 10 feet as they have already at
buoy 44097. With heavy rain, expect reductions to visibility.
Expect winds to diminish while turning out of the W towards
Wednesday morning.

Wednesday and Wednesday night...

Winds should not be much of a factor into early Wednesday afternoon.
However, east winds of 25 to 30 knots shifting to the south should
develop later Wed afternoon and night. Brief marginal gale force
wind gusts may develop, but inversion will keep those short-lived
if they do occur. Seas once again should build back to between 7
and 10 feet across our southern waters.

Outlook /Thursday Night through Sunday/...

NW winds possibly gusting as high as 30 kts initially with a low
risk of gale force, Thursday and Friday. Winds building with the
wave stress. Likely to see the development of ocean-effect showers.
Both wind and shower chances diminish as we go into the weekend.


CT...Dense Fog Advisory until 9 AM EST this morning for CTZ002.
MA...Dense Fog Advisory until 9 AM EST this morning for MAZ003-010-
MARINE...Gale Warning until 1 AM EST early this morning for ANZ231>235-
     Small Craft Advisory until 1 AM EST early this morning for


NEAR TERM...Frank/Nocera/Sipprell
LONG TERM...Sipprell
MARINE...Frank/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.