Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 230746

Area Forecast Discussion
National Weather Service Taunton MA
346 AM EDT Sun Oct 23 2016

A strong storm will move north through eastern Canada and will
continue to bring gusty winds but clearing skies today. A fast
moving low pressure may bring a period of light rain south of the
Mass Pike late tonight and early Mon as it tracks south of New
England. Dry and cool northwest flow will persist Monday afternoon
through Wednesday. High pressure will drifts east of New England
late Thursday followed by a front and possible showers late
Thursday night into Friday.


Comma head showers continue to rotate into New Eng early this
morning as mid level low moves north into Canada. Expect this
activity to gradually dissipate through 12z as mid level drying
begins to move in from the SW. Otherwise, clouds will give way
to increasing sunshine from SW to NE through the morning into
midday as this drying overspreads the region.

Regarding wind, soundings show good mixing up 850 mb with low
level lapse rates in this layer increasing to 8.5-9.5 C/km. 850
mb winds 45-50 kt and while we won`t mix all this to the surface
in gusts, taking an average of the 850 wind and the mean wind in
the mixed layer suggests occasional gusts to 30-40 kt (35-45 mph)
so we will continue the wind advisory. The strongest gusts are
expected over the higher elevations.

850 mb temps 0 to -2C will yield highs in the mid/upper 50s
except closer to 50 degrees over the higher elevations.


Tonight into Monday...
Models all show a fairly robust mid level short wave moving into
SNE late tonight and early Mon with a clipper type open wave
tracking south of New England. Deepening moisture ahead of the
wave overspreads the region late tonight and a W-E band of low to
mid level frontogenesis will combine with left exit region of the
upper jet to produce an area of decent mid level forcing. There is
some uncertainty with the location of the forcing and assocd
rainfall but consensus of the guidance and ensemble probs suggest
best chance of a period of rain south of the Mass Pike late
tonight into early Mon. Will have chc pops along and south of the
Pike with likely pops near the south coast. This is a quick moving
system so it appears most of the precip will occur in less than a
6 hour period through 12z. The guidance is showing potential for
around 0.25" within the band which may be across SNE but could
also end up south of New Eng.

Lingering clouds across SE New Eng early Monday will give way to
increasing sunshine by midday as clearing moves in from the
north. But another shortwave and strong mid level cooling moves in
during the afternoon which will lead to sct-bkn cu developing,
especially interior. As the wave moves to the east increasing NW
winds will develop in the afternoon with gusts 25-30 mph. Highs
Monday mid/upper 50s except closer to 50 over the higher terrain.



 * Cool and blustery through Tuesday.
 * Monitor for frost potential Tuesday night and especially
   Wednesday night.
 * Risk for wet weather returns late Thursday into Friday.

Overview and model preferences... Labrador trof will slowly meander
to the E as ridging upstream builds from the Great Lakes into New
England.  However, the trof maintains a constant draw of CP air
across the region right through mid week leading to cool, fall-like
conditions lingering.  Confidence remains high in these trends as
models remain in good agreement.  In fact, am noting that with the
00Z update, even the next trof associated with a clipper system
models are converging on a solution that suggests a passage of the
sfc low to the NW by late in the work-week.  While there are still a
few temporal/spatial issues to work out, feel we have enough to
begin using a blend of deterministic guidance as a baseline beyond
the mid week period.


Mon night into Tue night... Blustery period following secondary wave
passage early in the day on Mon.  Pres gradient remains tight
although the isallobaric couplet slowly shifts meridionally
suggesting winds will be shifting toward the N with time.  Still
expect diurnal gusts to reach 25-35 mph at times, diminishing
somewhat overnight, but not enough to fully realize radiational
cooling.  The only caveat may be Tue night, when NW valleys do
decouple somewhat, allowing for temps to cool in comparison to Mon
night.  At any rate H85 temps drop below 0C and as low as -8C
potentially Tue morning.  H92 temps aren`t far behind, dropping to -
2C around the same time.  Therefore, expecting overall temps below
normal with highs mainly in the mid 40s to mid 50s, while lows fall
into the 30s both nights.  Low risk for frost Tue night, but the
pres gradient may mitigate the impact, especially since the most
likely locations to see frost have already seen their growing season

Wed into Thu daytime... High pres will be moving in from the E,
which allows winds to shift mainly to the N and possibly even NE by
mid day on Wed.  This trajectory will help to initiate ocean effect
conditions as H85 temps remain near -6C with SSTs near +15C.
Therefore, plenty of low-lvl instability for showers and clouds to
impact portions of the Cape/Islands and even southern Plymouth
county in MA until winds shift by Thu morning.  Otherwise, mainly
dry conditions, but with lighter winds across the interior.  Highs
remain similar to previous days, mainly upper 40s into the 50s on
Wed, warming into the low-mid 50s.  However, Wed night, good setup
for radiational cooling suggests several locations could drop below
freezing, including a few spots in the 20s.  Will need to watch
this, as frost headlines may be needed for those locations where the
growing season has not ended.

Late Thu into Fri... Clipper low pres with (as previous forecaster
noted) a cold occlusion in process looks to pass NW of the region.
Models only now beginning to agree on this solution, so although
confidence grows, it is not necessarily high yet.  Noting triple-
point low potential which could increase the risk for precip as the
fronts move into S New England early Fri.  Ensembles have
probabilities near 70 percent for at least a quarter inch of total
precip.  Therefore will be featuring POPs through this period with
timing based on the more progressive GFS and slower ECMWF blend.
Temperatures closer to seasonal normals as both H85 and H92 temps
now exceed 0C.

Next weekend... Another round of high pres follows.  This particular
feature looks to feature temperatures closer to normal as it is
uncertain whether H92/H85 temps will drop below climatological
normals.  Ensemble probabilities are rather low at this time.


Forecaster Confidence Levels.

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

Short Term /through Monday/...

Through 12z...Mainly VFR cigs with areas of MVFR higher terrain
and Cape Cod improving by 12z. Sct showers western New Eng mixed
with snow higher elevations in the Berkshires will dissipate
08-12z. W wind gusts 25-35 kt, strongest over high terrain and SE
coastal areas.

Today...High confidence. VFR with clearing developing from SW to
NE during the morning. W gusts 30-35 kt with up to 40 kts over
high terrain.

Tonight...Moderate confidence. Mainly VFR, but may see areas of
MVFR develop south of the Mass Pike 06-12z as an area of rain
moves into the region. Diminishing wind but gusty into the
evening near the immediate coast.

Monday...Areas of MVFR possible early SE coastal areas in
lingering light rain, otherwise VFR with clearing skies.
Increasing NW winds with gusts to 20-25 kt developing, strongest
higher terrain.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Mon night through Tue night...High confidence.
Mainly VFR.  NW wind gusts 20-25 kt at times during the day inland,
but remaining into the overnight at  coastal terminals.

Wed and Wed night...High confidence.
VFR continues, but with lighter winds.

Thu into Fri...Moderate confidence.
VFR starts Thu, but a mix of MVFR/IFR possible as a front crosses
the region Thu night into Fri with SHRA.  Winds shift from the E, to
SE, with gusts near shore approaching 25 kt at times.


Forecaster Confidence Levels.

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

Short Term /through Monday/...High confidence.

Gale force west winds with gusts 35-40 kt will gradually diminish
through tonight. NW winds will increase again Mon with gusts
25-30 kt in the afternoon. Peak of the seas occurring early this
morning and will slowly subside but remain above SCA through Mon.
Vsbys may lower late tonight and early Mon in an area of rain,
especially south coastal waters.

Outlook /Monday Night through Thursday/...

Mon night into Tue night...High Confidence.
Winds gradually shift to the NW with time.  However gusts along the
waters should still reach 25-30 kt at times with seas still in the 5-
7ft range along the ocean waters. Small craft advisories continue
into the evening hours Monday, at which point conditions finally

Wed into Wed night...High confidence.
Winds and seas generally below small craft conditions although there
is a low risk for a lingering swell near 5 ft which will need to be
watched.  Otherwise, expect widespread showers across the eastern

Thu intro Fri...Moderate confidence.
Thu starts with conditions below small craft thresholds as winds
shift to the E.  However, gradual shift to the SE and increasing
wind waves will yield small craft conditions by late Thu and
continuing into Fri as a front approaches, then crosses the waters.
Winds peak 25-30kt with seas reaching 6-8 ft.


CT...Wind Advisory until 2 PM EDT this afternoon for CTZ002>004.
MA...Wind Advisory until 6 PM EDT this evening for MAZ002>024-026.
RI...Wind Advisory until 6 PM EDT this evening for RIZ001>008.
MARINE...Gale Warning until 11 PM EDT this evening for ANZ232>235-237.
     Gale Warning until 8 PM EDT this evening for ANZ230-236.
     Gale Warning until 2 AM EDT Monday for ANZ231-250-251-254>256.


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