Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 231402

Area Forecast Discussion
National Weather Service Taunton MA
1002 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.



10 am update...

Blustery W winds continuing lending to wind damage reports. Wind
Advisory continues through the afternoon hours with the threat of
wind gusts around 35 to 45 mph, up to 50 mph, resulting in downed
tree and tree limbs, isolated to scattered power outages, as well
as unsecured outdoor objects becoming airborne and difficulty in
driving high profile vehicles. Strongest winds more than likely
across the high terrain and over the warmer than ocean waters, thus
potential impacts along the immediate shoreline, Cape and Islands.
Will keep issuing local storm reports at least every other hour.

Overall, last of the vort lobe energy associated with a negatively
tilted trough lifts N/E into the Canadian maritimes along with the
present 979 mb surface low over the St. Lawrence River Valley. Up
against at 1025 mb high over the SE CONUS, combination of a tight
pressure gradient and isallobaric component of the winds, along
with boundary layer mixing up to H85 (3-4 kft agl) as colder air
moves in aloft allowing lapse rates to become close if not super
adiabatic, where the top of the mixed layer has sustained winds
around 40 to 50 mph, is yielding blustery W winds at the surface.
Agree with the previous forecaster that using the mean wind within
the mixed layer, and not simply the top of the layer itself, nets
the suggestion of occasional gusts of 35 to 45 mph at the surface.
Again, highest confidence of strongest winds is across the high
terrain and warmer waters.

In addition, blustery W winds will make for chilly than average
conditions. Highs around the mid to upper 50s especially in the
sunshine, but likely somewhat of a shock when in the shade.

An overall dry day as downsloping drier air as observed within the
latest isentropic analysis and water vapor imagery takes precedent.
Comma-head moisture lifting out with subsidence prevailing. Should
see conditions clear out completely if not so already.

Overall forecast is on track.



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.



*/ Highlights...

 * 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.

*/ Details...

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 end.

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/...

Today...High confidence.
VFR. 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...Moderate confidence.
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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