Area Forecast Discussion
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FXUS61 KBOX 201827

Area Forecast Discussion
National Weather Service Taunton MA
227 PM EDT Thu Oct 20 2016

Cold front stalls south of the region today then moves back north
as a warm front later tonight. A few showers or drizzle is
possible late this afternoon and tonight, then a more widespread
heavier rainfall is likely sometime Friday into early Saturday as
low pressure tracks across the region. Cooler and mainly dry
weather will follow Sunday into early next week.



230 pm update...

Clouds on the increase given diurnal heating from late this
morning along with WAA pattern developing over the region from the south
and west. Showers impacting northwest MA will continue moving
northeast this afternoon with a little break in the action for
this area and then showers redeveloping upstream over the Catskills.

Otherwise much of the region remains dry this afternoon with
clouds remaining on the increase. Temps have overachieved with
highs in the low 70s across portions of RI and CT. Thus have
bumped up temps a few degs.

Previous discussion...

High pressure moves east from northern New England today with
sunshine giving way to increasing clouds from west to east as
column moisture increases. As a frontal wave lifts NE along the
spine of the Appalachians a 40-50 kt low level jet will become
focused across central and northern NY this afternoon. The leading
edge of the jet approaches from the west late today which will
bring a chance of a few showers across mainly western New Eng as
weak ascent develops north of the stalled boundary, but best
forcing and deep moisture axis remains well to the west where main
focus for heavier rain will be.

Much cooler today with easterly flow but temps still above normal
with highs reaching mid/upper 60s south of the pike, cooler to the
north and along the east coast.



As mid level trof amplifies to the west, some mid level drying
will lift north into SNE during the night. Low level jet and best
moisture transport remains focused to the north and west where
best chance of steadier/heavier rain. However, moisture is
abundant below 850 mb with shallow lift likely leading to areas of
drizzle or light rain, and fog will likely become widespread and
locally dense as warm front lifts north into SNE with increasing
dewpoints. Expect rising temps into the 60s overnight south of
Mass pike with temps closer to 50 near NH border.


High amplitude trof moves east into the Great Lakes with deep
southerly flow developing from the surface through the mid levels.
Interesting set up developing with one area of heavy rainfall
to the west across New York assocd with right entrance region of
strong upper jet and strong frontogenesis along the mid level
front. Meanwhile, models indicate low pres lifting north toward
SNE with area of enhanced low level convergence and some
interaction with tropical moisture and elevated instability. This
will lead to more widespread rainfall and possible isold thunder
but there is low confidence on where the axis of potential heavy
rainfall will set up. It may be across SNE but it could also end
up to the east. This is something that will need to be evaluated
further with later forecasts.

SNE will be in the warm sector Fri with temps reaching the upper
60s to lower 70s and quite humid with dewpoints climbing well into
the 60s.



 * Rainy and unsettled Friday night into early Saturday.
 * Cooler and dry by Saturday night.
 * Seasonable early next week.

Overview and model preferences... With new 00Z update, noting the
good agreement at the synoptic scale continues.  However, it is the
lower level interactions that continue to show a lot of spread, and
this includes both ensembles and operational models.  At odds is the
interaction with weak tropical disturbance and attendant moisture
which will be captured early enough for cyclogenesis to occur over
or near S New England (ECMWF/CMC, several ensemble members) or
offshore (GFS, several other ensemble members).  This will
ultimately dictate how much rain falls Fri night, and how long the
wet wx lingers into Sat.  Looking at soundings, noting a fair amount
of moisture trapped in the lower lvls even as drier air builds over
through the day on Sat.  Given this fact, and that ECMWF has been a
bit more persistent, will add a bit more weight towards it`s
solution with this update.


Sat night and Sat... Strong cyclogenesis S or SE of S New England
will gradually shift to the NNE as it continues to strengthen and
becomes captured by the upper lvl cutoff.  With this update, suggest
some mod-heavy rainfall during the overnight hours as increased low-
lvl convergence and cyclogenesis occurs over portions of S New
England.  PWAT plume is highest offshore, but noting enough moisture
(PWATS near 1.5 inches, 2 std deviations above normal).  QPF
probabilities are near 70 percent for values of 0.5-1.0 inches.
Therefore, would not be surprised to see some areas receive nearly
1.00 inches during the overnight hours and into early Sat in the
comma-head precip as low pres shifts into N New England.  Still some
question on exactly where the peak precip will occur, primarily due
to the models continuing to struggle with the tropical interaction.
Stay tuned for updates as we approach and better refine the axis of
highest precip.  Timing wise, will allow pops to linger into mid day
on Saturday, slower than previous forecasts.

Temps remain near to above normal thanks to H85 not remaining above
+6C until Sat afternoon.  Looking at highs in the upper 60s, with
lows only falling into the low 60s. Also, strong NW flow especially
if mixing increases with some sunshine late Sat.  30-40 mph gusts
possible, with a low risk for some wind advisories.

Sat night through Sun... Strong NW flow continues with drier air
moving in aloft first.  Therefore, it may take some time for all low
clouds to clear out Sun night.  Otherwise, cold advection allows H85
temps to drop below 0C while H92 temps fall to near +4C.  Highs Sun
should remain in the 50s, while lows drop into the 30s.  Save for a
low-lvl instability induced sprinkle, conditions remain mostly dry.

Mon... Reinforcing shortwave quickly rushes through the region with
some moisture and weak insatiability below H7.  This should be enough
for some quick shra across the area.  These should end with the
evening hours and loss of any diabatic support.  Otherwise, winds
shift from W, to more N-NE by the overnight hours as the isallobaric
couplet shifts.  Increased risk for ocean effect clouds/rainfall
with this trajectory for the Cape, lower Plymouth county as SSTs
remain near +15C and H85 temps drop to -7C.   Highs in the 50s, but
lows may actually dip into the low-mid 30s, cooler than the weekend.

Tue into Thu... The strong trof settling in Atlantic Canada will
lead to building ridge upstream and allow for high pres to build
across the region.  H85 temps drop to about -5C at its lowest while
H92 temps drop near 0C.  Therefore, looking at a seasonably cool
period with this high pres.  Overnight mins especially could be
chilly with radiational cooling.


Forecaster Confidence Levels.

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

Short Term /through Friday/...

230 pm update...

Thru 00z...high confidence.

A combination of VFR and MVFR with any rain showers likely
confined to northwest MA and then a chance of showers along the
south coast of MA and RI toward 00z.

After 00Z...High confidence on trends but lower confidence on
exact timing and details. Widespread MVFR to start and then
lowering to IFR/LIFR after 02z/03z in drizzle/fog and scattered
showers. Localized LLWS possible with light easterly winds at the
surface and southerly winds 20-30 kt developing at 2K ft.

Friday...High confidence on trends but lower confidence on exact
timing and details. Widespread IFR/LIFR conditions persisting in
the morning...possibly lifting to MVFR at times in the afternoon
with rain becoming more widespread. Isold t-storm possible.

Friday night...High confidence on trends but lower confidence on exact
timing and details.  IFR/LIFR likely in periods of rain/drizzle
and fog.  Isold t-storm possible.

KBOS TAF...High confidence in trends.

KBDL TAF...High confidence in trends.

Outlook /Saturday through Monday/...

By Sat, although rains gradually diminish low clouds could linger
into early afternoon, suggesting MVFR conditions at least continue
through much of the day. Otherwise, winds shift to the W, with
LLWS overnight giving way to gusty (20-30 kt) gusts during the day
on Sat.

Sat night into Sun night...High confidence.
Some gradual improvement with more widespread VFR through this
period.  Winds remain an issue, with gusts (especially during the
day) reaching 20-30 kt out of the W.

Mon and Tue...High confidence.
Isolates shra on Monday, otherwise VFR throughout.  Winds shift to
the NW and continue to gust 20-30 kt.


Forecaster Confidence Levels.

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

Short Term /through Friday/...Moderate confidence.

10 am update...

ENE winds of 15-20 kt continue today. Given this long fetch seas
will build to greater than 5 ft across the ocean waters of MA and
RI. Hence SCA remain in effect for this afternoon for southern
RI and MA waters and then this evening for eastern MA waters.


Today...Increasing easterly winds with gusts to 20-25 kt
developing and building seas. SCA issued for the outer waters.

Tonight into Friday...Winds becoming SE later tonight and
persisting into Fri with gusts to 20-25 kt at times, strongest
eastern waters. Seas building to 6-8 ft outer waters during Fri.
SCA will be needed for outer waters.

Outlook /Friday Night through Monday/...

Fri night into Sat...High confidence.
Winds will gradually shift to the W, and as they do so, expect an
increase in gusts over the waters 25-30 kt.  This will actually
allow seas to diminish slightly initially but remain above 5 ft over
much of the waters.  Rain/fog reduce vsbys.  Small crafts likely.

Late day Sat into Sun...Moderate confidence.
W-NW winds continue but rainfall ends.  Wind gusts could reach 35 kt
at times this entire period, so a low risk for Gales.  Otherwise
building seas to 8+ ft on the ocean waters and high end Small Craft
Advisories can be expected.

Mon and Tue...Moderate confidence.
Winds shift to the NW fully, with another low end risk for Gale
force gusts late Mon and Mon night.  Otherwise 5-7 ft seas remain
and winds 20-30 kt suggest small crafts continue.


Astronomical high tides are subsiding with each tidal cycle. There
may still be one or two high tides Thursday and Friday that
threaten minor splashover at the more vulnerable spots on the
coastline, but the general trend is now moving away from that.


MARINE...Small Craft Advisory until 8 PM EDT Friday for ANZ250-254.
     Small Craft Advisory until 2 AM EDT Friday for ANZ255-256.


NEAR TERM...KJC/Nocera/Doody
TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.