BOX issues Area Forecast Discussion (AFD) at Oct 16, 2:05 PM EDT315
FXUS61 KBOX 161805
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
205 PM EDT Wed Oct 16 2024
.SYNOPSIS...
Dry and cool weather will continue through Thursday. An
offshore low pressure system passing well southeast of New England
could graze Cape Cod and the Islands with a few showers Thursday
night and Friday. Minor coastal flooding may affect the eastern
Massachusetts coast during high tide Friday. Several days of
dry and warm weather should prevail over the weekend and into
much of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Diurnal clouds formed on schedule but satellite loop shows cloud
cover diminishing this afternoon now that mid level trough has moved
through SNE and subsidence is occurring behind it. Expect skies to
clear as we approach sunset with loss of daytime heating.
Gusty W/NW winds will also subside later this afternoon, setting the
stage for ideal radiational cooling conditions tonight. This will
probably be the coldest night of the fall season as light winds,
clear skies, and a dry airmass allow temperatures to drop into the
20s and 30s overnight, but holding in the lower 40s along parts of
the immediate coast and in the larger cities.
Even though our Frost/Freeze program has ended for the season, we
will continue to include a mention of frost in the forecast for the
rest of the month. It's typically included for those locations where
the temperature falls to 36F or lower.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Key Point:
* Minor coastal flooding possible Fri along eastern MA coast.
High pressure remains in control with plenty of sunshine.
Temperatures will recover from a chilly start to the mid or
upper 50s in many locations Thu afternoon. The exception is
along the coast of SE MA where onshore flow from the developing
coastal low may bring enough moisture to form some lower clouds
in the afternoon, most notably on Cape Cod and the Islands.
The main concern revolves around potential impacts from an
offshore low pressure system Thu night-Fri which includes minor
coastal flooding along E MA coast. gusty NE winds, and perhaps a
few showers grazing Cape Cod and the Islands.
Good time to dust off our cool season forecasting procedures. Seeing
fairly good agreement among long range models/ensembles which depict
mid level trough closing off over Carolinas and ejecting out to sea
SE of 40/70 benchmark. Cluster analysis shows good agreement among
Canadian, GFS, and EC led clusters with fairly minor differences in
timing and location between each. All indicate very low chances
(<30%) of any measurable rainfall near Cape Cod and Islands Thu
night/Fri and virtually no chance (<5%) of gale-force winds on MA/RI
coastal waters. Even the deterministic models keep any rainfall SE
of Islands, including 12z NAM which shows more ridging over SNE. For
now, we'll stick with NBM PoPs at or below 30%.
We're entering a period of high astronomical tides this week and
persistent NE flow should bring a surge of around 1 foot in the
Thu/Fri timeframe. Right now the high tide of "greatest" concern is
midday Fri where Boston (1211 PM) and Nantucket (117 PM) could reach
their minor flood stages (and that would be a higher-end scenario),
resulting in less than one foot of flooding in more vulnerable
shoreline locations along E MA coast. Fortunately, wave impacts look
to be negligible with offshore seas under 10 ft.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Key Point:
* Several days of dry and warm weather follows into next week.
Following this system, we're in for several days of dry and
unseasonably warm late fall weather starting this weekend and
lasting into much of next week, thanks to ridging that builds into
region both aloft and at surface. Highs should easily reach well
into 70s away from coast for several days with large diurnal ranges
that should feature lows in 40s and 50s.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update: High confidence (90%). Only uncertainty deals
with potential low-end VFR ceilings (040) later tonight and Thu
near Nantucket, namely how quickly they form.
VFR SKC after diurnal clouds diminish later this afternoon,
although we may see ceilings AOA 10kft across CT, RI, and SE MA
Thursday afternoon/night. Potential for lower cigs (040) to
develop overnight and Thu near Cape Cod and Islands but only
confident enough to include at Nantucket.
NW winds gusting to 20-25kt subside late this afternoon to
around 10 kt, then veer to N/NE overnight and Thu. Should see
stronger NE winds, 15kt with gusts to 25kt, develop Thu
afternoon and night.
KBOS TAF...High confidence.
KBDL TAF...High confidence.
Outlook /Wednesday Night through Sunday/
Saturday through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Winds and seas will continue to subside through later afternoon
so we will allow SCAs to expire but extended it on outer waters
into the evening since it will take longer for seas to fall
below 5 ft there.
Low pressure tracking well SE of Nantucket will bring
increasing NE winds later Thu afternoon and especially Thu night
into Fri with with 25kt gusts on outer waters and seas building
to 6-8 ft, then high pressure is expected to dominate our
weather starting this weekend into most of next week.
Outlook /Saturday through Monday/...
Saturday through Saturday Night: Winds less than 25 kt. Seas up
to 5 ft.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Monday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
ANZ254>256.
&&
$$
JWD
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 16, 2:05 PM EDT----------------
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