BOX issues Area Forecast Discussion (AFD) at Sep 9, 7:23 PM EDT279
FXUS61 KBOX 092323
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
723 PM EDT Wed Sep 9 2026
.WHAT HAS CHANGED...
No significant changes to the forecast.
&&
.KEY MESSAGES...
- Frontal passage tonight into tomorrow morning brings scattered
showers and gusty southwest winds, especially over far
southeastern Massachusetts, Cape Cod, and the Islands.
- Dry weather, comfortable humidities and light onshore winds
Friday through Saturday night. Cool nighttime low temperatures
Friday night.
- Frontal boundary Sunday brings increased humidity and chances
for rain Sunday afternoon and evening.
- High pressure returns for early next week, bringing a return
to seasonable temperatures and low humidities.
&&
.DISCUSSION...
KEY MESSAGE 1...Frontal passage tonight into tomorrow morning brings
scattered showers and gusty southwest winds, especially over far
southeastern Massachusetts, Cape Cod, and the Islands.
The rest of today is largely dry outside of a sct'd warm advection
shower, as yesterday's cold front lifts back to the northeast, this
time as a warm front. A robust LLJ advects higher moisture into
southern New England as well, with PWATs climbing to near 2.0 inches
after 00z. Thus, there remains a low chance for showers throughout
this evening. Given the added cloud cover and winds overnight,
expecting a mild night with lows ranging from the upper 60s to lower
70s.
As the cold front approaches overnight, additional showers move into
the region during the predawn hours of Thursday, mainly 4-7 AM.
However, dynamics are lacking as the front reaches southern New
England. While there is a moisture-rich environment, the lack of
ideal forcing means rainfall isn't expected to be widespread or
necessarily heavy.
The wind will be more noticeable. As we've mentioned over the past
day or so, there is a robust LLJ with winds aloft ranging between 45
and 55 kt. While mixing will be limited inland due to the nocturnal
inversion, there should be enough mixing to allow gusts across the
interior to range between 20 and 30 MPH. Along and east of I-95,
gusts of 30-40 MPH remain possible, with a small area mainly near
the Cape and far southeastern Massachusetts where 40+ MPH isn't out
of the question prior to sunrise. Throughout the day Thursday, wind
direction shifts more to the west, with gusts ranging from 20 to 30
MPH.
Currently, we feel the greatest impacts will be for the marine
community. Gale Warnings are in effect around the Cape and Islands
for those stronger winds. By Thursday afternoon, the surface cold
front is offshore. However, temperatures aloft are slower to lower,
so it will still be fairly seasonable Thursday afternoon. Then comes
a reinforcement of colder air Thursday night, with 925 mb
temperatures falling from around +20C Thursday to +10C Friday.
KEY MESSAGE 2...Dry weather, comfortable humidities and light
onshore winds Friday through Saturday night. Cool nighttime low
temperatures Friday night.
Forecast for Friday into Saturday remains consistent in showing a
large high pressure area coming in from the eastern Great Lakes and
southeast Ontario Friday, then settling over the Northeast Friday
evening before moving offshore Saturday. This will bring dry and
pleasant weather conditions to Southern New England, with seasonably
mild days with full sun during the daytime hours Friday and Saturday
but a cool Friday night due to strong radiational cooling. Some of
the more typical sites which radiate well under clear skies and
light winds could see low temperatures drop into the mid 40s,
including areas around I-495, NW MA and Martha's Vineyard. High
temperatures in the mid 70s, with lower 70s near the Cape and
Islands. Conditions look favorable for outdoor plans Friday and
Saturday.
KEY MESSAGE 3...Frontal boundary Sunday brings increased
humidity and chances for rain Sunday afternoon and evening.
The high pressure moving eastward allows for an increasingly moist
airmass ahead of a cold frontal boundary which arrives Sunday
afternoon into Sunday evening. Most models show increasing rain
chances centered around Sunday afternoon or into the evening. While
there are good chances for rain in this Sunday afternoon to Sunday
evening timeframe, there is more uncertainty in terms of how much
rain falls. It looks as though the placement of the greatest
rainfall seems confined to the South Coast, Cape Cod and the
Islands. While it looks as though Sunday evening looks wet for these
areas, we're not expecting rainfall to become especially heavy as
the frontal boundary looks progressive.
KEY MESSAGE 4...High pressure returns for early next week,
bringing a return to seasonable temperatures and low humidities.
Behind the frontal boundary Sunday night, high pressure from Canada
builds back in, bringing seasonable temperatures, dry weather and
low levels of humidity for the early part of next week. The
potential exists for a couple of cooler nights Monday night and
Tuesday night with high pressure in the vicinity.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
VFR through at least 04-06z, with warm-frontal 6SM to P6SM light
SHRA. After 04-07z...latest guidance brings the current area of
moderate rain and embedded thunder marking a cold frontal
boundary over west- central NY eastward into SNE, but as a
period of MVFR-visby SHRA with OVC VFR ceilings. These showers
then continue into early Thursday. SW winds around 10-13 kt,
with gusts to 25 kt mainly for the Cape and Islands; however low
level wind shear is likely at most TAFs due to a SW jet of 50
kt.
Thursday and Thursday Night: High confidence.
Lingering SHRA possible for PVD and the Cape/Islands, but
trending drier with VFR conditions. Subtle windshift from SW to
WSW/W, with a better potential for winds to turn gusty (25-35
kt), especially for the terrain and the Cape/Islands.
VFR for the evening, but a secondary cold front brings a more
windshift to NW by 22-00z with winds 5-10 kt.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Friday through Monday/...
Friday through Saturday: VFR.
Saturday Night through Sunday: VFR. Chance SHRA.
Sunday Night through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Thursday Night...High confidence.
An approaching cold front will result in a developing southwest low-
level jet later today. The southwest low-level jet peaks later
tonight into early Thursday morning, when 925 mb winds reach 45-55
kt. While not all of this will mix down...we expect widespread
southwest wind gusts of 25-35 kt. Strong Small Craft headlines
continue for most waters, but brief gale-force gusts are certainly
possible. Gale Warnings continue for Buzzards Bay and Cape Cod Bay,
as well as Nantucket Sound. Based on pattern recognition...a brief
period of SW wind gusts of 35-40 kt appears reasonable and is
supported by BUFKIT soundings.
Winds ease and become more westerly into Thursday though seas remain
elevated. Any Gale Warnings likely will need to be converted to a
Small Craft Advisory through Thursday afternoon.
Outlook /Friday through Monday/...
Friday through Saturday: Winds less than 25 kt.
Saturday Night: Winds less than 25 kt. Slight chance of rain
showers.
Sunday: Winds less than 25 kt. Chance of rain showers.
Sunday Night: Winds less than 25 kt. Slight chance of rain
showers.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ230-
235>237-250-251-254>256.
Gale Warning until noon EDT Thursday for ANZ231>234.
&&
$$
DISCUSSION...Loconto/Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 9, 7:23 PM EDT----------------
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