BOX issues Area Forecast Discussion (AFD) at Aug 27, 6:54 AM EDT346
FXUS61 KBOX 271054
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
654 AM EDT Thu Aug 27 2026
.WHAT HAS CHANGED...
No significant changes to the forecast.
&&
.KEY MESSAGES...
- Scattered thunderstorms, some of which could be severe late
today. A few hit-and-miss thunderstorms possible again Friday
afternoon.
- Mainly dry and seasonable weather follows for this weekend
with comfortable humidity.
- A period or two of unsettled weather may return early next
week with a backdoor cold front in the vicinity of southern
New England. Large spread/high uncertainty on temperatures,
dependent on the location of this front.
&&
.DISCUSSION...
KEY MESSAGE 1...Scattered thunderstorms, some of which could be
severe late today. A few hit-and-miss thunderstorms possible
again Friday afternoon.
Still looking at a decent setup for a few strong to severe
storms across southern New England today. Modest most unstable CAPE
values projected between 1,000-1,500 J/kg combined with 0-1 km
storm relative helicity of 50-100 m2/s2 support this idea. The
primary limitation today will be the timing of it all. In other
words, can the peak helicity and instability arrive in southern
New England around the same time. Still thinking the greatest
threat from thunderstorms remains mainly to our west, and
perhaps as far east as the CT River valley. It appears that the
peak helicity should arrive after instability starts to wane
with sunset. This situation bears monitoring, albeit a level 1
of 5 threat. Mostly concerned about damaging straight-line winds
and perhaps some hail. The potential helicity does not
completely rule out the risk for a tornado either.
There is also a level 1 of 4 risk for localized flash flooding,
again mainly west of the CT River.
A cold front should finally reach southern New England late
tonight into Friday morning. Until this front completely moves
offshore some time Friday night, still looking at a risk for
showers and possible thunderstorms. Given the much different
time of day, not expecting severe weather for Friday.
KEY MESSAGE 2...Mainly dry and seasonable weather follows for
this weekend with comfortable humidity.
High pressure builds into our region for this weekend. The
result will be mainly dry and seasonable weather with
comfortable humidity.
KEY MESSAGE 3...A period or two of unsettled weather may return
early next week with a backdoor cold front in the vicinity of
southern New England. Large spread/high uncertainty on
temperatures, dependent on the location of this front.
Still a highly uncertain forecast for early next week. The key
synoptic feature will be the location of a backdoor cold front.
A slower timing of this front would lead to higher temperatures
across eastern MA Monday. This front still appears to be stuck
somewhere across eastern MA Tuesday into Wednesday, which should
direct a low pressure moving southeast from Canada right across
our region. While not raining this entire time, a prolonged
period where showers and thunderstorms are possible is expected
from Monday into Wednesday.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today and Tonight...High confidence in TAF trends. Low
confidence in areal coverage and eastward extent of scattered
showers and isolated t-storms.
High confidence in mainly VFR conditions into early evening,
outside of any scattered showers/isolated t-storms that
develop. MVFR to localized IFR conditions will gradually
overspread portions of the region from south to north later
tonight as more humid air arrives from over the colder ocean.
As for the scattered showers/isolated thunderstorm risk, still
uncertain on how far east activity advances into our region. The
main risk will be in the 20z to 03z time frame, generally across
interior MA/CT with the greatest risk west of the CT River Valley.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF. We will need to watch
for a few thunderstorms in the vicinity of the terminal later
today into tonight.
Friday...Moderate confidence.
Another risk for showers and a few thunderstorms until a cold
front finally moves east of our region. MVFR with areas of IFR
to start, improving to VFR toward mid morning. MVFR possible in
afternoon showers and t-storms.
Outlook /Friday Night through Monday/...
Friday Night through Saturday Night: VFR.
Sunday: VFR. Breezy.
Sunday Night through Monday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Friday...High confidence.
Winds become more S to SW late tonight, then increase late this
morning into this evening. Shower and thunderstorm chances
increase tonight, mainly around the Cape and islands after
midnight. Another round for afternoon showers and thunderstorms
possible nearshore Friday.
Outlook /Friday Night through Monday/...
Friday Night through Saturday: Winds less than 25 kt. Areas of
seas approaching 5 ft.
Saturday Night through Sunday: Winds less than 25 kt.
Sunday Night through Monday: Winds less than 25 kt. Slight
chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
DISCUSSION...Belk/Frank
AVIATION...Belk/Frank/BW
MARINE...Belk/Frank
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 27, 6:54 AM EDT----------------
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