023
FXUS61 KBOX 171531
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1131 AM EDT Sun Aug 17 2025

.SYNOPSIS...
Heat and humidity briefly returns today along with the risk for a
few showers and thunderstorms during the afternoon and evening as a
cold front crosses the region. Cooler/below normal temperatures
follow for much of the work week with a return to seasonable
temperatures by Friday and Saturday. Dry weather dominates too
outside a few brief showers possible at mid-week. Major Hurricane
Erin will bring dangerous rip currents and high surf to ocean
exposed beaches in the Wednesday through Friday time frame.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Messages...

* Hot & humid today with highs upper 80s/lower 90s
* Isolated strong to severe t-storms possible between 3-10 PM
* Turning much cooler late tonight...lows in the upper 50s/lower 60s

Details...

Today and tonight...

Southwest flow ahead of an approaching cold front today will result
in a brief return to hot and humid weather this afternoon. 850T
climb to between +17C/+18c and good mixing with at least partial
sunshine should push highs into the upper 80s to the lower 90s away
from the very immediate south coast. Dewpoints in the upper 60s to
near 70 will also bring a brief return to summertime humidity.

The main concern will be the expected scattered showers and t-storms
this afternoon and evening with an isolated severe weather
threat...mainly in the 3-10 PM time frame. The heat and humidity
will result in modest instability developing on the order of 1000
and 2000 J/KG. The mid level lapse rates though are poor and
effective shear is marginal on the order of 20 to 30 knots...so we
are not expecting a widespread/significant severe weather outbreak.
Nonetheless...impressive low level lapse rates/modest DCapes coupled
with convergence along the approaching cold front will result in an
isolated severe weather threat. The main threat will be
localized/isolated strong to damaging wind gusts...which is
supported by machine learning guidance including the CSU/Nadocast
probs. Again...not looking at a widespread severe weather outbreak
but an isolated/localized wind damage threat exists roughly between
2 and 10 pm this evening. Brief torrential rain/localized urban
street flooding is also possible with any storms.

Behind this scattered convection...much less humid and cooler air
will be ushered in on gusty NE winds especially near the coast.
Overnight low temps will bottom out in the upper 50s to the lower
60s by daybreak Monday.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
Key Messages...

* Much cooler less humid on Monday with highs mainly in the 70s
* Mostly clear & cool Mon night with lows in the upper 40s & 50s

Details...

Monday...

Large high pressure over Quebec will result in much less humid and
cooler weather on Monday. This will be accompanied by gusty NE winds
along the coast. NE wind gusts of 20 to 30 mph expected along the
coast especially through mid-afternoon. The onshore flow will result
in highs mainly in the 70s despite plenty of sunshine. In fact...a
few spots along the immediate eastern MA coast may struggle to even
break 70!

Monday night...

A ridge of high pressure building in from the north will result in
diminishing winds, mainly clear skies and an ideal night of
radiational cooling. Low temps should bottom out in the upper 40s
across the normally cooler outlying locations...to the 50s
elsewhere.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Key Messages...

* Below normal high temps 70 to near 80 Tue/Wed/Thu
* Dry weather dominates outside the risk for a brief showers mid-week
* High surf/dangerous rip currents Wed-Fri from major Hurricane Erin
* Warmer high temps mainly in the 80s return by Fri/Sat

Details...

Tuesday through Thursday...

High pressure over eastern Canada and into northern New England will
control our weather in the Tuesday through Thursday time frame. The
result will be below normal high temps in the 70s to near 80 with
overnight lows mainly in the 50s. Comfortable humidity will make for
very pleasant afternoons for outdoor activities.

Dry weather dominates over this time period given the influence of
high pressure. That being said...shortwave energy may be enough to
result in a few brief showers late Tue night into Wed but any
rainfall that occurs will be quite light.

Friday and Saturday...

Heights begin to rise a bit Fri into Sat ahead of the next shortwave
trough. This should allow for warmer high temps into the 80s for
most locations. Dry weather should generally prevail with lack of
deep layer moisture of synoptic forcing.

Dangerous Rip Currents/High Surf...Wed through Fri...

The biggest weather concern will be the likelihood of Dangerous Rip
Currents/High Surf in the Wed through Fri time frame. Although Major
Hurricane Erin will be making the N then NE turn with no direct
impact on our region...large southeast swell will generate high
surf/dangerous rip currents especially to south facing ocean exposed
beaches. Given pleasant weather and SST that are at their
climatology warmest this will be a big concern for beachgoers. High
Surf Advisories will eventually be needed.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

15z TAF Update:

Today: High confidence in TAF/trends, though moderate on TSRA
coverage.

Patchy MVFR stratus from overnight have started to lift/scatter
to VFR. Monitoring for thunderstorms after 21z Sun but the
coverage is still uncertain. TAFs with the best shot at seeing
TSRA is from BAF-ORH-PYM south and west, with a lesser,
decreasing chance for BED and BOS. SW winds 5-15 knots with the
strongest near the south coast where some 25 knot gusts are
possible by afternoon.

Tonight...High confidence.

The threat for scattered showers/t-storms should come to an end by
the latter half of the evening. Thereafter...will probably see a
period of MVFR cigs across much of the region overnight behind the
strong cold front. Winds shift to the NE at 7-15 knots with some 20
to 30 knot gusts near the coast after midnight...strongest of those
for the Cape/Nantucket.

Monday...High confidence.

Any lingering MVFR cigs should improve to VFR by mid-morning as
drier air works in from the northeast. NE winds of 7 to 15 knots
with some 20 to 30 knot gusts near the coast...strongest of those
for the Cape and Nantucket.

Monday night...High confidence.

VFR. Diminishing ENE winds.

KBOS terminal...High Confidence in TAF. Mainly VFR pre-frontal. Though
a limited risk for TS could exist between 23-01z, the overall
risk for TSRA seems to be on the downswing. A gusty N/NE
windshift likely by 02-03z with cold frontal passage (gusts
20-25 kt), with MVFR ceilings developing post-frontal.

KBDL terminal...High Confidence in TAF. Mainly VFR, although a
somewhat better chance for storms exists between 20-01z. A gusty
north windshift likely by 01-03z with cold frontal passage, with
MVFR ceilings developing post-frontal.

Outlook /Tuesday through Thursday/...

Tuesday: VFR. Breezy.

Tuesday Night: VFR. Slight chance SHRA.

Wednesday through Wednesday Night: VFR. Breezy. Chance SHRA.

Thursday: VFR. Windy with local gusts up to 30 kt. Slight
chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Monday night...High confidence.

Good mixing over the land ahead of an approaching cold front will
result in near shore south coast wind gusts of 25 knots this
afternoon. We have hoisted small craft headlines for some of our
southern sounds and Bays. While these winds temporarily diminish
early this evening...winds will shift to the NE and gust between 20
and 30 knots late tonight into Monday across most waters with good
mixing in the cool air advection pattern. Therefore...small craft
advisories are in effect for most waters over this time. These small
craft conditions should diminish late Monday/Monday evening as
gradient weakens.

Outlook /Tuesday through Thursday/...

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Tuesday Night: Winds less than 25 kt. Local rough seas. Slight
chance of rain showers.

Wednesday: Winds less than 25 kt. Areas of rough seas. Chance
of rain showers.

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 16 ft. Chance of rain
showers.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 17 ft. Slight chance of
rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 PM EDT Monday for ANZ231>235-237.
     Small Craft Advisory until 7 PM EDT this evening for ANZ236.
     Small Craft Advisory from 10 PM this evening to 8 PM EDT
     Monday for ANZ250-251-254.
     Small Craft Advisory from midnight tonight to 8 PM EDT Monday
     for ANZ255-256.

&&

$$

SYNOPSIS...Frank
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Frank
AVIATION...Frank/Loconto
MARINE...Frank/Loconto