Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 072324
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
724 PM EDT Fri Aug 7 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Elevated heat and humidity continues through the weekend. Scattered
  showers and thunderstorms possible tonight and Saturday 
  afternoon & evening. 

- Summer warmth and humidity continues along with a daily
  chance of a pop-up shower or thunderstorm.

&&

.DISCUSSION...
KEY MESSAGE 1...- Elevated heat and humidity continues through the weekend. 
Scattered showers and thunderstorms possible tonight and Saturday 
afternoon & evening. 

Day Cloud Phase satellite imagery shows development of diurnal 
cumulus across portions of southern New England this afternoon. 
SHowers and thunderstorms continue to develop across PA and NY along 
the periphery of a mid-level ridge shifted offshore of southern New 
England. For the rest of the afternoon, expect mainly dry 
conditions. With a few cells beginning to pop near southern NY, 
can't rule out an isolated thunderstorm in western MA/CT after 4 PM. 
Daytime heating has allowed instability values to rise into marginal 
ranges this afternoon to support pop-up showers/storms. An 
isolated shower or storm may possibly initiate of the sea breeze
boundary along the south coast as well late this afternoon. Hi-
res guidance continues to bring a more consistent batch of 
remnant scattered showers and a few storms after 8 PM tonight. 
The best chance for seeing a storm will be in western southern 
New England. With precipitable water values approaching 2 
inches, brief heavy downpours are possible. This batch of 
showers/storms are likely to weaken and diminish as they push 
east overnight. With increased cloud cover for much of the 
overnight and the warm airmass, overnight temperatures likely 
remain in the upper 60s and low 70s tonight. 

Saturday, the mid-level ridge pushes further southeast of the region 
with flow becoming more zonal. The warm/moist airmass will stay in 
place tomorrow with SW flow supplying advection of higher dewpoints 
in the low 70s. Expect another day of elevated humidity and 
slightly above normal temperatures in the mid to upper 80s. With
the added humidity it may feel closer to low to mid 90s. There 
still is potential for scattered showers and thunderstorms in 
the late afternoon/evening on Saturday. Model guidance indicated
a weak embedded disturbance moving through the flow which 
should help provide additional support for thunderstorms 
accompanied by the diurnal heating and moist/unstable airmass. 
However, there the CAMs continue to show a spread in solutions 
with regards to potential and location across southern New 
England. Some solutions indicate more isolated potential, 
keeping the higher activity south of the region. Others are more
robust, simulating a few clusters of thunderstorms pushing 
across southern New England Sat evening. The primary concern 
with any storms will be localized heavy downpours supported by 
PWATs approaching 1.8". Mid- level flow is sufficient to keep 
storms moving from west to east which minimizes the concern for 
more widespread flash flooding issues. Can't rule out localized 
flash flooding if a storm or two were to push over a more 
vulnerable area (urban/poor drainage, area of recent heavy 
rainfall). 

KEY MESSAGE 2...Summer warmth and humidity continues along with a daily
chance of a pop-up shower or thunderstorm.

There haven't been many notable changes to the extended portion of 
the forecast, which encompasses Sunday through the upcoming week. In 
general, this timeframe features continued summer warmth with 
manageable humidity and daily chances for afternoon showers or 
thunderstorms. As mentioned previously, the synoptic pattern trends 
toward a flattening mid-level ridge, with nearly zonal flow across 
the CONUS and the subtropical ridge expanding from the western 
Atlantic into the lower third of the CONUS. This will allow westerly 
flow with embedded shortwave disturbances to move through the region.

Temperatures aloft remain quite warm, with 925mb temperatures around 
+23C to +25C from Sunday through Tuesday. BUFKIT forecast soundings 
depict a well-mixed boundary layer, supporting afternoon 
temperatures well into the upper 80s to around 90F. Dew points will 
remain elevated, though should fall short of oppressive levels, 
generally in the 65F to 70F range. Nevertheless, this will 
contribute to heat indices in the lower 90s Sunday through Tuesday. 
A potential break from the summer warmth arrives during the middle 
portion of next week as a front moves through, though there remains 
a fair amount of spread among the guidance regarding the exact 
evolution of this feature. Given the uncertainty, stayed close to 
NBM guidance for Wednesday and beyond, with highs expected to be in 
the lower to middle 80s. Overnight temperatures will remain 
seasonably warm, with lows generally in the 60s.

Regarding thunderstorm chances, embedded shortwave disturbances 
moving through the zonal flow should provide sufficient lift for 
isolated to scattered thunderstorms each day. Storms should remain 
largely pulse-type and disorganized rather than evolving into 
organized severe convection. PWATs up to around 2.0 inches will 
further support the potential for localized downpours. Gusty winds 
and frequent lightning will be the primary hazards. That said, 
thunderstorms will be highly localized, and not every community will 
see one, with many locations remaining dry. As such, there is no 
reason to cancel outdoor plans.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

00Z TAF Update: 

Tonight: Moderate confidence. 

VFR at least initially, but a few things to monitor. One is SCT
TSRA mainly for BDL-PVD and perhaps into the Cape airports as
line of (currently) strong to severe storms in vicinity of NYC 
hubs moves ENE. VCTS shown for BDL at 00z and PVD at 03z where 
confidence was high enough for a thunder mention; also included 
VCSH for BOS and the Cape after 04z to delineate where storms 
could weaken and/or be a lesser risk. Meanwhile stratus/fog at
IFR-LIFR levels should again develop near ACK by 01z then
gradually expand northward to the south coast, but the risk for
storms casts more uncertainty with that than usual. W to SW 
winds around 5-8 kt, winds locally stronger in/near TSRA.

Saturday through Saturday Night: Overall high confidence, but 
lower on TSRA timing.

South-coastal sub-MVFR stratus/fog from overnight dissipates to
VFR. Main question mark is timing of TSRA, which again varies
between 18-20z at earliest to as late as 01z, then moving
eastward. Risk increases into the afternoon but this will need
refinement; for now have indicated PROB30s for a 4 hour window 
starting around the 21z timeframe. TSRA dissipates late Saturday
evening, with south-coastal fog/stratus returning with VFR
elsewhere. 

Winds on Saturday are SW around 5-10 kt with very low to nil 
risk for a seabreeze, then shifting to W/WNW overnight.

KBOS Terminal...Moderate confidence. Thinking TSRA stays enough
south for just a VCSH mention after 04z. W winds initally will
shift to SW around 5 kt by 04z. Seabreeze not likely Sat. 
Monitoring for TSRA Sat aftn/evening but not likely any sooner 
than 21z if they get close.

KBDL Terminal...Moderate confidence. VCTS 00-03z for ongoing 
complex of storms SW of HFD, moving ENE then VCSH 03-05z. VFR
otherwise, though another risk for TSRA Sat aftn/evening but
timing is still uncertain. 

Outlook /Saturday Night through Wednesday/...

Sunday: VFR. Breezy. Isolated SHRA, isolated TSRA.

Sunday Night through Monday: VFR. 

Monday Night: VFR. Slight chance SHRA.

Tuesday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Tuesday Night: VFR. Slight chance SHRA.

Wednesday: VFR. Chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Saturday... High Confidence.

High pressure remains positioned off of the east coast. This 
will continue to produce a SW flow across the entire region into
the weekend. Gusts to 20 kts possible over the southern waters 
Saturday, but under SCA. 

Outlook /Saturday Night through Wednesday/...

Sunday through Sunday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft. 

Monday through Monday Night: Winds less than 25 kt. 

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers. 

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers. 

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 8 PM EDT this evening for MAZ003>007-
     010>021-026.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001>007.
MARINE...None.

&&

$$

DISCUSSION...Dooley/Mensch
AVIATION...Loconto/Mensch
MARINE...Dooley/Mensch