Waltham Post Office Massachusetts Weather Forecast Discussion

689
FXUS61 KBOX 131918
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
318 PM EDT Mon Oct 13 2025
.SYNOPSIS...
A coastal storm will continue to impact coastal areas with
occasional heavy rain and gusty winds through tonight. The
coastal low will begin to move farther offshore Tuesday, with
decreasing rains and easing northerly winds. However, an
unseasonably cool airmass brings dry weather with below normal
temperatures and a return of breezy northwest winds for mid to
late this week. Temperatures then rebound back to above normal
levels for this weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Key Messages:
* Locally heavy rain focused across SE coastal MA through tonight
* Isolated t-storms with heavy rain possible across RI and SE MA
  late afternoon through tonight
* NE winds slowly diminish through tonight but remain gusty along
  the coast
Persistent heavy rain banding has been impacting Plymouth county
since the morning. Decent low level frontogenesis combined with
convergence at the land sea interface at the nose of the low level
jet contributing to the enhanced rainfall. Low level frontogenesis is
persistent across SE MA tonight within a weakening but nearly
stationary low level jet axis across SNE, with PWATs near 1.5 inches
along the coast. As a result, expect locally heavy rainfall with
additional amounts up to 2 inches across portions of Plymouth
county.
The other forecast issue through tonight will be the potential for a
few heavy convective showers or t-storms developing across RI and SE
MA. Elevated instability is increasing this afternoon through
tonight across SE New Eng. Soundings show up to 500 J/kg of elevated
CAPE above the frontal inversion. Many of the hi-res CAMs are
showing numerous convective showers moving in from the ocean and
impacting portions of eastern MA into RI which would enhance
rainfall in this area and could produce some localized flooding if
heavy rainfall occurred in a short time period. This is something
that will need to be monitored through tonight.
Otherwise, should see slow improvement further inland with bands of
light rain tapering off and ending overnight.
Regarding wind forecast, expect strongest winds with gusts 40-50 mph
through the afternoon across the Cape/Islands, with 30-40 mph gusts
near the coast slowly diminishing late today through tonight as
persistent and nearly stationary low level jet gradually
weakens.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Key Messages:
* Rain gradually ending across eastern MA late morning through
  the afternoon
* Gusty NE winds diminishing along the coast
Tuesday...
The morning looks wet across eastern MA as bands of showers will
continue to impact the region, with a risk of thunder over the
Cape/Islands as persistent low level jet acts on elevated
instability. Otherwise, it will be drying out further inland with
mainly dry conditions, especially western New Eng. Eventually the
rain in eastern MA will end during the afternoon as the coastal low
drifts offshore. NE wind gusts 25-35 mph along the immediate coast
will gradually diminish through the afternoon. Highs will range from
55-60 across much of SNE with lower 60s Cape/Islands.
Tuesday night...
As the coastal storm continues to pull away, ridging aloft builds
into the region with drier air in the column moving in form the NW
with decreasing PWATs. Expect partial clearing with diminishing wind
becoming light, with lows mostly in the 40s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Ensemble guidance is in good agreement for upper troughing
across the region Wednesday through Friday. The previous coastal
low slowly pulls offshore. This will keep an enhanced NW-SE
pressure gradient across southern New England supporting
"blustery" conditions through mainly Friday. A cooler airmass
will be in place through late week, especially for Thursday.
Residual moisture Wednesday-Thursday may support a few showers
across the Cape/Islands. More forecast details below...
Wednesday through Friday:
Breezy, cool, and mainly dry (for most). However, the combination of
a cooler airmass, residual moisture, and NW winds will bring cloudy
conditions to the Cape/Islands along with some ocean-effect showers
possible Weds/Thurs. A cooler, below normal airmass sinks across the
region within the upper trough. Temperatures trend at to slightly
below normal on Wednesday with highs in the upper 50s to low 60s.
Later Wednesday into Thursday, deterministic/ensemble guidance
indicates another push of cooler into the region. This will bring in
a below normal airmass with 850mb temperatures -3 to -1C. This will
likely yield high temperatures in the 50s for Thursday with even
upper 40s possible across the high terrain locations of the
interior. This is about 5-10 degrees below normal. With the added
element of wind, it may feel like 40s at times. Temperatures will
slowly moderate Friday as an upper ridge approaches from the west
bringing gradual height rises.
An enhanced NW-SE pressure gradient stay intact across the region
bringing breezy NW winds. Gusts 20-30 mph are possible on Wednesday
over land with gusts nearing gale force possible over the waters.
Stronger winds are possible on Thursday as a push of cooler air
drops southward late Wednesday into Thursday with NW downslope flow.
Cool advection should support a well-mixed boundary layer bringing
down gusty NW winds. Ensembles show gusts 25-35 mph with the higher
gusts more likely for the Cape/Islands. Can`t rule out a gust up to
40 mph across the Berkshires. The waters will likely be gale force
Thursday. Winds trend lighter for Friday as the gradient relaxes,
but may stay elevated over the waters.
Next Weekend:
Ensemble guidance shows a good consensus for a pattern change
developing Saturday into Sunday as a strong 500mb ridge pushes
across the northeast. This will advect in higher heights, warmer
temperatures aloft and keep conditions dry. There is potential for
850mb temperatures to rise to +12-14C by Sunday. Quite a difference
from Thursday! Overall this will favor a warming trend for the
weekend with temperatures closer to normal Saturday and potentially
above normal Sunday with ensemble members showing a range of upper
60s to low 70s at this time.
&&
.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 00z: High confidence in trends but lower confidence on
the timing.
Rain showers, a few embedded rumbles of thunder is possible over
the southern coast of RI & MA. IFR-LIFR ceilings and IFR- MVFR
visibilities in steady rain. Northeast winds 15-25 kt with
gusts 25-30 kt inland, and around 30-40 kt near the coasts.
Strongest LLWS up to 50 kt possible, especially towards the
Cape and Nantucket this afternoon.
Tonight and Tuesday: High confidence in trends but lower
confidence in the timing.
Showers continue overnight, cannot rule out rumbles of thunder
across RI and SE MA this evening and overnight. IFR/LIFR
ceilings tonight become MVFR/IFR later Tuesday morning into the
afternoon. Coverage of showers decreasing across the interior,
but still widespread towards eastern MA, gusty north- northeast
winds continue, but not as strong as today.
Tuesday Night: High confidence.
MVFR ceilings becoming VFR. Decreasing N to NW winds.
KBOS Terminal...High confidence in TAF trends. Moderate confidence in
timing.
There is a low chance for isolated TSRA this afternoon/evening,
but did not have high enough confidence to include in TAF.
KBDL Terminal...High confidence in TAF trends. Moderate confidence in
timing.
Outlook /Wednesday through Saturday/...
Wednesday: VFR. Breezy.
Wednesday Night: VFR. Windy with local gusts up to 30 kt.
Slight chance SHRA.
Thursday through Thursday Night: VFR. Windy with gusts up to
35 kt. Slight chance SHRA.
Friday: VFR. Windy with local gusts up to 30 kt.
Friday Night: VFR.
Saturday:
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Gale warnings continue across the coastal waters into this evening
before winds gradually diminish overnight through Tuesday. Small
craft advisory winds and rough seas will persist through Tuesday
before diminishing Tue night. Visibility reduced at times in
rain and fog into Tuesday.
Outlook /Wednesday through Saturday/...
Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 30 kt. Areas of rough seas. Slight chance of rain
showers.
Wednesday Night: Strong winds with gusts up to 30 kt. Rough
seas up to 9 ft. Chance of rain showers.
Thursday: Strong winds with gusts up to 40 kt. Rough seas up to
10 ft. Chance of rain showers.
Thursday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 11 ft. Chance of rain showers.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 11 ft. Chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt. Local
rough seas.
&&
.TIDES/COASTAL FLOODING...
Minor splashover possible for late afternoon high tide across
eastern MA coast from combination of 1-1.5 ft surge and up to 15
ft seas offshore.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 7 PM EDT this evening for MAZ007-
     015-016-019-022>024.
     Wind Advisory until 8 PM EDT this evening for MAZ022>024.
RI...Wind Advisory until 8 PM EDT this evening for RIZ008.
MARINE...Gale Warning until 11 PM EDT this evening for ANZ230.
     Gale Warning until 2 AM EDT Tuesday for ANZ231-233>235-237-251.
     Gale Warning until 4 AM EDT Tuesday for ANZ232-250-254>256.
     Small Craft Advisory until 7 PM EDT Tuesday for ANZ236.
&&
$$
SYNOPSIS...KJC/Mensch
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...Mensch
AVIATION...Dooley/Mensch
MARINE...KJC/Mensch
TIDES/COASTAL FLOODING...

NWS BOX Office Area Forecast Discussion