Office: BOX
FXUS61 KBOX 121848
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
248 PM EDT Sat Jul 12 2025
.SYNOPSIS...
Seasonably warm and humid conditions continue this weekend.
Chance for showers and thunderstorms across the interior into this
evening, then trending drier for Sunday. A better chance for showers
and thunderstorms then exists on Monday as a frontal system moves
through. Increasing heat and humidity around the middle of next
week, which then looks to break around Friday as a cold front
brings yet another risk for showers and thunderstorms.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Points:
* Continued warm and humid conditions
Showers and thunderstorms were chained to the east slopes of the
Berkshires this afternoon. Light SE flow across our region resulted
in just enough upslope to trigger showers and thunderstorms in an
otherwise mediocre environment. There is plenty of buoyancy, but
very little shear. This makes it most likely that any thunderstorms
rain on their own updraft, leading to shorter-lived storms. The risk
is these storms were not moving much or fast. The main concern is
downpours possibly leading to localized flash flooding. Already had
to issue a Flash Flood Warning for portions of Hampshire and
Franklin Counties.
Past sunset, expecting stratus and fog to return to most locations
across southern New England. It will remain quite muggy, so low
temperatures tonight are perhaps a few degrees lower than what we
had Saturday morning.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Points
* Dry with seasonably warm and humid conditions Sunday
Not much change to the air mass Sunday and Sunday night. Thus, not
anticipating much change to the forecast. Still thinking warm and
humid conditions persist. Stratus and fog gradually dissipates
after daybreak, then returns again after sunset. With a little more
southerly flow, temperatures should be a little higher starting
Sunday night.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Messages:
* Better chance at more widespread showers/t-storms Monday.
Threat for strong-severe storms low.
* Very warm to hot during the middle of next week, with elevated
heat indices around 95-100F. Heat headlines possible.
* Becoming more unsettled late Thursday-Friday with increasing
chances for showers/storms, especially Friday with a cold
front.
Details:
Monday:
Monday, a weak shortwave trough moves through the flow aloft.
Overall, forcing is quite weak with a subtle passage of a front by
Monday night. Daytime heating and the approaching wave will support
marginal instability with MLCAPE values 100-1000 J/kg and MUCAPE
values 200-1500 J/kg with the higher instability across western
southern New England. Plenty of moisture with an axis of richer
moisture positioned across the region, around 150-180% of normal.
Enough ingredients here to support showers and thunderstorms in the
afternoon-evening. Weaker winds aloft, will keep 0-6km bulk shear
values low. As a result, the threat for severe/more organized storms
will be low with regular thunderstorms more likely with brief gusty
winds, heavy downpours. Can't rule out a stronger storm or two, with
gusty winds and small hail. Weaker winds aloft will yield slower
storm motions, so we'll have to watch for localized flash flooding
potential in any storms. Highs temperatures will be in the low
to mid 80s accompanied by higher humidity (65-75%).
Tuesday-Thursday:
Tuesday through Friday, a mid-level ridge builds over the regions.
Temperatures aloft increase with 850mb temperatures peaking at
around 20C in the Weds-Thurs timeframe. A good amount of moisture
gets transported over the ridge by Wednesday adding humidity to the
mix. Temperatures Tuesday through at least Thursday will range in
the upper 80s to mid 90s with the exception of the immediate coast.
With the the added element of higher humidity, it will feel more
like mid to near 100 Wednesday and Thursday.
Overall, there are no major disturbances embedded in the flow during
that timeframe which will reduce the threat for widespread
showers/thunderstorms. Ensemble members display potential for a few
showers. Members are still spread across the board with timing and
given the low coverage nature has been difficult to message in the
forecast. Until better agreement on timing, no major adjustment have
been made to the forecast. There will be a better signal for forcing
later Thursday with corresponding increased chances for showers and
thunderstorms.
Thursday - Friday:
A mid-level trough approaches the region, Thursday into Friday.
This will shift the pattern to becoming more unsettled with
increasing potential precipitation starting later Thursday.
Ensemble members are still across the board when it comes the
the precipitation chances and the timing leading to lower
confidence this far out. A front will eventually push through on
Friday with the main trough axis. This should bring the highest
chances of seeing precipitation.
&&
.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today: Moderate confidence.
With little change to the weather pattern, expecting low stratus
and fog to lift and burn off between 14-17z, with the exception
of the Cape and Islands where CIGS may remain low all day.
VFR with pockets of MVFR again with lingering low level
moisture. Chance for scattered showers and thunderstorms again
this afternoon, although recent guidance has trended the
activity further west. Went with prob30 for TSRA at western
terminals for now, but future shifts may consider removing.
Tonight: Moderate confidence.
More IFR/LIFR Stratus builds north under light ESE flow.
Sunday: Moderate confidence.
IFR/LIFR stratus during the morning. VFR during the afternoon.
KBOS Terminal...High confidence in TAF.
IFR/LIFR CIGS through about 15z again, then VFR/MVFR through the
afternoon. Low stratus deck likely again tonight.
KBDL Terminal...High confidence in TAF.
MVFR/IFR through about 13z, then CIGS gradually improve to VFR.
Chance for thunderstorms again late this afternoon/evening, but
the threat has trended further west.
Outlook /Monday through Thursday/...
Monday: Mainly VFR, with local MVFR possible. Chance SHRA,
chance TSRA.
Monday Night: VFR. Slight chance SHRA.
Tuesday through Tuesday Night: VFR.
Wednesday: VFR. Breezy.
Wednesday Night: VFR. Slight chance SHRA.
Thursday: Breezy. Chance TSRA, slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Sunday...High confidence.
Weak pressure gradient will keep winds/seas below Small Craft
Advisory thresholds through Sunday: seas 2-4 ft with E winds
over the southern waters and SE winds over the eastern waters up
to 15 kts during the afternoon hours, remaining light in the
overnight hours. Main concern for mariners will be areas of fog
tonight that may redevelop Saturday night.
Outlook /Monday through Thursday/...
Monday through Wednesday: Winds less than 25 kt.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Belk/Mensch
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Mensch
AVIATION...Belk/Mensch
MARINE...Belk/Mensch
