Forecast discussion
What forecasters are seeing
Plain-English forecast narrative from the local NWS office. Issued by NWS BOX.
303
FXUS61 KBOX 150628
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
228 AM EDT Wed Jul 15 2026
.WHAT HAS CHANGED...
No significant changes. Monitoring the potential for early
morning strong thunderstorms slipping into northern MA.
&&
.KEY MESSAGES...
- Strong thunderstorms possible early this morning in northern
MA, then generally dry today.
- Very warm to hot today, but tempered by hazy/smoky conditions.
- Dangerous rip currents expected on south-facing beaches today.
- Seasonable temperatures with less humidity for the second half
of the week, though unsettled conditions with chances for
showers and thunderstorms remain possible into this weekend.
&&
.DISCUSSION...
KEY MESSAGE 1...Strong thunderstorms possible early this morning in
northern MA, then generally dry today.
Continuing to monitor developments regarding a cluster of
rather potent storms working their way into the Northern
Adirondacks and central VT as of 215 AM. Due to the presence of
mid- level lapse rates on the order of 8 C/km atop warm and
increasingly humid air, instability values remain sizable for
New England standards with CAPEs up to 3000 J/kg using a parcel
of air lifted from the lowest 100-mb of atmosphere. Strong WNWly
mid/upper level flow is contributing to straight hodographs,
and this hodograph shape is favoring more messy splitting-cell
structures vs a larger line of storms. These storms have had a
history of producing hailstones up to baseball size in central
St. Lawrence County in upstate NY, so they do mean business.
Severe Thunderstorm Watches are in place for adjacent southern
VT and southwestern NH until 7 AM, with this cluster of storms
expected to trek southeastward through the pre-dawn hours. High-
res guidance has really struggled to handle this activity, with
most depictions weakening these intense storms upon arrival.
But given its current track, some threat for strong
thunderstorms could exist during the 3 to 7 AM timeframe across
northern Worcester County eastward into the Merrimack
Valley/North Shore area and potentially into northern sections
of Metrowest Boston. Frequent lightning and hail (some possibly
large in the most intense of storms) are the main threats with
these. Although the better potential for severe weather exists
just to our north and west, remember that severe thunderstorm
watches mean that severe weather is possible in and near the
watch area.
These storms as they move offshore will then drape a frontal
boundary thru northern MA, with a considerable drop in dewpoint
temperatures and a WNW wind shift with it. This then slowly
sags southward toward the south coast by the afternoon. The
atmosphere becomes more strongly capped the further south and
west one goes, and its debatable if we can muster a triggering
source for possible afternoon storms into CT/western RI later
today. This aspect of the forecast is more uncertain as it won`t
take much of an impulse to get storms to fire, but this seems
unlikely at this time. Will offer generally dry weather the rest
of the day.
KEY MESSAGE 2...Very warm to hot today, but tempered by hazy/smoky
conditions.
Very warm and muggy conditions across Southern New England open
the morning, with some areas early this morning still not
having dropped below 80 degrees, with dewpoints in the upper 60s
to low 70s to boot. After coordination with NWS Albany and NWS
Upton, we opted to retain the Heat Advisory given the poor
overnight recovery, but during the day it probably ends up
being borderline, with peak heat indices in the mid to upper
90s. This is partly due to the sagging cold front bringing a
drop in humidity levels, but more because we are again looking
at an influx of smoky/hazy conditions from the ongoing wildfires
burning in northern MN and western Ontario. Highs were adjusted
well below NBM values, with forecasts in the mid 80s to around
90.
We saw yesterday the influence of the hazy, milky-looking skies:
being a significant reduction in temperatures. Latest guidance
from the 00z HRRR-Smoke and 00z RRFS vertically-integrated smoke
progs show another considerable concentration of smoke aloft
today and also into Thursday too. But unlike yesterday, there
are now some notable concentrations of near-surface smoke
developing this afternoon across the southern half of Southern
New England and the northern mid-Atlantic. Think it`s overdone
but there`s some solutions offering reductions in visibility,
too, in the smoke layer. Ended up adding haze or smoke in the
zone forecast for today. I think based on the near-surface smoke
progs that you could smell this smoke today. Remains to be seen
if air quality alerts would be needed, and recall that those
are issued by state environmental agency partners, with our role
being to relay those. Also added haze in for Thursday based on
output in the longer forecast range in the 00z RRFS smoke progs.
Expect rather milky looking skies with red/orange
sunrises/sunsets today and again on Thursday, likely to temper
stronger heating both days.
KEY MESSAGE 3...Dangerous rip currents expected on south-facing
beaches today.
WSWly breezes over the southern waters combined with lowering wave
heights of 4-6 ft still will support a high risk for rip
currents for those beaches exposed to the south and southwest.
Swim near vicinity of lifeguards and stay off jetties today.
KEY MESSAGE 4...Seasonable temperatures with less humidity for
the second half of the week, though unsettled conditions with
chances for showers and thunderstorms remain possible into this
weekend.
The upper level ridge that has been dominating the pattern for
much of this week will start to slide more SE of the region
for the second half of the week as an upper level trough with
broad cyclonic flow to our north takes hold. A cold front passes
through the region late Wednesday into early Thursday morning,
which will help usher in more seasonable temperatures for the
back half of the week. 925 mb temperatures fall to generally
around 18-20C, which will be more supportive of high
temperatures in the 80s. Thursday may be slightly warmer
compared to later days due to breezy westerly winds and
resultant downsloping, but drier air overall and lower
temperatures aloft (as mentioned above) may only push highs into
the low 90s. After that, expect 80s to persist into the start of
next week.
Latest guidance is hinting at the possibility for a ripple in
the NW flow aloft later in the week that could lead to more
unsettled conditions. Guidance is also indicating a shift to
more southerly flow for the weekend and a surge in PWAT values
as a result. A surface low approaches from the west Saturday
and with more of a NE track as currently indicated, its fronts
would likely drag through the region and increase the risk for
showers and thunderstorms through the weekend. Exact timing is
still quite uncertain this far out, but ensembles and
deterministic guidance suites remain favorable for a wetter
end to the week, both on Saturday and Sunday.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update:
Through 12z Wednesday: High confidence in trends but moderate on
TSRA coverage.
Monitoring strong/severe TSRA moving through central VT, which
are moving quickly southeastward. These storms could approach
ORH, BED and BOS between 08-11z but messaged as PROB30s for
now. Lightning and hail are the main risks in these storms. Will
proactively AMD if it looks like a direct hit is imminent. VFR
otherwise, with SW winds around 10-15 kt, with gusts to 25-28
kt Cape and Islands.
Today: High confidence in trends, but moderate on reduced visbys.
Mainly VFR, though hazy/smoky skies are expected. Haze/smoke could
reduce visibility to MVFR levels, mainly at BDL and PVD this
afternoon. Winds shift from SW to WNW around 10-15 kt today.
Tonight and Thursday: High confidence.
VFR, though hazy skies continue tonight into Thursday. WNW winds
around 5-10 kt tonight, then increasing to around 8-12 kt with
gusts to 20 kt Thurs.
KBOS Terminal...Moderate confidence. Possible TS near or north
of terminal 08-11z Wed. Otherwise mainly VFR but hazy/smoky
conditions may reduce visibility. Windshift to WNW around 13z
Wed.
KBDL Terminal...Moderate confidence. MVFR visibility
restrictions are possible today due to surface smoke from
Canadian wildfires.
Outlook /Thursday through Sunday/...
Thursday through Thursday Night: VFR. Breezy.
Friday through Friday Night: VFR.
Saturday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA, slight chance TSRA.
Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, slight chance TSRA.
Sunday: VFR. Breezy. 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 Thursday: High confidence.
SCAs continue on the southern waters through today, with WSW
winds gusting to around 25-30 kt with seas in the 4 to 6 ft
range, shifting to W/WNW late today. Into Thursday, westerly to
west/northwest winds should be around 15-20 kt, falling below
SCA criterion.
Monitoring the risk for strong thunderstorms on the northeastern
waters early this morning, which could become strong and produce
lightning, erratic winds and hail. Otherwise, hazy/smoky sky
conditions are expected today and Thursday. Some areas of
reduced visibility could be possible due to this smoke.
Outlook /Thursday through Sunday/...
Thursday through Thursday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.
Friday through Friday Night: Winds less than 25 kt.
Saturday: Winds less than 25 kt. Chance of rain showers.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Rain showers
likely, slight chance of thunderstorms.
Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers, slight chance of thunderstorms.
&&
.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 MAZ017>021.
High Risk for Rip Currents through this evening for MAZ020>024.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001>007.
High Risk for Rip Currents through this evening for RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
ANZ232>235-237-254>256.
&&
$$
DISCUSSION...Loconto
AVIATION...Loconto
MARINE...Loconto