Onset Massachusetts Weather Forecast Discussion

180
FXUS61 KBOX 062322
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
722 PM EDT Mon Oct 6 2025
.SYNOPSIS...
A ridge of high pressure in control of our weather will continue to
bring dry and unseasonably warm afternoon temperatures through
Tuesday. A cold front moves through Southern New England Tuesday
night into Wednesday, bringing much needed rainfall. Much cooler
temperatures follow Thursday and Friday with dry weather as well.
Monitoring a possible coastal storm late next weekend but confidence
in this outcome is low at this time.
&&
.NEAR TERM /THROUGH TUESDAY/...
Key Messages...
*Mild tonight with low clouds and fog once again possible,
especially south.
*SW winds becoming breezy in the late morning/afternoon with gusts
20-25 mph.
A broad area of high pressure remains centered south of the region
tonight, shifting slightly east during the day on Tuesday. This will
continue to direct mild and increasingly moist air in from the
southwest. What this means for us is the return of overnight low
level moisture in the form of fog and low stratus expanding from the
south coast. The NAM guidance is most bullish with the fog`s
northward expansion into the I-90/Boston area but it overdid this
morning`s fog as well so not leaning on that for the forecast;
overall only a low to moderate confidence as to the northward extent
of the stratus/fog and, leaning toward the lowest visibilities
staying south of Boston.
For the day on Tuesday, the fog and low clouds mix out by late
morning leaving a short period of more sun before high level clouds
arrive from the west in the afternoon. The additional cloud cover
throughout the day will help keep the already above normal
temperatures at least a few degrees cooler than today. The warmest
spots (low 80s) will be north with the least cloudcover, while the
south coast may not make it out of the low 70s. Winds will be
breezy, gusting 20 to 25 mph as the pressure gradient increases.
&&
.SHORT TERM /TUESDAY NIGHT/...
Key Messages...
* Rain arrives mainly late Tue night.
* Mild with lows in the mid to upper 50s.
A rather robust cold front will be approaching Tuesday night.
Forcing ahead of this feature, together with the mid level trough
over the Great Lakes will act on PWATs near 1.5" to produce
widespread rain showers spreading from west to east between 10pm and
sunrise. The elevated dewpoints ahead of the cold front will keep
lows from dropping below the mid to upper 50s at night. This will be
the last night of warmer than average temperatures; the average for
early October is in the upper 40s/low 50s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Messages...
* Widespread rain Wed AM ends by lunchtime across the interior, but
  may linger into the afternoon across parts of eastern MA/RI
* Dry but much cooler Thu & Fri with highs middle 50s to lower 60s
  with lows in the 20s/30s Thu night and frost/freeze conditions
* Potential for a Hybrid coastal storm to bring some rain/gusty
  winds Sun into Mon but only it it gets far enough north
Details...
Wednesday...
Strong shortwave/cold front will be crossing the region Wednesday.
Ahead of this front...a modest SW low level jet ahead of the front
will combine with Pwats over 1.50 inches. The result will be much
needed rain Wednesday morning with even the low risk for a rumble of
thunder. Total rainfall amounts of 0.50 to 1" with locally higher
amounts possible. Drier air will quickly work in from the NNW...so
across the interior expect most of the rain to be over by Wed
afternoon. Some rain probably lingers into the afternoon across
eastern MA/RI...particularly southeast of I-95. Still some
uncertainty with specific timing...so may have to refine this over
the next 24 hours. Early-mid morning temps in the 60s to near 70
will drop into the 55 to 65 degree range during the afternoon...so
it will be turning cooler behind the front.
Thursday and Friday...
Large high pressure from the Great Lakes builds southeast into our
region for Thu and Fri. This will bring dry weather but much cooler
temperatures. 850T drop to around 0C...so quite the change from our
recent weather. Highs Thu and Fri will only be in the middle 50s to
the lower 60s. The high pressure system centered over our region Thu
night will bring an ideal night of radiational cooling. Given the
cool/dry airmass in place...thinking the cooler MOS guidance is the
way to go. Low temps bottom out in the 20s and 30s across most
locations Thu night along with frost/freeze conditions.
Saturday/Sunday/Monday...
Dry weather should prevail Saturday and temps will moderate as upper
trough shifts east of the region. The forecast becomes quite complex
by Sunday and Monday. We will be watching a potential Hybrid coastal
storm off the mid-Atlantic/southeast coast. There is considerable
spread on whether or not this system will get far enough north to
bring some rain/gusty winds to the region sometime Sunday into
Monday or stays south and we remain dry. Not much more to say at
this point and might be a few days until we have a better idea.
Temperatures look to be seasonable for this time of year with highs
mainly in the 60s.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update...
Tonight...Low confidence.
VFR conditions persist this evening. Main concern is for areas
of fog developing very late tonight some of may which be locally
dense...but uncertainty on extent and areal coverage. Think the
typical low-lying locations are most at risk...where other
areas like BOS may remain VFR. So in a nutshell...a wide range
of conditions are possible across the region toward daybreak.
SSW winds generally 10 knots or less.
Tuesday...High confidence.
Any fog patches quickly burnoff by early-mid morning.
Otherwise...VFR with SW wind gusts of 20-25 knots developing by
mid=afternoon.
Tuesday night...Moderate confidence.
VFR becoming MVFR/IFR in RA from northwest to southeast
very late Tue night through daybreak Wed. SW winds 5-15 knots.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF. Main uncertainty is if
we see a period of patchy fog toward daybreak at the terminal.
Outlook /Wednesday through Saturday/...
Wednesday: MVFR/IFR conditions possible. Breezy. RA.
Wednesday Night through Thursday: VFR. Breezy.
Thursday Night: VFR. Areas frost.
Friday through Friday Night: VFR.
Saturday:
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Tuesday night...
SW winds 10-15 kts tonight with gusts of 20-25 knots developing
by Tuesday afternoon. Opted to issue a small craft advisory for
many of our southern near shore waters for Tuesday afternoon
into early evening given better mixing from diurnal heating.
Some choppy seas will develop across our waters by Tue
afternoon especially nearshore. Overnight/early morning fog
patches can be expected to reduce visby thru Tuesday morning.
Outlook /Wednesday through Saturday/...
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Rain. Local
visibility 1 to 3 nm.
Wednesday Night: Strong winds with gusts up to 30 kt. Seas up
to 5 ft.
Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft.
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. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM to 7 PM EDT Tuesday for
     ANZ231>235.
&&
$$
SYNOPSIS...BW/Frank
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Frank
AVIATION...BW/Frank
MARINE...BW/Frank

NWS BOX Office Area Forecast Discussion