501
FXUS61 KBOX 150703
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
303 AM EDT Tue Sep 15 2026
.WHAT HAS CHANGED...
No significant changes to the forecast.
&&
.KEY MESSAGES...
- Dry with cooler than normal temperatures today and tonight.
- Seasonably warm temperatures return mid-week, continuing
through Friday. A few showers possible sometime late Thursday
into early Friday, otherwise mainly dry.
- Potential for a shift to an unsettled pattern with chances
for rain for second half of weekend through early next week.
&&
.DISCUSSION...
KEY MESSAGE 1...Dry with cooler than normal temperatures today
and tonight.
Surface high pressure will be positioned the region today
bringing dry conditions and mainly sunny skies. A cooler airmass
will be in place with 925mb temperatures several degrees cooler
than Monday. This will yield more "Fall-like" temperatures with
high temperatures in the upper 60s and low 70s. Locations along
the immediate east coast may even be cooler in the mid 60s as a
result of the light easterly onshore flow. The high pressure
center shifts offshore tonight shifting winds to the S then SW.
KEY MESSAGE 2...Seasonably warm temperatures return mid-week,
continuing through Friday. A few showers possible sometime late
Thursday into early Friday, otherwise mainly dry.
A strong upper level ridge/high remains positioned across the
southeast CONUS mid-week, subtly building into the northeast mid-
week. An upper trough in northern Canada will hold off any stronger
ridging from building into the northeast, favoring a flatter/zonal
pattern overall. This should support warmer temperatures advecting
in within the SW flow. Highs Wednesday/Thursday rise back into the
mid and upper 70s with 80s in the valleys (seasonably warm for mid-
Sept). Surface high pressure should support mainly dry conditions
Wednesday and Thursday.
Ensemble/deterministic guidance indicates potential for a weak
shortwave trough to drop in from the northwest late Thursday into
Friday. Ahead of this shortwave, a plume of anomalous moisture
advects in from the west on Thursday. Across ensemble guidance,
the PWATs run around 170-200 percent of normal or more directly
put, PWATs 1.7-1.9". The anomalous moisture is being signal
across NAEFS guidance as well. This building moisture will bring
a more humid day for Thursday. There is some spread across
guidance with regards to the timing of the showers; however,
there is general agreement of the highest chances falling in the
late Thu afternoon to early Fri morning timeframe. That
timeframe should be able to be narrowed down as the details of
the pattern become more clear as we go through the week. Despite
the anomalous moisture, the weaker lift with this wave and
later timing has limited the potential for widespread heavy
rain. Ensemble QPF remains below 0.50" for most areas. We`ll
have to keep an eye on some embedded heavier showers that could
bring locally higher amounts. A drier airmass pushes in behind
the exiting shortwave Friday bringing dry conditions dominating
by the afternoon. A cooler airmass sinks across the region by
Saturday bring a return of Fall-like temperatures.
KEY MESSAGE 3...Potential for a shift to an unsettled pattern
with chances or rain for second half of weekend through early
next week.
Ensemble guidance hints at a transition to a more unsettled pattern
for the second half of the weekend and into early next week. A low
pressure system tracks eastward from the Great Lakes bringing
increased precipitation chances more likely in the Sun-Mon
timeframe. There indications of another wave or two bringing
periods of rain for early next week as well. Confidence in
precipitation chances and timing should increase as we get
closer.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update...
Through 12Z...High confidence.
VFR. Light N/NNE winds. Occasional gusts to 18 kts possible for
Cape terminals through 08Z (HYA/ACK).
Tuesday...High confidence.
VFR. NNE winds this morning shifting to the NE at 5-10 kts. Interior
terminals shift likely shift to the S/SSE early afternoon while
coastal terminals shift to E/ESE in the afternoon then shift to
the S/SSE 00-03Z.
Tuesday night...High confidence.
VFR. Winds becoming light S to SW. Patchy fog possible in
valleys.
KBOS Terminal...High confidence in TAF. NNE winds shift to NE
this morning then shift E/ESE 16-18Z at 5-10 kts. Winds shift
toward the SSE/S around 00Z becoming S/SSW by 03Z.
KBDL Terminal...High confidence in TAF.
Outlook /Wednesday through Saturday/...
Wednesday through Wednesday Night: VFR.
Thursday: Mainly VFR, with local MVFR possible.
Thursday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, slight chance TSRA.
Friday: VFR.
Friday Night: VFR. Breezy.
Saturday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
High pressure overhead today bringing light easterly winds today
and tonight. Winds shift around to the S/SW overnight tonight
into Wednesday as the high pressure center shifts offshore.
Outlook /Wednesday through Saturday/...
Wednesday through Thursday: Winds less than 25 kt.
Thursday Night: Winds less than 25 kt. Chance of rain showers.
Friday: Winds less than 25 kt. Slight chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
DISCUSSION...Mensch
AVIATION...Mensch
MARINE...Mensch
