Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 171119
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
719 AM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
A High Risk for rip currents was issued for south-facing ocean 
beaches today. Those heading to the coast should exercise caution.

&&

.KEY MESSAGES...

- Showers and extensive cloud cover lead to a cooler-than-
  normal and quite humid day. A High Risk for rip currents 
  remains in effect for south-facing ocean beaches.

- Mainly dry Tuesday, with only isolated showers possible 
  across eastern southern New England. Seasonable temperatures 
  continue, with a High Risk for rip currents along east-facing 
  ocean beaches.

- No washouts expected, though several opportunities for 
  showers return from mid to late week.

&&

.DISCUSSION...
KEY MESSAGE 1...Showers and extensive cloud cover lead to a cooler-
than-normal and quite humid day. A High Risk for rip currents 
remains in effect for south-facing ocean beaches.

Showers early this morning will continue into the afternoon, though 
coverage should be lower than earlier today. Southern New England is 
situated between two areas of low pressure, with the strongest 
forcing displaced to the north and south of the region. As a result, 
it may be difficult to fully capitalize on the higher PWATs of 1.8 
to 2.0 inches across the region. Nevertheless, periodic showers will 
continue through this morning and afternoon. 

The threat for heavy rainfall remains low. While an isolated heavier 
downpour cannot be ruled out, widespread heavy rainfall is not 
expected. Flooding is also a very low threat, with the primary 
concern limited to localized urban or poor-drainage flooding. 
Rainfall amounts have trended lower across interior southern New 
England, generally ranging from one-tenth to two-tenths of an inch, 
while areas along and east of I-95 may receive around one-quarter to 
one-third of an inch. Localized higher amounts, potentially 
approaching one-half inch, remain possible beneath areas of weak 
convection.

One final round of showers, and perhaps a thunderstorm or two, is 
possible with the passage of a cold front. However, abundant cloud 
cover will limit instability across much of southern New England. 
The greatest potential for thunderstorms will be across eastern New 
York, far western Massachusetts, and far northwestern Connecticut, 
where MUCAPE may exceed 800 J/kg. Instability decreases considerably 
farther east.

Given the cloud cover and onshore flow, highs today will only reach 
the lower to middle 70s across eastern Massachusetts, Rhode Island, 
and eastern Connecticut. Farther west, temperatures climb into the 
middle to upper 70s. Dew points in the upper 60s to lower 70s will 
make it feel quite humid. While it will not be a hot day, it will 
certainly feel sticky.

It will not be an ideal beach day, but it is important to note the 
High Risk for rip currents along south-facing ocean beaches. Those 
heading to the beach should remain aware of local conditions and 
check with lifeguards or beach staff regarding rip current risks at 
their specific location.


KEY MESSAGE 2...Mainly dry Tuesday, with only isolated showers 
possible across eastern southern New England. Seasonable 
temperatures continue, with a High Risk for rip currents along east-
facing ocean beaches.

Somewhat drier air advects into the region from the northwest late 
tonight into Tuesday, with PWATs lowering to around 1.3 inches by 
Tuesday afternoon. A weak area of surface low pressure east of Cape 
Cod, along with lingering weak forcing, may produce an isolated 
shower or two, mainly along and east of a KIJD-KORH-KFIT line. 
Otherwise, Tuesday will feature a mix of sun and clouds with 
seasonable temperatures in the lower to middle 80s. The eastern 
Massachusetts coast will likely remain a few degrees cooler, with 
highs in the upper 70s due to continued onshore flow.

A High Risk for rip currents is expected along east-facing ocean 
beaches Tuesday. Those heading to the beach should remain aware of 
local conditions and check with lifeguards or beach staff regarding 
rip current risks at their specific location.


KEY MESSAGE 3...No washouts expected, though several opportunities 
for showers return from mid to late week.

The flow aloft becomes generally zonal Wednesday through Friday, 
with a stronger shortwave trough moving through eastern Canada late 
Wednesday into Thursday. A leading shortwave may trigger a few 
showers late Wednesday night, though much of Wednesday should remain 
dry. The primary shortwave and an accompanying cold front move 
through Thursday, providing better lift along with PWATs increasing 
to around 1.5 to 1.7 inches. This should bring an increased chance 
for showers, though widespread or continuous rainfall is not 
expected.

High pressure is then expected to build eastward, bringing mainly 
dry conditions. However, model guidance continues to indicate the 
potential for a boundary to stall offshore, with a series of 
embedded shortwaves moving along it from Friday into the weekend. 
This could result in periodic chances for showers, and perhaps a few 
thunderstorms, with the greatest risk generally focused across the 
south coast and Cape Cod and the Islands.

Wednesday will be the warmest day of this period, with highs in the 
middle to upper 80s and tolerable humidity as dew points remain in 
the 60s. Temperatures trend downward by a degree or two Thursday and 
Friday, with cooler conditions expected this weekend as highs 
generally range from the upper 70s to near 80 degrees.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

Today...Moderate confidence in trends, lower confidence in timing.

Periods of SHRA during the early morning hours become more scattered 
through the morning and afternoon as the steadier precipitation 
shifts east. Cannot rule out an isolated TSRA during the afternoon 
as a cold front approaches, though limited instability should keep 
coverage sparse. IFR to MVFR ceilings are expected this morning, 
with gradual improvement during the afternoon. Confidence remains 
low regarding the timing and extent of improvement. Southeast winds 
early become east, then northeast during the afternoon, eventually 
shifting to the north by 00Z Tuesday.

Tonight...Moderate confidence in trends, lower confidence in timing.

SHRA gradually end, though IFR conditions may persist overnight with 
areas of DZ and pockets of FG. Light northerly winds, becoming calm 
across the interior.

Tuesday...Moderate confidence.

MVFR to IFR conditions to start, with improvement to VFR from west 
to east between 15Z and 20Z. Eastern terminals, including Cape Cod, 
may experience a later improvement to VFR, possibly not until 22Z to 
00Z. Light northwest winds across the interior, with north to north-
northeast winds across eastern Massachusetts at less than 10 kt.

KBOS Terminal...Moderate confidence.

MVFR with SHRA this morning. Ceilings should generally remain 
low- end MVFR, though periods of IFR conditions are possible, 
especially after 15Z with continued SHRA. Southerly winds become
east- southeast by 10Z, then shift to east-northeast late this 
afternoon.

KBDL Terminal...Moderate confidence.

Conditions oscillate between MVFR and IFR with periods of SHRA 
throughout the day. Light east-southeast winds.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday Night: VFR. 

Thursday: VFR. Slight chance SHRA, slight chance TSRA.

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. 

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

Through Tuesday...Moderate confidence.

A weak area of low pressure moves south of the waters today, then 
shifts east of the waters Tuesday. Southeast winds around 20 kt this 
morning become easterly this afternoon, with gusts up to 25 kt. Seas 
build to 4 to 6 ft, with isolated seas up to 7 ft possible across 
the outermost southern waters, though confidence in widespread 7 ft 
seas is low. Small Craft Advisories have been modified to reflect 
the latest forecast, with the advisory across the eastern waters 
canceled due to a downward trend in both winds and seas. Conditions 
improve Tuesday as the low shifts farther east. Seas subside to 2 to 
4 ft, with light northerly to north-northwest winds generally less 
than 15 kt.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. 

Wednesday through Wednesday Night: Winds less than 25 kt. 

Thursday: Winds less than 25 kt. Slight chance of rain showers.

Thursday Night through Friday: Winds less than 25 kt. Chance of
rain showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents through this evening for MAZ023-024.
RI...High Risk for Rip Currents through this evening for RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ232.
     Small Craft Advisory until 8 PM EDT this evening for 
     ANZ233>235-237.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ254.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ255-256.

&&

$$

DISCUSSION...Dooley
AVIATION...Dooley/RM
MARINE...Dooley