BOX issues Area Forecast Discussion (AFD) at Jul 31, 2:29 PM EDT235
FXUS61 KBOX 311829
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
229 PM EDT Thu Jul 31 2025
.SYNOPSIS...
Cloudy weather with much cooler conditions are expected today
into Friday, with the potential for a flooding rainfall across
portions of southern New England. An extended stretch of dry
weather then develops for this weekend into early next week.
Temperatures are seasonable with lower humidity levels this
weekend, but with a warming trend for early next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Widespread showers and isolated t-storms with locally heavy
rainfall will be focused across interior MA to N-NW CT
through the afternoon
* Flood Watch is in effect for northern Connecticut from 2 PM
today through 8 AM Friday, but may need to be expanded with
later forecasts.
Scattered convection lifting E-NE across northern CT and
central MA this morning and is assocd with the 850 mb front.
Area of more stratiform rainfall further north assocd with mid
level forcing. The 850 mb front is forecast to lift a bit north
into northern MA this afternoon before moving back southward
toward the coast tonight. As a result we expect more widespread
and heaviest rainfall with isolated thunder across interior MA
into N-NW CT through the afternoon which is where best forcing
and deepest moisture is focused. Near the coast, moisture is
more shallow with some mid level drier air noted so any showers
will be more spotty with an isolated t-storm possible given
better instability is confined near the south coast. Warmest
temps into the low-mid 80s will be near south coast with 70s
elsewhere, but expect falling temps this afternoon.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Key Messages:
* Widespread rainfall ending from NW to SE Friday.
In general, still thinking that most areas should see rainfall
up to 2 inches when this event is over Friday morning. The
latest HREF probability matched mean rainfall remained
consistent with a potential upper limit of 4 inches in a few
spots. Decided to leave the Flood Watch over CT, which will be
closer to the stronger convection. Based on the latest timing,
did trim the end time back to 8 AM Friday.
Quite the switch from the past few days with below normal
temperatures anticipated tonight and Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Key Messages:
* Seasonably cool weekend ahead
Saturday and Sunday
The weekend is shaping up to be nearly perfect weather-wise as
high pressure builds in from the north, ushering in dry and
seasonable conditions with mostly sunny skies. High temperatures
on Saturday warm into the mid-70s to low 80s with light
northerly winds. Dewpoints on Saturday range from the upper 40s
inland to mid-50s near the coast, making it feel very
comfortable outside. Temperatures warm slightly on Sunday into
the low to mid 80s with dewpoints in the mid to upper 50s.
Next week.
High pressure remains in control for the first half of next
week. High temperatures stay in the 80s with dewpoints around
60F. As for precipitation, we are unlikely to see any until late
in the week as guidance hints at a shortwave exiting the Great
Lakes.
&&
.AVIATION /19Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18Z Update: Widespread convection has developed from SW to NE
roughly from N CT through to NE MA. Convection and low clouds
have brought MVFR and IFR conditions to much of the airspace.
IFR conditions will be favored under areas of heavier rain while
MVFR will be favored elsewhere.
Otherwise, the previous discussion remains in good shape.
-----------------------------------------------------------
Today...Moderate confidence, mainly due to timing issues.
VFR for most this morning. IFR towards the Cape and islands.
MVFR develops this afternoon. Timing of lower conditions most
likely in the mid to late afternoon, but could hold off until
tonight. Risk for a few thunderstorms this afternoon.
Tonight...High confidence.
MVFR and IFR most of tonight in widespread rainfall. Risk for
thunderstorms diminishes after sunset, but is not an
impossibility overnight, especially south of the Mass Pike.
Becoming breezy late tonight.
Friday...High confidence in trends. Moderate confidence in
timing. Winds diminishing into the afternoon.
MVFR/IFR improving to VFR from NW to SE during the day.
KBOS terminal...Moderate confidence in TAF, mainly due to timing.
KBDL terminal...Moderate confidence in TAF, mainly due to timing.
Outlook /Friday Night through Monday/...
Friday Night through Saturday: VFR. Breezy.
Saturday Night through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Friday...High confidence on winds and seas, lower
confidence on timing and areal coverage of potential
thunderstorms.
Patchy dense fog possible early this morning around Nantucket.
Increasing winds tonight as a low pressure passes by south of
the waters. Gusts up to 30 kt possible, along with seas
approaching 5 feet.
Outlook /Friday Night through Monday/...
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain
showers.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday through Monday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Friday morning for CTZ002>004.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 2 AM EDT
Saturday for ANZ231>235-237.
Small Craft Advisory from 2 AM to 8 PM EDT Friday for ANZ236-
251.
Small Craft Advisory from 8 PM this evening to 8 AM EDT
Saturday for ANZ250-254>256.
&&
$$
SYNOPSIS...Belk/Hrencecin
NEAR TERM...KJC
SHORT TERM...Belk
LONG TERM...KP
AVIATION...FT
MARINE...Belk/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 31, 2:29 PM EDT----------------
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