BOX issues Area Forecast Discussion (AFD) at Aug 25, 4:19 AM EDT861
FXUS61 KBOX 250819
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
419 AM EDT Mon Aug 25 2025
.SYNOPSIS...
Showers across Cape Cod and the Islands expected this morning
with the passage of a low pressure system. Scattered showers and storms
possible this afternoon with an approaching cold front. Dry
conditions favored with surface high pressure in place through
late week while also trending cooler with temperatures slightly
below normal. Next chance for precipitation arrives by Friday
with another cold front.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Round of scattered showers/thunderstorms possible this
afternoon/early evening.
A weak low pressure system will pass offshore this morning bringing
showers to the Cape and Islands with the higher chances for rain for
Nantucket. Majority of the showers will end before mid-morning as
the system exits to the northeast.
Low clouds from overnight will slowly scatter/break this morning
into the early afternoon allowing for breaks of sunshine today. A
trough/cold front will slowly approach the region from the west
before moving through later tonight. This will provide a period of
weak lift paired with marginal moisture and instability to support
shower/thunderstorm chances later this afternoon. MLCAPE values
range around 200-1000 J/kg. Mid-level lapse rates are fairly weak,
although low level lapse rates are sufficient. 0-6km shear will be
sufficient (30-40 kts) given a jet present aloft. The limiting
factor will be the timing of the best forcing (cold front) as it
does not align with peak heating. This will bring a more likely
scenario of more limited coverage of showers/thunderstorms with a
low likelihood of being severe. Across the CAMs, it is still a
bit of a mixed bag of solutions when it comes to coverage and
exact timing of the showers/storms. Some do reflect the lack of
forcing around in the afternoon in SNE with a higher chance for
storms further north as they trigger off the higher terrain of
NH. If showers and thunderstorms do develop, most solutions show
between 3- 6 PM more likely. Given the isolated nature and
lacking agreement of high-res models, this will translate to a
fairly low probability for storms this afternoon (< 30%).
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Key Messages:
* Cold front moves through tonight. Dry with near-seasonable
temperatures Tuesday.
A cold front moves through tonight resulting in a cooler night. Low
temperatures drop into the low to mid 50s for the interior and upper
50s to around 60 closer to the coastline. Can't rule out some
patchy fog in the valleys.
Behind Monday's cold front, a cooler airmass settles across the
southern New England for Tuesday through the remainder of the week.
Expect dry conditions Tuesday with highs in the mid to upper 70s.
Winds will be out of the west with a few gusts up to 20 mph.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages:
* Cooler and mainly dry through late week.
* Next chance for showers/precipitation late Thursday-Friday.
Tuesday night, another reinforcing push of cooler air moves into
southern New England with 850mb temperatures ranging from +7 to
+10C. This will bring a period of cooler temperatures through the
end of the week. High temperatures will stay mainly in the mid 70s.
High pressure will bring dry conditions and mainly clear conditions
through Thursday. Cool nights will result from the optimal
radiational cooling with potential for some patchy fog in the
valleys. Overnight lows will likely range in the upper 40s to 50s
with the cooler temperatures across the interior. Can't rule out
even cooler temperatures for the higher terrain spots.
Ensemble guidance shows a general consensus with a shortwave moving
through late week. Solutions become a little less agreeable on the
details of timing, but most generally have a cold front dropping
across the region sometime later Thursday-Friday. This will bring
our next chance for precipitation. Details such as amounts, exact
timing, coverage are less certain, but should become more clear
further along in the week.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z Update...
Monday...Moderate Confidence.
MVFR and IFR early this morning with periods of LIFR possible
for Cape/Islands. A weak low pressure system will pass offshore
bringing a period of showers to the Cape/Islands through 12z.
Improving to VFR 14z-16z for most, but likely a bit later for
the Cape/Islands terminals. Potential for isolated
showers/thunderstorms this afternoon. However, confidence is low
on timing and overall potential. Included as PROB30 for BOS/ORH
as there is currently better potential for storms to develop
east of the CT Valley. Winds light SSW Monday morning, becoming
SW during the afternoon with speeds 8-10 kts for the interior
terminals. SE winds at coastal terminals this morning, becoming
E at BOS at 7-10 kts and shifting N early afternoon. Winds
switch SW at all terminals by 00z.
Monday Night...High Confidence.
Cold front moves through after 03z shifting winds W/WNW at 5-10
kts. VFR for most locations, with potential for some lower
clouds to sneak into the Cape/Islands. Confidence not high
enough to include in TAF at this time.
KBOS Terminal...Moderate confidence in TAF.
Will see bouncing between VFR, MVFR, and IFR early this AM
before improving to VFR 14-16z. A low pressure system passes
east of the terminal this AM. Low chance for an isolated shower
during the Monday morning push. Low-end VFR cigs Monday with a
low chance for a pop-up thunderstorm in the late afternoon,
after 20z. Included as a PROB30 as models have been consistent
in shower/storm activity, but they are still struggling on
location of the activity.
KBDL Terminal...High confidence in TAF.
Outlook /Tuesday Night through Friday/...
Tuesday Night through Wednesday Night: VFR.
Thursday: VFR. Breezy.
Thursday Night: VFR.
Friday: VFR. Breezy. Chance SHRA, slight chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through tonight...High Confidence.
Elevated seas on the outer waters of 4 to 6 feet, have extended the
Small Craft Advisory through 2 AM. The second-half of the night seas
are less than 5 feet on the outer waters and 2-3 feet near shore.
Monday and Monday Night...High Confidence.
Area of low pressure moves up the coast, increasing waves and brings
rain showers mainly to the eastern waters through late Monday
morning. A cold front moves across the waters from west to east late
Monday afternoon through Monday night. A isolated shower or two is
possible during this time. Seas are building 5 to 6 feet across the
outer waters before diminishing Tuesday. Likely will need another
Small Craft Advisory for this period.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday through Thursday Night: Winds less than 25 kt.
Friday: 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 6 PM this evening to 5 AM EDT
Tuesday for ANZ235-237.
Small Craft Advisory from 8 PM this evening to 8 AM EDT
Tuesday for ANZ250.
Small Craft Advisory from 2 PM this afternoon to 8 AM EDT
Tuesday for ANZ254>256.
&&
$$
SYNOPSIS...Mensch
NEAR TERM...Mensch
SHORT TERM...Mensch
LONG TERM...Mensch
AVIATION...McMinn/Mensch/KP
MARINE...Dooley/McMinn
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 25, 4:19 AM EDT----------------
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