BOX issues Area Forecast Discussion (AFD) at Jun 9, 4:15 PM EDT417
FXUS61 KBOX 092015
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
415 PM EDT Mon Jun 9 2025
.SYNOPSIS...
An upper level disturbance will bring showers and embedded
thunderstorms with locally heavy rainfall on Tuesday. Dry and
warm conditions return Wednesday and Thursday. A cold front late
Thursday may bring scattered showers and thunderstorms. Temperatures
will turn cooler on Friday and into the weekend, though they'll
remain near seasonal norms. While some unsettled weather is
possible, a widespread washout appears unlikely.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Key Messages:
* Low clouds and areas of fog tonight with a few isolated
showers
Details...
Expect low clouds to persist overnight with a few showers.
Precipitable water values gradually increase into early Tuesday
ahead of an approaching shortwave trough. Model soundings show a
cooling lower boundary layer with some subtle WAA aloft. This
will support development of low stratus and increase potential
for fog. High-resolution models such as the HRRR have been on
the aggressive side with tanking ceilings and visibilities
around sunset across E and SE MA spreading westward. This is
still plausible given the diurnal cooling post-sunset.
Confidence at this point is higher in the lowering clouds and
mist persisting this evening and overnight. The Cape and
Islands will have the highest chances for seeing fog overnight;
however, fog remains lower confidence elsewhere, but potential
worth considering.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Key Messages:
* Showers & embedded t-storms with locally heavy rainfall Tue
Details...
Tuesday:
A piece of upper level shortwave energy moves through the
region on Tuesday. This will track a surface low across southern
New England. The position of the upper level jet will support
large scale lift accompanied by advection of deep moisture with
a LLJ jet offshore. The moisture will be plentiful with
precipitable water values around 1-2 standard deviations above
normal. Combined with sufficient synoptic ascent/moisture, model
guidance shows marginal instability building into the
afternoon. MLCAPE is on the lower side generally less than 100
J/kg. MUCAPE values range 50-600 J/kg, perhaps a tad higher out
in western MA. This will support a more substantial round of
rainfall with potential for some embedded thunderstorms. Given
the deeper/above normal moisture and marginal instability,
localized heavy rainfall is possible, but severe weather is
unlikely. Overall, not seeing a signal for significant flooding
impacts. HREF PMM rainfall shows a low probability (10-30%) for
localized areas above 1" with a 30-50% probabilities across
central MA and CT. However, no solutions showing potential for
3"+. Winds aloft will be also be strong enough to keep
rain/storms moving as well limiting the higher end flooding
risk. With all that said, localized/urban street flooding is
possible within the heavier cells tomorrow. Otherwise, most
areas will get a round of heavier rain that pushes across. Can't
rule out a lightning strike or two, but this will be sparse.
Timing- wise, HREF ensembles show this more substantial bulk of
rain moving across from west to east in the 16-22z timeframe.
Temperatures for the day will rise into the upper 60s to lower
70s with more humidity around.
Tuesday Night:
The bulk of the rainfall exits the region early evening Tuesday.
General trend Tuesday night will be drying conditions and
clouds gradually clearing into Wednesday morning as higher
pressure works in.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Messages:
* Dry and warm conditions return Wednesday and Thursday. A cold
front late Thursday may bring scattered showers and thunderstorms.
* Temperatures will turn cooler on Friday and into the weekend,
though they'll remain near seasonal norms. While some unsettled
weather is possible, a widespread washout appears unlikely.
No significant systems on the horizon, though few instances of rain
and/or thunderstorm activity continues due to summer-like pattern.
The mid-level pattern develops an amplified ridge across the western
third of the CONUS, leading to deep northwest flow. The ridge begins
to flatten out, becoming more zonal for Friday, and re-amplifies as
we heading into the weekend. At the surface, the main player will be
a Bermuda High, guidance has this sitting between 1025mb and 1030mb,
and brings in southwest flow at the surface. Looking at a warm week
with manageable humidity. Highs for Wednesday and Thursday range
between the upper-70s across the higher elevations and at the coast,
while the else where we climb into the lower to mid-80s. If any day
were to overachieve, Thursday could be the day, DESI probabilities of
highs greater than 90F are around 20 to 30 percent for urban areas
like Hartford and Boston. Dewpoints reach the lower 60s, so it feels
a bit humid, but not overly oppressive. Cold front passage Thursday
evening results in somewhat cooler conditions Friday, with highs in
the middle and upper-70s, warmest areas are the lower Connecticut
River Valley where the highest chance reaching 80F and greater. With
unsettled conditions this weekend, temperatures trend cooler into
the 70s.
It's worth mentioning, because of the nice weather Wednesday, folks
heading to the beach should be aware of the risk for rip currents.
For additional details, please see the marine section of the AFD.
As for precipitation, there is a couple instances of rain and/or
thunderstorm activity. First chance comes late Thursday as a result
of a weak mid-level shortwave and cold front. PWATs are roughly
around 1.0" and 1.5", which is slightly above seasonal norms, MUCAPE
values are greatest across Connecticut and Rhode Island between 500
and 1000 J/kg, cannot rule out a late day shower or thunderstorm.
After, the next chance will come sometime late Friday or Saturday.
PWATs this weekend range between 1.2" and 1.5", while there is
sufficient moisture the lack of sensible forcing should mean less in
the way of widespread rain. So good news, looks less of a washout
and more of a nuisance showers. Plus, an area of high pressure off
shore could help shunt any activity further southwest of the region.
As this is still several days out there are pounds of time for
changes. And believe me, this forecaster would really enjoy a rain
free weekend.
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update...
This Afternoon and Tonight...Moderate confidence.
Onshore flow will result in MVFR-IFR conditions persisting
through tonight. Some localized LIFR conditions possible
especially tonight along with areas of fog. Lower confidence on
the timing of the fog. Highest chances for seeing fog/LIFR will
be over the Cape and Islands. Low chance of an isolated shower.
E winds 5 to 12 knots this afternoon, slightly stronger over
the Cape/Islands. Lighter E/NE flow overnight less than 10 kts.
Becoming SE for the Cape/Islands.
Tuesday...Moderate confidence.
IFR-low end MVFR conditions Tuesday. Expect periods of showers
in the morning with higher chances 16-22Z for widespread rain
and a few embedded thunderstorms. Locally heavy rainfall
possible. Light E winds becoming SE less than 10 kts.
Tuesday Night...Moderate Confidence.
A few residual showers about early Tuesday evening otherwise
expect a dry night. Ceilings gradually improve through the night
toward VFR. Light W winds. Chance for patchy FG/BR in spots.
KBOS Terminal...Moderate confidence in TAF.
IFR conditions with a chance for LIFR conditions tonight. Lower
confidence in FG potential/timing tonight. Some guidance has FG
arrive as early as 23Z this evening. This has resulted in a low
probability for now until we can more clearly see the trends
for this evening.
KBDL Terminal...Moderate confidence in TAF.
Outlook /Wednesday through Saturday/...
Wednesday through Thursday: VFR. Breezy.
Thursday Night: VFR. Slight chance SHRA.
Friday: VFR. Slight chance SHRA, isolated TSRA.
Friday Night: VFR. Slight chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
* Building seas late Tuesday afternoon through Wednesday may require
a Small Craft Advisory for the southern waters.
* Result of the building seas, increase risk of Rip Currents for
ocean-facing southern beaches.
Tonight through Tuesday Night: High Confidence.
Warm front lifts across the waters tonight with hit or miss rain
chances into Tuesday. A cold front moves across the waters late in
the afternoon into early Tuesday evening. A couple of thunderstorms
and periods of heavy rain are possible. The cold front pushes east
of the waters overnight Tuesday into early Wednesday morning.
Easterly wind with gusts less than 15 knots overnight. Direction
becomes southwest on Tuesday with gusts less than 20 knots. Seas
increase late Tuesday into Tuesday night, building to 5 feet across
the southern waters Tuesday night through Wednesday. Opt'd to not
issue the Small Craft Advisory for the southern waters due to the
marginal seas, though if grows, later shifts could
issue this headline.
With building seas off shore and long period swells, greater than 8-
10 seconds, there's a risk for rip currents on Wednesday. At this
time the risk looks moderate for for ocean-facing southern beaches
and a high risk for Nantucket's southern-facing beaches.
Forecasters will want to monitor this closely given conditions look
ideal for a day at the beach. On Wednesday, inland locations have
the potential for highs well into the 80s. If trends continues, a
Rip Current Statement could become necessary on Wednesday.
Outlook /Wednesday through Saturday/...
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Wednesday Night: Winds less than 25 kt. Seas up to 5 ft.
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Thursday Night: Winds less than 25 kt. Slight chance of rain
showers.
Friday: Winds less than 25 kt.
Friday Night: Winds less than 25 kt. Slight chance of rain
showers.
Saturday: Winds less than 25 kt. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Dooley/Mensch
NEAR TERM...
SHORT TERM...Frank
LONG TERM...Dooley
AVIATION...Dooley/Mensch
MARINE...Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Jun 9, 4:15 PM EDT----------------
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