033
FXUS61 KBOX 132337
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
737 PM EDT Sat Jul 13 2024

.SYNOPSIS...
Widespread showers, and some downpours, move offshore this
evening. Hot on Sunday, but slightly less humid with sunny
skies. Hot and humid Monday through Wednesday, with the chance
for afternoon thunderstorms Monday and Wednesday. Cold frontal
passage late Wednesday/Thursday will give way to a much more
comfortable airmass to end the work week.

&&

.NEAR TERM /THROUGH SUNDAY/...

7:45 PM Update...

A weak, broken line of downpours and weak thunderstorms
continues to very slowly work across southern New England; a few
lightning producing cells have crept into far NE MA, which was
well modeled by the ARW and NAMNest this evening. With
instability waning after sunset, should see these storms die
down quickly over the next hour or two, resulting in little more
than a quick downpour for an one locality.

Previous update...

Canceled the rest of
the Flood Watch, as the heaviest rainfall has moved farther
offshore. Any lingering convection this evening should be
isolated, and not particularly strong.

A nearly stationary front across souther New England should
finally get pushed out to sea late tonight into Sunday. Humidity
expected to drop slightly overnight, but still be quite muggy by
New England standards. A risk for showers until midnight or so,
but expecting coverage to really drop off after sunset given
the weak dynamics in place.

&&

.SHORT TERM /SUNDAY NIGHT/...
Still expecting more of a mid level ridge and weak high
pressure at the surface to our west. Expecting rain-free weather
with slightly lower humidity. At least dew points should be
mainly in the 60s away from the immediate coast. A little
reprieve from the tropical humidity we have been experiencing
for most.

winds expected to generally be light W to NW. This light flow
should result in seabreezes along the coast. Even so, expecting
high temperatures to be higher tomorrow given the lower humidity
and more sunshine.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
* Another round of dangerous heat and humidity builds into the
  region Monday through Wednesday with the potential for
  scattered thunderstorms and showers

* Cold frontal passage Wednesday night/Thursday will bring
  relief from the heat

* More comfortable dewpoints and seasonable temperatures by next
  weekend

Monday through Wednesday...

Southern New England remains nestled between high pressure
across the Atlantic and broad trough across Quebec/Ontario
that very slowly drops south into the Great Lakes early next
week. This pattern results in a prolonged period of muggy, hot
conditions with 850mb temperatures ranging from 18 to 21C,
supportive of widespread highs in the mid 90s away from the
immediate coastline. On par with the previous forecast, heat
looks to peak on Tuesday, where heat index values have the
potential to climb in excess of 105-107F by mid afternoon. Given
high confidence in the early week heat, elected to hoist a Heat
Advisory for much of the region away from the coast and outside
the high terrain on Monday, with a more expansive Excessive
Heat Watch in place for Tuesday (which only excludes the Cape
and Islands). Given heat on Wednesday will be dependent on the
timing of, the later mentioned, cold front, elected to leave the
decision on a watch up to later shifts.

Minor shortwave feature looks to develop the second half of
Monday in the vicinity of Lake Erie and shifts east across New
England by afternoon. Given high instability, SBCAPE potentially
exceeding 2000J/kg, in place driven by the heat and humidity,
lift provided by the shortwave may be enough to generate some
pop up afternoon thunderstorms, particularly across interior
MA. As with most of our convection, timing of storm development
will be critical with instability falling off quickly after
sunset. Mid level lapse rates look so-so, around 6-6.5C/km, so
even as instability wanes a residual EML may be able to keep
storms alive a few hours past 00Z. Instability remains high
again on Tuesday but with less forcing, shower/thunderstorm
activity looks to be much more isolated.

Trough digs deeper into the Ohio River Valley by late Wednesday
evening/Thursday and resulting cold front will likely generate
our best chance for widespread precipitation/Thunderstorm
activity on Wednesday evening.

Thursday and Beyond...

Airmass behind the cold front will be quite refreshing, so while
there is potential for some lingering showers Thursday morning,
dewpoints will fall into the upper 50s/low 60s with highs in the
upper 70s/low 80s to round out the work week and begin the
weekend. This will be quite a welcome change for many across
southern New England give the prolonged period of 65F+
dewpoints the region has experienced over the last several
weeks.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

Tonight...Moderate Confidence

Very low chance for a rumble of thunder in the vicinity of
BDL, BED, or BOS through 02Z. Any remaining scattered showers
should diminish during the early evening. Otherwise, MVFR-IFR
ceilings will pretty much be confined to areas near the south
coast. However, light- calm winds/high dewpoints may allow for
patchy ground fog to develop, especially at the typically prone
locations. Cape and Island terminals will be impacted by dense
fog after 03Z.

Tomorrow...High Confidence

VFR. Light northwest winds becoming more westerly during the
afternoon. Winds may be weak enough to support sea-breezes along
the coast.

Tomorrow Night...High confidence. VFR.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy. Chance SHRA, isolated TSRA.

Monday Night: VFR. Slight chance SHRA, isolated TSRA.

Tuesday through Tuesday Night: VFR. Breezy. Slight chance SHRA.

Wednesday: VFR. Breezy. Chance SHRA, isolated TSRA.

Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy.
SHRA likely, isolated TSRA.

Thursday: VFR. Chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

A front moves offshore late tonight into Sunday, with high
pressure to follow late Sunday into Sunday night. Showers and
fog this evening and overnight with occasionally lower
visibility around 1 mile. Improving visibility with rain-free
conditions Sunday and Sunday night.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt.

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 20 kt. Seas up to 5 ft. Slight chance of rain showers,
isolated thunderstorms.

Wednesday Night: Winds less than 25 kt. Local rough seas. Rain
showers likely, isolated thunderstorms.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, isolated thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 8 AM to 8 PM EDT Monday for CTZ002>004.
     Excessive Heat Watch from Tuesday morning through Tuesday
     evening for CTZ002>004.
MA...Heat Advisory from 8 AM to 8 PM EDT Monday for MAZ003-005>007-
     010>015-017>019-026.
     Excessive Heat Watch from Tuesday morning through Tuesday
     evening for MAZ002>021-026.
RI...Heat Advisory from 8 AM to 8 PM EDT Monday for RIZ001>004.
     Excessive Heat Watch from Tuesday morning through Tuesday
     evening for RIZ001>004-006-007.
MARINE...None.

&&

$$

SYNOPSIS...Belk/KS
NEAR TERM...Belk/KS
SHORT TERM...Belk
LONG TERM...KS
AVIATION...Belk/KS
MARINE...Belk/KS