001
FXUS61 KBOX 040612
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
212 AM EDT Thu Jul 4 2024

.SYNOPSIS...
A warm front lifts north across the region late tonight
bringing increasing humidity levels and a few showers or
thunderstorms in the interior on Thursday. Very warm and humid
weather this weekend and into early next week. Saturday will
have the highest humidity levels. While there is a risk of rain
and thunderstorms throughout the weekend and early next week,
it won`t rain continuously. There will be significant dry
periods, with Saturday into Saturday night having the greatest
chance for heavier rains.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
950 PM Update:

Forecast looks to be in good shape with only very minor changes
to incorporate/blend in current obs to the forecast.

Previous discussion:

High pres near the SNE coast drifts offshore tonight with broad SW
flow in place. A mid level warm front will move across the region
late tonight and will be accompanied by a modest instability burst
as higher PWAT air and decreasing static stability advect into the
region from the west. This may result in a few showers developing
late tonight in the interior. Otherwise mainly dry conditions with
increasing clouds. The evening will start out with just some high
clouds so will likely see a period of radiational cooling with lows
dropping to 60-65 before temps stabilize overnight.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Thursday...

A few morning showers possible with the mid level frontal
passage, otherwise partial sunshine although expect more clouds
than sun as the column will be quite moist with PWATs exceeding
2 inches. A weak shortwave approaches from the west in the
afternoon which may lead to a few showers or a t-storm
developing across interior MA into CT where marginal instability
exists with CAPES around 500 J/kg. But areal coverage will be
limited. No instability in the coastal plain which should remain
dry. Temps aloft are pretty warm with 17C at 850 mb but cloud
cover will prevent temps from achieving full potential. Highs
generally low-mid 80s, except upper 70s near the south coast.
But humidity levels will be increasing as dewpoints rise to the
mid- upper 60s.

Thursday night...

Any lingering evening convection in the interior should dissipate,
then will have to watch for a renewed area of showers and
isolated t- storms possibly developing and moving across the
region late Thu night as a weak front sags south into the
region. Areal coverage of any convection is uncertain as hi-res
CAMs are not in agreement on the most preferred location. 2+
inch PWAT axis will shift southward but the south coast will
remain on the northern edge of these higher PWATs and this may
be where best chance of showers and a few t- storms will be.
Given the high PWATs and a weak boundary, localized heavy
rainfall will be a risk with any convection that develops. It
will be a mild and humid night with lows 65-70.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Friday:

There could be some lingering showers in the late morning along the
south coast from the exiting frontal boundary, otherwise subtle
height rises will lead to mainly dry conditions. There is a low
chance for a low topped shower in Western MA and CT with a few
hundred J/kg of SBCAPE. Temperatures and dewpoints will be on the
rise as strong southerly flow kicks in with highs nearing 90F and
dewpoints nearing 70F. Heat indicies Friday stay in the low 90s due
to partial sunshine with diurnal cumulus clouds and high cirrus
clouds filtering in ahead of the shortwave.

Saturday:

Shortwave trough exits out of the Great Lakes, but latest guidance
has trended it further north keeping the forcing out of SNE. MUCAPE
values do jump into the 1000-1500 J/kg range with sfc-6km bulk shear
values nearing 30-40 knots. PWATS will be above 2.0 inches, possibly
approaching 2.5 inches with warm cloud depths between 11kft to 13kft.
This environment is supportive for severe thunderstorms with very
heavy rain and isolated flash flooding. The main questions that
remains ahead of Saturday is how much capping will be present
and if there will be enough forcing to overcome the cap.

Not quite as warm saturday due to the chance for precip and
extensive cloud cover. Highs should be in the low to mid 80s with
dewpoints in the low mid 70s. Even with could cover, the high
dewpoints will push heat indices into the low 90s.


Sunday:

Upper level shortwave retreats to the NE with subtle mid level
height rises in the afternoon. The column begins to dry out which
will keep the region dry, but dewpoints remain near 70F. Mostly
sunny skies will allow temperatures to reach the low 90s.


Next week:

The week starts out dry with rising heights. More unsettled weather
looks possible going into middle to end of next week as the upper
level ridge breaks down a bit. Temps stay warm early in the week in
the upper 80s to low 90s, trending slightly cooler towards the
middle to end of next week.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

06Z TAF Update:

Through 12z Thursday: High confidence.

Largely VFR; can`t rule out a brief period of IFR-visby fog for
the Cape and Islands thru 10z. Offered TEMPO 1 SM BR for these
TAFs. Light south winds, calm at times especially SE MA.

Today: High confidence, though lower on SHRA/TS
development and timing.

Increasing VFR cloudiness likely in multiple layers. Can`t rule
out SHRA after 16z anywhere, but prospects for showers increase
after 18-20z largely from ORH westward. Possible rumble of
thunder but SHRA should predominate for the western airports.
Indicated VCSH or SHRA for the western/central airports but left
eastern TAFs dry due to lower prob of SHRA. SW winds increase to
around 8-12 kt, strongest southeast MA.

Tonight: Moderate confidence.

General deterioration expected for most airports with at least
BKN VFR-MVFR bases. Weak low pressure passing thru s`rn CT and
RI/MA South Coast favors 3-6 SM visby SHRA mainly BDL-PVD-Cape
airports on southward starting 01-03z, with best chance at MVFR/IFR
ceilings for these airports. Less certain/lower prob on SHRA
coverage north of this area. SW winds begin to decrease to 5 kt
or less; best chance at mist/fog is largely south of the Mass
Pike.

Friday: Moderate confidence.

Anticipated sub-VFR ceilings more likely for PVD and the South
Coast; it could take some time for these conditions to improve
if they do so at all. Should see BKN VFR ceilings elsewhere,
with possible pop-up SHRA/TS in the aftn hrs; best chance from
ORH westward. S to SE winds under 10 kt.

KBOS TAF...High confidence in TAF. SCT-OVC VFR ceilings through
at least early tonight. Better chance at MVFR bases and -SHRA
after 03z Fri, with improvement toward SCT-BKN VFR after 12z
Fri. SW winds around 10-12 kt today, easing to 5 kt or less
thru late tonight.

KBDL TAF...High confidence in TAF. VFR most of the day, though
risk for SHRA/possible rumble of thunder after 20z Thu until
07z Fri. Sub-VFR possible in this timeframe. SW winds increase
to around 10 kt today, then ease to around 5 kt tonight.

Outlook /Friday Night through Monday/...

Friday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Friday Night: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.

Saturday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
isolated TSRA.

Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, isolated TSRA.

Sunday through Monday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Thursday night...High confidence.

Winds and seas below SCA thresholds. Light SW winds tonight, then SW
10-20 kt Thu and Thu night. Areas of fog and reduced vsbys should
develop Thu night with scattered showers and possibly a t-storm late
Thu night.

Seas through the period generally 3 ft or less on all waters.

Outlook /Friday Night through Monday/...

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

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers, isolated thunderstorms.

Saturday through Saturday Night: Winds less than 25 kt. Seas up
to 5 ft. Chance of rain showers, isolated thunderstorms.

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers, isolated thunderstorms.

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

Monday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...KJC/KP
NEAR TERM...KJC/Loconto
SHORT TERM...KJC
LONG TERM...KP
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley