BOX issues Area Forecast Discussion (AFD) at Aug 2, 1:55 AM EDT480
FXUS61 KBOX 020555
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
155 AM EDT Fri Aug 2 2024
.SYNOPSIS...
Hot and humid conditions will continue Friday, with scattered
afternoon and evening showers and thunderstorms. It remains
warm and humid through the weekend, but will be unsettled with
scattered showers and thunderstorms. Locally heavy downpours
possible at times. Sunday may be the more active day of the two
weekend days. Turning drier early next week with more
comfortable humidity levels.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
2 AM update...
Dry weather overnight with short wave ridging moving across the
area. It will be a warm and humid with lows upper 60s and lower
70s. Given dew pts will be in the same range, expecting some
patchy fog.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Friday...
* Heat advisory with heat indices mid-upper 90s
* Scattered afternoon and evening showers and t-storms developing,
especially interior
* Primary risk is locally heavy rainfall but strong wind gusts also
possible
Another hot and humid day across SNE. 925 mb temps 24-26C will
support highs 90-95 but cooler along the immediate east and south
coasts as sea-breezes develop. PWATs increasing to near 2 inches in
the afternoon so it will be rather humid with dewpoints in the lower
70s during peak heating. Heat indices will max out in the mid-upper
90s and heat advisories continue.
Robust mid-upper level trough moves into the Ohio Valley which
initially results in downstream ridging across New Eng. However,
guidance is indicating a lead shortwave approaching from the west
during the afternoon which will likely result in scattered showers
and t-storms developing in the afternoon, with focus in the
interior. Not expecting much convection across RI and SE MA through
the day. Mid level lapse rates are poor but heat and humidity will
contribute to CAPES 1000-2000 J/kg. Given high PWATs, heavy rainfall
will be the primary threat. Deep layer shear is weak so not
expecting organized storms but this will be a wet microburst
environment with moderate instability, weak shear and high
dewpoints/PWATs so can't rule a strong storm capable of localized
wind damage. CSU machine learning probs and Nadocast both
highlighting a low prob for a wind threat.
Friday night...
Scattered showers and storms will likely linger into the evening and
eventually spread to the south coast overnight as shortwave moves
into the region. Modest SW flow and high dewpoints will resulting a
rather warm and humid night with lows 70-75.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Saturday and Sunday
A deamplifying short-wave traverses over The Northeast this weekend.
With a tropical like air mass in place, expect periods of scattered
showers with embedded thunderstorms both Saturday and Sunday
afternoon. PWATs greater than 2 inches and surface instability
greater than 1000 J/kg will allow some of these showers and storms
to produce locally heavy downpours. Boundary layer winds will be on
the weak side, so some localized flooding is a concern, but with the
generally weakly forced environment in place the risk is on the low
side. The Weather Prediction Center has most of southern New England
in a marginal risk for excessive rainfall for both Saturday and
Sunday. CSU machine learning probabilities are a bit more aggressive
on Saturday with a 15 percent chance of rainfall exceeding flash
flood guidance across portions of western MA and CT on Saturday
afternoon. Aside from potential localized flooding, the risk for
severe weather is low as there will only be modest amounts of shear
(25-30 knots in the 0-6 km layer), and poor mid-level lapse rates
less than 6 C/KM. Nonetheless, some rumbles of thunder will be
likely. For areas that are able to dodge the scattered showers and
thunderstorms, the forecast calls for partly to mostly cloudy skies
and highs in the mid to upper 80s under modest south/southwest
winds. The active heat advisory may need to be extended into
Saturday across eastern MA as dewpoints in the upper 70s and temps
in the upper 80s may support another consecutive day of 95+ degree
heat indices.
Next Week
After another day with highs in the mid to upper 80s on Monday,
model guidance suggests a cold front pushing through The Northeast
ushering out the warm/humid air mass. This will be followed by more
seasonable afternoon temperatures in the upper 70s to low 80s for
much of next week with more comfortable dewpoints in the 60s. While
the flow aloft will be more zonal behind the frontal passage, a few
embedded short-waves could trigger some diurnal
showers/thunderstorms each afternoon.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z TAF Update
Friday...High confidence on trends, lower on exact
details/timing.
VFR and dry weather thru 18z. Then after 18z,MVFR/VFR cloud
bases as scattered showers and thunderstorms develop. Activity
most numerous across CT into northern MA. Heavy rain, frequent
lightning and gusty winds are possible with strongest storms.
Light and variable winds this morning, become S-SW this
afternoon, except becoming SE along the eastern MA coast,
including KBOS.
Friday night...Moderate confidence.
MVFR/VFR, lowering to IFR/LIFR across the interior overnight in
stratus. Some uncertainty how widespread IFR/LIFR will be across
the interior. Scattered showers with embedded thunder in the
evening, probably lingering much of the night. A few heavy
downpours, gusty winds and frequent lightning in the strongest
storms, especially in the early evening. South winds 10-15 kt.
Saturday...Moderate confidence.
IFR/LIFR across the interior and MVFR elsewhere during the
morning, slowly lift to MVFR/VFR all terminals in the afternoon.
Showers possible early, then likely a period of dry weather
before the risk of showers/thunderstorms increases late in the
day, especially across western MA/CT. S-SW winds 10-15 kt with
gusts up to 20 kt over southeast MA.
KBOS TAF...High confidence.
Sea breeze develops around 14z Fri. Low risk for a t-storm Fri
afternoon. VFR in the morning, then MVFR/VFR cloud bases in the
afternoon.
KBDL TAF...High confidence.
VFR in the morning. Then risk for thunderstorms in the afternoon
along with MVFR/VFR cloud bases. Confidence for -TSRA is low,
so only include VCSH for now.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, isolated TSRA.
Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, isolated TSRA.
Sunday Night: VFR. Breezy. Chance SHRA, isolated TSRA.
Monday through Tuesday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Friday night...
Winds and seas will be below SCA thresholds through the period. SW
gusts to 20 kt will diminish this evening, then another period of SW
winds 10-20 kt develop Fri, becoming SE along the eastern MA coast
as sea-breezes develop. Areas of fog may reduce vsbys over south
coastal waters tonight into Fri morning, then more widespread fog is
possible Fri night along with scattered showers and a few t-storms.
Outlook /Saturday Night through Tuesday/...
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers, isolated
thunderstorms.
Sunday through Sunday Night: Winds less than 25 kt. Local rough
seas. Chance of rain showers, isolated thunderstorms.
Monday through Monday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft. Slight chance of rain showers, isolated
thunderstorms.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 7 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 7 PM EDT this evening for MAZ005>007-
011>021.
RI...Heat Advisory until 7 PM EDT this evening for RIZ001>004.
MARINE...None.
&&
$$
SYNOPSIS...KJC/Nocera/RM
NEAR TERM...Nocera
SHORT TERM...KJC/Nocera
LONG TERM...RM
AVIATION...Nocera/RM
MARINE...KJC/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 2, 1:55 AM EDT----------------
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