BOX issues Area Forecast Discussion (AFD) at Jul 3, 9:51 PM EDT268
FXUS61 KBOX 040151
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
951 PM EDT Wed Jul 3 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 THURSDAY 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 THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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 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 /02Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight: High confidence.
VFR cigs. Low risk of a shower 09-12z in the interior. SW wind
5-15 kt.
Thursday: High confidence.
Mainly VFR cigs, but patchy MVFR possible over higher
elevations. Isolated morning shower possible, then a few
showers or a t-storm possible in the afternoon in the interior.
SW wind 10-20 kt.
Thursday night: Moderate confidence.
Cigs gradually lowering to MVFR with IFR possible near the south
coast. A few evening showers possible, then scattered showers
and possibly a t-storm near the south coast after midnight.
KBOS TAF...High confidence in TAF.
VFR. SSW winds around 10 knots continue overnight and through
tomorrow. Not expecting a sea breeze to develop with 2000ft
winds over 20 knots.
KBDL TAF...High confidence in TAF.
VFR with SSW winds around 10 knots tonight and tomorrow. Low
chance for a weak shower tomorrow afternoon
Outlook /Friday 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 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...KJC/Loconto/KP
MARINE...KJC/Loconto/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 3, 9:51 PM EDT----------------
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