BOX issues Area Forecast Discussion (AFD) at Aug 31, 7:15 AM EDT051
FXUS61 KBOX 311115
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
715 AM EDT Sat Aug 31 2024
.SYNOPSIS...
Turning a bit humid today with considerable cloudiness focused
across the interior, but peeks of sunshine too. An approaching cold
front will bring scattered showers and perhaps an isolated
thunderstorm or two later tonight into Sunday...but not expecting a
washout. It will be quite humid on Sunday ahead of the approaching
cold front. Dry and seasonable Monday through late next week. Optimal
radiational cooling conditions will yield chilly morning lows, in
the 40s, several days next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
7 AM Update...
Patchy morning fog that developed across parts of eastern MA and
the Cape/Islands has already begun to dissipate. Conditions
across the Cape and SE MA are actually quite spectacular this
morning with clear skies and light winds, while much of interior
SNE is engulfed in a mid level cloud deck. Am expecting clouds
to scatter out a bit along the I-95 corridor later this morning,
so took the opportunity to mix in some more optimistic guidance
(HREF) during this update. Rain continues to look delayed until
after 00Z tonight, so while humidity will be building on
south/southeast flow, it should be a good day for outdoor
activities to start this holiday weekend.
345 AM Update...
* Considerable clouds across the interior today but peeks of
sunshine & increasing humidity with highs in the upper 70s/near 80
High pressure continuing to shift east of the Maritimes was allowing
a southerly flow of increasing low level moisture. The return of
this moisture has resulted in areas of low clouds developing across
the region early this morning with the focus to the northwest of I-
95. This along with warm advection will result in considerable
cloudiness persisting today across the interior...but we do expect
peeks of sunshine with the most of it across eastern MA/RI. 925T
warming to +18C should allow for highs to reach the upper 70s to
near 80. It will also be turning a bit more humid as dewpoints rise
into the 60s.
Shortwave energy remains to the west of our region today and there
is actually some mid level ridging. This should keep our weather
generally dry today...although low risk for a few spot showers late
today across the distant interior.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Key Points...
* Scattered showers and perhaps an isolated t-storm or two overnight
and it will be quite mild with lows only in the middle to upper 60s
* Humid Sunday with scattered showers & perhaps a few t-storms but
not a washout with highs in the upper 70s to the lower 80s
Details...
Tonight...
Shortwave energy approaches from the west tonight. The energy should
be deamplifying a bit as it runs into some mid level ridging.
Nonetheless...there still is enough forcing for scattered showers
and perhaps an isolated t-storm or two mainly late tonight into the
overnight hours. Pwats nearing 2 inches may result in brief
localized downpours...but activity should not last too long in a
given location. Southerly flow will also allow plenty of low clouds
to develop and with increasing dewpoints only expect low temps to
drop into the middle to upper 60s.
Sunday...
Lingering scattered showers and perhaps an isolated t-storm or two
will be possible Sunday morning. We then will need to watch for
another round of scattered showers and perhaps a few t-storms during
the afternoon...but certainly not a washout with much of the day
ending up dry. A pre-frontal trough and approaching surface cold
front in the afternoon will allow surface Capes on the order of 800
to 1500 J/KG to develop. High should be in the upper 70s to the
lower 80s...but with dewpoints near 70 it will be humid. The overall
severe weather threat is quite limited...given poor mid level lapse
rates and lack of strong synoptic scale forcing. The CSU Machine
learning probs just show a small area of low severe weather probs
for wind and in fact the HRRR Neural network keep those low probs to
our southwest.
So in a nutshell...scattered showers and perhaps a few t-storms will
be possible on Sunday. The severe weather threat is low and even if
it were to occur the threat would just be a very localized wind
threat.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
* Seasonably chilly conditions early next week lead to a gradual
warming trend
* High pressure leads to dry conditions through the period
Trough/cold pool nestles over southern New England behind departing
cold front late Sunday night into early Monday as surface high
pressure builds over the region. High pressure will dominate through
at least Thursday, yielding dry conditions as mid level ridging
returns by Wednesday. In fact, there are no significant chances for
precipitation Monday through Thursday with even the NBM spitting out
"0" PoPs for the duration of the forecast. Longer range guidance
shows trough development in the Friday-Saturday period in addition
to the potential for a coastal low of some sort that will likely
increase rain chances by next weekend, though, the interaction of,
or lack thereof, those two features will need to be closely
monitored.
With cold pool aloft, surface high pressure, light winds and clear
skies, expect optimal radiational cooling conditions Monday through
Wednesday nights as morning lows on Tuesday look to dip into the 40s
in most towns outside of our urban centers. It's possible that a few
spotty locations in the high terrain of western MA could drop into
the 30s. Given optimal radiational cooling, did stray from the NBM
using a blend of the bias corrected SREF and MOS guidance for each
morning through Thursday. With dry airmass in place, PWATs as low as
0.4" early next week, temps will rebound quickly each day, into the
70s. Cold pool shift to our east by late week so do anticipate both
highs and lows to warm a few degrees each day.
&&
.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update...
Today...Moderate Confidence.
Areas of MVFR with even localized IFR ceilings will develop
through daybreak with the bulk of them to the northwest of
I-95...but can not rule out some brief/scattered lower ceilings
near the southeast New England coast. Mainly VFR conditions
probably continue through the afternoon along the coastal plain
and some improvement expected across the interior this
afternoon...perhaps even to VFR conditions in spots.
S winds 5 to 10 knots.
Tonight...Moderate Confidence.
Ceilings should lower tonight to mainly MVFR-IFR thresholds. A
round of scattered showers and perhaps a rumble or two of
thunder are possible mainly during the latter half of the night.
S winds 5-10 knots.
Sunday...Moderate Confidence.
MVFR-IFR ceilings early should improve to mainly MVFR/VFR
conditions by afternoon. Scattered showers and a few t-storms
are possible at times...but activity likely hit or miss. SSW
5-10 knots.
KBOS TAF...Moderate confidence in TAF. Some patchy MVFR this
morning will give way to a long stretch of VFR through at least
03Z tonight. Showers expected to develop, along with lowering
ceilings after that time. Low probability of a rumble of thunder
but confidence too low to include a PROB30 around 12Z Sunday
morning.
KBDL TAF...Moderate confidence in TAF. MVFR this morning,
expecting VFR conditions to develop later this afternoon before
deteriorating to MVFR or IFR tonight as showers overspread after
00Z. Generally expect rain to be done at the terminal by 14/15Z
Sunday though spotty showers possible after that time. Rumbles
of thunder cant be ruled out but confidence much too low for
PROB30 inclusion.
Outlook /Sunday Night through Wednesday/...
Sunday Night: VFR. Breezy.
Labor Day through Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Sunday...High Confidence.
High pressure shifts further east and away from the Canadian
Maritimes today as a cold front slowly approaches the region late on
Sunday. This will result in SSE winds of 10 to 15 knots today
shifting to the SSW at the same speeds tonight with some gusts to
20+ knots expected on Sunday. So while seas may become a bit choppy
on Sunday...conditions should remain below small craft advisory
thresholds.
Outlook /Sunday Night through Wednesday/...
Sunday Night: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms.
Labor Day through Monday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.
Tuesday through Wednesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Frank/KS
NEAR TERM...Frank/KS
SHORT TERM...Frank
LONG TERM...KS
AVIATION...Frank/KS
MARINE...Frank/KS
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 31, 7:15 AM EDT----------------
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