BOX issues Area Forecast Discussion (AFD) at Nov 19, 12:30 PM EST569
FXUS61 KBOX 191730
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1230 PM EST Tue Nov 19 2024
.SYNOPSIS...
Dry and tranquil weather will continue through Wednesday
afternoon with cool nights and pleasant days. A slow-moving and
well-developed area of low pressure looks to spread cool
overcast conditions along with welcomed rains to Southern New
England Thursday into Friday. Rain could mix with wet snow
above 1500 feet elevation by Friday. Our weather turns drier for
the weekend into early next week, with a mix of clouds and sun
and seasonable temperatures.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
855 AM Update...
* Sunny with highs mainly in the upper 50s/near 60 today
Dry/northwest flow will continue today with the combination of
low pressure east of the Canadian Maritimes and high pressure to
our west. This will result in sunny skies with highs mainly in
the upper 50s to near 60. Decent mixing will yield northwest
wind gusts of 20 to 25 mph mainly east of the CT River into
early afternoon...but these winds should slacken by late
afternoon as mid level ridge axis begins to build into our
region.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Tonight
Winds continue to weaken tonight as a mid-level ridge axis and
associated surface high pressure builds over The Northeast.
Model forecast soundings suggest that many locations across
interior southern New England will decouple overnight which will
allow more efficient radiational cooling. Expect lows temps in
the low to mid 30s across the region with possibly some upper
20s across northeastern MA. Generally a quiet/chilly night for
the region.
Tomorrow
Weak surface high pressure supports a quiet day on Wednesday.
Winds gradually shifting east in response to a deepening low-
pressure system over The Midwest that will eventually reach the
forecast area on Thursday (see long-term section). Winds will
still be light around 5 mph which will alleviate the elevated
fire weather potential we've been experiencing of late. Column
remains rather dry, so expect another day with more sun than
clouds. High temps once again close to normal in the mid to
upper 50s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights:
* Slow-moving frontal system brings overcast and much-welcomed rains
Thurs into Fri, which could mix with wet snow at locations above
1500 ft elevation Thurs night and Fri. Temps cool to seasonable
levels.
* Turning drier this weekend into early next week, but still remains
blustery and somewhat unsettled with seasonable temps.
* Gradual warming trend early next week.
Details:
A substantial pattern change takes place in this forecast period, as
a deep and slow-moving upper level low moving into the Northeast
brings about a trend toward cooler, cloudier and unsettled weather
as we move into late this week and the weekend. Heralding that
pattern change is a frontal system moving in late Wed night into
Fri, in which there continues to be growing confidence on a
significant rain event with perhaps a light accumulation of wet snow
in the highest of elevations into Thurs night/Fri as colder air
starts to filter into the region. While some of the details are
still unresolved, it is a pattern that should be much welcomed when
considering the protracted dry weather and the brushfires having
broken out over the past several weeks in Southern New England.
Wednesday Night through Friday:
Increasing clouds toward overcast is expected Wed night as a
frontal occlusion moves into Southern New England, with
possible low pressure development along the boundary offshore of
Long Island around late Wed night/Thurs. This feature looks to
spread wetting rains to Southern New England by Thurs AM (PoPs
into the Categorical range) which then lifts gradually from
south to north. This feature will be working with favorably
strong dynamics for ascent, precipitable water values rising to
around 0.7 to 0.8 inches with an upslope enhancement given ESE
winds. Besides focus rounds of steadier light to moderate
intensity stratiform rains, we could also easterly winds near
the south coastal waters reach to near Gale force for a time Wed
night into early on Thurs especially if we can get a secondary
area of low pressure to develop along the occluded frontal
boundary. The location and track of both the upper level low and
surface low pressure are still a bit uncertain, as well as the
potential for a drier punch of air aloft to move from south to
north later Thurs night, which could transform initial rains
Thurs to more of an intermittent/showery character. But still,
ensemble QPF probs through Thurs night support high (70-90%)
probs of 24 hr rains of at least a half inch, with lower to
moderate (15-60%, highest in the Berkshires and interior
Southern New England) probs of 24 hr rains of at least an inch.
Moving into Thurs night and Fri...colder air starts to filter
in on WSW flow aloft. Dynamic cooling associated with the cold
pocket of air aloft along with continued QPF falling across
interior western New England should favor a gradual transition
from rain over to a mix of rain and wet snow mix at elevations
above about 1500 ft AGL. For these areas, it is a little early
for accumulations at this range but any accumulation likely
would be on the light side with rain mixing in at times.
Otherwise, just looking at overcast with more intermittent,
showery rains for the vast majority of the area for Thurs night
and Fri. A second spoke of energy rotating around the broad
upper low late Fri into Fri night could bring a period of
steadier light rains to eastern and southeast MA but its exact
placement is still uncertain.
Temperatures...gradual cold advection takes place in this period,
toward a slow cooldown in high and low temps, although persistent
overcast also favors a narrower diurnal range. Should still see
highs in the 40s/around 50 in the interior and lower 50s coastal
areas on Thurs, then cooling off into the 40s (upper 30s/low 40s
higher terrain) Friday. Lows in the mid 30s to low 40s on Thurs
night, cooling off into the lower to middle 30s for Fri night.
The Weekend into Early Next Week:
Still under broad cyclonic flow aloft with a cool pocket of air
which could keep our weather somewhat unsettled, with at least
partly to mostly cloudy weather around (more clouds north, less so
south and east). However we should start to see a return to dry
weather by the weekend. Though it may be fairly blustery in this
period, temps also slowly start to moderate back into the upper 40s
to lower 50s, which are close to seasonable.
&&
.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update...
This afternoon and tonight...High Confidence.
VFR. NW wind gusts diminish by late afternoon. Winds then
gradually become calm/Light NW tonight.
Wednesday...High Confidence.
VFR. Light N winds becoming NE.
Wednesday night...Moderate Confidence.
We expect conditions to deteriorate to MVFR-IFR levels as Wed
night wears along...but specific timing of this remains
uncertain. We also expect widespread rain to overspread the
interior toward daybreak and be entering the coastal plain
somewhere in the vicinity of 12z. NE winds 5-10 knots but we may
see some 20+ knot gusts developing toward daybreak along the
coast.
KBOS Terminal...High Confidence in TAF.
KBDL Terminal...High Confidence in TAF.
Outlook /Thursday through Saturday/...
Thursday: Mainly MVFR, with areas IFR possible. Windy with
local gusts up to 30 kt. RA.
Thursday Night: MVFR/IFR conditions possible. Breezy. Chance
RA.
Friday: MVFR/IFR conditions possible. Chance RA.
Friday Night: Mainly VFR, with areas MVFR possible. Breezy.
Chance RA.
Saturday: Mainly VFR, with areas MVFR possible. Breezy. Slight
chance RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Wednesday...High Confidence.
A ridge of high pressure builds in from the west on Tuesday
which will allow winds/seas to diminish below small craft
thresholds across most waters by late Tue afternoon. Winds
continue to diminish Tue night and no marine headlines will be
needed. Calm/tranquil conditions carry into Wednesday with
light winds and seas less than 3 feet.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Chance of rain.
Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Rain.
Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 8 ft. Chance of rain.
Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain.
Friday Night: Winds less than 25 kt. Local rough seas. Chance
of rain.
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain.
&&
.FIRE WEATHER...
Today...
In terms of headlines for today...we've opted for a Red Flag
Warning for MA after partner feedback indicated active brushfire
activity yesterday; while opting for a special weather
statement for CT and RI based on fire weather partner feedback
in those states.
Northwest wind gusts of 15 to 25 mph are expected Tue with the
strongest of those gusts across eastern MA. Minimum afternoon RH
values are expected to drop to between 30 and 40 percent on Tue.
Wednesday...
High pressure building in from the west will result in much lighter
winds Wed...generally less than 10 mph. Minimum afternoon RH values
are expected to drop between 45 and 55 percent.
Thursday...
A much needed widespread 0.50 to 1"+ of rain is on tap for Thu. This
should result in significant easing of the current Fire Weather
concerns.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Red Flag Warning until 6 PM EST this evening for MAZ002>024-
026.
RI...None.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for
ANZ231>235-237-250-251-254>256.
&&
$$
SYNOPSIS...Loconto/RM
NEAR TERM...Frank
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Frank/Loconto
MARINE...Loconto/RM
FIRE WEATHER...Loconto/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Nov 19, 12:30 PM EST----------------
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