BOX issues Area Forecast Discussion (AFD) at Nov 27, 1:32 PM EST572
FXUS61 KBOX 271832
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
132 PM EST Wed Nov 27 2024
.SYNOPSIS...
Dry and seasonable today as high pressure builds to the south.
Another low pressure tracks near the coast on Thanksgiving,
bringing rain with some accumulating snow possible at the higher
elevations. Drying out Friday with seasonable temperatures, then
colder this weekend into early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
18z Update:
Not a ton of change from the previous forecast. Made some minor
edits to the precipitation probabilities to reflect recent
guidance on the rainfall timing early tomorrow morning. Main
message still stands for tomorrow's coastal system. Rainfall for
most people with perhaps a periods of light wet snow mixing in
for elevations above 1000 ft mainly tomorrow AM.
Previous Discussion:
Not much going on this morning, other than some icing on
untreated surfaces. Temperatures should rise above freezing by
mid-morning. Main changes this morning were to bring the
forecast back in line with observed trends.
Previous discussion...
High pressure builds into the central Appalachians today. This
will maintain dry weather across southern New England, along
with a steady west wind. Near to slightly below normal
temperatures expected today.
&&
.SHORT TERM /THURSDAY/...
The high pressure to our south expected to move over the North
Atlantic tonight, opening the door for a low pressure to
pass through southern New England on Thanksgiving. Some
uncertainty in the onset timing. The GFS is on the faster end,
with the HREF on the slower side. The consensus timing window
places the onset of widespread precipitation during the morning
hours Thursday. Although if the HREF is correct, this timing
could be fast by about 3 hours. In just about all cases,
expecting precipitation to be ongoing mid day into the late
afternoon.
The lack of a high pressure over Quebec will make it more
difficult to keep colder air near the ground. East to southeast
winds with water temperatures generally in the 50s should result
in mainly rainfall across southern New England. At the higher
elevations at or above 1 kft some light snow is possible,
especially if the precipitation begins at night. The consensus
for these areas is for about 1-3 inches of snowfall, although
there are some ensemble members that suggest higher amounts are
possible. The ECMWF in particular is more aggressive than the
GFS-based ensemble. At this time, not planning on any winter
weather headlines for Thursday.
Precipitation comes to an end Thursday night. Near to slightly
below normal temperatures expected.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Key Points
* Rain and high-elevation snow continues Thursday night, ending
by Friday morning.
* Colder for the weekend with ocean-effect rain/snow showers
possible.
The low pressure system begins to pull off to the NE and into
the Gulf of Maine Thursday night. Rain and high-elevation snow
continues Thursday night, but accumulations will be lighter
than Thursday afternoon. Precipitation ends by Friday morning
with only lingering showers over the Cape and Islands. Behind
the system, cold and dry air advects into the region. High temps
will likely be achieved early on Friday in the mid to upper 40s
before temperatures crash into the 30s shortly after sunset.
Overnight lows Friday into Saturday drop into the low to
mid-20s, with low 30s near the coasts.
Another shortwave passes through Saturday, bringing a
reinforcing shot of cold air to the region. High temperatures
Saturday should be in the upper 30s to lower 40s, then
struggling to top 40F by Sunday. Overnight lows will likely be
some of the coldest we have seen this season, dropping into the
upper teens to low 20s both Saturday and Sunday night. With
mid level dry air, not expecting anything more than an isolated
rain/snow showers this weekend with the passing of the
shortwave. There could be some ocean-effect rain/snow showers
over the waters with cold air advecting over warm ocean waters,
still in the 50s.
The dry and cold conditions will continue into early next week
as the upper level closed low, and the 500mb cold pool over
Ontario and Quebec remains stalled, sending continued
reinforcing shots of cold air down. High temperatures will
likely continue to struggle to top 40F, with low 30s in the high
terrain of northwest MA. Overnight lows should remain in the
upper teens to lower 20s.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today...High confidence.
VFR. W-WNW wind 5-15 kt.
Tonight into Thursday...High confidence. Moderate on timing of
rain & cigs...
Tonight:
VFR most of the night with clouds developing from west to east.
Ceilings lower to MVFR as rain overspreads the region 08-13z,
mixing with snow across the higher elevations of interior MA.
Thursday:
Rainfall arrives to terminals likely by 14z with ceilings
dropping toward MVFR. In 16-20z timeframe IFR cigs spread across
the region generally from west to east with onset of moderate
rain. E winds during the day Thursday at 08-14 kts with gusts
up to 30 kts for the Cape/Islands and closer to 20 kts near BOS.
Winds shift toward the N closer to 00z.
KBOS Terminal...High confidence in TAF. Moderate on timing of
rain & cigs.
Tonight:
VFR conditions most of the night with mid-level ceilings moving
in after midnight. W/WNW winds this afternoon at 08-12 kts
decreasing after 21z. Light SW winds overnight transitioning to
E/SE by 12Z. Low chance for rain to move in earlier in the
09-13z timeframe.
Thursday:
Rain moves in fully by 14z dropping ceilings MVFR then
deteriorating to IFR category after 17z. East winds at 08-14
kts with gusts up to 20 kts, transitioning toward the north
around 00z.
KBDL Terminal...High confidence in TAF.
Outlook /Thursday Night through Monday/...
Thursday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance RA, slight chance FZRA.
Friday: VFR. Breezy.
Friday Night: VFR. Chance SHRA.
Saturday through Sunday: VFR. Breezy.
Sunday Night: VFR.
Monday:
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Thursday...
Winds and seas diminish further this morning, with relatively
tranquil boating conditions tonight into Thursday morning. Winds
and seas build once more late Thursday as a low pressure
approaches the waters. Rain develops Thursday morning with
periods of poor to fair visibility.
Outlook /Thursday Night through Monday/...
Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Chance of rain.
Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain, slight chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Chance of rain showers.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.
Sunday through Monday: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Belk/KP
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...KP
AVIATION...Belk/Mensch/KP
MARINE...Belk/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Nov 27, 1:32 PM EST----------------
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