BOX issues Area Forecast Discussion (AFD) at Dec 21, 3:00 PM EST926
FXUS61 KBOX 212000
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
300 PM EST Sat Dec 21 2024
.SYNOPSIS...
Light snow shower activity diminishes through this afternoon. Bitter
cold temperatures tonight through tomorrow morning as gusty winds
contribute to feel like temperatures in the negatives, with Cold
Weather Advisories for the Berkshires through tomorrow morning.
A weak clipper system may bring very minor snow accumulations
late Monday night into Christmas Eve morning. Otherwise...dry
weather dominates the rest of the Holiday week with temperatures
moderating back to seasonable levels. &&
.NEAR TERM /THROUGH TONIGHT/...
* Light snow showers ending this afternoon
Regional satellite imagery shows a mid level cloud deck moving from
northwest to southeast over much of southern New England as moisture
streams off the Great Lakes beneath a mid level ridge axis. This
shortwave and cyclonic flow aloft together with moisture between 850-
900 mb will continue to keep a mix of sun and clouds in the forecast
this afternoon. As we head into the evening increasingly dry air is
advected in, bringing an end to most light snow and decreasing
cloudcover. This cold, dry NW flow however will then bring us the
coldest night of the season overnight. As high pressure builds into
the eastern Great Lakes it will funnel frigid air into SNE, as cold
as near 0F in the high elevations of the Berkshires and single
digits/low teens elsewhere. The unfortunate part is that the
pressure gradient between the exiting low and incoming high will
remain tight enough to keep winds gusty overnight, making it feel
even colder. Wind Chill values will dip into the negative low teens
in the highest elevations of the Berkshires and negative single
digits elsewhere. A Cold Weather Advisory is in effect for Berkshire
county where widespread wind chill values of at least -15F are more
certain.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Messages...
The very cold airmass settles over us on Sunday making for the
coldest day of the forecast period. Given the closer proximity of
the high pressure, winds will be less gusty than Saturday, but gusts
to 20-25 mph are possible, especially early on. This means
temperatures topping out in the teens and low 20s will feel more
like single digits on either side of 0. Dry weather expected, but
the one exception is a low probability of some ocean effect snow
showers reaching the outer Cape Sunday afternoon/night. This is
because as the high approaches winds shift from the NW to more NNW
which pushes the trajectory from over the ocean to clipping the
Cape. Looking into the overnight hours we yet again see our coldest
night of the season (beating Saturday night). Thanks to high
pressure, clear skies, and light winds, we'll radiate very
efficiently so expect low temperatures to drop into the negative
single digits in the high elevation interior while elsewhere will be
"warmer" in the single digits above zero. It will actually feel
warmer than the night previous, though, owing to the lack of wind.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Key Messages...
* Mon dry & still cold...highs middle 20s to the lower 30s
* Light snow showers late Mon night/Tue AM...Dusting to 1" for most
* Temps moderate to near normal by mid to late in the Holiday Week
* Mainly dry Wed/Thu/Fri/Sat outside brief spotty very light precip
Details...
Monday...
A dry and frigid early Mon morning...except for perhaps a few
leftover ocean effect light snow showers/flurries across the
Cape/Nantucket which will be winding down. High temps will still be
cold/below normal on Monday...it will be several degrees milder than
Sunday with less wind too as large high pressure crosses the region.
Currently expecting highs Monday afternoon to generally be in the
middle 20s to the lower 30s.
Monday night and Tuesday...
Dry weather prevails Monday evening...but a weak clipper system and
its associated shortwave will cross the region late Monday night
into Tuesday morning. The better dynamics/forcing looks to pass
north of our region. That being said...there is enough forcing for a
brief period of light snow showers. This will be short-lived though
and there with limited moisture...thinking a dusting to 1" of snow
for most. It is possible a few locations in northern MA see up to 2"
of snow or so if we can muster enough forcing as suggested by the
RGEM. Either way...this will not be a big storm with mainly dry
weather by Tue afternoon. Highs should also recover well into the
30s across much of the region with perhaps even some lower to middle
40s across the Cape and Islands.
Wednesday through Saturday...
A mid level ridge axis will build into southern New England for the
second half of the Holiday Week. EPS/GEFS indicate well above normal
height fields...but a high pressure system in the vicinity of
northern New England and the Canadian Maritimes will offset this to
some degree. So while temps will moderate to seasonable
levels...they will not get too mild with that high to our
north/northeast. Highs probably in the 35 to 45 degree range for the
second half of the upcoming week. Generally dry weather is
anticipated for much of this time...but low level onshore flow may
result in spotty very light precipitation at times with the best
chance near the coast. Regardless...dry weather will dominate with
no significant storms for the second half of the Holiday Week.
&&
.AVIATION /20Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
This afternoon...High confidence.
VFR. NW wind 10-20 kt with some higher gusts.
Tonight and Sunday..High confidence.
VFR, but ocean effect clouds may lower cigs to MVFR at times
over the outer Cape, mainly along and east of HYA. NW wind 10-20
kt with higher gusts near the coast, diminishing Sunday
afternoon.
Sunday night...High confidence.
VFR. NW winds 5-10 kts.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Monday through Wednesday/...
Monday: VFR.
Monday Night through Tuesday: Mainly VFR, with local IFR
possible. Chance SHSN.
Tuesday Night: VFR. Breezy.
Christmas Day: VFR. Breezy. Slight chance SHSN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Key Messages:
* Small Craft Advisory in effect through Sunday night.
Tonight into Sunday...High confidence.
High pressure moving overhead. NW winds 15-20 kts gusting to 25
kts. Seas 5-7 ft. A few ocean effect snow showers are possible
Sunday across the eastern waters.
Sunday night...High confidence.
High pressure overhead. NW winds 10-15 kts. Seas 2-5 ft.
Outlook /Monday through Wednesday/...
Monday: Winds less than 25 kt.
Monday Night: Winds less than 25 kt. Chance of rain showers,
chance of snow showers. Local visibility 1 to 3 nm.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers. Local visibility 1 to 3 nm.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers, slight chance of snow
showers. Local visibility 1 to 3 nm.
Christmas Day: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers, slight chance of snow
showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Sunday for ANZ231-232-251.
Small Craft Advisory until 10 PM EST this evening for
ANZ233>235-237.
Small Craft Advisory until 4 AM EST Monday for ANZ250-254>256.
&&
$$
SYNOPSIS...Frank/BW
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Frank
AVIATION...Frank/BW
MARINE...Frank/BW
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 21, 3:00 PM EST----------------
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