BOX issues Area Forecast Discussion (AFD) at Dec 3, 12:20 AM EST572
FXUS61 KBOX 030520
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1220 AM EST Tue Dec 3 2024
.SYNOPSIS...
Mainly sunny and dry weather is expected through Tuesday,
although a cold airmass will continue to yield below normal
temperatures and periods of ocean effect cloudiness for the
Cape and Islands. Next chance for precipitation comes Wednesday
night into Thursday, as a clipper system brings rain near the
coast and accumulating snowfall in the interior. An colder
airmass moves in Friday and into the weekend, likely with the
coldest air of the season thus far.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Sct-bkn strato-cu lingering across portions of SNE but these
clouds are expected to clear tonight. Otherwise, ocean effect
strato-cu developing over the ocean north of Cape Cod and these
clouds expected to fill in across the outer Cape and Nantucket
through the night. Otherwise, a mainly clear night with light
WNW winds becoming near calm overnight. This means another very
chilly night is in store with strong radiational cooling
expected. With little change in thermal airmass, largely used
persistence as a basis for tonight's lows. The lone exception is
across the Mid-Cape and Outer Cape where an increasing coverage
of ocean effect stratocumulus and modest NW breeze should limit
radiational cooling and bring lows closer to the mid/upper 20s.
The larger metro cities should stay in the lower 20s but most
areas elsewhere should dip into the teens.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
120 PM Update:
Little change in the governing synoptic regime for Tues, with
high pressure to our south supplying continued dry weather and a
light westerly wind. The shift in the winds to more of a
westerly flow, a less favorable direction for ocean effect over
land, should in turn shut off ocean effect cloudiness over the
Outer Cape early in the day. Thus mostly clear skies but still a
rather chilly and dry day with highs in the 30s, but may
struggle to reach the freezing mark over the higher terrain of
the Berkshires and hills in Worcester and Tolland Counties.
For Tues night, modest change takes place with 500 mb longwave
trough axis and associated 925-850 mb thermal trough moving
eastward and offshore. Although we still expect clear skies and
light winds favoring efficient radiational cooling, we will see
more in the way of lower- tropospheric warm advection. Still
ends up being another rather cold night, and though it may not
necessarily feel much different, lows should be a couple degrees
warmer in the upper teens to the mid 20s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Messages...
* Accumulating snowfall likely Wed night into early Thu,
especially west of I-495 with mainly rain in the coastal
plain.
* Turning colder Thu night into the weekend with temps well below
normal
* Strong wind gusts developing Wed night Cape/Islands and late Thu
into Fri rest of SNE
Wednesday...
Surface ridging moves across SNE then to the east by days end ahead
of next approaching system from the Gt Lakes. Plenty of sunshine to
start the day, then developing warm advection pattern within SW flow
will bring increasing clouds in the afternoon. However, it should
remain dry through the day with precip holding off until evening.
Highs will range from the mid 30s to lower 40s with increasing SW
winds 10-20 mph in the afternoon.
Wednesday night into Thursday...
Deep upper level low dives into the Gt Lakes Wed night before moving
across New Eng on Thu. Diffluent flow aloft Wed night ahead of the
trough with favorable left exit region of the upper jet will provide
strong large scale forcing for ascent. Decent SW low level jet will
bring increasing moisture with saturated column developing through a
deep layer. This will bring a period of widespread precip Wed night
into early Thu with expected QPF amounts of 0.25 to 0.50". The
column is cold enough for snow in the interior west of I-95 with
mostly rain along and SE of I-95, although a rain-snow mix is
possible along the I-95 corridor. Highest snow amounts will be over
higher elevations where temps will be coldest. Preliminary forecast
accums of 3-6 inches is possible over the Berkshires and Worcester
Hills, with 1-3 inches across the rest of the interior. This is line
with ECWMF and GEFS ensembles showing high probs (60-90%) of 3+
inches over the elevated terrain, with high probs (90%+) of 1 inch
across the interior. No snow accums are expected near the coast.
Fortunately, the bulk of the snow will begin after the Wed evening
commute although the morning commute will be impacted.
Best moisture will be lifting out Thu morning so interior snow will
begin to taper off, although scattered rain and higher elevation
snow showers likely to continue as the upper low and arctic front
moves into the region. Clearing Thu night and windy and colder with
lows dropping into the upper teens to mid 20s.
Decent SW low level jet developing Wed night will likely bring a
period of strong wind gusts across the Cape/Islands. Model soundings
suggest potential for a period of 40-50 mph gusts here and wind
advisories may eventually be needed. Then strong W wind gusts will
develop across rest of SNE late Thu and especially Thu night in the
cold advection with marginal wind advisory criteria possible.
Friday through Monday...
Blustery and cold Fri as 850 mb temps bottoming out near -14C. Highs
will range from the upper 20s to mid 30s and the cold conditions
will continue into Sat but with less wind. Another fast moving
northern stream shortwave and clipper may bring some light snow
sometime Sat or Sat night but low confidence on timing. Drying out
Sunday, then next system approaches next Monday with rain or a mix
as milder air will be moving in as southerly flow develops.
&&
.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update:
Today and tonight: High confidence.
VFR. Light WNW winds early this morning except 5-8 kt for BOS
and the Cape airports. For today, winds become more WNW to W,
then become light W to WSW for tonight.
Wednesday: High confidence.
VFR. Light W winds increase to 5-10 kts becoming SW then S.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: MVFR/IFR conditions possible. Windy with gusts
up to 35 kt. SN, RA.
Thursday: Mainly MVFR, with local IFR possible. Windy with
gusts up to 35 kt. Chance SHRA, chance SHSN.
Thursday Night: VFR. Windy with gusts up to 35 kt.
Friday: VFR. Windy with gusts up to 30 kt.
Friday Night: VFR. Breezy.
Saturday: VFR. Breezy. Slight chance SHSN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Generally tranquil winds and sea conditions for boaters through
Tuesday night. WNW to W winds around 10-15 kt thru Tue, then
becoming W/WSW around 15 kt for Tue night. Seas thru Tue night 3
ft or less all waters. Dry weather is expected, although ocean
effect cloudiness over the eastern waters could produce a
sprinkle or flurry over the outer waters.
Outlook /Wednesday Night through Saturday/...
Wednesday: Winds less than 25 kt. Slight chance of rain.
Wednesday Night: Low risk for gale force winds with gusts up to
35 kt. Areas of rough seas. Rain.
Thursday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Rain showers.
Thursday Night: gale force winds with gusts up to 40 kt. Rough
seas up to 14 ft. Slight chance of rain showers.
Friday: Strong winds with gusts up to 35 kt. Rough seas up to
11 ft.
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers, slight chance of snow
showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from Wednesday evening through Thursday evening for
ANZ232>235-237-255-256.
&&
$$
SYNOPSIS...KJC/Loconto
NEAR TERM...KJC/Loconto
SHORT TERM...Loconto
LONG TERM...KJC
AVIATION...KJC/BW
MARINE...KJC/Loconto
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 3, 12:20 AM EST----------------
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