BOX issues Area Forecast Discussion (AFD) at Dec 5, 4:09 AM EST981
FXUS61 KBOX 050909
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
409 AM EST Thu Dec 5 2024
.SYNOPSIS...
This morning's storm system will lift out today bringing an end to
widespread rain and snow by mid day. A strong cold front will then
bring a few snow squalls and strong winds in the afternoon. Gusty
conditions and below normal temperatures continue Friday into
Saturday with a low chance of an isolated snow shower or snow
squall. A weak clipper system passes through northern New England
early Sunday and brings a light snow shower to areas mainly north of
Route 2 in northern Massachusetts. Then the first-half of next week
features mild temperatures and a more active weather pattern.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Rain and snow are ongoing this morning and will continue
through mid to late morning, exiting from mid morning (western
MA/CT) to late morning (eastern MA) as the parent low currently
over the eastern Great Lakes moves to northern Maine. A
particularly heavy band over RI/eastern MA has enough intensity
for dynamic cooling to overcome marginal temps (33-35F) and
bring some accumulating snow over the coastal plain of southeast
MA and RI as far south as Providence and east as Boston. Temps
should only be increasing on SW flow, but accumulations of up to
an inch or so will be possible even over southeast MA and
central Rhode Island which may be enough to cause minor issues
with the morning commute.
Later an impactful (to highway travel) period of scattered snow
squalls arriving in western MA/CT around noon accompanying the
passing cold front and deep mid level trough. Lingering low level
moisture combined with several favorable instability parameters
(steep 1000-700 mb lapse rates and several hundred J/kg of CAPE)
will set the stage for a few decent snow squalls. These will bring
the potential for rapid reduced visibility in blowing snow as well
as dropping a quick half inch to inch of snow. Boundary layer
temperatures will be more moderate along and east of the I-95
corridor so a rain/snow mix or plain rain showers are more likely in
the 2-5pm window.
Speaking of blowing snow, more widespread strong W/NW winds will
kick up over all of southern New England as cold advection leads to
good mixing of the boundary layer up to near 800 mb where we have a
~50 kt LLJ. The strongest winds (gusting 40-50 mph) are expected
over western/central MA, CT, and the Cape/Islands where a Wind
Advisory is in effect. However, it will be gusty over the rest of
SNE as well, more in the ballpark of 35-45 mph.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Key Messages...
*Below normal temperatures and gusty winds Friday
Tonight we're placed between a low to our northeast and a high to
our southwest. The resultant tight pressure gradient leads to
continued gusty winds overnight, generally 30-40 mph. Post frontal
cold advection brings 925 mb temps down to -7 to -9C overnight which
results in lows as cold as the upper teens (high elevations) to
upper 20s (along the coast). However, given the gusty winds it will
feel more like the single digits to low 20s respectively. Friday not
much change in the synoptic pattern so winds remain elevated with a
much colder airmass overhead. Highs won't make it out of the 20s in
the high elevations and mid 30s elsewhere.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Key messages:
* Blustery and cold to start the weekend
* Chance for a snow shower, particularly in the Berkshires, Friday
night/early Saturday morning
* Milder, unsettled conditions to start the week
Friday and Saturday
The clipper system continues to move out of the region and high
pressure moves in to take its place. Between these systems, winds
are expected to continue to be gusty (up to 25 mph) primarily from
the west before high pressure fully takes over by the evening hours
Saturday. The latest guidance has a small chance for some
orographically-forced snow showers in the Berkshires, but that
chance remains low for the time being. There is not significant CAPE
in the models to indicate a strong signal for snow squalls, but a
small signal for some snow is present. Snow or not, it will be cold;
850 mb temps are still forecast to settle at and just below -15C as
an arctic airmass sinks in over southern New England. Friday and
Saturday night lows are very likely to be in the teens and 20s, and
highs Saturday are likely not getting out of the 30s.
Sunday onward
Winds die down considerably and shift more southerly, and
temperatures become more mild as the arctic airmass exits the
region. Another clipper system is expected to pass to the north and
the moisture associated with it is expected to remain there. Some
chances for snow showers, particularly in northern MA, may be
present, but the chances are low. High temperatures should increase
to the upper 30s/low 40s.
To start the work week, S to SW flow persists and a warming trend
takes hold. 850 mb temps climb out of the negatives and sit closer
to +5C by early Tuesday morning. Highs Monday through Wednesday are
expected to be more in the low to middle 50s. Ensembles still have a
signal for rain starting Monday afternoon going through Wednesday,
but it's important to note that this far out, timing is still very
likely to change.
&&
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update...
This morning...Moderate Confidence.
Widespread low end MVFR- IFR conditions with periods of LIFR
conditions across the interior through 15-18z. Across the
interior terminals precip type will be SN.
Ptype will mainly be snow northwest of I-495 with generally
rain southeast of that region overnight into Thu morning. Ptype
could mix with or change to snow towards the I-95 corridor for
a brief time before the bulk of the precipitation ends Thu
morning. Snow accumulations of 2-6" are expected across much of
the interior with the higher end amounts confined to the higher
elevations. Lower amounts as you go east from Worcester Hills.
Little if any snow accumulations on the I-95 corridor with
precipitation mainly in the form of rain.
SSW winds increasing this morning with gusts up to 35 kts by
12z. Cape/Islands trend higher with gusts up to 40 kts.
Thursday...Moderate confidence.
MVFR/IFR changing to MVFR/VFR. Widespread RA/SN ending 15-18z
from west to east but scattered snow squalls will be possible in
the afternoon briefly dropping visibilities with a quick
coating of snow. Winds turn from SW to W/NW increasing in the
late morning and afternoon, gusting 25-40 kts.
Thursday night...High confidence.
VFR. Gusty NW winds 25 to 35 kts.
Friday...High confidence.
VFR. NW winds gusting 20-25 kts.
KBOS Terminal...Moderate confidence in TAF.
This morning: Rain may turn to snow this morning but
accumulation isn't expected. Main batch of precip exits 13-16z
with a few showers possible behind it through the afternoon.
Will see some improvements in ceilings this morning with periods
of VFR possible in between showers. Chance for brief RA/SN
showers/squalls in the afternoon. Timing/chances lower
confidence due to hit or miss nature of showers.
KBDL Terminal...Moderate confidence in TAF.
Today: Main batch of precipitation exiting by 13-15z. Brief
improvements in ceilings toward MVFR in the AM in between
showers, even brief VFR possible. Chance for brief
showers/squalls in the afternoon with brief vis reductions and
increased precip rates. Strong SW to W winds with gusts up to 40
kts.
Outlook /Friday Night through Monday/...
Friday Night through Saturday: VFR. Breezy.
Saturday Night: VFR. Slight chance SN.
Sunday: VFR. Breezy. Slight chance RA, slight chance SN.
Sunday Night: VFR.
Monday: MVFR/IFR conditions possible. RA likely.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
* Gale Warnings tonight through Thu night with 45 knot gusts
Today and tonight...
SSW wind gusts of 30 to 45 knots early this morning. The
strongest of those winds tonight are across the southern
waters.
A strong cold frontal passage crosses the region today. Winds
become westerly this afternoon, gusting 35 to 45 knots and
continuing through tonight. Gale Warnings are in effect on all
waters though this time and seas will be quite high and rough.
Friday...
Dry with gusty NW winds 25 to 35 kts. Seas 4-8 ft.
Outlook /Friday Night through Monday/...
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of snow.
Saturday through Saturday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft. Chance of rain, chance of snow.
Sunday: Winds less than 25 kt. Local rough seas. Chance of
rain.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from 10 AM this morning to 10 PM EST this
evening for CTZ002>004.
Winter Weather Advisory until 10 AM EST this morning for
CTZ003.
MA...Wind Advisory from 10 AM this morning to 10 PM EST this
evening for MAZ002>004-008>012-026.
Winter Weather Advisory until 10 AM EST this morning for
MAZ002>004-008>012-026.
Wind Advisory until 10 PM EST this evening for MAZ022>024.
RI...Wind Advisory until 10 PM EST this evening for RIZ008.
MARINE...Gale Warning from 7 AM this morning to 7 AM EST Friday for
ANZ230.
Gale Warning until 7 AM EST Friday for ANZ231>237-250-251-
254>256.
&&
$$
SYNOPSIS...BW/Hrencecin
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Hrencecin
AVIATION...BW/Hrencecin
MARINE...BW/Hrencecin
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 5, 4:09 AM EST----------------
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