BOX issues Area Forecast Discussion (AFD) at Dec 30, 10:39 AM EST266
FXUS61 KBOX 301539
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1039 AM EST Mon Dec 30 2024
.SYNOPSIS...
A cold front moving through western New England will bring a
period of windswept downpours during this morning's commute
along with southerly gusts to 35 mph. Drying trend begins this
afternoon from west to east, with dry and mild weather lingering
into tomorrow. Another low pressure system should bring rain
New Years Day. Then colder and drier weather should follow into
the first weekend of 2025.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1030 AM Update:
No major updates needed. Only adjustment was pushing back the
breaking/clearing of clouds an hour or two as the rain/clouds
trended slower. Expect a few showers behind the main front for
the next hour or two with gradual clearing into the afternoon.
405 AM Update:
Back edge of brief cold frontal downpours has now made it into
the Berkshires, with the steadiest and at-times heaviest rains
currently located over Worcester and Windham Counties. Gusts
have been up to 35 mph within this band of brief heavy
downpours, and that should continue to be expected as it moves
eastward into Rhode Island and eastern Massachusetts. Observed
responses on MRMS CREST unit streamflow products indicate rain
is not heavy enough to be causing flooding but there could be
some nuisance poor drainage issues in some of the urban areas
for commuters. All this is handled well in the going forecast so
no major changes needed attm.
Previous discussion:
Key Messages:
* Brief period of downpours over western MA moving east through
5 to 8 AM. Main impacts are a slower AM commute, and at worst
isolated poor drainage ponding. Clearing off the coast by
late morning.
* Southerly gusts 30 to 35 mph near the south coast, perhaps
near 40 mph at times, but no impacts are expected.
* Decreasing clouds by early in the afternoon, with temps slowly
cooling off with decreasing WSWly winds.
Overcast but quite mild by late-December standards, and although
there are still some pockets of colder air (upper 30s/low 40s)
that continue to struggle to scour out in portions of the CT
Valley and northern MA, many areas this morning are in the low
to mid 50s.
Main story for this morning revolves around a band of rain
showers which is now moving into the Interstate 91 corridor per
composite radar imagery. This is in association with a cold
front/frontal occlusion boundary tied to potent low pressure
over the Gt Lakes region. This band of rain showers will be
accompanied by a brief period of downpours capable of reducing
visibility as it moves eastward into central MA/eastern CT by
the pre-dawn hours, and into eastern MA and RI between 6-8 AM,
then off the coast by the mid to late morning hours. There has
not been significant changes as far as rainfall totals go, and
while there could be some pockets of nuisance water ponding
where water doesn't drain as well, it will otherwise just make
for some tougher travel during the Monday morning commute. There
may be some local gusts embedded within the line to around 35
mph, but would be more windswept downpours than anything rising
to the level of adverse impacts. Forecast rains around a half to
near an inch, and much of that will fall in a couple hours'
time. Rapid clearing is likely in the post- frontal and blsutery
SWly flow airmass with modest cool advection taking place.
Did opt to boost southerly wind gusts ahead of the line of showers
up to around 35 to 40 mph into the mid morning hours in central
and southern RI, southeast MA and the Cape and Islands.
Southerly gusts have slowly increased here in response to the
mild temps, with some gusts up to 30 mph currently taking
place. 950 mb low level jet of around 60 kt moves over these
areas during the early to mid morning hours, but we're too
inverted to mix much of this down. However it is notable the
gusts that have developed over Long Island, which have been as
much as 40 mph near JFK. With the expectation that we won't mix
very well, not expecting any real impacts from these gusts,
other than if you had some leftover holiday decor out.
Highs take place pre-frontal, with values in the mid to upper
50s. Though there will be more sunshine late in the day behind
the front, cool advection should allow temps to hover or
gradually cool off by sundown into the mid 40s to around 50.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
405 AM Update:
Key Messages:
* Variable cloudiness tonight with above-freezing lows.
* Clear skies early on Tue, though clouds increase late in the
day with above normal highs.
For tonight...WSWly gradient flow takes place as potent
shortwave trough passes to our north and west. This will also be
accompanied by a cooler airmass (925 mb temps around +2C) but
also a layer of RH that should be responsible for a layer of
stratocumulus into our northwestern MA and perhaps into Hartford
County overnight. So, it may be more of a variable cloudiness
setting with more clouds north and west and less east. Dry
weather is expected though. Lows are a little tricky given the
variable cloud cover and still some WSW winds around, but
offered lows in the mid/upper 30s east and low-mid 30s west.
For Tuesday...pattern then quickly transitions back to a brief
period of warm advection and shortwave ridging aloft ahead of
our next storm system that arrives midweek. Clear skies and full
sun start the day, but clouds increase from SW to NE by the
afternoon to more of a midlevel OVC by sundown. Still some
variance as far as timing of warm frontal showers, did leave a
mention of showers but the bulk of them should hold off until
Tue evening. Should see another mild day Tue with upper 40s to
mid 50s for highs, although if cloud cover does come in sooner
in the day and cuts into diabatic heating, then those highs
could end up being a few degrees too warm.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
410 AM Update:
Key Messages
* An area of low pressure will bring another soaking rain to
southern New England Tuesday night into Wednesday
* Brief period of snow possible across portions of interior southern
New England behind an exiting cold front
* Cooler/drier conditions settle over the region for Thursday and
persist through the weekend
Tuesday night and Wednesday
Short-wave energy traversing over The Midwest Tuesday night into
Wednesday will support the development of a surface low-pressure
system that will bring another soaking rain to southern New England
Tuesday night into Wednesday. The air mass in place remains mild, so
not expecting any frozen precipitation at this time. Sufficient
forcing and ample moisture to the tune of nearly 1 inch of
precipitable water will allow rain accumulations between 0.5 and 1
inch across the region. As mentioned previously, the air mass in
place will be mild with 925 hPa temps around 5 Celsius, so we'll
have another above normal temperature day with highs ranging from
the upper 40s across the interior northwest to the low to mid 50s
over the coastal plain. Bulk of the rainfall should take place
Tuesday night through Wednesday morning. A few lingering showers
possible in the afternoon, but overall model guidance has been
adamant on a drying trend for Wednesday afternoon. As the associated
cold front pushes through the region Wednesday night into Thursday,
925 hPa temps plummet to sub-freezing temperatures. This may allow
for a brief period of snow showers over the elevated areas of
western MA and CT post frontal passage.
Thursday through next weekend
Gusty winds may be in the cards for Thursday behind the exiting cold
front. Cold advection aloft will support efficient diurnal mixing on
Thursday afternoon when a 30 to 40 knot low-level jet will be
present at 925 hPa. With steep low-level lapse rates expected during
the day Thursday, there will be a risk for 30 to 40 mph surface wind
gusts during the day Thursday. This potential will depend on the
timing and strength of the low-level jet, but ensembles support a 30
to 50 percent chance of wind gusts greater than 35 mph on Thursday
afternoon. Other than the gusty winds, expect cooler temperatures in
the upper 30s/low 40s Thursday afternoon.
The cold advection pattern persists through the weekend but with a
more modest low-level jet. Thus, expect cold and breezy conditions
next weekend with highs/lows in the 30s/teens-20s respectively.
&&
.AVIATION /16Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update:
Today: High confidence.
Any early VFR deteriorates to MVFR-IFR visbys/ceilings
associated with a solid band of downpours currently moving thru
central MA and east CT. Areas of low-level shear will also
accompany this rain, with southeast winds 10-13 kt with gusts to
25 kt.
Rapid improvement takes place from west to east between 14-16z
with rains moving offshore, low level shear ending and ceilings
trending to VFR. Windshift to SW around 10 kt after rain
clears.
Tonight: High confidence.
VFR for the airports, though couldn't rule out an MVFR ceiling
in the Berkshires. SW/WSW winds around 10 kt.
Tuesday: High confidence.
VFR SKC early, but will fill with midlevel OVC deck late in the
day. SW winds ease to around 5-8 kt.
KBOS TAF...High confidence in TAF. Brief period of 2-3 SM +SHRA
13-16z with MVFR ceilings, along with gusty SE winds gusting to
20-22 kt. Low level shear may also take place embedded in the
rain. Rapid improvement to VFR after 16z with SW winds around
10-12 kt.
KBDL TAF...High confidence in TAF. MVFR/IFR in rain early but
conditions already starting to improve and improving trends are
expected with VFR by 15z. S winds around 10 kt today.
Outlook /Tuesday Night through Friday/
Tuesday Night: MVFR/IFR conditions possible. Breezy. RA.
New Years Day: MVFR/IFR conditions possible. Breezy. RA likely.
Wednesday Night: Mainly VFR, with local MVFR possible. Windy
with gusts up to 35 kt. Chance RA, slight chance SN.
Thursday: VFR. Windy with gusts up to 35 kt.
Thursday Night: VFR. Windy with areas of gusts up to 30 kt.
Friday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High- greater than 60 percent.
415 AM Update:
Made a couple changes to marine headlines. The first was to
upgrade the eastern marine zones to gale warnings. Noting a few
of the buoys south of Long Island are showing gusts around 30 kt
early this morning, and with the increase in the low level jet
expected to take place by mid to late morning, there may be just
enough where lower-end Gale conditions seems more likely to
develop, even though mixing is still expected to be poor. The
next was to extend the SCA on the southern outer waters through
daytime hrs Tue. As Gale warnings get pulled down later today,
SCAs will need to replace those and those will likely need to go
into Tue as 6-10 ft seas will be slow to subside.
Period of visibility-reducing downpours expected during the
morning hours, then moving offshore with rapid clearing. Winds
will also shift to WSW and decrease in speed to around 15-25 kt
for tonight, and decrease to around 15 kt for Tue.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Rain.
New Years Day: Moderate risk for Small Craft Advisory winds
with areas of gusts up to 30 kt. Rough seas up to 10 ft. Chance
of rain.
Wednesday Night: Strong winds with gusts up to 40 kt. Rough
seas up to 12 ft. Chance of rain.
Thursday: Strong winds with gusts up to 35 kt. Rough seas up to
12 ft.
Thursday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 11 ft.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Areas of rough seas.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ230.
Gale Warning until 4 PM EST this afternoon for ANZ231-232-250-
251-254-255.
Small Craft Advisory until 7 AM EST Tuesday for ANZ233>235-237.
Small Craft Advisory until 1 PM EST this afternoon for ANZ236.
Small Craft Advisory until 7 PM EST Tuesday for ANZ256.
&&
$$
SYNOPSIS...Loconto
NEAR TERM...Loconto/Mensch
SHORT TERM...Loconto
LONG TERM...RM
AVIATION...Loconto/RM
MARINE...Loconto/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 30, 10:39 AM EST----------------
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