000
FXUS61 KBOX 061741
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1241 PM EST Wed Dec 6 2023

.SYNOPSIS...

Snow showers have all but come to an end. Dry, but cold,
weather follows this afternoon into Thursday. Tranquil and dry
weather prevails Friday into early this weekend, with a steady
warming trend to temperatures starting on Thursday and trending
above normal Friday into this weekend. A strong frontal system
for later Sunday into Monday may bring a period of downpours,
gusty south winds, and possible minor coastal flooding, but
specific details are not yet set in stone.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Light snow has all but ended as winds shifted to the north and
northeast. The bullseye for snowfall was Rockland and Hanover
MA where we saw 3.5 and 3.3 inches of snow respectively.

Previous Discussion...

Latest near term guidance and regional radar data favored
slightly lower precipitation this morning. Winds remained mainly
from the N early this morning, which continued to steer ocean
effect showers across portions of Cape Ann, and Cape Cod. Only
very light precipitation has been reported so far. Winds will
need to turn more NE in order to bring these showers across more
of eastern MA. Latest guidance suggested that may not occur
until after 4 AM or so, but that could still be enough time for
some impact on the morning commute, even if it is just poor
visibility at times.

Still thinking snowfall across most of the eastern half of MA
and portions of RI will generally be up to one half inch.
Locally higher amounts across portions of Norfolk and Plymouth
Counties possible, but that is only a 30-50% chance of snowfall
greater than 2 inches. Probabilities drop to less than 30% for 3
inches of snowfall across Plymouth County. Thus, still thinking
the South Shore is where the focus of snowfall will be today.
Water temperatures still around 50 degrees, so locations along
the immediate coast likely to see less snowfall this morning.

Winds turn N to NW this afternoon, which will bring a quick end
to any remaining snow showers, except perhaps across Cape Cod.
By that point, temperatures should be high enough to result in
mainly rainfall.

Below normal temperatures continue.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Turning colder and drier tonight into Thursday as NW winds
continue. Well below normal temperatures expected, especially
tonight. Mainly clear skies, except across mid and outer Cape
Cod. Increasing clouds for all Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Updated: 3:20 AM

* Tranquil conditions and increasing temperatures through Saturday.

* Trending mild and mainly dry Sunday, but an approaching system
  could bring impactful wind, marine conditions, and rain overnight
  into Monday.

* Drier and potentially warmer next week.

Thursday night through Saturday: There were no major changes made to
this part of the forecast. From a synoptic point of view there are
increasing 500mb heights with mid-level ridging across the east and
a 1030mb surface high located to the south of the region, near the
island of Bermuda. WAA sets us up for warmer temperatures, a nice
break from the highs of the mid-30s that we have experienced early
on this week. Friday afternoon, temperatures reach into the mid-40s
while on Saturday temperatures top out in the low to middle-50s. The
overnight overnight temperatures are increasing too, Thursday night
into Friday morning is likely the coldest morning of the long term
with lows in the low to middle-20s. Gradually warmer Saturday
morning in the low-30s and then upper-30s and lower-40s by Sunday
morning. Ensemble guidance is still in similar agreement that Friday
will more than likely be the sunnier of the two days with majority
of members showing partly to mostly sunny... while Saturday trends
are more clouds than sun. Either way, both days are dry. Winds are
WSW Friday, becoming more southerly on Saturday.

Sunday through Monday: As advertised, this is the most active period
of the forecast. From a synoptic point of view, the mid-level ridge
shifts east with decreasing 500mb heights over southern New England.
An amplified trough digs south, before becoming negatively tilted, a
signal for potential intensification. At the surface, there remains
a good deal of uncertainty with the origin of a developing low
pressure system, global guidance doesn`t have a good handle on this
as of yet. But as of early Sunday there is a weak low around the
Great Lakes, which the GFS, ECMWF, and GEM show deepening while
moving east. Parked off shore is a 1030mb high, generating a tight
pressure gradient over the northeast.

A bit of better news, Sunday is beginning to look like a drier day,
at least during the daylight hours. A forward shift in the timing
likely to bring a multi-hazard system late Sunday night into Monday.
Keep in mind there remains a bit of uncertainty with the fine timing
of the event, but what has remained consistent, the strong southerly
winds, periods of heavy rain, and potentially dangerous marine
conditions.

GFS, ECMWF, and GEM continue to indicated a robust LLJ with 900mb
wind roughly between 70 and 90 knots. It is still to early to say
how much of the wind could mix to the surface, but even a fraction
would lead to fairly gusty conditions. As you could imagine the
strong wind will lead to building seas, some guidance suggests some
rather high waves by Monday morning. On top of dangerous conditions
on the water, potential coastal flooding if max surge were to
coincide with the high tide, in addition to the potential for
coastal erosion. Lastly, WPC has placed much of western MA and CT
in a marginal risk for excessive rainfall for this system. Ensembles
are in pretty good agreement we will see at least 1/2 inch of rain,
with modest probabilites of up to an inch west of Route 146. Even
low probabilites, less than 20 percent, of 2 or more inches of rain
in far western MA.

In addition, will be quite warm for early December, highs in the mid
and upper-50s on Sunday, then cooling off to near normal highs on
Monday near 50 degrees. More to come over the coming days, stay
tuned!

Tuesday into Next week: Trending drier and slightly warmer than
average, per CPC there is between a 40 and 50 percent chance for
above normal average temperatures.

Highs trend in the mid-40s where as lows trend towards the
mid-30s.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18Z update...

This afternoon...High Confidence in TAF.

Mix of VFR ceilings across southern New England this morning
with pockets of MVFR towards the east coast of MA. Wind
continues to become more NW through the evening with improvement
to VFR.

Tonight through Thursday night...High Confidence.

VFR.NNW winds tonight 10-15 kts diminishing and becoming W on
Thursday 5-10 kts. Turning NW 5-10 kts on Thursday night.

KBOS Terminal...High confidence in TAF. Light snow through 15z
leading to periods of MVFR conditions. NNE wind becoming NNW
this afternoon, then WNW overnight. CIGS becoming low end VFR by
18, then clearing out overnight.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Thursday Night through Saturday Night: VFR.

Sunday: Mainly VFR, with local MVFR possible. Windy with local
gusts up to 30 kt. Slight chance RA.

&&

.MARINE...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

High Confidence.

Winds and seas remained below Small Craft Advisory thresholds
early this morning. However, low pressure tracking well southeast
of the 40N/70W benchmark today will generate a surge of winds
and higher seas later today into tonight. Expecting winds and
seas to diminish by Thursday.

Outlook /Thursday Night through Sunday/...

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday through Saturday Night: Winds less than 25 kt.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas locally approaching 5 ft. Slight chance of rain.

&&

.EQUIPMENT...
KBOX is down due to a mechanical failure. Technicians will need
to assess before repairs can be completed. At this time there is
no estimate for return to service.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 PM EST this evening for
     ANZ231>235-256.
     Small Craft Advisory until 10 AM EST Thursday for ANZ254.
     Small Craft Advisory until 7 AM EST Thursday for ANZ255.

&&

$$
SYNOPSIS...Belk/Loconto
NEAR TERM...Belk/BW
SHORT TERM...Belk
LONG TERM...Dooley
AVIATION...BW/Dooley
MARINE...Belk/Dooley
EQUIPMENT...Belk/Dooley