681
FXUS61 KBOX 221351
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
851 AM EST Fri Nov 22 2024

.SYNOPSIS...
Strong low pressure near western CT early this morning will
continue to move westward today into southern NY, then meanders
east and northeast into the Canadian Maritimes through the
weekend. Rains gradually decrease early this morning, with a
lull in the rain for most of today, but rain chances increase
again late this afternoon and tonight before pulling away into
early Saturday. Considerable cloudiness for this weekend with
gusty northwest winds. Brief dry weather returns on Monday. The
rest of the week looks active, with one storm system around
Tuesday spreading rain showers. Blustery, cooler and dry for
Wednesday, then monitoring for additional storminess around
Thanksgiving or Black Friday.

&&

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

850 AM Update...

* Scattered showers especially this morning but not a washout
* Highs from 45 to 55 with the mildest readings in eastern MA

A well developed vertically stacked system across eastern NY
will gradually sink southward today. In response...a mid level
dryslot has overspread the region allowing for some partial
sunshine across eastern MA and RI. The cold pool aloft has
resulted in some instability with the partial sunshine and
allowed scattered showers to develop. There was even some
graupel being reported with the activity given the cold temps
aloft. Meanwhile...temps are cold enough along the highest
terrain in the east slopes of the Berkshires to support some wet
snow this morning. Any accums will be very minor slushy and not
impactful.

Otherwise...while we may continue to see hit or miss showers
into the afternoon...not expecting a washout and much of the
time will be dry. Another slug of more widespread rain will be
working into the area by late afternoon/early evening with the
greatest coverage expected across eastern MA.

High temps should range from mainly the 40s across the
interior...but across eastern MA and RI will probably see highs
reach between 50 and 55 given the partial sunshine during the
morning.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Key Messages

* Another round of showers develops Friday afternoon and
  continues into Saturday morning

* Gusty northwest winds around 35 mph expected Saturday afternoon

Tonight

Showers continue overnight as the aforementioned short-wave energy
approaching from the southeast pivots north into The Gulf of Maine.
Expect the heaviest precipitation over The Cape/Islands and
east/northeastern MA. An additional 0.25 to 0.5 inches will be in
the cards for these areas. Further across the interior, only
expecting modest shower activity with a tenth to a quarter of an
inch possible. As the surface low moves north into The Gulf of
Maine, winds will shift to the north/northwest. This will advect
cooler air into southern New England and support chilly temperatures
tonight into tomorrow morning. In fact, the cooler air aloft may
support some snow at elevations above 1500 feet in The Berkshires or
northern Worcester Hills, but no significant accumulations or impacts
are expected. Low temps bottom out in the low to mid 30s west of I-
495 and mid to upper 30s east of I-495.

Saturday

Coastal low-pressure system continues to meander over The Gulf of
Maine for most of the day Saturday. This will continue to support
showers across the eastern areas. Further west we should begin to
see some gradually clearing as northwest flow advects drier air into
the region. Air mass will be cooler with 925 hPa temps aloft
close to the freezing mark. This would translate to surface high
temps in the mid to upper 40s on Saturday afternoon.

Of greater concern for Saturday will be the potential for gusty
northwest winds. Latest model guidance has trended toward a stronger
low-level jet on Saturday afternoon with 925/850 hPa wind speeds
peaking between 35 and 50 knots respectively. BUFKIT soundings
support momentum transfer of 35+ knots to the surface or perhaps
even higher depending on the model. The tricky part of this forecast
will be the determining the efficiency of mixing in the boundary
layer,particularly across eastern MA where cloud cover will be
more extensive. Model derived low-level lapse rates are coming
in around 8 to 9 C/Km for Saturday afternoon, which would imply
enough mixing to support stronger northwest wind gusts. Right
now thinking 30 knots (~35 mph) gusts on Saturday afternoon will
be in the cards for much of southern New England. Some
locations across southeastern MA, The Cape, and Islands may
even approach wind advisory criteria (40+ knot gusts, 45+ mph).
Confidence in reaching those values is not high enough to
warrant wind headlines at this time, but we will be monitoring
this portion of the forecast closely over the next 24 hours.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights:

* Gradually drying out this weekend with seasonably cool temps, but
  with NW gusts 25-40 mph Sat night into Sun early PM.

* Tranquil and seasonable Mon.

* Frontal system for Tue spreads lighter showers early on Tue, then
  dry and blustery for Wed.

* Monitoring more active weather around the Thanksgiving holiday or
  Black Friday, some of which could be wintry, but uncertainty is
  very large.

Details:

Saturday Night and Sunday:

Strong low pressure over the Canadian Maritimes will continue to
slowly move ENE through the rest of the weekend. Tight NW pressure
gradient will continue to drive blustery NW winds. Approach of
secondary shortwave disturbance moving through Ontario SE into New
England late Sat night into early on Sun will increase a NWly low-
level jet, which global models indicate ~40-45 kt at 850 mb. Expect
a cloudy and blustery night Sat night with gusts 25-35 mph, on the
higher end of that range over the higher terrain. As mixing depth
increases with a bit more in the way of sun on Sunday, we could see
gusts punch into the 30-40 mph range into the early afternoon, near
Advisory levels, then decreasing into the mid afternoon as the
low level jet weakens. The gusty conditions will make it feel
much cooler than forecast temps; lows Sat night in the mid to
upper 30s may feel more like the upper 20s to near freezing with
the NW breeze, and highs 45-50 on Sunday. Clearing skies will
lead to a chilly Sun night with lows in the upper 20s to the
lower to mid 30s, but will feel cooler with a continued NW wind
around 10-15 mph. Monday:

Monday likely to be the pick of the forecast with high pressure
ridging in, offering full sun and a slackening wind. Modest warm
advection with 925 mb temps up to around +4 to +6C brings highs into
the low to mid 50s.

Monday Night thru Tuesday Night:

The 500 mb pattern becomes more active starting in this period,
continuing into the workweek, as spokes of shortwave trough energy
from the West Coast move across the CONUS. A lead shortwave moves
into the Gt Lakes and Northeast region into Tue, bringing a risk for
showers. However models vary on the strength of this wave with the
ECMWF on the weaker side, while the GFS and Canadian are a little
stronger and would offer a little more QPF. Highs around the 50s.

Wednesday:

Low pressure will have moved into the Maritimes early on Wed, and
other than northwest breezes, early look at conditions for the
biggest holiday travel day seem favorable with partly to mostly
sunny conditions and highs in the 40s to near 50.

Thursday/Friday:

Pacific frontal system moves across the central US, leading to a
developing storm system in the central Plains around Thurs. Quite a
bit of uncertainty exists in the details, though there appears
to be enough colder air in place to allow for some wintry
weather possibilities Thurs and/or Fri, provided there is a
favorable storm track. Kept PoP on the higher end of Chance but
will be monitoring model developments very closely.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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


Today: Moderate confidence.

Intermittent light rains with MVFR clouds for the interior, but
for RI and eastern MA, a lull in rains are expected for part of
the day with SCT-BKN VFR bases and southerly gusts around 20-25
kt.

Late in the day (thinking after 20z, although exact timing is
still a bit uncertain), another round of steadier rains develops
over the southeast waters and rotates NNW into at least eastern
MA and RI by 00z. As this rain moves in, expect ceilings
lowering to MVFR levels, S winds shifting to SE/E around 10-12
kt and visbys around 4-6 SM in -RA/RA.

Tonight: Moderate confidence.

VFR/MVFR deteriorates to MVFR/IFR ceilings at most airports,
with steadier RA at 4-6 SM vsby for at least eastern MA and RI,
possibly as far west as BAF/BDL but the western extent is still
uncertain. Rain should pull away toward the NE after 06z. SE/E
winds become NE around 10 kt thru midnight, and then NW around
5-10 kt overnight before increasing in speed to 10-15 kt by
daybreak Sat.

Saturday: Moderate to high confidence.

BKN/OVC MVFR/VFR ceilings with slow improvement trends. Gusty
NW winds around 15 kt with gusts 25-35 kt.

KBOS Terminal...A few scattered showers for a couple more hours
this morning. Shower activity should wane by 13Z as skies
scatter out from east to west. Otherwise, VFR with S around
10-15 kt/gusts to 25 kt most of the day. Another round of rain
develops after 20z with developing SE/E winds and deteriorating
cigs.

KBDL Terminal...Moderate confidence in TAF. IFR/MVFR ceilings
with MVFR rains on N winds initially. Abrupt windshift to SE/S
08-10z with categories trending MVFR. Otherwise, MVFR with more
intermittent -RA today on S winds around 10 kt.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Mainly VFR, with local MVFR possible. Windy
with gusts up to 35 kt. Slight chance RA.

Sunday: VFR. Windy with gusts up to 35 kt.

Sunday Night through Monday: VFR. Breezy.

Monday Night: Mainly VFR, with local MVFR possible. Chance RA.

Tuesday: Mainly VFR, with local IFR possible. Breezy. Chance
RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Saturday

Low-pressure shift northwest away from the coastal waters today.
This will support diminishing winds for this morning and tonight.
Winds become more southerly today and while weaker, will still be
blowing from to 10 to 20 knots. Gale force wind gusts come to an end
this morning and generally become bounded by sustained winds or
perhaps a few knots over (~15 knots). As the afternoon progresses,
low-pressure approaching the waters from southeast of Nantucket will
introduce a new round of rain along with a return to easterly winds
which will shift to the north/northwest tonight into Saturday
morning. Conditions begin to deteriorate again on Saturday with
sustained northwest winds rising to 20 to 30 knots with gusts up to
40 knots by Saturday evening. Gale Warnings will be likely for the
coastal waters Saturday afternoon through most of Sunday. Seas
gradually come down with winds today as well and may fall below SCY
criteria overnight. This will of course will be short-lived as the
gale force winds expected Saturday afternoon brings seas back to the
5 to 8 foot range over the outer marine zones.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 11 ft. Chance of rain.

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 10 ft.

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

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

Monday Night: Winds less than 25 kt. Chance of rain.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for
     ANZ231>234-251.
     Small Craft Advisory until 9 PM EST this evening for ANZ235-
     237.
     Small Craft Advisory until 7 AM EST Saturday for ANZ250-
     254>256.

&&

$$

SYNOPSIS...Loconto/RM
NEAR TERM...Frank
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Loconto/RM
MARINE...Loconto/RM