916
FXUS61 KBOX 250822
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
322 AM EST Mon Nov 25 2024

.SYNOPSIS...
High pressure builds into the region today, with seasonable
conditions along with diminishing northwest winds. Another
period of welcomed rains moves in on Tuesday as a frontal system
passes to our northwest. Blustery, cooler and dry weather
returns Tuesday night and Wednesday. Continuing to monitor a
storm system moving in on Thanksgiving Day which looks to bring
rain with some accumulations of wet, clumpy snow for the higher
elevations. Improving conditions by Friday, although it turns
blustery with below normal temperatures into the weekend.

&&

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


Key Messages for Monday

* Northwest winds gradually weakening this morning

* Sunny/seasonable day with highs near 50

Today

Monday will feature clear skies and calm weather as a mid-level
ridge axis builds in from the west. This will support a weakening
pressure gradient that will allow steady northwest winds to
gradually diminish throughout the day. High temps near normal in the
upper 40s to low 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...

Key Messages

* Quiet tonight with increasing cloudiness

* Rainy tomorrow with mild temperatures south of I-90

Tonight

A mid-level ridge axis and associated surface high pressure
shifts east of southern New England this evening. This will
support a return flow from the south/southwest that will lift
the edge of a surface warm front over the region. As the warmer
air aloft overruns the cooler air at the surface, we can expect
increasing cloudiness overnight from west to east. While winds
will be light, increasing cloudiness will limit radiational
cooling. Thus, expect low temperatures to be close to normal in
the low to mid 30s for much of the forecast area. Areas near the
coast stay a bit more mild in the upper 30s to near 40. An area
of low-pressure advancing from the west will support increasing
rain chances toward day-break, but generally expecting most of
the precipitation to take place during the day Tuesday.

Tomorrow

An area of low-pressures moves over southern New England on
Tuesday supporting wet conditions for most of the day. Showers
begin to spread into western MA/CT roughly during the morning
commute before reaching areas east of Worcester by late
morning/early afternoon. This will be a progressive system with
modest forcing, so we`re not expecting a heavy precipitation
event, but still substantial. The latest run of the HREF model
is revealing little spread between the 25th and 75th percentile
QPF forecast. Precipitation amounts in the 25th to 75th
percentile range anywhere from 0.3 to 0.5 inches of rain across
the region. This rainfall will be welcome as the region tries
to make up recent precipitation deficits that have supported
significant drought conditions. Not expecting any significant
impacts from this system, but warm sector air is likely to
support milder temperatures south of I-90 in the mid to upper
50s making this will a "warm" rain event by November standards.


&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights:

* Dry Tue night into Wed, but cooler and blustery.

* Storm system on Thanksgiving into early Fri AM appears to be
  trending to a mainly rain event for Southern New England,
  although some potential for accumulations of wet snow over the
  higher elevations. Confidence in the details is still low,
  which will hinge on the storm`s still-unclear track.

* Blustery with below normal temperatures for Fri into the weekend,
  potentially running some 10 degrees colder than normal.

Details:

Tuesday Night and Wednesday:

Drying out early Tue night after the rain event during the daytime
hrs. That will usher in a cooler, drier airmass with mostly clear
and blustery conditions for Tue night into Wed. Lows in the upper
20s to mid 30s, with highs Wed ranging from low 40s in the terrain
to the upper 40s/near 50 near the coasts.

Thanksgiving Day:

Still monitoring developments relating to low pressure which moves
NE from the mid-MS Valley into the mid-Atlantic region. Over the
last couple days, ECMWF EPS and GFS ensemble member lows seem to be
converging toward a couple of storm track possibilities: (1) from
the mid-Atlantic to either along or just inside of the I-95
corridor, or (2) from the mid-Atlantic to near/south of Nantucket.
There are now very few ensemble members indicating a
western/interior New England track. There still is uncertainty in
which track pans out, which will ultimately drive what impacts
we could see.

First track is a stronger, warmer and wetter outcome, favored
largely by the ECMWF and most of its EPS ensemble members. Although
interior New England would still see some snow, which would also be
of the wet/dense, gloppy type with low snow-to-liquid ratio, an
influx of warm air would lead to a largely rain event, with nearly
all rain favored for the coastal plain in that possible outcome. EPS
Ensemble snow indicate moderate probs (50-70%) for 3"+ of snow at
10:1 snow to liquid ratio in the high terrain, and low to moderate
(30-50%) probs of accums of 6" or more at 10:1 SLR. With snow to
liquid ratios likely to be lower than 10:1, these probs are still
viewed as worst-case. The second track cluster is a weaker,
suppressed, cooler and less-QPF outcome favored by the GFS and its
GEFS, where most of the interior could miss out on precip
(potentially entirely) in regime of 500 mb SWly confluence, with
already marginal thermal profiles lending itself to a plain
rain or rain mixing with wet, slushy snow as it pulls away.

It is still too early to favor any one outcome, as well as provide
precipitation and accumulation amounts with much confidence. Expect
there to be continued adjustments in the coming days. However there
continues to be higher confidence that the coastal plain sees mainly
rain. There has also been a tendency for the storm`s effects to be
felt primarily on Thanksgiving Day, with conditions trending more
optimistically, if still quite a bit colder, for Black Friday.

Friday through This Weekend:

Low pressure will have pulled away into the Maritimes by Fri
morning, bringing a cold cyclonic flow both at surface and aloft
to Southern New England. This will usher in the coldest
airmass we`ve seen to this point in the late Fall, carrying us
into the December 1st start of meteorological winter. 925 mb
temps should run around -2 to -6C by the weekend. Expect a
chilly, blustery late week into the weekend, with below normal
temperatures, which could be some 5-10 degrees colder than
normal to close out the month of November. Some areas not
getting out of the 30s by Sunday.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

06Z TAF Update:

Through 12z Monday: High confidence.

VFR. NW winds around 5-12 kt, strongest near the coast with
occasional gusts into the low-20s kt range.

Today: High confidence, though moderate on gusts.

VFR. NW winds may pick up/gust into the 25 kt range in the
morning mainly for eastern airports. But the trend will be
downward in both speeds and gusts through the afternoon.

Tonight: High confidence.

VFR, although increasing clouds toward OVC for the second half
of the evening. Outside chance that BAF/BDL see cigs drop into
the MVFR range by the predawn hrs but think VFR should prevail.
Light W winds become S and then SE overnight around 5-10 kt.

Tuesday: Moderate confidence.

Deterioration to MVFR, possible IFR ceilings with 4-6 SM -RA as
frontal system moves through. Areas of low level wind shear or
turbulence possible given forecast 950 mb 25-35 kt southerly
jet. SE to S winds around 5-10 kt thru early afternoon, with
winds becoming WSW/W after 18z from west to east.

KBOS Terminal...High confidence in TAF. VFR. NW winds have eased
overnight to around 10-13 kt, but we could see another period of
gusts in the lower-20s kt range this morning before easing into
the afternoon. Winds become S and then SE later in the
overnight with increasing cloud cover.

KBDL Terminal...High confidence in TAF. VFR. NW winds around
5-10 kt today, easing into tonight while becoming light S to SE.
Outside chance at MVFR ceilings by 10z but more likely after
then.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: VFR. Breezy.

Wednesday Night: VFR. Slight chance RA.

Thanksgiving Day: Mainly MVFR, with local VFR possible. Breezy.
RA likely.

Thursday Night: MVFR/IFR conditions possible. Breezy. RA
likely.

Friday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Tuesday

SCY level northwest wind gusts continue for a few hours this
morning before gradually diminishing by mid-late morning. Seas
up to 5 feet remain within SCY criteria over the outher marine
zones through this evening, but will eventually fall below SCY
criteria before midnight. Relatively calm conditions overnight
will be followed by minor deterioration as a progressive low-
pressure system moves over the coastal waters. This is not
expected to be a strong system, but it may bring some 20 to 25
knot wind gusts out of the southeast/southwest during the day
Tuesday. SCY headlines may be needed, but likely only for the
outer marine zones.


Outlook /Tuesday Night through Friday/...

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain.

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.

Wednesday Night: Winds less than 25 kt. Slight chance of rain.

Thanksgiving Day: Winds less than 25 kt. Seas locally
approaching 5 ft. Chance of rain. Local visibility 1 to 3 nm.

Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Rain.

Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for ANZ230-
     236.
     Small Craft Advisory until 4 PM EST this afternoon for
     ANZ231>235-237-250-251-254>256.

&&

$$

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