NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
834
FXUS61 KBOX 090849
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
349 AM EST Mon Dec 9 2024
.SYNOPSIS...
Milder conditions expected for much of this week, with a period of
rain Monday, and again by Wednesday into Wednesday night along with
strong winds. A temporary period of shallow cold air later today
into Tuesday with Quebec high pressure system may lead to some icing
along and north of Route 2. Drier and more seasonable temperatures
expected late this week into next weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages...
* Dry to start Monday then rain and some high elevation icing move
in late Monday/Monday night
Expect a quiet start to the work week as weak mid level ridging
follows the exiting trough axis during the first part of the day. As
Monday wears on though we`ll see increasingly thick cloudcover out
ahead of our next storm system. At the synoptic scale we have
another low developing over the western Great Lakes with a secondary
low induced over southern New England. As the associated shortwave
passes this evening it will interact with a deep plume of moisture
(PWATs near 1") and warm SW flow to induce widespread precipitation
over western MA/CT by early afternoon and eastern MA by evening. The
warm advection which brings relatively mild temps on Monday (highs
in the mid 30s to mid 40s) will mean rain for the vast majority of
SNE. The exception may be the highest elevations of the Berkshires
and Worcester Hills where pockets of freezing rain/light ice
accumulations are possible. Given the placement of a high pressure
over Quebec subfreezing air may linger at the surface while
soundings indicate a decent warm nose at 850 mb. A Winter Weather
Advisory has been issued for the northern slopes of the Berkshires
and northern Worcester Hills where a coating of ice may make for
hazardous driving conditions by the Tuesday morning commute.
Elsewhere a decent amount of rainfall is expected before majority of
the precip exits by midnight; odds favor a quarter to half inch of
rain.
&&
.SHORT TERM /TUESDAY/...
Tuesday we`ll be between systems with continued moist low level
easterly flow keeping low clouds socked in. Even lacking any
synoptic forcing saturated low level onshore flow may lead to areas
of drizzle and perhaps even some freezing drizzle in the high
elevation interior, though confidence in icing is low at this
point.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages:
* Rain starts to move in late Tuesday night/early Wednesday morning
and sticks around through Thursday morning
* Winds pick up from the south as storm moves in
* Drying out during the day Thursday before another chance for
unsettled weather Sunday
There is high confidence in the main synoptic pattern early in this
period. Following a shortwave Tuesday morning, more rain is expected
to move in by early Wednesday morning with the arrival of a surface
low coming in from the Mid-Atlantic region. Rain should move out of
the region Thursday. Temperatures aloft continue to be warmer than
normal; 850 mb temps across the ensembles and the deterministic
guidance are likely to be up to +10C by Wednesday afternoon, which
is a good signal for the warmer than normal highs in the forecast;
some spots in SE MA could reach close to 65F. Winds are also
expected to pick up from the south as the jet associated with this
system moves over southern New England.
In terms of rainfall amounts, there is still some uncertainty as to
where the highest amounts will be. GEFS and GEPS have the highest
probs for greater than 2" of rain over the event in western MA down
into CT while the ENS shifts that chance over towards the Cape. The
NBM has probs up to 88% for greater than 2" across RI up into Boston
over a 48 hour span and an 81% chance for that same criteria over in
the eastern slopes of the Berkshires. There is also a 50% chance for
amounts greater than 3" over eastern RI in a 48 hour span. Suffice
to say, there is still a range of where the most rain could fall
over the course of this event. Some localized flooding could be an
issue depending on the presence of some partially frozen ground, but
the extent of any flooding impacts is still unknown this far ahead
of the event.
As the low moves out and the rain comes to an end, cold air
following a cold front is expected to make its way into the region.
Preceding this cold front, the forcing from it could lead to some
rumbles of thunder from CT through RI and up into eastern MA and the
Cape. Some snowflakes could fall across western and central MA as
this colder air begins its progression eastward, but not much
accumulation over a coating looks favored at this time.
Surface high pressure moves in, drying out the region going into
Friday and the weekend. Temperatures are also expected to drop once
again -- especially Thursday night -- and return to more seasonable
levels.
&&
.AVIATION /09Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z update...
Today...High Confidence.
Winds light and variable. VFR to start then lowering to
MVFR/IFR by evening in RA.
Tonight... High Confidence.
IFR with embedded IFR in RA/-RA through about 06Z. Low ceilings
persist through Tuesday morning with easterly winds becoming
north/NNW by 12Z Tuesday.
Tuesday...High Confidence.
IFR/MVFR cigs with light winds, slight chance of RA.
KBOS Terminal...High Confidence.
KBDL Terminal...High Confidence.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Mainly IFR, with areas MVFR possible. Breezy.
RA.
Wednesday: Mainly IFR, with areas MVFR possible. Windy with
gusts up to 35 kt. RA, isolated TSRA.
Wednesday Night: MVFR/IFR conditions possible. Strong winds
with local gusts up to 40 kt. RA.
Thursday: VFR. Breezy. Slight chance RA, slight chance SN.
Thursday Night: VFR. Breezy.
Friday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today and Tonight...High confidence.
Winds increase out of the east southeast this afternoon ahead
of an approaching low pressure system that will bring rain to
the coastal waters this afternoon and evening. Gusts to 30 kt
are possible on the outer eastern waters. The surface low
pressure center moves over the coastal waters tonight which
will result in variable wind direction with northeast winds over
the eastern zones and west winds over the southern waters. Seas
may increase to near SCY levels on outer waters.
Tuesday...High confidence.
NE winds on the eastern waters with SW winds on the southern
waters early, then all shifting to the SE in the afternoon. Seas
3-4 ft.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain.
Wednesday: Low risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Rain, isolated thunderstorms.
Local visibility 1 to 3 nm.
Wednesday Night: Strong winds with gusts up to 40 kt. Rough
seas up to 18 ft. Rain. Areas of visibility 1 to 3 nm.
Thursday: Strong winds with gusts up to 30 kt. Rough seas up to
14 ft. Chance of rain.
Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 11 ft. Slight chance of
rain.
Friday: Winds less than 25 kt. Local rough seas.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Winter Weather Advisory from 3 PM this afternoon to 10 AM EST
Tuesday for MAZ002-004-008-026.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for
ANZ254>256.
&&
$$
SYNOPSIS...BW/Hrencecin
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Hrencecin
AVIATION...BW/Hrencecin
MARINE...BW/Hrencecin