Somerville, Massachusetts 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

269
FXUS61 KBOX 221130
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
630 AM EST Sun Dec 22 2024

.SYNOPSIS...
Blustery and very cold today with wind chills only recovering into
the single numbers and teens. Winds drop off tonight and Monday as
high pressure builds into the region, but very cold conditions will
continue. A weak clipper system may bring very minor snow
accumulations late Monday night into Christmas Eve morning.
Otherwise, dry weather dominates the rest of the Holiday week with
temperatures moderating back to seasonable levels.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Updated: 3:30 AM

Key Messages:

* Very cold and dry conditions for today.

* Ocean effect snow showers may lead to periods of festive flurries
  across the outer Cape this afternoon and evening.

Well, winter officially arrived yesterday morning and did not take
long to unpack and get settled. It is down right COLD this morning
as an Arctic area of high pressure builds in to the west across the
Great Lakes. Early morning temperatures are expected to be in the
single digits for many, with the urban centers and immediate coast
in the lower teens. BUT, when you factor in the northwest wind it
will feel MUCH colder, sub-zero wind chills. Areas in far western
Massachusetts, Berkshire County are under a Cold Weather Advisory
this morning due to widespread wind chill values at least 15 below
zero. Much of our area will experience wind chill values 5 to 10
degrees below zero, with isolated spots along the border with
Berkshire county 10 to 15 below zero.

There will be little improvement this afternoon as the high nudges
closer to southern New England. Expect a well-mixed boundary layer,
mixing between 950mb and 900mb, will be able to transfer down gusty
northwest winds between 15 and 25 mph through late morning, easing
winds this afternoon and tonight. 925mb temperatures -20C to -16C
result in high temperatures in the teens and low 20s near the coast.
These temperatures are nearing record coldest highs in places like
Boston, where the recorded lowest high for today is 17F, our current
forecast calls for a high of 19F. Will include more details on
record lowest highs in the climate section of the AFD. Lastly, the
wind chill remains sub-zero through at least mid morning with minor
improvements to the single digits later this afternoon.

While it is frigid, there will be plenty of sunshine across much of
the region, with the exception of Cape Cod and the islands. With a
persistent NNW wind direction, an Arctic airmass over relatively
warm SSTs in the 40s, ocean effect snow streamers are possible today
and into the evening. These features can be tough to pin down,
have opt to leave `chance` POPs over most of the outer Cape for
today and then `slight chance` this evening. PWATs are 0.1"
this afternoon so there is not much moisture to tap into, but
festive snow showers could lead to a coating, with the worst
case scenario up to an inch for the outer Cape through tonight.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Updated: 3:30 AM

Key Messages:

* Very cold tonight with temperatures between 10F and -5F! Still
  cold on Monday, but slightly `warmer` than Sunday.

No change in the airmass for tonight with sprawling high pressure to
the west, will have easing winds and clear skies overnight too. This
will set up for effective radiational cooling, leveraged the CONSMOS
for tonight, will have lows ranging between 5F and -5F, at the coast
it is slightly warmer in the lower teens. A few spots may come near
the daily record lowest minimum temperature, like Providence where
the forecast low is 7F and the record is 2F. As mentioned above will
have more details on records in the climate section of the AFD.

Dry and cold, but will continue chance of a few ocean effect snow
showers during the late evening, but as winds ease over the waters
that should end those snow showers.

Monday, the 1035mb high traverses across southern New England
leading to a sunny but still chilly day, just not as cold as
Sunday. Temperatures at 925mb moderate, -12C to -8C, while still
chilly, highs are in the middle to upper 20s, with far
northwest Massachusetts still in the upper teens to lower 20s.
Sunshine gives way to increase in clouds later in the day ahead
of a weak clipper system, more on that in the long term section
of the AFD.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Updated: 3:30 AM

Key Messages:

* Light snow showers late Mon night/Tue AM with accum 1 inch or less

* Mainly dry Christmas Day into Sat, with just a low risk for spotty
  light precip at times

* Temps moderate into the 30s Tue through Thu with some 40s by
  Friday, but cold nights

Details...

Monday night and Tuesday...

A shortwave approaches from the Gt Lakes with a weak clipper system
moving through the region. Large scale forcing increases ahead of
the shortwave with moistening of the column leading to a period of
light snow showers late Mon night into Tue morning. Ptype will be
mostly snow but warming boundary layer may lead to change to rain
showers for Cape/Islands. However, the column never fully saturates
so not looking at much snow, a coating to an inch, with perhaps 1-2
inches in northern MA where ensemble guidance indicates moderate
probs for 1+ inch of snow. The system is a quick mover and the
precip should be moving out in the afternoon as much drier air moves
in from the north as PWATs drop to less than 0.2". Highs will be in
the 30s, with lower 40s Cape/Islands.

Wednesday through Saturday...

Overall a quiet period as New Eng will be dominated by ridging aloft
although there could a shortwave interruption sometime around Thu.
However, deep layer moisture will be limited as strong high pres
builds to the north. But this will also set up a persistent low
level N-NE flow which may lead to periods of low clouds along with
spotty light precip or drizzle at times, especially near the coast.
But largely a dry period for much of the time with no storms through
next weekend. Despite warming temps aloft, the strong high to the
north will bring shallow cooler air so temps will be slow to respond
with highs generally in the 30s Wed/Thu warming into the lower 40s
Fri/Sat, with chilly nights.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

12z TAF Update...

Today and tonight...High confidence.

VFR, but ocean effect clouds with areas of MVFR cigs and
scattered flurries over the outer Cape, mainly along and east
of HYA. NW gusts to 20-25 kt diminishing later this afternoon
then becoming light tonight.

Monday...High confidence.

VFR. Light N wind becoming S-SW 5-10 kt in the afternoon.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night: Mainly VFR, with local IFR possible. Chance SN.

Tuesday: Mainly VFR, with local MVFR possible. Chance SN,
chance RA.

Tuesday Night through Thursday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Updated: 3:30 AM

Key Messages:

* Small Craft Advisory in effect through tonight.

* Light icing from freezing spray for the waters surrounding
  Nantucket through Sunday afternoon.

Today through Monday...High confidence.

High pressure moving overhead from the Great Lakes region. NW
winds 15 to 20 knots gusting to 25 knots through mid afternoon
with seas 5 to 7 feet. A few ocean effect snow showers are
possible through this evening across the eastern waters. Wind
becomes light and variable overnight with seas falling below 5
feet. Monday, wind turns to the southwest 10 to 15 knots with
seas 2 to 4 feet.

Outlook /Monday Night through Thursday/...

Monday Night: Winds less than 25 kt. Chance of rain, chance of
snow. Local visibility 1 to 3 nm.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain, chance of snow. Local visibility 1 to 3 nm.

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers, slight chance of snow
showers. Local visibility 1 to 3 nm.

Christmas Day through Wednesday Night: Winds less than 25 kt.
Areas of seas approaching 5 ft. Slight chance of rain showers.

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

&&

.CLIMATE...
Record Lowest Maximum Temperature: 12/22

BOS: 17F (1989)
BDL: 11F (1989)
PVD: 17F (1989)
ORH:  9F (1989)

Record Lowest Minimum Temperature: 12/23

BOS: -12F (1883)
BDL:  -5F (1989)
PVD:   2F (1989)
ORH:  -2F (1989)

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for ANZ231-
     232-251.
     Small Craft Advisory until 4 AM EST Monday for ANZ250-254.
     Small Craft Advisory until 10 PM EST this evening for ANZ255.
     Small Craft Advisory until 1 PM EST this afternoon for ANZ256.

&&

$$

SYNOPSIS...KJC/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...KJC
AVIATION...KJC/Dooley
MARINE...KJC/Dooley
CLIMATE...Dooley