Lexington, Massachusetts, USA

11/22/2017 10:29pm 
  • Lexington Conditions: Mostly cloudy
  • Temperature: 38.1°F / 3.4°CColder 0.7°F than last hour.
  • Dew Point: 33.8°FDecreased 1.3°Fsince last hour.
  • Humidity: 84%Decreased 2.0% since last hour.
  • Wind: NNW 3 mph, gust: 8 mph
  • Barometer: 29.87 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.71 in

Area Forecast Discussion
for Boston, MA

FXUS61 KBOX 230312

Area Forecast Discussion
National Weather Service Taunton MA
1012 PM EST Wed Nov 22 2017

Quiet weather Thursday and Friday with dry and cool conditions. 
Milder air returns Sat ahead of a cold front but will have to watch 
a coastal storm to the south. Blustery and cooler weather follows 
Sunday into Monday, then dry and milder conditions again Tuesday 
into Wednesday.



1000 PM Update...

Trend in the forecast remains on track for tonight. Gusty NW
winds continue this evening but should begin to slacken off
within the next hour or two for the CT valley and in a few hours
for the rest of the region. 00z ALY sounding shows a lot of
moisture in the mid-levels which has kept bkn clouds cover over
the region. This is limiting temps from truly radiating out.
Model soundings show the profile beginning to dry out around 06-10z
which will help temps drop quickly. Thus temp forecast looks on

Previous Discussion... 
Clearing skies tonight as low level dry air moves in. Gusty NW 
winds to 30-35 mph this evening behind departing low pres, then 
mass fields show enough of a slackening in the pres gradient to 
support some decoupling with clearing.

Leaned most heavily on MET/MAV data for overnight mins, 
featuring mainly low-mid 20s outside of the urban compacts.


Very weak ridging follows the shortwave passage overnight and
ahead of weak opening wave approaching from the Great Lakes by
late day. The resulting subsidence inversion suggests mainly dry
conditions, and soundings support this. The inversion will also
limit diurnal mixing to H92 where a slight increase in temps to
near -1C should allow highs to rebound in the low 40s based on 
expected sunshine alone. However, given winds shift to the W 
based on isallobaric component with high pres shifting slightly,
downsloping will allow some locations to reach the mid and even
upper 40s in spite of the cool start. All-in-all, a pleasant 
albeit cool day to head over the river and through the woods.

Tomorrow night...
The weak aforementioned wave will pass mainly across N and
central New England with the sfc reflection being a very weak
secondary cold front. Although soundings do suggest an every so
slight increase in upper lvl moisture, this is frontal passage
is quite dry. Therefore, expecting little fanfare as it moves
through outside of an increase in evening clouds. The primary
impact will be to limit overnight diurnal temp drop off thanks
to less decoupling. Mins hold mainly in the mid-upper 20s in the
coolest spots.



* Dry and cool Fri, then warming Sat with a low risk of showers
* Blustery and cooler Sun/Mon
* Turning mild again Tue/Wed with mainly dry conditions


Models are advertising a progressive pattern in the long term period 
as -AO/-NAO pattern trends to neutral. This will result in a 
changeable temp regime in the extended period. Amplifying northern 
stream trough moves into New Eng Sun which will be preceded by a 
warming trend, especially Sat, then colder Sun/Mon. As trough 
approaches models indicating coastal development S of New Eng Sat 
assocd with a southern stream shortwave and this will need to be 
watched as it could bring some rain if it trends northward. Next mid 
level trough moving through the Rockies and central US early next 
week with downstream ridging in the east will bring another warming 
trend through midweek. Significant model differences in the large 
scale flow toward the end of the period which will determine if 
another period of wet weather moves in by Wed or it remains dry and 

Friday into Saturday...

High pres south of New Eng moves offshore which will bring a warming 
trend through Sat with temps likely getting back well into 50s Sat. 
Dry conditions Fri, then a bit more tricky for Sat as a coastal low 
assocd with a southern stream shortwave is forecast to develop south 
of New Eng while cold front approaches from the west. NAM is a 
western outlier with a slug of heavy rain on Sat while GGEM has 
heavier rain just off the coast. ECMWF/GFS/UKMET remain offshore but 
several GEFS members bring some rain Sat night. Odds favor a dry day 
but a shift to the north and west would jeopardize a dry forecast, 
especially SE New Eng. Otherwise, can't rule out a brief shower in 
the west as front approaches. 

Sunday and Monday...

Deep mid level trough moves into New Eng Sun then moves to the east 
Mon. Expect blustery and colder conditions Sun into Mon but warm 
advection will commence during Mon. Below normal temps. 

Tuesday and Wednesday...

Milder Tue with increasing SW flow, then uncertainty for Wed as GFS 
brings a front with showers into the region while ECMWF keeps it dry 
and mild. Deterministic GFS does not have support of most GEFS 
ensemble members which are dry so we kept a dry forecast. Above 
normal temps.


Forecaster Confidence Levels...

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

Short Term /through Thursday Night/...High confidence.

Through 02z...
MVFR/IFR Cape/Islands and SE coastal MA will rapidly improve to
VFR as skies clear. NW gusts to 25-30 kt. 
Aft 02z tonight into tomorrow night...
Mainly VFR. NW winds continue to gust around 25 kt through the 
overnight hours but then drop off during the early morning. 
These winds shift to mainly W tomorrow and tomorrow night.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.
Outlook /Friday through Monday/...

Friday: High confidence. VFR. 

Friday Night: High confidence. VFR. Breezy. 

Saturday: Moderate confidence. Mainly VFR, with areas MVFR possible. 
Breezy. Slight chance SHRA.

Saturday Night: Moderate confidence. Mainly VFR, with local MVFR 
possible. Breezy. 

Sunday through Monday: High confidence. VFR. Breezy.


Forecaster Confidence Levels...

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

Short Term /through Thursday Night/...

Tonight...High confidence.
NW winds increase through the evening, with gusts mainly 25-30
kt across the waters into early tomorrow morning, there is a low
risk for Gale gusts mainly on the outer waters, but these will
be few and far between and only support a high end small craft
advisory at this time. Seas will build with the increase in
winds, peaking at around 8-9 ft on the SE outer waters.

Tomorrow and tomorrow night...High confidence.
Winds shift to the W, with gusts generally remaining below 20 kt
after sunrise. Seas however will take some time to fully
diminish, and will require small craft advisories to linger much
of the day. Advisories have been extended for the outer waters
into tomorrow night given 5 ft lingering swells are expected.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt. Seas up to 5 ft. 

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. 

Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers. 

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers. 

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Local rough seas. Slight chance of rain showers. 

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 9 ft. 

Monday: Winds less than 25 kt. Local rough seas.


The KBOX radar is currently down due to an equipment failure.
The radar may remain down into Thanksgiving.


MARINE...Small Craft Advisory until 4 AM EST Thursday for ANZ230>234-
     Small Craft Advisory until 1 AM EST Thursday for ANZ236.
     Small Craft Advisory until 6 PM EST Thursday for ANZ235-237.
     Small Craft Advisory until 7 AM EST Friday for ANZ250-254>256.