Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 180530

Area Forecast Discussion
National Weather Service Taunton MA
130 AM EDT Sun Mar 18 2018

Dry but unseasonably cold weather will continue into early next
week. A multi-part storm system moves to the Mid Atlantic states
midweek. This system may affect parts of Southern New England Wed
and Thu, but it is also possible the storm stays to our south with
little impact. However uncertainty remains high on the evolution of
this storm especially its eventual track. High pressure builds with
drier weather Friday.


10pm update...

With SKC conditions across all of SNE, the first in several
nights, along with a slackening pres gradient, we have seen
pretty good decoupling already so far this evening. This is
likely helped by an established snowpack. 2m raw temps a little
better than MOS, but will still leave some weight on the
coolest MOS with this update as well. Otherwise forecast on
track, the primary update will be on colder temps/dwpts.



Cold and dry NW flow continues with more sunshine than clouds.
However a chilly day with highs only 30-35 with upper 20s across the
high terrain. These temps are about 10-15 colder than normal. The
only good news is fairly light winds will not contribute to much of
wind chill.

Sunday night...

Another cold night with 1034 mb high pres over Ontario building
southeast into New England, decoupling winds away from the urban
areas and high terrain. Another round of mins in the teens.


Dry but cold NW flow continues. Not as cold with highs in the mid to
upper 30s, low 30s high terrain. Fairly light winds and more
sunshine than clouds will make the cold conditions a bit more

Monday night...

Potentially good radiational cooling with ridge of high pres
cresting over the area combined with mostly clear skies, light winds
and a very dry airmass. Mins in the teens once again outside of the
urban areas.


*/ Highlights...

 - Tuesday into Wednesday, keep it cold and dry, N winds
 - Wednesday night into Thursday, monitoring potential storm
 - Friday into Weekend, keep cool, dry pattern for now

*/ Overview and discussion...

Evaluating potential storm development. At set, SE Canadian gyre as
Pacific energy train continues. La Nina tendencies still at play, N-
Pacific H5 ridge re-emerges poleward. N-stream energy dislodged, the
trof-ridge-trof pattern amplifies downstream thru the week ... but
where exactly? NE CONUS perspective, progged upstream energy, even
NW CONUS, bowls within a preferred H5 trof. Yet downstream pattern
becomes lax, opens, suppressive wave presently slips E, NAO forecast
positive. This as a mild Pacific C CONUS punch emerges. A wave-train
nudge E allowing cyclonic trof digging further offshore? Or can N-
stream energy, colder air cut S faster, sharper-amplified baroclinic
setup closer coastal, less flat, more pronounced, per enhanced H5 C
CONUS ridging?

Lot of moving parts, chaotic, expect adjustments in later forecasts.
Focus late Wednesday into Thursday when suppressive, confluent flow
can eject E as N-stream cyclonically digs through preferred H5 trof
pattern, creating a favorable environment towards storm development
near NE CONUS. Believe any activity prior will be suppressed S, off-
shore, beneath confluent flow aloft, only maintaining cold air. Only
certainty, looks chilly through the end of the month.

Threats, impacts, precipitation amounts? Way too early to say with
any specificity. Proximity of any storm, thermal fields, intensity,
time of day, etc., etc., all fairly unknown for now. Best advice,
stay informed, keep tuned to later forecasts.


Forecaster Confidence Levels...

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

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

Through this evening...
VFR. FEW-SCT CU mainly 040-060 across SW MA/CT this evening.
Winds mainly N-NW gusts to around 20 kt occasionally this

Tonight into Mon...
VFR. NW winds generally lighter than previous days, mainly
around 10 kt.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday through Thursday/...

Tuesday: VFR. Breezy.

Tuesday Night: Windy with areas gusts to 30 kt. Slight chance

Wednesday through Wednesday Night: Windy with gusts to 35 kt.
Slight chance SN.

Thursday: Windy with gusts to 35 kt.


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


Gales concluded. Small crafts in effect. NW winds continue behind
a dry Arctic front as high pressure settles in N/W. Low risk of
areas of light freezing spray across the eastern MA waters.

Sunday thru Monday night...

Modest NNW winds with possible areas of light freezing spray eastern
MA waters at night, then diminishing Mon night as ridge of high pres
builds across the waters.

Outlook /Tuesday through Thursday/...

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Slight chance of snow.

Tuesday Night: Low risk for gale force winds with gusts up to
35 kt. Local rough seas. Slight chance of rain, slight chance
of snow.

Wednesday: Moderate risk for gale force winds with gusts up to
35 kt. Rough seas up to 10 ft. Chance of snow, chance of rain.

Wednesday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 11 ft. Chance of snow.

Thursday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft. Slight chance of snow.


MARINE...Small Craft Advisory until 2 AM EDT early this morning for
     Small Craft Advisory until 6 AM EDT early this morning for


LONG TERM...Sipprell
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