Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 240252
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
952 PM EST Fri Feb 23 2018

.SYNOPSIS...
A weak wave of low pressure moves offshore tonight followed by
drier air later tonight into Saturday. Another frontal system
will bring more rain and interior mixed precipitation Saturday
night and Sunday. A near-seasonable, quiet pattern for early
next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
950 PM update...
Area of rain has moved offshore, but still some lingering
drizzle across SE MA. Drying trend overnight as winds shift to
west and pronounced mid level drying moves in. Low clouds and
patchy fog will gradually lift overnight but may take until
morning along the immediate south coast and Islands where low
level moisture lingers.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday...

Dry weather returns Saturday as a high pressure builds into the
region from the NW. Lingering fog is possible after 12z along
the southern coast, but should quickly burn off due to surface
heating. Clouds will continue clearing, with most of the
interior seeing periods of sun by midday. With NW flow, temps
will reach well into the 50s across the interior and coasts.
Cooler upper 40s over higher elevations NW MA.

Saturday night...Rain showers expected after midnight, with a
chance of higher elevation seeing freezing rain and sleet just
before sunrise.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...

* Widespread precip on Sunday with wintry mix in the interior
* Dry and above average for early next week
* Stormy pattern emerging for the beginning of March

Overview...

12z guidance is in general agreement with the extended forecast.
Just some minor differences related to thermals which provide
different outcomes in p-type for late Saturday night into Sunday.
Deamplifying trough across the CONUS as potent shortwave moves up
into the Great Lakes bringing occluded system and triple point low
into southern New England on Sunday. Afterwards high pressure and
strong ridge takes hold over the eastern CONUS by early next week.
The GEFS and EPS continue to show anomolous high pressure building
over Greenland which will influence a cut-off low to either
retrograde towards the Maritimes or remain across the North
Atlantic. This all due to the NAO turning negative by early March.
While the pattern begins to jam up, digging shortwave out of the
southern Plains on Thursday needs to be watch as it could be the
first of several waves impacting southern New England.

Details...

Late Saturday night into Sunday...Moderate confidence.

Potent wave will eject out of the desert Southwest producing a
surface low pressure system up into the northern Great Lakes.
Stalled front to the south will begin to lift northward as a warm
front. This will result into another overrunning precip set-up as
moisture from the south increases as warm front begins to lift
northward. Surface high pressure will be set-up north to northeast
of the region allowing for surface temps to fall. Triple point low
developing along the stalled front, will reinforce the cold air
especially in the 950-925mb layer leading to cooler temps at the
surface, esp across the high terrain.Models are always to quick at
warming temps above freezing, so trended towards cooler 2m temps and
wet-bulb effects.

P-type will once again be the issue as models are still struggling
with the warm layer. EC continues to remain on the cold side with
the 12z NAM as the warmest. GFS/CMC and now 18z NAM are in the
middle of the ground and thus trended towards the ensembles
guidance. As with the prev forecaster, kept a bit of snow/sleet at
the onset, as cold air looks to be deep enough north of the Pike and
esp Route 2. In fact with good omega in the snow growth region,
could see a few inches of snowfall. Once the mid-level warm front
pushes into the region, a transition to more freezing rain event
will occur leading to slick travel across the interior. Highest
confidence will be across the east slope of the Berkshires and the
Worcester Hills as the higher terrain locations will see the coolest
surface temps. This is due to warm layer remaining around 800mb.
Cannot rule out northern CT and the higher terrain of RI for some
wintry weather impacts, but confidence is higher across northern MA.
South of the Pike and especially across RI and SE MA conditions look
to warm for any wintry weather, but still will have to watch as a
change in just a few degrees will impact p-type.

This system continues to be quite robust resulting in more
widespread precip, esp as we continue to tap into that Gulf
moisture. PWAT values are around 2-3 STD above normal for this time
of year. When this system is all said and done, could see about an
inch across the south coast with a half of an inch near the MA/NH
border. Guidance from NERFC suggest that the rivers should remain
within their banks, but may need to watch some of the flashier
streams.

Lastly, with the surface warm front trying to push northward, may
have a large gradient in surface temperatures somewhere across
southern New England. While warm fronts tend to struggle to lift
northward this time of year something to watch as we could see low
50s across the south coast and mid 30s across the interior.

Sunday night into Wednesday...High confidence.

Surface cold front will push through the region resulting in a
drying trend for Sunday night. Strong high pressure over the Ohio
Valley will begin to strengthen Monday into Tuesday as anomolous ridge
sets-up over the Mississippi Valley. This high appears to stay in
place into middle of next week before a quick moving wave from the
southwest gets kick into the flow. Thanks to ridging and surface
high, dry weather will prevail as temperatures turn slightly above
average.

Thursday and beyond...Low confidence.

To many pieces to the puzzle to have confidence in the forecast for
the end of the week. Approaching shortwave from the southern Plains
will spawn a surface low, just uncertain on its direction and
location as it will depend on large scale features downstream.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...Moderate confidence.

Tonight...MVFR/IFR conditions will gradually improve to VFR from
north to south after 06z. Low cigs and fog may linger along the
south coast until 12z.

Saturday...Fog may linger along the southern coast and islands
past 12z. Conditions will improve to VFR across the region by
early morning.

KBOS Terminal...Moderate confidence. MVFR with rain ending near
2z. Improving conditions around 6z.

KBDL Terminal...Moderate confidence. MVFR/IFR through this
evening. Patchy fog in the AM, burning off by 11z. VFR
conditions to follow.

Outlook /Sunday through Wednesday/...Moderate confidence.

Saturday night into Sunday: MVFR/IFR conditions possible. Windy
with gusts to 30 kt. RA, chance FZRA across northern interior.

Sunday Night: Mainly VFR, with local IFR possible. Slight
chance RA.

Monday through Wednesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

Tonight...Winds shifting to west with gusts up to 20 kt. Areas
of fog will limit vsbys over south coastal waters.

Saturday...Diminishing westerly winds becoming northerly in the
evening. SCA might be needed for the southern waters early
Saturday where seas reach 5 feet.

Outlook /Sunday through Wednesday/...

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Areas of rough seas. Rain.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain.

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

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

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.

Tuesday Night through Wednesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Nocera/Dunten/Correia
NEAR TERM...KJC
SHORT TERM...Nocera/Correia
LONG TERM...Dunten
AVIATION...KJC/Nocera/Dunten/Correia
MARINE...Dunten



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