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Area forecast discussion 
National Weather Service Taunton Massachusetts
733 PM EST Thursday Mar 5 2015

snow will exit Cape Cod and the islands early evening followed by
Arctic high pressure tonight and Friday. The high moves south of New
England this weekend allowing temperatures to moderate. Two weak
fronts may bring a period of snow showers or flurries...first Sat
night and again Sun night into Monday morning. Next week mainly dry
weather prevails along with temperatures warming to near normal.


Near term /until 6 am Friday morning/...

*** Winter Storm Warning confined to Cape Cod and the islands
until 10 PM ***

Back edge of the snow near the Cape Cod canal at 7 PM and will
continue to move east as middle level trough axis moves east as well.
Thus have let the Winter Storm Warning expire for the South Coast
and let warnings go until about 10 PM for the cape and islands.
Previous forecast handles this well so no major changes with this
update. Earlier discussion below.


Regional radars indicate back edge of snow shield blossoming
somewhat across NYC area/Long Island and coastal CT. This is
in response to middle level trough still west of the region and
its associated SW flow aloft across the region. This moist SW flow
aloft is over-running a cold dome across the area. Additional lift
being provided by strong upper level jet streak of 200kt across
northern New England into the Maritimes...with rrq over southern
New England. Given middle level trough axis doesn't move offshore until
after 00z...will extend Winter Storm Warning for Cape Cod and the
islands until 10 PM...7pm elsewhere.

Once middle level trough moves offshore Arctic airmass with dew points
below zero over northern New England and New York state will surge
southward into our region. This combined with a replenished
snowcover will result in a frigid night. Earlier discussion below.

Tonight...behind this snow...dewpoints will continue to plunge
into the single digits. Temperatures will crater through the night
as skies clear and winds become calm. This will result in
excellent radiational cooling with temperatures dropping into the
single digits both above and below zero aside from the cape and
islands where temperatures will be in the teens.


Short term /6 am Friday morning through Friday night/...
Friday and Friday night...high pressure builds into the area from
the Midwest and then slides south of southern New England Friday
night. Quiet but chilly weather expected during this time with
temperatures roughly 20 degrees below normal for early March.


Long term /Saturday through Thursday/...

* temperatures...not as cold this weekend and moderating to near
normal next week

* precipitation...relatively dry with any precipitation events very minor

Good model agreement on the large scale flow with West Coast and
eastern Pacific Ridge holding on through the weekend into early next
week. This results in a continuation of a downstream long wave
trough and associated colder than normal temperatures over the Great Lakes
into New England. However there is a good agreement among the 12z
gefs and 00z eps ensembles along with 12z deterministic guidance that
this ridge moves into the central US middle of next week...yielding
mean middle level trough axis to move east of New England. This results
in deamplification of the pattern and temperatures moderating to possibly
seasonable levels /highs in the 40s and lows in the 20s/ next week.

As for precipitation...northern branch remains the dominant air stream
across New England this weekend into early next week. This keeps middle
level confluent zone south of New England precluding streams from
merging/phasing at this longitude...resulting in a fairly dry
pattern. However the northern stream will deliver a few moisture
starved short waves/fronts to zip across the area during this time.
The first short wave and risk of light snow/flurries arrives Sat
night followed by another trailing impulse Sun night into early
Monday. Otherwise dry weather prevails much of next week.


Aviation /01z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /through Friday night/...high confidence.

7 PM update...


IFR/MVFR confined to Cape Cod and the islands and will improve to
VFR by 02z-04z. VFR elsewhere and continues into Friday night.

Kbos taf...high confidence.

Kbdl taf...high confidence.

Outlook...Saturday through Tuesday...moderate confidence.

Mainly VFR with light to modest winds. Brief MVFR ceilings/visibilities
possible Saturday night and again Sun night in widely scattered snow


forecaster confidence levels...

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

Short term /through Friday/...moderate confidence.

High confidence. Winds and seas will continue to diminish as high
pressure builds over the waters Friday. Small craft advisories
currently in place will no longer be needed by Friday morning.

Outlook...Saturday through Tuesday...moderate confidence.

Saturday...modest west-southwest wind of 20-25 knots ahead of cold front. Visibility may
lower briefly in scattered snow showers Sat night.

Sunday...modest west-northwest winds behind the front. Then winds become SW at
night ahead of next front. Visibility may lower briefly in scattered snow
showers Sun night.

Monday...SW winds in the am with scattered snow showers...then west-northwest in
the PM behind frontal passage.

Tuesday...looks tranquil with high pressure building into New England.


Box watches/warnings/advisories...
Massachusetts...Winter Storm Warning until 10 PM EST this evening for
Rhode Island...none.
Marine...Small Craft Advisory until 6 am EST Friday for anz235-237.
Small Craft Advisory until 1 PM EST Friday for anz250-254>256.
Freezing spray advisory until 5 am EST Friday for anz250-251.


near term...nocera/rlg
short term...rlg
long term...nocera

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