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Area forecast discussion 
National Weather Service Taunton Massachusetts
359 PM EDT Thursday Apr 24 2014

Synopsis...
winds diminish tonight as high pressure builds into New England
from the west...providing chilly temperatures but then rebounding
nicely Friday with mild conditions and light winds. Low pressure
then brings rain Friday night into Saturday...followed by a drying
trend Sunday and continuing into early next week along with seasonable
temperatures as high pressure returns to the area.

&&

Near term /until 6 am Friday morning/...
340 PM update...

Powerful late season occluded low south of Nova Scotia will
continue to generate windy conditions across southern New England
through sunset and then begin to diminish with nightfall and
especially after midnight. The combination of diminishing
winds/clear skies and a very dry airmass with dew points in the teens
and 20s will result in a chilly night across southern New England.

A blend of all data sources yields mins tonight in the 30s
regionwide...except upper 20s in the deeper interior valleys such
as the CT River Valley. The other exception will be in the city of
Boston...Cape Cod and the islands where winds will not completely
diminish and keep min temperatures around 40.

As for frost/freeze headlines...the growing season has only begun
along the South Coast. Here across coastal Rhode Island and south coastal Massachusetts
temperatures will dip into the m30s for a time from about 3 am to 7 am.
This will be sufficient for widespread frost. Given growing season
is already in progress here will issue a frost advisory. Did not
include communities near Narragansett Bay as winds will likely not
decouple here keeping temperatures in the u30s and l40s. Thus lower risk
of widespread frost.

Elsewhere/inland temperatures will be colder however no headlines given
growing season for most locations doesn/T start until sometime in
may.

&&

Short term /6 am Friday morning through Friday night/...
Friday...

Real nice day with light winds as high pressure crest over the region.
Deep layer subsidence will provide lots of sunshine with strong April
sun angle warming airmass into the low and middle 60s inland. Cooler
along the coast with developing seabreezes but overall a nice day
by late Apr standards and considering what the weekend and extended
forecast offers.

Friday night...

Robust trough over the Southern Plains this afternoon continues
moving eastward and arrives here Friday night. Models in very good
agreement on this system...with parent low entering western New York
early Sat...while secondary low spins up near Long Island New York. Rain
overspreads western portions of CT and Massachusetts 8 PM to 2 am...then
across Rhode Island and eastern Massachusetts 2 am to 8 am. A period of heavy rain
possible given modest Atlantic inflow and jet dynamics toward 12z
Sat.

&&

Long term /Saturday through Thursday/...

Highlights...

* unsettled weather is expected on Saturday...low conf on washout
* unseasonable temperatures and unsettled weather middle next week

Models and confidence...
12z synoptic pattern is in good agreement. However the ec is more
progressive on pushing out the blocking pattern then the GFS.
Overall continued focusing the forecast base on the ensembles as
the deterministic guidance is still somewhat spread out. However
with both the nao and ao forecasted to be negative and with the
pna expected to be more positive...there is increasing confidence
of a blocking/trough over the northeast allowing for more
unsettled weather.

Quick moving shortwave over the Great Lakes will move into the
region pushing a double barrel low through New England by Saturday.
These low pressure systems will evolve into a cut off upper level
low which continue to influence the region by wobbling over the
Maritimes into Monday. However a closed trough/low over The Rockies
on Monday will eventually be forced eastward across the eastern US
by Wednesday in a developing Rex block setup as warming ridges build
strongly over the western US.

Details...

Saturday...
a double Barrow low will move over southern New England on
Saturday. As the first low moves through the deterministic models
agree that heavy precipitation will occur Sat morning into the early
afternoon hours thanks to good Atlantic moisture plume and descent
jet dynamics. Believe that the heaviest precipitation will occur on the
northwest portion of the low. As the first low moves through and the
second shortwave moves into the region...another shot of
precipitation...more showery weather... will move through during the
evening hours. So there is a low probability that there may be a
break in the precipitation on Saturday. During the evening hours the
region loses the good moisture plume however...some of the
moisture may move on the backside of the low. Yet the jet dynamics
are not in favor for heavy rain...so have moderate confidence in
more showery weather Saturday evening into the overnight hours.
Guidance continues to indicate some elevated instability moving
through on Saturday so have inserted isolated thunder for now. However
focused more on the southern half of the region where the better
parameters are located.

As the surface low approaches...easterly winds will develop on
Saturday resulting in a much cooler coast then originally though.
Have drop temperatures down into the upper 40s to low 50s. However across
the CT valley...if clouds break out then temperatures could soar into the
middle 50s thanks to the high April sunshine. Any adjustments in the
track of the low could cause changes in the temperatures.

Sunday into Monday
northerly flow will continue into Sunday keeping temperatures
down in the low to middle 50s across the region. However with the
strong low pressure system just offshore appears that there could
be some lingering showers.

Northwesterly flow will continue on Monday and Tuesday. Conditions
look to be breezy on Monday with the departing low moving offshore
and weak high pressure trying to move into the region...increasing
the pressure gradient. Temperatures will be close to average.

Tuesday into Thursday...
blocking pattern appears to set-up over the region during the middle
to perhaps the end of next week. As an upper level low wobbles
across the Midwest...appears that a trough will set up over the
northeast. This low will allow for easterly winds across the
region as well as cloudy skies. Therefore have increasing
confidence that temperatures will be well below average for this
time of year and expect several rounds of precipitation. However have a
low confidence on when exactly each round of precipitation will occur and
where the heaviest will reside. For now...have increasing
confidence that cool temperatures and unsettled weather will occur.

&&

Aviation /20z Thursday through Tuesday/...
low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term /through 12z Saturday/...high confidence

4 PM update...

Through 00z...gusty northwest winds 30-40 knots continue then beginning to
diminish around sunset. VFR as well.

After 00z...VFR with a diminishing wind.

Friday...VFR with light winds...seabreezes along the coast.

Friday night...VFR to start then quickly lowering to MVFR with
rain overspreading western CT/Massachusetts 00z-06z then into Rhode Island and eastern
Massachusetts 06z-12z. Low risk of IFR toward 12z Sat. East-southeast winds
may increasing up to 25 knots toward 12z Sat across Rhode Island and eastern
Massachusetts.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Saturday through Tuesday...

Saturday...moderate confidence. Mainly VFR. Brief periods of
MVFR/IFR conditions in rain showers/fog.

Sunday into Tuesday...low confidence. VFR. Some showery weather
possible on the East Coast on Sunday.

&&

Marine...
forecaster confidence levels...

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

Short term /through Saturday/...high confidence.

Tonight...
northwest gales until 8 PM or so followed by diminishing winds overnight.
Strongest winds near shore.

Friday...high pressure crest over the region yielding light winds with
seabreezes near shore. Dry weather and good visibility.

Friday night...rain overspreads the waters from west to east. Rain
heavy at times toward sunrise Sat. Low risk of thunder south
waters. As low develops south of Long Island east to southeast
winds may increase to 20-30 knots toward sunrise Sat with strongest
winds south of Nantucket and Marthas Vineyard.

Outlook...Saturday into Tuesday...

Saturday...low to moderate confidence. S winds and seas increase
as a low pressure system approaches the waters. Visibilities may
be reduced at times in rain showers. Small craft advisories may be
necessary. Winds shift to the northwest as the cold front crosses the
waters.

Sunday...moderate confidence. North/northwest winds will increase as surface
pressure gradient tightens over the waters. Seas will build in
response. Small craft advisories may be needed.

Monday into Tuesday...upper level low over the Maritimes will
continue to keep pressure gradient tight keeping the winds up as
well as seas. Small craft advisories may be needed through the
period.

&&

Fire weather...
elevated fire weather conditions continue until sunset and then
diminish with nightfall. Until then expect northwest winds 20-30 miles per hour with
gusts up to 45 miles per hour and relative humidity values 15-25 percent. Recent rainfall
in central and eastern new eng will preclude red flag conditions
in these areas. However...less rainfall occurred in the CT valley
thus red flag warning continues for CT.

&&

Box watches/warnings/advisories...
CT...red flag warning until 8 PM EDT this evening for ctz002>004.
Massachusetts...Wind Advisory until 7 PM EDT this evening for maz004>007-
012>021-026.
Frost advisory from 3 am to 7 am EDT Friday for maz020-021.
New Hampshire...Wind Advisory until 7 PM EDT this evening for nhz011-012-015.
Rhode Island...Wind Advisory until 7 PM EDT this evening for riz001>007.
Frost advisory from 3 am to 7 am EDT Friday for riz006.
Marine...Gale Warning until 8 PM EDT this evening for anz230>237-250-
251-254>256.

&&

$$
Synopsis...nocera/dunten
near term...nocera
short term...nocera
long term...dunten
aviation...nocera/dunten
marine...nocera/dunten
fire weather...staff