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Area forecast discussion 
National Weather Service Taunton Massachusetts
419 am EDT Wednesday Apr 1 2015

Synopsis...
dry but chillier weather moves through today...followed by warming
on Thursday. A few waves of low pressure ahead of a slow moving
cold front will bring periods of showers late Thursday night into
Saturday morning with mild temperatures. Dry and chillier weather
follows later Saturday into Saturday night. Fast moving low
pressure may bring a few rain and/or snow showers to the region
Sunday into Sunday night. Periods of unsettled weather possible
for the first half of next week...but confidence is quite low.

&&

Near term /until 6 PM this evening/...
msas shows deepening low pressure colocated with an area of convection
well S of Nantucket this morning. This convection has usurped much
of the moisture and shifted the best lift to the S of the region.
In fact...even though there are light returns on ack...observation suggest
this is not reaching the ground at this time. Dry air is gradually
entraining in from the north now that winds are north-northwest. Already have
issued an Special Weather Statement for black ice across CT where temperatures have dropped
below freezing...but will need to watch through the early morning
hours for portions of southern Rhode Island and southeast Massachusetts where light rain could
allow for light black ice development early this morning.

Otherwise today...plenty of sunshine is expected as high pressure
moves in from the west. Cold advection aloft will lead to full
mixing...and 850 mb temperatures -6c to -8c will keep high temperatures below
normal in spite of this. Therefore...expect highs mainly in the
middle 40s. Breezy early with northwest wind gusts to around 20 miles per hour at
times.

&&

Short term /6 PM this evening through 6 PM Thursday/...
tonight...
dry weather prevails most of the night as high pressure crests over the
region. The combination of this dry air...and mass fields
suggesting weak pressure gradient...and feel we have a good setup for
radiational cooling early. Will likely see a few middle-high clouds
spill over from the west late which will slow the process...but given
the potential...will likely see temperatures fall back into the 20s
across much of the region in spite of the increasing clouds late.

Tomorrow...
warm front will be sliding mainly north of the region...but the nose
of attendant low level jet and middle level moisture will sliding across the northern
tier of southern New England. Although there is some middle level moisture
and light overruning lift to work with...it will be entering a
generally dry airmass with high pressure and subsidence just offshore.
Therefore...will continue with mainly dry probability of precipitation. However...not out
of the question some daytime showers are noted especially across
the north. Otherwise...strong SW pressure gradient will lead to gusts
25-35 miles per hour at times. This will mitigate East Coast sea breezes but
likely enhance S coastal sea breezes. Therefore...with 850 mb temperatures
warming as the front moves through will see high temperatures shift above
normal in spite of the clouds. Mainly middle 50s.

&&

Long term /Thursday night through Tuesday/...
highlights...

* mild Thursday night/Friday and possibly into part of Sat
* periods of showers Thursday night into Sat am but not a total washout
* much cooler sun/Sun night with even a few rain/snow showers poss.
* Unsettled weather possible at times for first half of next week

Details...

Thursday night and Friday...

An approaching shortwave will result in a burst of instability/middle
level lift late Thursday night into Friday am. Scattered showers are
expected and we can/T rule out a few embedded thunderstorms with
marginal elevated instability. Precipitable waters 1 to 2 Standard deviations
above normal may result in some brief localized heavy rainfall...but
not significant flooding problems are expected. Precipitation will
be showery so not expecting the entire period to be a washout. May
even see a lull in the activity later Friday am into the afternoon
north of the Massachusetts Pike...as drier air briefly works into the region.

Low temperatures Thursday night will only fall into the 40s...but may see some
areas already above 50 by daybreak Friday with strong southwest low
level jet and warm advection. Inversion will keep strongest winds
off the deck...but some southwest wind gusts of 25 to 35 miles per hour are
possible especially in heavier showers. High temperatures on Friday are
tricky and will depend on if we can muster any breaks in the cloud
cover...but think there is a pretty good chance much of the area
breaks 60. Low risk some locations reach between 65 and 70 if more
sunshine occurs then currently expected.

Friday night in Saturday...

Second and stronger area of low pressure will track across a cold
front that will be sagging to our south Friday night and Sat am. The
models disagree on the track with the GFS tracking the system across
the far southeast New England coast...while the European model (ecmwf) tracks in the
furthest northwest into interior southern New England. Uncertainty
remains on the exact track...but it looks like we will see a decent
period of rain sometime Friday night into Sat am. There is a low risk
rain could end as a bit of wet snow Sat am...mainly in the higher
terrain. The GFS is most aggressive in this scenario even showing
the risk for a few inches in the high terrain...but again remains
the cold outlier so a low probability at this point.

Saturday night and Sunday...

Chillier air works back into the region later Saturday and into
Saturday night. A wave of low pressure may approach from the west
Sunday and/or Sunday night. Right now the models have the system
tracking near or just north of our region...keeping the bulk of the
precipitation so would just expect a few rain or snow showers.
However...track very uncertain in this time range so if it shifts
south that will increase our chances in a period of steady rain or
even wet snow based on colder thermal profiles.

Monday into Wednesday of next week...

Forecast confidence is quite low. A Battle Ground will setup with
very cold air to our north across eastern Canada and much milder air
to our south...as low pressure approaches from the west. The 00z
GFS/ggem have the initial low pressure system tracking to our west
eventually putting US on the mild/showery side of the system.
Meanwhile...the 00z European model (ecmwf) and even a few of the gefs ensembles are
much further south resulting in a cold rain and even some
accumulating wet snow. Whether or not we see any snow across any of
our region...probably smart to lean on the cooler side with temperatures
given time of year and high pressure to the north. Regardless...a
lot of uncertainty at this point.

&&

Aviation /07z Wednesday through Sunday/...
forecaster confidence levels...

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

Short term /through Thursday/...high confidence.

Today and tonight...
VFR. Mainly clear today with a few more middle clouds by early Thursday
morning. North-northwest wind gusts 15-20 knots during the day today diminish
tonight.

Thursday...
mainly VFR. More clouds expected and maybe an isolated shower in
the west. Winds shift to the SW.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook...Thursday night through Sunday...

Thursday night through Saturday am...moderate confidence. Mainly
MVFR conditions with even some IFR ceilings/visibilities possible at times.
Periods of showers with even a few isolated thunderstorms possible
late Thursday night into Friday am. Also...low level wind shear expected with southwest
winds of 60 to 70 knots between 2 and 3 thousand feet late Thursday night
into Friday.

Saturday afternoon into Sunday...moderate confidence. Mainly VFR
conditions but a period of MVFR-IFR conditions are possible sometime
Sunday and/or Sunday night in a few rain/snow showers.

&&

Marine...
forecaster confidence levels...

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

Short term /through Thursday/...high confidence.

Today into tonight...
high pressure moving in from the west will lead to gusty northwest winds
early...to about 25 knots. Wind driven seas of 5-6 feet possible.
Therefore...current small craft advisories will continue through
this morning/early afternoon. Lighter winds tonight with a period
of quiet boating weather expected.

Thursday...
winds shift to the SW and increase by Thursday afternoon. Gusts to
around 20 knots on the ocean waters...but may reach 25-30 knots near
shore. Expect gradually building swell as well. Small Craft
Advisory may be needed for the afternoon/evening timeframe.

Outlook...Thursday night through Sunday...

Thursday night and Friday...moderate confidence. South to southwest
wind gusts of 20 to 30 knots expected later Thursday night into Friday am
with strong low level jet. Low risk of some brief marginal gale
force wind gusts in heavier showers/isolated thunderstorms...but
given inversion will not hoist a gale watch.

Saturday and Sunday...moderate confidence. Strong northwest Small Craft Advisory wind
gusts expected in the cold air advection pattern behind a cold front
Sat afternoon into Sunday. Even a period of marginal gale force
wind later Sat into Sat night in the strong cold air advection
pattern.

&&

Climate...
model output statistic /MOS/ has switched from cool season to
warm season equations with last evening/S 00z 4/1 model run.
Early in the Spring season this sometimes lends itself to MOS
having a warm temperature bias during anomalous cool temperature regimes.
Tomorrow may be an example when 925 and 850 mb temperatures run about -1
Standard deviation colder than climatology.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 2 PM EDT this afternoon for anz231-
251-256.
Small Craft Advisory until noon EDT today for anz235-237.
Small Craft Advisory until 6 PM EDT this evening for anz250.
Small Craft Advisory until 2 am EDT Thursday for anz254-255.

&&

$$
Synopsis...Frank/doody
near term...doody
short term...doody
long term...Frank
aviation...Frank/doody
marine...Frank/doody
climate...

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