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Area forecast discussion 
National Weather Service Taunton Massachusetts
948 am EDT Monday Mar 30 2015

Synopsis...

A cold front sweeps across New England today bringing a few
rain and snow showers. A fast-moving area of low pressure passes
south of New England Tuesday night...potentially bringing more
light rain and/or snow showers. A more significant storm may
approach late this week.

&&

Near term /until 6 PM this evening/...

10 am update...

Weak forcing within the low- to middle-levels of available moisture
on up to around 700 mb is lending to a band of light to moderate snow
across S New England. Reductions in visibility down to 2 miles or
less...otherwise the roads remain wet. Snow dragging down colder
air and blustery winds to the surface. Gusts up to 25 miles per hour. Will
see snow push offshore over the next hour or two allowing for a
lull in the weather and SW-flow to push temperatures up to around
the mid-40s...roughly 5 to 10 degrees below-normal for this time
of year with respect to highs.

Thereafter focus becomes along the cold front presently situated
across the east Great Lakes. As it sweeps southeast could see some shower
activity develop with frontogenetical forcing of available
moisture. Main forcing offshore of west-Atlantic moisture with a
strengthening 300 mb jet axis and attendant left-exit-region. Precipitable waters
and 700 mb moisture shifting east with aforementioned features that are
succinct with the present snow-band over east New England.

Yet main middle-level energy associated with the trough axis aloft
should yield enhanced ascent along the accompanying cold front.
Enough altogether to warrant at least chance probability of precipitation. Near-term
mesoscale guidance mixed on outcomes likely due to the diagnosis
of available moisture which in some cases is very dry. Yet
upstream activity is present. Confidence is highest along the
west-slopes of higher terrain with orographic tendencies...and across
far southeast New England where middle- to upper-level forcing is more
apparent.

SW-flow continuing along and ahead of the front 20-25 miles per hour...
backing out of the west/northwest gusting 20-30 miles per hour behind.

&&

Short term /6 PM this evening through 6 PM Tuesday/...

Tonight...
cold advection continues to support mixing into the night. Winds
above the surface will be 30-40 knots...expect some of this to mix
to the surface in gusts. Based on temperatures upstream...expect
lows in the middle 20s to lower 30s.

Tuesday...
weak high pressure will keep the weather dry much of the day.
Another northern stream shortwave races southeast across the Great
Lakes during the day. This will support a clipper low that moves
across the Middle Atlantic States during the afternoon. Forecasts
from the 00z model suite are farther north than previously with
the European model (ecmwf) farthest south. All models bring some measurable precipitation
into CT by evening...the GFS covers areas south of the Mass
Pike...and the NAM has measurable precipitation everywhere.

Temperature profiles suggest rain most places except snow in the
hills. Timing of the precipitation would be after 21z. We have shifted
our probability of precipitation farther north with chance probability of precipitation reaching to along/south of
the Mass Pike by 00z.

&&

Long term /Tuesday night through Sunday/...

Highlights...

* Alberta clipper moves through Tuesday night
* moderating Spring-like temperatures late this week
* increasing chances for precipitation during the Easter weekend

Overview...

Northwest flow will continue over the northeast with an Alberta
clipper moving through Tuesday night. Ridging over the Great Lakes
will build into New England by Wednesday into Thursday. Western trough
will move across the Continental U.S. As a cold front reaching the northeast
late Thursday through Sat. This system is also aided by an upper low
circling around Hudson Bay which will lower heights in the northeast
by next weekend.

Overall trend in the guidance has lead to a lower confidence. Model
guidance has trended northward with the run for the Alberta clipper
increasing precipitation for southern New England. 00z guidance continues
to show high pressure on Wednesday but the overall cold front is split
amongst guidance. The GFS remains quicker with the surface front
through the northeast/mid-Atlantic Friday compared to the other
guidance. Therefore continued to blend with wpc until the models
are more in agreement.

Details...

* Tuesday night...moderate confidence.

Next shortwave will quickly dive through the flow from Canada and
move just south of southern New England. Overall guidance has
trended towards which is increasing confidence that rain/snow will
occur. Believe that locations along and south of the Pike have the
best chance to see any snow accums once temperatures drop due to
wetbulbing. Still need to watch this system closely as there is
still spread amongst the models. Right now anticipate a quick 1-2
inches of snow along the South Coast...cape and island.

* Wednesday into Thursday...high confidence.

Weak ridge will build behind the clipper system Wednesday into Wednesday night.
This will allow for strong high pressure to build over southern New England. Latest
trends in the guidance suggest that Thursday will stay dry as high
pressure is slow to move offshore. Temperatures will be on the
increase with middle 40s on Wednesday and middle 50s on Thursday as warm air advection
increase ahead of approaching system.

* Thursday night into Saturday...low confidence in timing. Moderate
confidence in precipitation occurring.

Quasi-zonal flow will support changeable temperatures... modulated
by the surface cold front Thursday into Sat. Overnight min temperatures will be on
the mild side in advance of the cold front finally getting above
freezing for New England. In fact temperatures could be the warmest
they have been in over four months for the region. However as the
front passes expect temperatures to return to below average by about 5-15f.

Anticipate this cold front to cross the area either Thursday
night/GFS or Friday/ec and CMC. Appears that a wave will develop
along the front sometime late Friday or Sat. Because of the timing
difference...decided to blanket this time frame with chance probability of precipitation and
hopefully within the next 24 hours can put better detail into the
forecast. Can stay that this system does look warm so expect precipitation
type to be more of the rain form. However on the back side of the
front could see some wet flakes.

Sunday...moderate confidence.

High pressure begin to build into the region behind the cold
front. Temperatures will continue to be below average for this
timeframe.

&&

Aviation /14z Monday through Friday/...

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.

MVFR-IFR with -sn. Otherwise low-end VFR to MVFR ceilings. Cold front
sweeps terminals around middle-afternoon with some scattered -shra. Gusty
SW-flow ahead with gusts 20-25 kts...backing west/northwest with frontal
passage with gusts of 25-30 kts.

Tonight...
VFR. Gusty west winds behind the front may reach 25-30 knots.

Tuesday...
VFR. MVFR ceilings/visibilities possible across CT and Rhode Island toward evening.

Kbos taf...-sn and IFR visibilities clearing by 14z. Scattered -shra/-shsn
activity through the remainder of the day...but feel impacts will
be no lower than MVFR.

Kbdl taf...will hold impacts at low-end VFR. Could see brief
periods of MVFR ceilings.

Outlook...Tuesday night through Friday...high confidence.

Tuesday night...VFR for most of the period. May see MVFR south of
Mass Pike in rain/snow showers.

Wednesday into Thursday...VFR.

Friday...MVFR in showers...could see IFR conditions by Friday evening.

&&

Marine...

Forecaster confidence levels...

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

Short term /today through Tuesday/...high confidence.

10 am update...no major changes.

Today...a cold front crosses New England during the afternoon and
moves across the waters toward evening. Southwest winds will gust
to near 25 knots in advance of the front. West winds trailing the
front will gust 25-30 knots. Seas will build to 5-7 feet on the
outer waters and rhode islands/Block Island sounds. Small Craft
Advisory continues on all waters.

Tonight...gusty west winds continue overnight. Seas of 5-7 feet
linger on the outer waters and Rhode Island sounds. Small Craft
Advisory continues.

Tuesday...gusty winds will diminish as weak high pressure builds
briefly over the waters. Lingering small crafts on the outer
waters.

Outlook...Tuesday night through Friday...moderate confidence.

Tuesday night...quick-moving system will move over southern
waters. This will keep both seas and winds above Small Craft
Advisory thresholds. There is a low probability of gales force winds.

Wednesday into Thursday...high pressure will arrive...allowing
for seas and winds to relax.

Friday...another cold front approaches the waters...resulting in
increasing southwest winds and seas.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 11 am EDT Tuesday for anz231-232.
Small Craft Advisory until 3 am EDT Tuesday for anz230-233-234-
236.
Small Craft Advisory until 4 PM EDT Tuesday for anz235-237-256.
Small Craft Advisory until 8 PM EDT Tuesday for anz250-254-255.
Small Craft Advisory until 9 am EDT Tuesday for anz251.

&&

$$

Synopsis...wtb/dunten
near term...wtb/dunten/sipprell
short term...wtb
long term...dunten
aviation...wtb/dunten/sipprell
marine...wtb/dunten

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