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Area forecast discussion 
National Weather Service Taunton Massachusetts
959 PM EDT Monday Mar 30 2015

Synopsis...
a quiet night of weather prior to a clipper-low sweeping south of
the region bringing a mix of rain and snow to southern-most
portions of New England. Warmer temperatures towards the end of
this week then a more significant storm may approach late this
week.

&&

Near term /until 6 am Tuesday morning/...
10 PM update...
may see a few of the remnant rain showers/shsn associated with the cold
front still just to the west spill into the east slopes of the
Berkshires and portions of the CT valley until mainly about 1 am.
At which point drier air and the lack of additional support should
bring most of these to an end. Forecast on track otherwise. Main
adjustments are to bring probability of precipitation up to peed with this thinking.

Previous discussion...

Quiet weather. Scattered rain / snow showers conclude with only
remnant middle- to high-level clouds remaining. Breezy west-winds with
the potential for gusts up to 25 miles per hour. Cold air advection in wake
of the front which will sweep across the region into this evening.
Expect overnight lows to drop to around the low-30s...near-
seasonable for this time of year.

&&

Short term /6 am Tuesday morning through Tuesday night/...
Tuesday into Tuesday night...

Dependence of the forecast upon the track of the clipper disturbance
through the base of the broader cyclonic flow and its surface low
pressure reflection in areas of favorable baroclinicity / thermal
packing. The closer to the S New England shoreline...the greater the
impact. Went with a consensus blend of the forecast guidance noting
the ec / NAM along the north-end of the envelop with all other forecast
guidance suggesting a swing and a miss.

Forecast guidance consensus has clipper low track off the Delaware-Maryland-Virginia
coast along a west-east zonal-flow. Over-running precipitation appears
largely absent though west-east setup...discreet outcomes apparent with
frontogenetical banding along the parent warm front to the clipper
low around h7-8. In addition better moisture and qg-forcing maintain
S of New England parent with the low with consensus of guidance.

So feel the bulk of precipitation will remain offshore. Any activity
will be light mostly S of the Mass-Pike. Subsequently with dry low-
levels at onset feel wetbulbing / dynamic cooling of low-levels will
be minimal against highs that are forecast to warm into the low- to
middle-40s with daytime heating prior to the onset of the storm which
is expected to be late. Yet proceeding into a evening along with an
isallobaric response of winds that will funnel out of the north absent
of Arctic high pressure...feel precipitation-type will vary between rain /
snow from which am not expecting much in the way of accumulation.
If any...a trace at most on lingering snowpack / elevated surfaces.

Greatest impacts will be along the immediate S-coast and islands.
Majority of the impacts will be due to visibility restrictions with
snow...if anything.

&&

Long term /Wednesday through Monday/...
highlights...

* moderating more Spring-like temperatures late this week
* increasing chances for precipitation late this week into the weekend

Discussion...

Models are in good agreement on the broad scale with some expected
detail differences throughout the long term. A series of shortwaves
will move across the northeast Continental U.S. With attendant surface low
pressure centers/cold fronts moving over southern New England.
This will bring several chances of rain to the region throughout
the long term period of the forecast.

Wednesday...high pressure builds over southern New England bringing
dry weather and cooler temperatures. Expect below normal temperatures.

Thursday...temperatures begin to moderate as high pressure moves
offshore and low pressure moves into Quebec. Temperatures will
remain below normal but only by a few degrees. Excellent mixing...
coupled with a strong low level jet will likely result in gusty
winds.

Thursday night through Saturday...two shortwave troughs and their
attendant low pressure systems will move over the northeastern
United States...bringing a widespread rainfall to southern New
England. At this point...looking at mainly rain showers with
around an inch of quantitative precipitation forecast. There are still detail differences in the
models for this period so quantitative precipitation forecast amounts are likely to change.

Warmest day of the week should be Friday when they will actually
climb above normal...possibly giving US our first 60+ degree day of
the Spring. Temperatures fall Saturday...dropping back below normal
behind the cold front that trails the last low pressure system.

Sunday...high pressure builds in with dry weather and temperatures
well below normal for early April.

Monday...another chance of rain as low pressure moves into the Great
Lakes...pushing high pressure offshore. Temperatures begin to
moderate once again...creeping back towards normal.

&&

Aviation /02z Tuesday through Saturday/...
forecaster confidence levels...

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

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

00z update...

Lingering scattered -shra/-shsn concluding towards 02z. VFR. Cold front
sweeps across the terminals late into the evening hours behind
which winds veer W/NW. Gusts up to 25 kts.

Tuesday into Tuesday night...

Storm sweeping S of New England. Lowest conditions across S-most
New England with potential IFR with -sn. Otherwise low-end VFR /
MVFR ceilings and visibilities mostly S of the CT-RI-MA border. North/northwest winds
increasing late with gusts up to 25 kts for coastal terminals.

Kbos taf...gusty west-winds overnight.

Kbdl taf...quiet weather period.

Outlook...Wednesday through Saturday...

Wednesday and Thursday...high confidence. VFR. Gusty southwesterly
winds are possible Thursday.

Thursday night through Saturday...moderate confidence. MVFR
conditions are likely in rain showers. IFR conditions are possible
Friday night in fog.

&&

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.

Cold front sweeping the waters during the evening hours. SW-winds
backing northwest during which time gusts up to 25 kts will be possible.
Seas above 5 feet mainly on the outer waters...though could be
some lingering issues for Rhode Island / bi sound.

Tuesday into Tuesday night...
10 PM update...
have extended timing of east intra-coastal waters small craft
advisories as recent trend suggests stronger wind gusts with the
frontal passage later tonight into tomorrow morning. Went through 12z for
now to allow for better assessment of overnight model trends.
Also...will be adding Narragansett Bay and Boston Harbor with this
update.

Previous discussion...

Storm system sweeps S of New England. North/northwest flow...which will
increase towards the later half of the period. Will be a lull in
wind and wave action during which time a rain / snow mix will be
an issue mostly for the S-waters with potential visibility impact.
Then waves increase in excess of 5-feet with enhancing N/NW-flow.

Small-craft headlines continue for the outer waters throughout the
forecast period...while inner-waters expire overnight.

Outlook...Wednesday through Saturday...

Wednesday and Thursday...seas diminish as high pressure builds over
the waters. Northwesterly winds shift to the southwest diminishing
through the period. Occasional 25 knots gusts are possible on the
outer waters at times.

Thursday night through Saturday...seas increase as two separate low
pressure centers and their cold fronts approach the waters.
Southwesterly winds 15 to 20 kts shift to the northwest Saturday
morning. Gusts up to 30 kts are possible at times. Small craft
advisories are likely for both winds and seas at least on the
outer waters...if not on the interior bays and sounds at times.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 8 am EDT Tuesday for anz230>234-236-
251.
Small Craft Advisory until 2 PM EDT Tuesday for anz235-237.
Small Craft Advisory until 8 PM EDT Tuesday for anz250-254-255.
Small Craft Advisory until 5 PM EDT Tuesday for anz256.

&&

$$
Synopsis...rlg/sipprell
near term...doody/sipprell
short term...sipprell
long term...rlg
aviation...rlg/sipprell
marine...rlg/sipprell

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