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Area forecast discussion
National Weather Service Taunton Massachusetts
136 am EDT Wed Mar 29 2017

wet weather continues through tonight. Improving into Wednesday
into Thursday as high pressure delivers cool and dry weather.
Low pressure from the Ohio Valley Friday will redevelop south of
New England Friday night into Saturday. This bring snow, mixed
precipitation and rain Friday into early Saturday, followed by
dry weather Sunday and Monday.


Near term /until 6 am this morning/...
10 PM update...
with low pres continuing to very slowly deepen, and now about
100nm east of the Delmarva, the deformation banding across much of
S New England continued to contract. This will continue to have
two impacts, in that it will allow the rain to end across west and
northwest portions of Massachusetts/CT over the next few hours, but increase
rainfall rates across portions of east Massachusetts and Rhode Island through early am.
Will taper pops toward latest hrrr which continues to capture
this progression well. Otherwise, bulk of the forecast remains
on track with this update.

Previous discussion...

Widespread rain with a low risk of thunderstorms. If any, mainly
isolated. Anomalous deep-layer moisture with precipitable waters
in excess of an inch undergoing deep layer forcing ahead of a
low emerging out of the mid-Atlantic and sweeping east immediately
S of New England. Watching closely attendant frontal boundaries
including that of The Kink across our region for focused areas
of frontogenetical convergence and subsequent moderate to perhaps
heavy rain, as well as any instability that creeps north as indicated
by the latest Storm Prediction Center mesoanalysis into S New England.

Latest hrrr / rap model trends seem to be highlighting trends well
enough. A blend is preferred. Continued thinking of a decent slug
of rain. Amounts of 0.50 to 0.75 with the heavier amounts focused
S/E. Some locations, especially along the S coast may see higher
amounts where there is a greater risk for convection.

Otherwise low clouds, dreary, light east flow. With the increasing
moisture across the region, will see clouds lower resulting in
patchy dense fog redeveloping across the region, especially over
the high terrain. Visibility down to a quarter mile or less in
spots. More than likely holding through midnight, a gradual west
to east progression of fog erosion as winds turn northwest ushering into
the region cooler and drier air towards morning.

Temperatures mainly holding in the 40s but dropping into the
30s via cold air advection, either via North/East winds with initial
high pressure damming, or behind the departing low late with the
aforementioned north/west cool, dry winds. Temperatures should remain
above freezing across all of S New England, so no concerns at
the moment for black ice developing on area roadways.


Short term /6 am this morning through 6 PM Thursday/...
Wednesday and Wednesday night...

Drying out and turning breezy. Departing low pressure deepens out
across the Georges Bank as a 1030+ high pressure builds S out of
Canada. Combination of the tight gradient and pressure rises, cold
air advection proceeding with an increasing component of isallobaric
flow, will see winds increase out of the northwest with gusts up to 30 to
35 mph late in the day into evening, especially out across east/southeast MA,
given stronger winds aloft at times during efficient boundary layer
mixing up to 850 mb.

Conditions clearing during the morning. A mix of sun and clouds thru
the remainder of the day and clearing overnight. Given the late-
March sunshine with a warm airmass aloft lingering, albeit cold air
advection will be ongoing, temperatures warm up around the upper 40s
to low 50s around midday. Dropping down into the 20s overnight. Dry
air and breezy winds through the day, roads should dry out.


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

* dry and seasonable Thursday
* snow and rain developing Fri and continuing into early Sat
* plowable snow likely over higher elevations
* dry and seasonable Sunday and Monday

*/ discussion...


High pressure builds across new eng which will bring sunshine and
seasonable temps. It may be a bit breezy in the morning across
eastern new eng given the pressure gradient in place, but trend will
be for diminishing wind during the day. 850 mb temps around -5c in
the afternoon supports highs mid 40s to around 50 degrees.

Thursday night through Saturday...

Complex forecast evolving as potent southern stream trof approaches
Fri into Sat and interacts with northern stream energy. Result will
be a primary low lifting through the Ohio Valley and eastern lakes
Fri with deepening secondary low expected south of New England
Friday night into Sat. As is typical at this time range there are
model differences in track and intensity of the low pres which will
affect qpf, thermal profile and potential snow accum.

There will be two periods of precip, the first assocd with the warm
advection ahead of the primary low during Fri, with a second pulse
Fri night into early Sat and this may be heavy at times depending on
the track and intensity of low pres to the south.

Expect precip to overspread southern New England from west to east after midnight Thu
night to daybreak Friday. With strong high pres to NE the column
will be sufficiently cold for most areas to begin as snow. However,
due to marginal boundary layer temps snow may mix or even change to
rain at times when precip intensity is light, especially near the
coastal plain. During heavier periods, the precip will likely be
snow given cold temps aloft. Minor accum are possible all the way to
the coastal plain but any accum during the day will be confined to
colder surfaces with most roads remaining wet. Exception is across
higher elevations in interior Massachusetts and northern CT where colder temps
may result in some accum on roadways.

The second period of precip will be Fri night into early Sat assocd
with comma head from intensifying low pres to the south. There are
differences in the track which will impact intensity of precip but a
period of heavy precip is possible. The uncertainty is temps will be
warming aloft from SW to NE so ptype is very much uncertain,
especially north of the Pike. Expect mainly rain possibly mixed with
sleet at times south of the Pike. To the north, expect snow changing
to sleet, freezing rain and rain but this is uncertain and subtle
changes in the thermal profile and timing would yield different
outcomes. Several inches snow accum possible north of the Pike with
best chance of warning level snow over the east slopes of the
Berkshires and northern Worcester Hills. There is also a risk of
some ice accretion over the higher elevations as precip transitions
to rain with temps hovering around freezing.

Precip should taper off Sat morning with improving conditions in the


Showers may linger late Saturday evening into Sunday
morning as the low pressure system moves offshore. With the low
offshore and a high pressure area building into the region, skies
will clear throughout the day. Winds will continue to diminish along
the coast, with winds gusting to 20 mph throughout the day. As the
high pressure moves in, northerly winds will become westerly.
Temperatures will be seasonable Sunday with high temperatures in the
upper 40s to low 50s across the region.

Monday and Tuesday...

Both days will be seasonable with temperatures ranging in the upper
40s to mid 50s. Monday will be dry as the high pressure remains
overhead. Skies will be mostly sunny throughout the day with near
calm winds.

A low pressure approaches from the southwest Tuesday, bringing
widespread precipitation to the area. Precip will move into the area
after midnight, moving from west to east across southern New
England. Rain accumulations around a quarter inch are expected, with
locally high amounts of a half inch.


Aviation /06z 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/...

Through 18z...high confidence in trends, lower confidence in
exact timing.
Rain and low clouds will be gradually shifting east through late
morning. This will allow LIFR/IFR to gradually give way to MVFR
then VFR as the low clouds break from W-E. Timing may be off a
bit in tafs.

This afternoon and tonight...high confidence.
VFR except for maybe some spotty MVFR ceilings across Cape Cod and
the islands late this afternoon and evening. Otherwise, breezing
northwest flow with gusts 25-30 across east Massachusetts/Rhode Island and 20-25 kt across west
Massachusetts and CT. These dissipate somewhat late tonight.

Tomorrow...high confidence.
VFR. Northwest flow weaker than today.

Kbos taf...high confidence in taf trends, a return to brief IFR
this morning possible before improvement after sunrise. Timing
may be off a bit.

Kbdl taf...high confidence in taf trends, a return to brief IFR
this morning possible before improvement after sunrise. Timing
may be off a bit.

Outlook /Thursday night through Sunday/...

Thursday...high confidence. VFR. Winds diminishing.

Friday-Saturday...moderate confidence. Conditions lowering to IFR
with areas of LIFR with snow and mixed rain/snow transitioning to
rain south of the Pike Fri evening. Snow changing to rain and
freezing rain north of the Pike Fri evening. Precip ends Sat
morning with improving conditions in the afternoon.


MVFR conditions becoming VFR in east Massachusetts as showers linger
in association with a low pressure area moving offshore. VFR
conditions for the remainder of the area.


forecaster confidence levels...

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

Short term /through Thursday/...

Through Wednesday night...

Rain and some visibility restrictions will impact the waters
overnight as an area of low pressure passes over the S waters.
Exiting east out over the Georges Bank as high pressure builds S
out of Canada, northwest flow increases with the potential for gusts up
around 30 kts developing Wednesday evening and continuing over-
night with a low risk of gales. Seas build towards 6 to 8 feet
on the outer waters. Small craft advisories issued accordingly
with the increasing north winds beginning Wednesday into Wednesday

Outlook /Thursday night through Sunday/...

Thursday...high confidence.

Small Craft Advisory northerly gusts 25-30 kt in the morning eastern waters
diminishing in the afternoon.

Friday into Saturday...moderate confidence.

Easterly winds below Small Craft Advisory Fri. Increasing southeast winds Fri night with
Small Craft Advisory gusts likely then shifting to NE Saturday. Vsbys reduced in
rain and fog mixed with snow Friday.

Sunday...moderate confidence

Low pressure area moving off the coast of New England will result in
diminishing winds along the southeast waters. Small Craft Advisory may
be needed.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory from 11 am this morning to 8 am EDT
Thursday for anz231>234-251.
Small Craft Advisory from 5 PM this afternoon to 8 am EDT
Thursday for anz230.
Small Craft Advisory from 8 PM this evening to 8 am EDT
Thursday for anz235>237.
Small Craft Advisory from 5 am early this morning to 8 am EDT
Thursday for anz250-254>256.


near term...doody/sipprell

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