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Area forecast discussion
National Weather Service Taunton Massachusetts
1022 am EDT Fri Mar 24 2017

Synopsis...
high pressure along the eastern Seaboard moves offshore and
brings warmer and gusty weather this afternoon. A cold front
will push south across the region Saturday. This stalled front
will move northward on Sunday, resulting in a battle of
airmasses. This could bring a period of wintry precip Saturday
night, and again Sunday night. Heavy precipitation is possible
Monday as low pressure system moves over southern New England.
Another shot of precip is possible late Tuesday from passing
cold front.

&&

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

Low level southwest jet of 30-40 knots showed up on the morning
soundings, along with a temperature inversion 200-mb deep. Both
are signs of the warm advection starting to take place aloft.
Surface dew points are also climbing as the moisture content
increases. Radar shows echoes now moving over western and
northeastern sections of southern New England, but with signs of
diminishing as they move over the drier air. More substantial
echoes over the Catskills of New York are moving east and will cross
southern New England during the early afternoon. This may be
our best chance for any precipitation.

Most of the mid-morning temperatures were 3-5f milder than the
hourly forecasts, another sign of the milder air moving in. We
adjusted the temperature forecasts up a little based on that.
Based on these temps, we would expect the precipitation to be
mainly rain. Could be a little snow/sleet where enough
evaporative cooling takes place, but amounts would be light.

&&

Short term /6 PM this evening through 6 PM Saturday/...
tonight...

Clouds and a southwest flow of milder air will keep temperatures
from falling too much, and most of that should be this evening.
Still thinking temperatures may even rise a little overnight.
With a front just to our north, maintained a chance of rain
across northern MA, but low values for pops.

Saturday...

This front slowly moves south across our region. Near normal
temperatures expected, so any precipitation should be rain. Not
expecting a washout. The greatest risk for these showers will be
toward the western half of southern New England.

&&

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

* a period of wintry precip is possible Saturday night and again
Sunday night
* unsettled weather pattern will continue into Wednesday
* improving conditions during the later half of next week

Pattern overview...

00z models and ensembles are in agreement with the general
synoptic pattern for the extended. Still some timing and
thermal issues but overall confidence is improving. Active
pattern for the region with split flow aloft and several
shortwaves ejecting in from the Pacific. First wave is a 500mb
closed low over the Midwest on Sunday. This low deamplifies into
an open wave as it approaches the northeast Monday. Due to the
confluent flow aloft, high pressure persists over northern New
England keeping surface temperatures cool, resulting in mixed
precip at times for the weekend into early next week. Heavier
precip possible on Monday as first open wave moves overhead. A
second wave will follow a similar path from the plains towards
the northeast before meshing or partially interacting with the
northern jet stream on Tuesday. This will result in another
system for New England tues/Wed with high pressure to follow.

Details...

Saturday night into Sunday...moderate confidence.

Confluent flow aloft with surface cold front south of southern
New England. Cold air drainage from the high pressure over
northern New England will drop surface temps below freezing.
This is shown in surface winds which are due north. Mid-level
ridging will keep a warm layer around 850 mb which would aid in
the potential for mixed p-type. Biggest question is if there is
enough low level lift and/or overrunning for precipitation to
develop overnight. The higher Theta- E values are well south of
the Pike and moreso near the South Coast, which would limit the
mixed precip type as surface temps should remain above freezing
that far south. Still a lot of uncertainty with this time, but
believe that with the flow aloft, there appears to be enough low
level moisture for some spotty precip. If this occurs than a
Winter Weather Advisory may be needed for the freezing rain
potential.

For Sunday, cold front will stall near the mid-Atlantic as high
pressure moves southeast into the Gulf of Maine. Guidance
indicates that low levels will dry out Sunday morning keeping
the first half of the day dry. However, with mid-level ridge
axis overhead will see and increase in moisture thanks to
southwesterly flow aloft. At the surface easterly flow will
begin to dominate increasing the low levels throughout the day.
This could result in low clouds and drizzle. Surface temps will
warm above freezing thanks to mid-level ridge, but some areas
may struggle as cold air may be slow to dislodge/cold air
damming. Still a lot of uncertainty with this time frame.

Sunday night into Monday...moderate confidence.

Stalled front south of the region looks to return back north as
a warm front late Sunday into Monday, as surface low pressure
moves into the Great Lakes. Although warmer air aloft should
move easily back into the region, the low-level cold air may be
a little tougher to dislodge this time due to the nearby surface
high pressure. Believe this is the timeframe where we will see
the heaviest precip due to passage of the open wave and
development of a secondary low over the region. Still some
uncertainty with the thermal profiles but cross-sections,
soundings and even cips analogs show this timeframe has the
potential for icing especially north of the Pike. Still some
uncertainty with this timeframe as a difference of a degree or
two in the thermal profiles will change the p-type. Will
continue the mentioning of snow, sleet, ice and/or rain. Winter
weather advisories may be needed.

Monday night into Wednesday...moderate confidence.

Weak ridging aloft as surface low moves offshore. Any lingering
showers will come to an end. 850 mb temps will continue to warm
overnight which will help keep surface temps above freezing.

Second wave will move into the region late Tuesday into
Wednesday. This wave will drag a cold front across the region
bringing a periods of rain. Temperatures will remain seasonable
for both days.

Thursday into Friday...moderate confidence.

Cold front will be offshore as upper level trough begins to take
hold over the northeast. Appears to be the potential for another
Arctic front with high pressure to follow.

&&

Aviation /14z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /through Saturday/...moderate confidence.

This afternoon and tonight...

Mainly VFR with scattered MVFR possible in heavier showers. The
greatest risk for MVFR conditions will be north of the Mass
Pike, and especially across the higher terrain. Any frozen
precipitation should change to rain during late morning/early
afternoon. Southwest winds will gust 25-30 knots during the day,
highest along the coast and higher terrain. Winds diminish
later tonight.

Saturday...periods of light rain with areas of MVFR cigs and
local MVFR-IFR vsbys.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Saturday night through Tuesday/...

Saturday night...high confidence. Northerly winds with spotty
precip overnight. Terminals north of the Mass Pike have the best
chance for wintry precip.

Sunday into Monday...moderate confidence. Showery weather to
start with possible MVFR to IFR cigs. Precip chances increase
into Monday which could result in mixed precip for terminals
north of the Mass Pike.

Tuesday...moderate confidence. Dry to start with showers in the
afternoon from passing cold front. Cigs may start out as VFR
lowering to MVFR.

&&

Marine...
forecaster confidence levels...

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

Short term /through Saturday/...

This afternoon...moderate confidence.

High pressure moves well offshore, bringing southwest winds to
the waters. Potential for wind gusts 25-35 knots. This will
build seas with 5 foot heights on many of the waters this
afternoon. Patchy light rain may bring brief visibility
restrictions.

Gale warnings for the eastern outer coastal waters, where
confidence is highest for a period of 35-40 kt gusts. Potential
for similar gusts across the other coastal waters near the cape
and islands, just not enough confidence there will be a long
enough duration to warrant a Gale Warning. Will continue the
small craft advisories across the remaining southern New England
coastal waters.

Tonight...high confidence.

Southwest winds diminish overnight, and become west toward
morning. Rough seas linger across the outer coastal waters, and
ocean-exposed south coastal sounds. Small craft advisories
will lower on Boston Harbor and Narragansett Bay, but linger
on the remaining waters.

Saturday...high confidence.

West winds becoming north to northwest as a cold front pushes
slowly south across the waters. This front is not expected to
push south of the waters until late afternoon.

Outlook /Saturday night through Tuesday/...

Sunday...moderate confidence. Cold front will be south of the
waters as surface high pressure moves northeast of the region.
Conditions should remain below Small Craft Advisory but if the front gets closer
than seas and winds may be a bit stronger.

Monday...moderate confidence. Approaching upper level system and
passing warm front will increase precip as well as wind and seas
of the waters. Small Craft Advisory may be needed.

Tuesday...moderate confidence. Cold front will pass over the
waters increasing them to above 5 feet. Small Craft Advisory may be needed.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 6 am EDT Saturday for anz232>235-
237.
Small Craft Advisory until 8 PM EDT this evening for anz230.
Gale Warning from 4 PM this afternoon to 9 PM EDT this evening
for anz231.
Small Craft Advisory until 10 PM EDT this evening for anz236.
Gale Warning until midnight EDT tonight for anz250-254.
Small Craft Advisory until 3 am EDT Saturday for anz251.
Small Craft Advisory until 6 PM EDT Saturday for anz255-256.

&&

$$
Synopsis...Belk/dunten
near term...wtb/Belk/dunten

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