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Area forecast discussion 
National Weather Service Taunton Massachusetts
705 PM EDT sun Aug 2 2015

Synopsis...
the threat of showers and thunderstorms returns Monday evening into
Tuesday. After a dry day Wednesday...a period of unsettled weather is
possible sometime Thursday into Saturday...but confidence is low on
the timing of potential wet weather.

&&

Near term /until 6 am Monday morning/...
7 PM update...
diurnal cumulus dissipating with loss of heating which will lead to a
mainly clear evening. A warmer night is expected with southwest
flow slowly increasing the dewpoints across southern New England.
Main concern will be this increasing moisture and flow off the
water resulting in fog...low clouds...and drizzle developing on
the South Coast later tonight.

&&

Short term /6 am Monday morning through Monday night/...
areas of fog...low clouds...and drizzle on the South Coast will
diminish by midday.

Then...an anomalous upper low in Ontario will have the most
influence on our weather...particularly Monday night. As low
pressure moves into Quebec on Monday it will pull a cold front
through New York state and portions of northern New England. Much
if not all of Monday will be dry for southern New England as the
front stays to the west of the region until late in the evening. If
anything...a few stray showers and thunderstorms may move into
northwestern Massachusetts by late in the afternoon to early
evening as the front approaches.

Likely a hot...humid summery day with highs in the upper 80s away
from the South Coast where onshore flow will keep temperatures in
the lower 80s.

Monday night is somewhat of a puzzle. The cold front moves slowly
into southern New England overnight and stalls by early Tuesday
morning. Ordinarily this would not be a particularly good time for
strong storms or even thunderstorms and the models tend to indicate
as much with very little in the way of quantitative precipitation forecast exhibited in quite a few
of the models. This is a bit of a red flag as if we are going to
have storms we have to have some quantitative precipitation forecast. However...we also have
increasing instability through the night as the dewpoints shoot up
ahead of the front. All the models are indicating the cape
increasing to 1000-2000 j/kg as we move through the night. Middle
level lapse rates and 0-6km bulk shear values also increase after
06z Tuesday. So cannot rule out a strong to severe thunderstorm
across the area and expect at least showers and thunderstorms for
much of southern New England during the overnight period. The
greatest threat with these storms will be gusty to damaging winds
and perhaps some small hail.

&&

Long term /Tuesday through Sunday/...
highlights...
* showers and thunderstorms possible Tuesday
* unsettled weather possible for the end of the week into Sat...but
confidence is low on timing
* temperatures trending below normal the end of the week into the weekend

Overview...
models agree on large scale pattern through the end of the week
featuring a broad trough across the Great Lakes into the northeast...but
there are significant differences on the handling of shortwaves
rotating through the flow and timing/track of a wave of low pressure
approaching the region toward the end of the week. This has an
impact on sensible weather for the end of the week into the
weekend...especially regarding the timing of potential wet weather.
Above normal temperatures Tuesday will trend below normal toward the end of
the week into the weekend.

Dailies...

Tuesday...
cold front will be nearly stationary or moving very slowly east across
southern New England during the day as it waits for upstream shortwave energy to move
through. Potential eml advects into the region with middle level lapse
rates near 7 c/km. This will result in sbcapes up to 2000 j/kg
across east new eng where dewpoints climb near 70 ahead of the front. 0-
6km shear near 40 knots where maximum instability suggesting potential for
strong to severe thunderstorms...mainly east half new eng. The one red flag is
the GFS/European model (ecmwf) not generating any quantitative precipitation forecast as timing of the front and how
quickly drier air moves in from the west is not certain so not a
high confidence forecast. If storms do materialize...timing will be
earlier than what is normally expected...likely in the morning
through early afternoon as drier air will be moving in from the west
pushing instability axis offshore. Temperatures will reach well into the
80s with a few locations possibly touching 90.

Wednesday...
middle level shortwave and cooler air aloft move through new eng. Low
probability for a few showers as attending surface trough provides weak low level
convergence...but expect mainly dry weather. Temperatures ranging from middle
70s higher terrain to lower 80s coastal plain.

Thursday through Saturday...
low confidence forecast as models differ on handling of shortwave
energy and low pressure approaching the region. It is likely that a
period of unsettled weather will affect the region but timing is
uncertain. GFS is an outlier and brings a slug of rain through on
Thursday while European model (ecmwf)/ggem/UKMET bring rain mostly on Friday...possibly
lingering into Sat. We have highest probability of precipitation Friday into Sat but
confidence is low. Temperatures below normal.

Sunday...looks mainly dry with high pressure moving into the region.
Temperatures slightly below normal.

&&

Aviation /00z Monday through Friday/...
forecaster confidence levels...

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

Tonight...VFR and dry weather for most of the region. Area of
concern is South Coast of Rhode Island and Massachusetts where IFR in low ceilings/fog and
drizzle is possible. High confidence inland...lower confidence
along the South Coast.

Monday...IFR possible South Coast of Massachusetts and Rhode Island in patchy fog and
drizzle. Improving as the day progresses. VFR elsewhere with low
risk of T-storms western Massachusetts and CT late in the day. Moderate
confidence.

Monday night...mainly VFR. MVFR/IFR conditions with scattered rain showers and
thunderstorms and rain. Low risk of a strong storm towards daylight Tuesday
morning.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Tuesday through Friday/...

Tuesday...moderate confidence. VFR much of the time. MVFR/IFR
within any scattered showers and thunderstorms through the period.
A low risk for a strong storm is possible.

Wednesday...moderate confidence. VFR.

Thursday into Friday...low confidence. A period of showers and
MVFR/IFR possible but timing is uncertain. Latest indications are
that best chance for wet weather will be on Friday.

&&

Marine...
forecaster confidence levels...

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

Short-term /through Monday night/...moderate confidence.

Tonight...quiet boating weather with increasing southerly to
southwesterly winds. Low clouds...fog...and drizzle are likely to
develop along the South Coast of mass and Rhode Island limiting
visibilities at times.

Monday...south-southwesterly winds and seas increase throughout the
day in advance of an approaching cold front. Small craft conditions
expected by late afternoon so have hoisted a Small Craft Advisory
for the outer waters and for Rhode Island and Block Island Sound for
late Monday afternoon through Monday night.

Monday night...Small Craft Advisory up for outer waters and Rhode
Island and Block Island sounds. Seas increase to 5 to 6 feet by
early Tuesday morning with southerly winds gusting to near 25 kts as
a cold front begins to move over the western waters.

Outlook /Tuesday through Friday/...moderate confidence.

Tuesday...moderate confidence. A period of prefrontal SW gusts to 25
knots possible especially over the S coastal waters into Tuesday
evening...then winds diminishing and becoming west overnight. Seas
building to 5-7 feet over the outer southern waters.

Wednesday...moderate confidence. West/SW winds below Small Craft Advisory but gusts to
20 knots possible. Seas subsiding.

Thursday into Friday...low confidence. Winds and seas will depend on
track and timing of low pressure approaching the region. Could see a
period of gusty NE winds...especially Friday.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 4 PM Monday to 6 am EDT Tuesday for
anz235-237-250-254>256.

&&

$$
Synopsis...kjc/rlg
near term...kjc/rlg
short term...rlg
long term...kjc
aviation...kjc/rlg
marine...kjc/rlg

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