Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
404 am EDT Tuesday Aug 4 2015

thunderstorms are once again expected today...but mainly across
the eastern half of the area. Some of these may become severe.
Dry...warm and less humid weather arrives Thursday. A period of
unsettled weather is possible Thursday night into Saturday but
confidence is low on the timing of potential wet weather.


Near term /through Wednesday/...
convection developing in PA and southeast New York continues to diminish as it
approaches the NE...where dry air and some subsidence continues to
limit the convection as it approaches. Only some showers just now
entering the lower CT valley. Stronger storms are staying to the
S...mainly where the highest cape values are per latest mesoscale-
analysis. Therefore...outside of a shower...or mainly an isolated
rumble of thunder in the west suspect most of the morning to remain

The rest of the day...still remains somewhat uncertain. At odds is
the ability to generate surface instability as a cold front sweeps
through from about 14z - 22z. Upper level instability is likely
somewhere between the moist NAM and the drier GFS...but with a
modified eml and 6.0-7.0c/km lapse rates and around 2000j/kg of mu
cape...there is plenty available. Shear increases as the front
approaches as well. Sref probs continue to highlight greater than
50 percent probability of MUCAPES greater thank 2000/shear greater
than 40 knots...especially across the eastern 2/3 of the region...where
Storm Prediction Center has upgraded to a slight risk. The surface connection...will be
based on the amount of cloud cover that remains over the area from
the weakened convection this morning and low stratus across southeast
mass. Latest quantitative precipitation forecast on mesoscale guidance is higher than previous
runs...which increases confidence that better destabilization will
occur later in the day in spite of the early cloud
cover...therefore...will increase afternoon/evening probability of precipitation...and be
adding enhanced/severe wording with this update.

Some dry air at the surface...and shear suggest that strong winds and
downdrafts are the primary concern. Some hail possible especially
given NAM shows hail convective available potential energy approaching 500+. Precipitable waters increasing to
near 2.0 inches will once again support heavy rain...but storms
should be moving. Shear also high enough to support the risk of a
weak tornado...reflecting current thinking by Storm Prediction Center.
Therefore...stay tuned to updates through the day.

Otherwise...heat and humidity remains today ahead of the
front...with dewpoints in the upper 6os to near 70. Highs mainly in
the middle-upper 80s.


Short term /Wednesday night through 6 PM Wednesday/...
cold front will be slowing to a near stall between 00z and 04z
this evening just offshore. This will allow a continuation of
T-storm risk mainly across coastal regions until drier air moves
in from the northwest and convection shifts S toward better instability.
Therefore...gradual improvement expected. Some fog possible where
rainfall occurs. Otherwise...temperatures a little cooler...mainly in
the lower 60s across the area...or even in the 50s across northwest Massachusetts.

cyclonically curved flow remains in place across the region
combined with 500 mb temperatures abnormally cold...around -13c. Stalled
frontal boundary remains to the S...but one final shortwave will
be rotating through to the north. This may lead to some scattered
showers/T-storms mainly north of the Mass Pike. With the very cold 500 mb
temperatures...there is a risk for hail as well. Key will be how
much dry air builds through the column. Not expecting
showers/storms to be as widespread as today...but some low chance
or at least slight chance probability of precipitation are needed to reflect the risk.
Warmer temperatures remain in place...mainly the low-middle 80s.


Long term /Wednesday night through Monday/...

* unsettled weather possible around Friday
* temperatures trending below normal during this period

Overall...the models have rather poor agreement on the general
pattern and timing through the long term. In some time periods it
seems that the GFS may just be slower than the European model (ecmwf). In others...
they are just completely different. The ensembles are not much
help in that the European model (ecmwf) ensembles look very similar to the operational
model and the gefs is very similar to the GFS. Basically have two
fairly different solutions for much of the long term. However...
general trends are similar. Looking at a period of unsettled
weather with temperatures trending below normal through much of
the week.

Wednesday...looks to be the warmest day of the period with
temperatures around or just above normal. Despite the potential for
a few showers or thunderstorms across the northwestern zones as a
shortwave pushes into the region...expect much of the day and much
of the area to remain dry.

Thursday...much of the day looks to be dry with high pressure
building into the area. This is one of those times the timing is
off between the European model (ecmwf) and the GFS. The European model (ecmwf) is quick to move the
high pressure out of the region...pushed by low pressure moving
into the middle-Atlantic from the Great Lakes. The GFS keeps that
high pressure over southern New England and the low pressure in
the Great Lakes.

Thursday night through Saturday...this looks to be the most
unsettled time with low pressure moving into the middle-Atlantic and
then possibly up the East Coast over the 40/70 benchmark southeast
of southern New England. The European model (ecmwf) is the most bullish with this...
tracking the low directly over the benchmark and bringing an
extended period of rain to much of southern New England. The GFS
develops some sort of boundary along which several areas of low
pressure travel...bringing periods of rain to the region. Below
normal temperatures are a given with lowering heights/temperatures aloft
and mostly cloudy to overcast skies for much of this time.
Wouldn/T be surprised to see temperatures top out in the upper 60s to
lower 70s on Friday.

Sunday and Monday...much of this forecast will depend on how Friday
and Saturday shake out...but in general the weather looks drier and
quieter with rebounding temperatures.


Aviation /07z Tuesday through Saturday/...
forecaster confidence levels...

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

Short-term /through Wednesday/...

Through 12z...moderate confidence.
Mainly VFR...will have to watch some leftover rain showers/thunderstorms moving
through New York/PA which may impact mainly CT during the early morning

Today...moderate confidence.
Depending on sunshine...expect some thunderstorms and showers to
develop middle day and continue...from west-east into the evening hours.
Some of these storms may be severe...with strong winds and well as brief MVFR/IFR conditions.

Tonight into Wednesday...high confidence.
After storms/rain sweeps offshore late this evening...expect
improvement to VFR which will linger into the daylight hours on
Wednesday. An isolated shower or thunderstorm is then possible mainly north
of the Mass Pike on Wednesday...but not as widespread as Tuesday.

Kbos terminal...high confidence in taf. Lower confidence in timing
of any afternoon storms.

Kbdl terminal...high confidence in taf. Lower confidence in timing
of any afternoon storms.

Outlook /Wednesday night through Saturday/...

Wednesday night through Thursday...high confidence. VFR. Low
probability of a few showers/storms across northwest Massachusetts Wednesday. Any
storms that develop may have MVFR/IFR conditions.

Thursday night through Saturday...low confidence on timing...higher
confidence on trends. MVFR/IFR conditions in widespread rain likely
sometime during this period. VFR before and after period of rain.


forecaster confidence levels...

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

Short-term /through Tuesday night/...

Through today...moderate confidence.
SW winds remain in place and with some gusts potentially
approaching 25-30 knots at times. This will allow seas...which are
already running around 5 feet on the S waters to increase...possibly
increasing to as high as 7 feet by the evening. Small craft
advisories currently out reflect no changes.

Tonight into Wednesday...moderate confidence.
Front moves further offshore...outside of any
storms/showers...winds and seas will gradually
expect these small craft advisories to gradually be dropped
through the period.

Outlook /Wednesday night through Saturday/...moderate confidence.

Wednesday night through Friday...high confidence. Quiet boating
weather with light winds and seas below 5 feet expected. Rain is
likely Thursday night through Friday...limiting visibilities at

Friday night and Saturday...moderate confidence. Easterly winds
and seas increase as low pressure passes south of the waters.
Small craft advisories will likely be needed for the outer waters.
Rain is likely Friday night into Saturday...limiting visibilities
at times.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory until 8 PM EDT this evening for
Small Craft Advisory until 8 am EDT Wednesday for anz235-237-


near term...doody
short term...doody
long term...Belk

National Weather Service Glossary of Abbreviations