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Area forecast discussion 
National Weather Service Taunton Massachusetts
424 PM EDT Tuesday Jul 7 2015

Synopsis...
a warm front will weaken as it moves north across the region
today. A cold front moves across the region Wednesday bringing
showers and thunderstorms...some with heavy downpours. The front
moves south of New England Wednesday night bringing showers.
Cooler temperatures expected on Thursday behind a cold
front...with a risk for a period of showers mainly late Thursday
and Thursday night to the south of the Massachusetts Turnpike.
High pressure will then bring dry and warm weather
Friday...Saturday and probably into much of Sunday. A period or
two of unsettled weather may arrive early next week.

&&

Near term /until 6 am Wednesday morning/...

Middle-level shortwave over PA will continue to move northeast towards
the region. This diffuse shortwave combined with the area being in a
tropical airmass has triggered showers and isolated thunderstorms across
southern New England. K index does show a minimum over the I-95 corridor which has
kept the showers at Bay this afternoon. Precipitable water values are quite
high...over 1.8 inches which has lead to heavy downpours. Pretty
uniform but weak flow aloft is allowing for some training and
slow moving cells. Cannot rule out some heavy downpours/localized
flooding especially across the western half of the region...where
confidence is highest. Low risk of any strong winds as the
shortwave is weak and ml cape is marginal. In fact cloud cover is
just now beginning to break out...so a late day rally for cape of
possible. However...shear values are low and lapse rates are
pretty poor. So a strong storm potential is low but not zero.

Low level jet is beginning to pick up across the area...which is allowing for
mixing. Gusts could reach near 20 to 25 miles per hour. Otherwise after
sunset...anticipate both winds and precipitation to begin to wane as we
lose the diurnal heating. Also temperatures aloft are quiet warm squashing
the elevated thunder potential tonight. Finally we are on the
backside of the wave...so subsidence will take hold of the area.

Mostly cloudy skies overnight and dewpoints in the 70s will not
allow for temperatures to cool very much. In fact many sites will
struggle to get below 70f. Still some mixing could occur...especially
across the coastal regions which could limit fog potential. Still
cant rule it out as well as low stratus. Low confidence on how
wide spread if/it will get so for now believe that patchy fog may
occur.

&&

Short term /6 am Wednesday morning through Wednesday night/...

Tomorrow...

Another shortwave will move across western New England tomorrow.
This will bring a cold front across the region. There is still a
large spread in guidance on timing of the front with the hi-res/NAM
faster vs the GFS/ec/rgem. Went conservative and played down the
middle of the Road for timing.

Southwest flow continuing into the morning hours...and with a cold
front approaching could see scattered showers and thunderstorms develop
by late morning lasting into the evening hours. Biggest threat
with the storms will be heavy rain leading to localized flooding.
In fact it appears that the front will slow down its southward
movement and stall somewhere across the the South Coast. With this
slow movement and the winds being parallel with the front...could
see training cells. Also appears that there will be good bl
moisture convergence along the front.Considered issuing a Flash
Flood Watch for tomorrow after...especially for the 95 corridor and
points south and east for 2+ inch precipitable waters ...combined with training
cells...but have a low confidence. Something the next shift may
need to think about.

Cannot rule out a few strong thunderstorms tomorrow...but have a low
confidence as shear and lapse rates are still weak. Temperatures aloft
barely cool a degree keeping the atmosphere pretty stable and with
the front being displaced by the shortwave...really losing a good
amount of forcing. Still with 70f dewpoints cant dismiss the
potential for a quick spin-up or wet microburst.

Tomorrow night...

Weak cold front will stall somewhere across the South Shore
overnight. A middle-level wave will ride along the front developing a
weak low pressure system. As this system moves closer...could see
scattered showers and perhaps a thunderstorm develop overnight. Storm
motion will be moving form the SW to the NE and increase in areal
coverage through the night. Temperatures will be cooler as frontal passage
will bring in lower dews and temperatures. A comfortable night ahead...but
a few scattered showers.

&&

Long term /Thursday through Tuesday/...

Highlights...

* cooler Thursday/Thursday night but uncertain if we see a period of showers
* mainly dry and warm Friday/Sat and probably into much of Sunday
* a period or two of unsettled weather possible early next week

Details...

Thursday and Thursday night...

Cooler and less humid weather will be ushered in on Thursday behind
a cold front. Departing wave may result in some left over morning
showers....especially across southeast New England.

Otherwise...a lot of clouds expected on Thursday. Main uncertainty
is if some of our area is affected by an mesoscale convective system late Thursday into Thursday
night. We will be on the cool side of the boundary with basically
no surface instability. Many times these mesoscale convective system/S tend to gravitate to
where the highest instability resides...which in this case will be
to our southwest. So would not be surprised if much of the area
ended up dry late Thursday/Thursday night. Nonetheless...a period of showers
is certainly possible with the best chance south of the Massachusetts Pike and
especially northern CT. Not concerned about thunder or severe
weather with limited instability. High temperatures on Thursday will mainly be
in the 70s...and may struggle to reach 70 on the immediate eastern
Massachusetts coast.

Friday through Sunday...

Northwest flow aloft should provide dry weather with warm
afternoon/S. Highs should reach into the 80s in most locations
Friday/Sat and sun away from the coast. Its possible that a few
locations flirt with 90 on Sunday...if clouds and any scattered
precipitation with an approaching shortwave hold off until Sun night
or Monday.

Sunday night through Tuesday...

Low confidence forecast especially with timing...but a period or two
of unsettled weather is certainly possible. The models do show a
few shortwaves dropping into our region in northwest flow aloft...so
the risk for a period or two of showers with some embedded
thunderstorms exists. Timing uncertain...so will carry low probability of precipitation Sun
night into Tuesday but not expecting a washout. Seasonable temperatures much
of the time.

&&

Aviation /20z Tuesday through Sunday/...
forecaster confidence levels...

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

Short term /through Wednesday night/...

Before 00z...moderate confidence. Patchy MVFR ceilings across the
region thanks to a tropical airmass. Cannot rule out -shra or a
-tsra across the I-90 corridor.

Tonight...moderate confidence. Conditions lower to MVFR to
localized IFR. Some guidance keeps stratus at Bay...but believe
that is underdone. MVFR fog may develop as well across the
interior. Could see IFR visibilities across coastal region tonight.

Wednesday into Wednesday night...moderate confidence.
Approaching cold front will bring scattered -shra and -tsra across the
region. Anticipate MVFR/IFR ceilings within any -tsra as well as visibility
restrictions. Otherwise VFR for the day. Front will stall across
South Shore allowing for showers to overspread tomorrow night.
Ceilings could drop to MVFR.

Kbos terminal...high confidence in taf.

Kbdl terminal...moderate confidence in taf.

Outlook...Thursday through Sunday...

Thursday and Thursday night...moderate to high confidence. Mainly
VFR conditions but can no rule out a period of MVFR ceilings/visibilities in a
cluster of showers...highest risk south of Massachusetts Pike late Thursday into Thursday
night.

Friday and Saturday...high confidence in mainly VFR conditions.

Sunday...moderate confidence. Mainly VFR but may see MVFR-IFR
conditions develop across the interior late sun or Sunday
night...but that is highly uncertain.

&&

Marine...
forecaster confidence levels...

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

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

Tonight...may see leftover 20-25 knots gusts this evening then
diminish after sunset. Patchy fog develops with reduced
visibilities...below 3 miles.

Wednesday...SW winds will increase...with gusts up to 20 knots on the
southern outer waters. Expect seas to remain below 5 feet...though
may briefly reach 5 feet at times. Chance of showers/thunderstorms
some with heavy rainfall.

Wednesday night...front will sit across the South Shore...with a
low pressure riding along it could see increase in seas and
winds. Showers will also increase for the southern waters.

Outlook...Thursday through Sunday...

Weak pressure gradient should keep winds/seas below Small Craft
Advisory thresholds through the weekend. Overall...nice boating
weather expected.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 10 PM EDT this evening for anz250.
Small Craft Advisory until 8 PM EDT this evening for anz231-
251.
Small Craft Advisory until 6 PM EDT this evening for anz230.

&&

$$
Synopsis...Frank/dunten
near term...dunten
short term...dunten
long term...Frank
aviation...Frank/dunten
marine...Frank/dunten

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