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Area forecast discussion 
National Weather Service Taunton Massachusetts
706 am EDT Sat Aug 1 2015

Synopsis...
seasonably warm this weekend with a risk of scattered showers and
thunderstorms middle to late this afternoon. Warm conditions will
continue into early next week. There will be the threat of showers
and thunderstorms Monday into Tuesday. Pattern change by middle-week will
keep temperatures below average into the weekend.

&&

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



700 am update...

Showers across Berkshires Colorado continue to move eastward into
western zones. These showers are associated with a lead shortwave
and should move into northern mass over the next few hours. Aside
from a few tweaks...forecast remains on track.

This morning...

Lead short wave moving across the eastern Great Lakes and the St
lwrnc River Valley is triggering showers and T-storms over northern
state early this morning. Farther south and east a few isolated
showers were occurring across northern Massachusetts into Vermont and New Hampshire. This
will be the theme early this morning with isolated to widely
scattered showers possible across western and northern Massachusetts. Otherwise
remainder of the region remains dry.

Large temperature spread this morning with locations observing clear skies
and light winds...temperatures have fallen into the u50s. Meanwhile mostly
cloudy skies in the CT River Valley have temperatures in the 60s.

This afternoon...

Trailing short wave energy currently moving across the Great Lakes
advects through New England later today. This results in cooling temperatures
aloft with 500 mb temperatures going from -9c this morning to about -12c by
days end. This will result in steepening lapse rates. Modest forcing
for ascent associated with this short wave trough as it crosses the
region. Limiting factor for convection with this feature is column
is fairly dry along with surface dew points in the 50s. This will
likely limit areal coverage to isolated or widely scattered.

Convection may be more numerous with stronger updrafts along the
South Coast as dew points here will be higher...in the 60s due to SW
wind. This greater instability will provide a low risk of one or two
stronger T-storms in this area. The combination of deep layer shear
of 30-40 knots and inverted /\ sounding signature suggest one or two
stronger storms may yield gusty winds and possibly small hail.
Overall most if not all storms will be sub-severe and should be
short in duration.

Otherwise a fairly typical Summer day with temperatures climbing into the
80s along with a few showers/T-storms.

Beach forecast...

Increasing south-southwest winds this afternoon may be sufficient to
kick up the surf to 3 to 4 feet on south facing ocean beaches. This
may support moderate rips.

&&

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

Any lingering convection early this evening should be confined to
the South Coast and will dissipate shortly after sunset given
cooling blyr. Thereafter subsidence behind departing short wave
overspreads the region. This will support dry weather 2nd half of
the night. Seasonably cool with mins in the 60s /u50s northwest Massachusetts/
and comfortable humidity with dew points in the 50s.

Sunday...

Nice day with short wave ridging and associated subsidence providing
dry weather and abundant sunshine. Highs in the 80s but tolerable
humidity with dew points in the 50s.

&&

Long term /Sunday night through Friday/...
highlights...

* showers and thunderstorms Monday into Tuesday
* pattern change by middle week bringing below average temperatures

Overview...

00z guidance is in descent agreement until the middle week where models
diverge. Appears guidance is having an issue handling the upper
level low over the Hudson Bay as well as potent northwest low and
how it will respond downstream. The GFS is the most progressive
while the ec is more amplified in the extended. Latest gefs appear
to side towards the ec as well as the eps. Because of the
discrepancies trended the forecast closer to the ensembles. Overall
upper level low of the Hudson Bay will keep the region in
southwesterly flow. Several waves through the flow will kick off
showers and thunderstorms Monday into Tuesday. Pattern change by middle-
week as low moves eastward dropping temperatures and heights for New
England. Several fronts will keep reinforcing the cooler airmass for
southern New England through the remainder of the period.

Dailies...

Monday into Tuesday...moderate confidence.

Upper level low over Hudson Bay will begin its eastward trajectory.
Shortwave will round the low pushing a cold front across the Great
Lakes and into New England. Significant timing issues with the front
as the GFS is quicker than the NAM/ec. Ec is also less amplified
than the GFS and hardly has any quantitative precipitation forecast over the region on Monday.
Therefor have a moderate confidence in this portion of the forecast
until details can be settled...hopefully over the next run or two.

As cold front approached the region late Monday...could see scattered
showers and thunderstorms develop out ahead as Theta-E values
increase as well as instability. Dewpoints will also be increasing
as southerly low level jet strengthens. Descent instability values amongst
guidance...with 1000-2000 j/kg and steepen middle-lapse rates. A duel
jet appears to be in place putting the region in favorable lift. So
with all of the above believe that thunderstorms will develop with
some being strong late Monday. Best region looks to be across
western mass and CT as shear values are strongest in that
region...30-40 kts. However most of the region has the potential for
thunderstorms. Although this is 3 days out...if everything lines up
could be a severe storm or two...but low confidence at the moment.

Front will slowly slide through the region overnight. Appears that
there is still enough instability...high Theta-E and k values over
32c to keep the thunderstorm potential going into the night.

Tuesday will still have cyclonic flow over the region and depending
on where the front is set-up could still see some showers over the
region. Because of the cyclonic flow...temperatures on Tuesday will be
cooler than Monday as there will be more clouds around. It wont be
until late Tuesday into early Wednesday when cooler temperatures and low
humidity takes hold over the region.

Wednesday and beyond...moderate confidence.

Closed low aloft will move eastward as ridge build over the central
Continental U.S.. potent shortwave will move through the flow dropping temperatures
and heights over the region. The lowering heights overhead will keep
temperatures below average and it will be somewhat less humid as well.
Temperatures will mainly be in the 70s into the 80s for Wednesday through
Saturday. No 90s in the near future. Overnight lows will mainly be
in the upper 50s to 60s.

Additionally potent shortwave from the upper low appears to develop
a southern stream surface low. The lows placement has a large spread
amongst guidance with the GFS over the middle-Atlantic and the ec over
the Carolinas. Because of the spread and looking at the ensembles
kept slight chance of precipitation with higher confidence across the South
Coast thurs-Fri. But this can change as it is 6 to 7 days out.

&&

Aviation /11z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term /through Sunday/...moderate to high confidence...
except only low to moderate confidence in development and areal
coverage of any convection this afternoon.

Today...VFR but isolated to widely scattered showers and T-storms
likely this afternoon and early evening. One or two storms may
contain small hail and gusty winds...however most if not all of
the activity will be sub-severe.

Tonight...VFR with any lingering evening T-storms rapidly
diminishing with sunset.

Sunday...VFR/dry weather and good visibility.

Kbos terminal...high confidence in taf. Widely scattered thunderstorms
should develop across Logan/S airspace this afternoon and early
evening but not enough confidence to reflect in taf at this time.

Kbdl terminal...high confidence in taf. Isolated to widely
scattered thunderstorms possible this afternoon and early evening.

Outlook /Monday through Wednesday/...

Monday into Tuesday...moderate confidence. VFR much of the time with
a low risk for scattered showers and thunderstorms through the
period.

Wednesday...moderate confidence. VFR.

&&

Marine...
forecaster confidence levels...

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

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

Today...south-southwest wind increase to 15-20 knots this afternoon. This long
fetch will likely increase seas to 3 to 6 feet across the south
coastal waters. Thus Small Craft Advisory remains in effect and also included Rhode Island
Sound. Scattered showers and T-storms likely this afternoon.

Tonight...south-southwest winds 15 to 20 knots ease and become west late. Thus seas
will subside. Any early evening showers and T-storms will dissipate
with sunset.

Sunday...light west winds in the morning becomes SW in the
afternoon. Dry and tranquil boating weather Sunday.

Outlook /Monday through Wednesday/...moderate confidence.

Monday into Tuesday...approaching cold front will increase showers
and thunderstorms for the waters. SW winds will increase ahead of
the front building seas up to 5-6 feet. Winds could be gusty
requiring Small Craft Advisory.

Wednesday...seas will slowly relax however westerly winds will still
be gusty. Could still need Small Craft Advisory for the waters.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory for hazardous seas from 11 am this
morning to 2 am EDT Sunday for anz235-255-256.

&&

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

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