Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
740 am EDT Wednesday may 27 2015

Synopsis...
warm and muggy conditions will increase through tomorrow.
Scattered showers and thunderstorms are expected each day...
with today and tomorrow having the higher potential for strong
storms. Cooler and less humid conditions arrive late this weekend
into early next week.

&&

Near term /until 6 PM this evening/...
740 am update...

Have updated the forecast mainly for visibilities and fog potential as it is
not as widespread as previously advertised. In fact...only The
Vineyard shows visibilities below 5 sm. Otherwise the bulk of the forecast
remains on track. Brought near-term conditions back in line with
observed trends. Starting to have concerns marine stratus along
the South Coast will not develop as quickly as previously thought.
Latest guidance has started to slow the timing. This will need to
be monitored through the morning hours.

Today...

Warm...muggy conditions continue for today. Southwesterly winds will
gust between 20-30 kts as high temperatures warm into the upper 70s to middle
80s.

Upper level ridge continues to dominate the region through much of
the day as a cold front slowly works it way eastward across the
Great Lakes. Feel today has the better potential to see a few strong
thunderstorms within the pre-frontal trough and modest southerly
flow...especially across CT and western Massachusetts. Aside from the abundant
moisture...cape values will range between 1500-2000 j/kg with about
25 kts of shear. Precipitable water values will be about 1.5 inches...combined
with a descent southerly low level jet and warm cloud processes per BUFKIT
soundings...any thunderstorm has the potential to produce very heavy
rain. Have continued enhanced wording to the forecast for heavy
rain. Could see some strong winds gusts as well...especially across
Franklin County.

Showers and storms should develop by the late afternoon and linger
into the evening hours. Storm Prediction Center has the Pioneer Valley in a slight risk
for severe thunderstorms. An isolated severe wind gust cannot be
ruled out...but overall feel is that storms should remain below
severe limits with the potential for heavy rainfall.

The question for this evening is how far east the convection will
get. Believe that the marine influence and proximity of the upper
ridge will most likely weaken the storms considerably as they move
near the Central Hill of Worcester County. In fact believe precipitation
will struggle after 3/4z.

Areas of fog are expected to develop along the South Coast by the
evening hours limiting visibilities. Dense fog advisory may be
needed.

&&

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

Muggy conditions will continue overnight...with the potential for
areas of fog especially across the South Coast/cape and islands.
Some locations could see locally dense fog.

Probability of precipitation do slowly increase to low chance for the western portions of
the region overnight as the pre-frontal trough remains nearby and
elevated instability could promote development of a few
showers/storms.

Tomorrow...

Upper level shortwave will pass through northern New England on
Thursday pushing a cold front across the region. 00z guidance shows
the front pushing through by the afternoon/evening hours which could
be a source of lift for any convection. However appears that the better
dynamics will be north of the region...in Maine and New
Hampshire. Still cant rule out a few scattered showers/thunderstorms as
guidance suggests a narrow corridor of heating with descent shear
between 25-30 kts and marginal middle-level lapse rates.

Precipitable water values are still high...around 1.6 inches which may yield to
the potential for heavy rainfall within any strong thunderstorm.

&&

Long term /Thursday night through Tuesday/...
overview and model preferences...

Not much change from previous guidance runs. Main synoptic pattern
remains largely in place through the rest of this week...with a
deep ridge in place over the Atlantic Ocean. This will keep the
heat and humidity in place. Will likely have to wait until late
this weekend or early next week for a reprieve...as this ridge
gradually moves farther offshore.

Generally favored a consensus blend of the guidance to smooth over
the relatively minor differences into this weekend. These
differences become more significant Monday into Tuesday. Still
favored a consensus blend to deal with the uncertainty.

Details...

Thursday night...will see areas of fog...locally dense...develop
across south coastal areas. Isolated to scattered showers end
from west to east.

Friday...expecting a mainly dry day...as our region is between
two systems...with weak surface ridging. It should be slightly
less humid...but still muggy.

Saturday...high pressure repositions off the eastern Seaboard...so
SW winds increase again...bringing a return of more humid air.
Another cold front starts to approach out of Great Lakes and
western Quebec. Also noting increasing instability parameters
ahead of this front. We could see some thunderstorms Saturday
afternoon...which could last though Sat night. With the humidity
already in place...heavier downpours are possible with any
convection.

Sunday...cold front slowly moves across the region Sunday
morning...then reaches the South Coast by Sunday night. Expecting
at least a chance for showers and thunderstorms. With the slow
movement of this front...expecting scattered rainfall to continue
through Sunday night.

Monday-Tuesday...somewhat lower confidence due to timing and
placement differences with a front...and whether it stalls near
the South Coast or offshore. At this point...kept chance probability of precipitation
across central and southern areas through Monday afternoon. Low
probability for thunderstorms early...then instability works
offshore.

Have kept slight chance probability of precipitation going for southern areas into Tuesday
as front looks to linger nearby...then may try to make a run back
NE as the high pushes off into the Gulf of Maine.

&&

Aviation /12z Wednesday through Sunday/...
forecaster confidence levels...

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

Today...moderate confidence. VFR to start. Western sites could
drop to MVFR within any -shra/-tsra that develops. Expect SW winds
to gust up to 20-30 knots at times mainly across Rhode Island/southeast Massachusetts.

The big question will be the potential development of IFR/MVFR
stratus along the South Coast. This is the lowest confidence
portion of the forecast.

Tonight...moderate confidence. Conditions deteriorate to IFR
along the South Coast...cape...and islands as maritime fog and
stratus roll in.

Thursday...moderate confidence. Cold front will pass across the
region switching the southerly winds to the west during the day.
IFR...fog and stratus is possible before frontal passage along southeast
taf sites. Cannot rule out a few showers/T-storms along the front
dropping conditions to MVFR. Otherwise VFR will prevail.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf. Could see conditions drop
to MVFR within any thunderstorm today.

Outlook...Thursday night through Sunday...moderate confidence.

Friday...VFR. May see local MVFR-IFR conditions early morning
along S coast in patchy fog...then may lower again late Friday night
to MVFR-IFR.

Saturday...patchy early morning fog with MVFR-IFR conditions...
will improve. Scattered rain showers/thunderstorms and rain Sat afternoon through Sat night...
with local MVFR-IFR conditions. SW winds gusting to 20-25 knots
mainly along the coast Sat afternoon/evening.

Sunday...scattered showers/thunderstorms linger...but should end late Sunday
night. May see brief MVFR conditions.

&&

Marine...
forecaster confidence levels...

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

Short term /through Thursday/...high confidence.

New set of small craft advisories are up today and into tonight.
Expect near shore waters to see gusts near 25 kts...just like
yesterday. Otherwise southerly swell will continue to build
increasing outer water seas to 5ft.

In addition...areas of dense fog are likely to develop on the
waters later today and tonight...substantially reducing
visibilities.

Outlook...Thursday night through Sunday...moderate confidence.

Friday...light north-NE winds become east during the day...then shift to
S-SW Friday night. Expect winds and seas below small craft criteria.

Saturday-Sunday...SW winds may briefly gust to 25 knots during Sat on
the eastern waters...as a cold front approaches the waters.
Otherwise...expecting gusts up to 20 knots. Seas build again to
around 5 feet across the outer waters.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 10 PM EDT this evening for
anz231>234.
Small Craft Advisory from noon today to 8 PM EDT this evening
for anz230-236.
Small Craft Advisory until 8 PM EDT this evening for anz235-
237-251.
Small Craft Advisory from 11 am this morning to 8 am EDT
Thursday for anz250-254>256.

&&

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

National Weather Service Glossary of Abbreviations