Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Taunton Massachusetts
324 PM EDT sun Apr 20 2014

Synopsis...

High pressure will remain in control through early Tuesday. While
warmer on Tuesday...wet weather will follow Tuesday night into
Thursday behind which breezy and cooler conditions follow towards
the end of the week. Another chance of wet weather is anticipated
late Friday into the weekend.

&&

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

215 PM update...no major changes to the forecast. Tweaked near
term forecast to reflect latest observed trends.

Tonight...
a high pressure will shift farther east of our region...but its
ridge will elongate west-east across our region. This will keep dry
conditions in place. May see some clouds here and there overnight.
The light wind flow in place will start off from the east...then
will veer to the southeast and south overnight. Wind speeds will
remain less than 10 knots...with calm conditions at many locales
after midnight. With the light southerly flow aloft...and 925 mb
and 850 mb temperatures starting to rise...not expecting lows to
be quite as cold as Sunday morning with readings mainly in the
30s.

&&

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

A high pressure ridge gradually shifts southeast through this
period...but will still be close enough to keep our weather dry.
Winds will continue to shift south...and increase for Monday
afternoon. Currently thinking the pressure gradient will be weak
enough for weak sea breezes to develop along the East Coast of Massachusetts.

Temperatures will rise to above normal levels...except along
the immediate coastline. The proximity to the colder ocean will
keep temperatures in the 50s there...especially along south-facing
coasts. Once the sea breezes die off tomorrow afternoon along the
East Coast of Massachusetts...temperatures will rise quickly. Latest
guidance temperatures looked very reasonable.

Higher clouds increase Monday night ahead of a cold front
approaching southern New England.

&&

Long term /Tuesday through Sunday/...

*/ highlights...

- cold front and showery weather for late Tuesday and overnight
- breezy and cooler for Wednesday and Thursday under high pressure
- another period of showery weather Friday into the weekend

*/ overview and model preference...

A consensus blend is preferred through the midweek period as mass
fields are in pretty good balance albeit some amplitude differences.
Thereafter you are in one of two camps towards the late-week: either
an amplifying negatively-tilting trough over the southwest Continental U.S. And
subsequent slower wave progression...or a fast-stretched zonal-flow
regime. Prefer the former with the 20.12z GFS showing a tightening
cyclone to the Lee of The Rockies climatologically preferred this
time of year. This should lend to the weekend disturbance across the
NE Continental U.S. To linger a bit longer.

*/ Day-to-day details...

Tuesday into Tuesday night...

Cold front sweeps through the forecast region towards the later half
of the forecast period. Initially h925 temperatures +10-12c and sunshine
should allow highs into the 70s with cooler conditions along the
shore with an east-component of onshore flow. Thereafter sufficient
lift-dynamics should allow for a band of rain along the front with
embedded heavier showers. Perhaps a slight chance of thunder
though convective indices are on the low-end of thresholds. Some
hint per the 20.12z NAM of showers becoming diffuse across New
England and perhaps this attributable to lingering high pressure and
dry air as well as a weakening jet structure aloft. But feel low-
to middle-level ascent of precipitable waters up to 1.5 inches will be significant
to yield the likelihood of showery weather across much of the
region.

Wednesday into Thursday night...

High pressure building across the region against an intensifying low
across Nova Scotia. Blustery northwest flow and likely scattered-broken
cloud decks on Wednesday will make conditions feel cooler. H925
winds of 30-40 kts coupled with good boundary-layer mixing up to
850 mb. May need consider wind-advisories considering the level of cold
advection aloft coupled with the late-April sun.

Clouds clear overnight into Thursday under the increasing influence
of high pressure. Winds should begin to relax...but likely not until
late. It will remain blustery but below Wind-Advisory thresholds.

Though it will be dry with relative humidity-values likely around 30-percent over
the interior...the region is above-normal for precipitation for the month
of April. Thus am not thinking there will be an elevated fire
weather potential.

Friday into Friday night...

Warm front lifts NE across the region with attendant showery weather
subsequent of strong SW Gulf-moisture flow undergoing broad-scale
ascent ahead of the warm-front beneath increasing divergence aloft.
Widespread rain with perhaps some embedded heavier showers. A slight
chance of thunder though once again convective indices are on the
low-end of thresholds. Much of this activity looks to occur during
the evening period.

Saturday into Sunday...

Pending better model consistency...a series of cold-fronts will
usher renewed chances for showers albeit moisture deprived...so
expect light activity. Breezy northwest flow to the rear results in the
return of cooler conditions towards the end of the weekend and into
early next week.

&&

Aviation /19z Sunday through Friday/...

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

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

VFR conditions continue. Winds continue to shift southeast...then
south late tonight into Monday. South winds increase Monday
afternoon...then diminish Monday night.

Kbos terminal...high confidence in taf. Expecting a weak sea
breeze to develop from middle morning into early afternoon...mainly
from 15-21z.

Kbdl terminal...high confidence in taf.

Outlook...Tuesday into Friday...

Tuesday into Tuesday night...high confidence.

Cold front sweeping terminals. Initial VFR lowering to low-end VFR /
MVFR overnight. Rain showers. Low confidence thunderstorms and rain. Breezy SW flow...with
gusts up to 25 knots over southeast New England...backing northwest and increasing.
Improving by Wednesday morning.

Wednesday into Thursday...high confidence.

VFR. Scattered-broken low-end VFR ceilings for Wednesday. Sky clear Thursday. Blustery
northwest winds with gusts up to around 35 kts.

Friday...moderate confidence.

Lowering ceilings towards late with increasing chances for showers along
with increasing SW winds.

&&

Marine...

Forecaster confidence levels...

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

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

Cancelled the Small Craft Advisory for the coastal waters south
and east of Cape Cod. Expecting winds and seas to remain below
advisory thresholds.

Outlook...Tuesday into Friday...

Tuesday into Wednesday...high confidence.

Cold front sweeping the waters by Monday morning with showers. No
visibility issues anticipated. Gusty SW winds up to around 25 kts
possible ahead of the front. Will see waves build up to 5 feet on
the outer waters requiring small-craft advisories.

Cold front sweeping terminals. Initial VFR lowering to low-end VFR /
MVFR overnight. Rain showers. Low confidence thunderstorms and rain. Breezy SW flow backing northwest
and increasing. Improving by Wednesday morning.

Wednesday night into Thursday...high confidence.

Winds backing northwest and gusting in excess of gale force with gusts up
to 40 kts. Will likely need gale-force warnings for the period.
Waves building up to around 7 to 9 feet on the outer waters.
Gales should drop off by the end of the day requiring conversion
to small- craft.

Thursday night into Friday...moderate confidence.

Northwest winds diminishing and turning out of the SW. This will allow wave
energy to dissipate. Small-craft advisories should drop off.

&&

Hydrology...

Minor flooding remains along portions of the mainstem CT river.
See the latest flood statement for details.

Flood warnings remain posted along CT river at...

Hartford and Middle Haddam

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...none.

&&

$$

Synopsis...Belk/sipprell
near term...Belk
short term...Belk
long term...sipprell
aviation...Belk/sipprell
marine...Belk/sipprell
hydrology...Belk