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Area forecast discussion 
National Weather Service Taunton Massachusetts
504 am EDT Friday Aug 29 2014

Synopsis...
high pressure centered over the Great Lakes will build over New
England with dry weather and low humidity today and Saturday.
Rough surf and rip currents will diminish by tonight. A front will
slowly push across New England late Sunday and Monday bringing a
period of showers and scattered thunderstorms. Some showers and a
few thunderstorms may linger into Tuesday. Warm...dry conditions
look to set up by late next week.



&&

Near term /until 6 PM this evening/...
high pressure builds over New England at the surface and aloft while
yesterday/S upper trough moves off through the Maritimes. While
there will be some lingering pressure gradient this morning...this
should become light as the high moves overhead. The light gradient
will allow for sea breezes developing later this morning and this
afternoon along all coastlines.

Cross sections of relative humidity show a layer of high moisture
also lingering between 800 and 850 mb. Mixing will reach to at
least the base of that layer. Expect another round of diurnal
cumulus...but with increasing subsidence the sky cover should be
less than yesterday.

Temperatures at 850 mb will be 8-10c which supports maximum surface temperatures in the
70s...possibly near 80 in a few warm spots such as the lower CT
valley. Sea breezes will buffer coastal temperatures...water temperatures are in
the 60s east of mass and around 70 along the South Coast. So
coastal temperatures should be in the 60s and lower 70s.

A 5 foot south swell lingers on the southern waters this
morning...but should be trending lower through the day. We will
continue the high surf advisory through the morning but bring the
ending time forward to 2 PM.

&&

Short term /6 PM this evening through 6 PM Saturday/...
high pressure moves offshore tonight and remains in place to our
east on Saturday. This will bring increasing flow from the
south...except southeast near the east mass coast. Dew points will
start to rise...but this trend may hold off until the flow picks
up on Saturday. At that point...dew point values will climb
through the 50s to near 60 by Saturday evening.

Tonight...
the light wind/fair skies will allow another cool night tonight
with surface temperatures in the upper 40s and 50s. This will be close
enough to saturation for patchy fog. Best chances would be in the
CT valley and in the low spots of eastern mass.

Saturday...
sunshine through cirrus on Saturday will mean a pleasant day. The
sunshine will be filtered a little...but temperatures in the mixed layer
will be a little milder than today. So surface temperatures should be at
least the same as today and probably a little milder. Based on a
mixed layer to 900 mb or a little above...we went with maximum temperatures
75 to 80.

&&

Long term /Saturday night through Thursday/...

Overview and model preferences...
noting overall changes on the medium range models toward a broad
ridging pattern developing across the eastern Seaboard...more of a
typical Summer pattern though late in the season...as opposed to
the long wave troughing that has been across the east over the
last several months.

Will continue with trend of broad troughing to start off this
portion of the forecast...then transition toward nearly zonal
northern tier upper flow which the models/ensembles have been
advertising over the last few nights. Model solution differences in
the steering currents work in beginning early next week...so some
question as to timing of surface systems to the eastern Seaboard.

Leaned toward a blend of available guidance through late Monday...
which showed good run to run consistency over the last several days.
For Tuesday and beyond...went closer a blend of the ec/gefs ensemble
means. With solution timing issues...have lower confidence during
this timeframe.

Details...

Saturday night through Sunday night...
large surface high slowly pushes east of New England during this
timeframe. Looks like this will be slow to clear the coast...so
have carried dry conditions. Persistent SW winds will bring in
more humidity toward the region especially on Sunday ahead of an
approaching front. Dewpoints forecasted to increase to the middle 60s to
around 70 degrees during Sunday. Will see patchy fog develop Sat
night mainly after midnight with lows in the Lower-Middle 60s.

A frontal system will shift slowly east during Sunday...so will see
clouds increasing as well as the humidity. Will start to see showers
and some scattered thunderstorms push into western areas during the
afternoon...with the best shot for precipitation during Sun night. Models
signaling a sharp increase in precipitable waters as well...on the order of 2.1 to
2.3 inches...which runs close to 3 South Dakota above normal for early
September by Sun night. So...will probably see some heavy downpours
with some of these showers and storms. Pretty good instability also
moving across with k indices in the Lower-Middle 30s...along with a
band of below zero showalter indices crossing the region Sun night.

Highs on Sunday will be steamy...in the Lower-Middle 80s...with lows
Sun night between 65 and 70 degrees.

Monday...
front crosses the region as it washes out...but moisture lingers
across the region along with the high humidities. Kept chance probability of precipitation
going during the day into evening hours mainly due to diurnal
heating. Also have mentioned chance for thunder across central and
southern areas. Expect precipitation to weaken Monday night. Will remain
warm and humid.

Tuesday...
another cold front approaches...so will see another round of scattered
showers/tstms. Warm and humid conditions will continue with highs
again in the Lower-Middle 80s. The front should clear the coast Tuesday
night...but wind flow remains from the west with the drier air
remaining north of the region.

Wednesday and Thursday...
somewhat drier air will work into the region during this
timeframe...but temperatures look to remain on the warm side as a ridge
builds across the eastern U.S. Still some questions with the
evolving upper level pattern across the Continental U.S....so lower
confidence on this portion of the forecast.

&&

Aviation /09z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /today through Saturday/...high confidence.

VFR. Patchy IFR fog possible across the CT-River Valley early this
morning. Patchy IFR fog again later tonight/early Saturday in the
CT valley and in the low spots of eastern Massachusetts. Light
winds late this morning and afternoon will allow sea breezes to
develop all coasts. This will diminish toward evening.

Kbos terminal...high confidence in taf. Sea breezes develop
initially turning northeast late morning...then southeast by middle
afternoon and south at sunset.

Kbdl terminal...high confidence in taf.

Outlook...Saturday night through Tuesday...

Saturday night and Sunday...moderate confidence.
Mainly VFR. S/SW winds gusting up to 20-25 knots during Sunday.
MVFR- IFR ceilings/visibilities possible along the S coast Saturday night.
Chance for rain showers/thunderstorms and rain across central and western areas beginning
around midday Sunday Onward.

Sunday night and Monday...low confidence.
Mix of low end VFR to MVFR. Widespread rain showers across the terminals.
Possible thunderstorms and rain across the interior Monday. Continued S/SW winds.

Tuesday...moderate confidence.
Cold front sweeping across the terminals late Tuesday/Tuesday night. Low
end VFR. Chance of shra/tsra. Winds backing out of west behind the
front Tuesday night.

&&

Marine...
forecaster confidence levels...

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

Short-term /tonight through Friday night/...high confidence.

Today...high pressure builds over the waters. This means north
winds will diminish and become light. Light winds will allow sea
breezes to develop near shore. A 5 foot south swell from
Cristobal lingers on the exposed waters but is showing a lowering
trend. We will continue the Small Craft Advisory for a few more
hours...ending it on the sounds by 8 am...and on all outer waters
by 2 PM.

Tonight...seas will be below 5 feet and winds light.

Saturday...winds increase from the south...but sea will remain
below 5 feet.

Saturday night and Sunday...moderate confidence.
S-SW winds gusting up to 20 knots mainly on the southern outer
waters along with seas building up to around 5 feet. Patchy fog with
reduced visibilities. Scattered showers/thunderstorms possible on the near shore waters
late sun.

Sunday night and Monday...moderate confidence.
S-SW winds gusting up to 20 knots with seas around 5 feet mainly on
the southern outer waters. May see patchy fog develop late Sun
night into Monday morning.

Tuesday...moderate confidence.
Expect SW winds below small craft criteria along with seas below
5 feet.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...high surf advisory until 8 am EDT this morning for maz020-023.
High surf advisory until 2 PM EDT this afternoon for maz022-
024.
New Hampshire...none.
Rhode Island...high surf advisory until 8 am EDT this morning for riz006>008.
Marine...Small Craft Advisory for hazardous seas until 8 am EDT this
morning for anz235-237.
Small Craft Advisory for hazardous seas until 10 am EDT this
morning for anz250.
Small Craft Advisory for hazardous seas until 2 PM EDT this
afternoon for anz254>256.

&&

$$
Synopsis...wtb/evt
near term...wtb
short term...wtb
long term...evt
aviation...wtb/evt
marine...wtb/evt

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