Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
211 am EDT Friday Oct 24 2014

the early season coastal storm that brought strong winds and
heavy rains to the region Thursday will continue to move slowly out to
sea today. This will result in showers becoming less numerous and
a drying trend this afternoon. Weak ridge of high pressure provide
dry and seasonably mild weather Saturday. A quick moving cold
front will bring the risk of scattered showers Saturday night.
Behind the front...dry but blustery weather follows for Sunday
into early next week. A cold front may bring more rain late
Wednesday into Thursday.


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

2 am update...

Light rain showers continue to circulate cyclonically across
southern New England from the occluded low over Georges Bank.
These showers will continue to affect the region through the morning
hours. Northerly winds continue to slowly diminish. Previous
forecast verifying nicely so no major changes with this update.


Short term /6 am this morning through 6 PM Saturday/...
gradual improvement Friday as low slowly pulls toward Maritimes. May
see few leftover showers especially Thursday morning and closer to
coast. Cross sections indicate Little Hope for significant
clearing until Friday clouds will dominate until then...
although some breaks of sun are certainly possible in western New

Stayed close to blend of model guidance for temperatures...which gives
highs in 50s Thursday and back into 40s Thursday night.


Long term /Saturday night through Thursday/...
* chance of showers Saturday night into Sunday
* drier weather for Monday and Tuesday with high pressure around
* rainy Wednesday night into Thursday with a cold frontal passage


The period starts with an upper level subtropical high around
Arizona and Texas with troughs flanking either side of the ridge in
the center of the country. The upper level low from today exits the
region to the east on Saturday giving way to another shortwave for
Saturday night that moves west to east...passing to the north of the

The subtropical high moves east Monday and brings drier air into the
region especially on Tuesday. On the back end of the high pressure
system...southwest winds precede another cold front. Decent
agreement amongst the models that the front arrives Wednesday night
into Thursday. This looks to have good wind dynamics and above
normal precipitable waters for good moisture Transfer. During this
period...ensembles are hinting at the ao becoming more and more
positive which would also imply at good moisture transport to the
northeast US.


Saturday...cloudiness and moisture from the upper level low leaves
the region and weak ridging arrives so we can expect drying on
northwest winds.

Towards the evening and into Sunday...a shortwave arrives from
central Canada that scoots west to east just north of the region.
The cold front looks washed out so only weak scattered showers are
possible. Decent shear exists and wind gusts could be around 30 kts
especially as showers mix the 30 to 35 knots 925 mb winds to the
surface. The middle level lapse rates are around 7c/km especially up in
northern New England as the cold pool aloft arrives...but cape is
low so the thunder risk is low enough to not be included in
the forecast at this time.

Sunday afternoon dries out on the encroaching northwest winds and
rising heights. Winds are gusty still as 30 knots winds are able to mix
to the surface.

Monday and Tuesday...the middle level ridge moves east and impacts the
region. Monday looks colder...more cloudy and breezy than Tuesday.
Monday/S highs should be in the upper 50s and Tuesday/S high should
be in the low 60s.

Wednesday and Thursday...the West Coast trough will arrive in our
area with an associated cold front. This cold front has precipitable waters from
1.25 to 1.5 inches which is 2 Standard deviations above normal with
a strong low level jet for good moisture transport along with upper
level divergence around so precipitation amounts should be watched.
Showalter and lifted indices are positive and cape is very low so
thunder remains to be seen at this point. However the k-index and
total totals index are where you want them to be for thunder.

It is also interesting that the European model (ecmwf) has a negatively tilted trough
early Thursday morning while the GFS keeps it positively the whole
time with the cutoff low farther south in southeast Canada.
Negatively tilted troughs are helped along by stronger winds on the
western side of the trough...however the European model (ecmwf) has stronger upper
level winds on the eastern side which would mean a more positively tilted
trough. This is also the first in the European model (ecmwf)/S model runs that does
this. This timeframe is still very far out and will need further
ironing before details are smoothed out.


Aviation /06z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /through Saturday/...moderate confidence today then
increasing to high confidence tonight and Sat.

Through 12z...

Not much change with IFR over southeast Massachusetts and MVFR elsewhere.
Scattered light rain showers will persist. Modest north winds continue
over eastern Massachusetts.

After 12z...

Slow improvement with showers dissipating and moving offshore.
Also ceilings and visibilities lifting to MVFR and VFR from west to east. North
winds becoming more north-northwest with time.

skies become clear along with VFR visibilities as winds become west-northwest.


VFR along with a modest west wind.

Kbos...moderate confidence in taf today but increasing to high
tonight and Sat.

Kbdl...moderate confidence in taf today but increasing to high
tonight and Sat.

Outlook...Saturday night through Monday...

Saturday through Tuesday...moderate confidence. VFR. Low
probability of scattered showers late Saturday.


forecaster confidence levels...

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

Short term /through Friday night/...

10 PM update...

Increased seas across the eastern Massachusetts waters from stellwagon bank
northward. Buoys reporting seas 12 to 16 feet. Also removed mention
of thunder given risk appears very low. Otherwise previous
forecast remains on track. Earlier discussion below.


* Conditions gradually improve *

Coastal storm passes southeast of Nantucket this evening and to Maritimes
Thursday and Thursday night. This will bring gradually diminishing winds and
especially seas...which will take a couple of days to subside.

Maintained gale warnings on most waters through tonight as we
expect another surge of north gales later this afternoon and
evening...before winds diminish tonight and Thursday.

Scattered showers and isolated storms through this evening...
especially around Cape Cod and islands. Otherwise few leftover
showers Thursday morning.

Outlook...Saturday through Monday...

Saturday and Sunday...moderate confidence...after a brief
lull...seas and winds will increase ahead of a cold front. Small
craft advisories will likely be needed for at least a portion of the
waters as the winds rise above 25 kts and the seas have 5-8 feet

Monday...moderate confidence...winds and seas diminish as high
pressure builds over the waters.

Tuesday...moderate confidence...winds and seas below Small Craft Advisory
threshold as high pressure is still over the region.


Box watches/warnings/advisories...
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory until noon EDT today for anz231>234.
Small Craft Advisory until 10 am EDT this morning for anz230-
Small Craft Advisory until 6 am EDT early this morning for
Small Craft Advisory until 6 am EDT Saturday for anz254-255.


near term...nocera
short term...jwd
long term...99

National Weather Service Glossary of Abbreviations