Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
1020 PM EDT Monday may 4 2015

mild weather prevails this evening and overnight ahead of an
approaching cold front. This boundary may trigger isolated to
widely scattered showers Tuesday. High pressure builds in behind
this front Wednesday...providing mild temperatures but lower humidity
than Tuesday. Warmer weather follows Thursday and Friday as the high slips
south and then east of New England. A cold front late this weekend
into early next week may yield scattered showers. Otherwise dry...
warm and slightly more humid weather prevails this weekend.


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

1027 PM update...

Mild southwest flow continues ahead of an approaching cold front.
While winds have diminished some with the loss of daytime
heating...still enough wind off the deck to keep them from
decoupling. This was allowing late evening temperatures to still be in the
60s to near 70...despite relatively dry air in place.

Dry weather continues for most of the night...but middle/high level
cloudiness will increase ahead of the cold front. As the cold front
approaches toward daybreak a few spot showers may develop but
nothing significant/widespread expected. Its so dry in the low
levels of the atmosphere and instability is quite limited.
Therefore...while a few spot showers possible toward daybreak dry
weather will dominate. Removed mention of thunder as instability
appears too limited. Low temperatures by daybreak should only drop into
the upper 50s to near 60 by daybreak for most locations...but it
will be a few degrees cooler across the South Coast/cape/islands.


Short term /6 am Tuesday morning through Tuesday night/...
a weakening cold front will provide a focus for isolated to
scattered showers across southern New England. Instability is not
great...but cannot completely rule out the possibility of an
isolated thunderstorm or two. The most likely scenario is for
scattered showers...especially during the morning hours.

The front continues to weaken during the afternoon...with weak
ridging arriving during Tuesday evening and overnight. This should
mean a slow drying trend Tuesday night.

Temperatures will still be slightly above normal Tuesday and
Tuesday night.


Long term /Wednesday through Monday/...
348 PM update...


* Spring to Summer-like temperatures much of the period
* mainly dry weather Wednesday through Sat with increasing risk of showers

Synoptic overview and model/guidance evaluation...

00z ecens/eps and 12z gefs ensembles in good agreement on the large
scale flow this period which features an anomalous closed low
evolving over the northwest Atlantic of about -3 Standard deviations from
climatology...along with a ridge centered over the Great Lakes and Ohio
Valley. This places New England in a dry northwest flow regime Wednesday
through Friday. By the weekend the upper air pattern becomes somewhat
progressive with the closed low moving into the central Atlantic
allowing Great Lakes ridge/height anomaly to advect eastward into
New England...continuing the dry weather into at least the first
half of the weekend. Then by late in the weekend and especially
early next week the question becomes how quickly does the ridge
erode as upstream trough approaches. In addition...ridge becomes
somewhat of a dirty ridge with moisture from remnant closed low over
the southeast states advecting northward up the eastern Seaboard. As
expected at this time range the deterministic runs of the 12z European model (ecmwf)
and 12z GFS handle this differently along with ensembles. Thus
forecast confidence becomes low on shower potential later this
weekend into early next week.


Brief cool down or better labeled as not as warm Wednesday /low to middle
70s/ in the Post frontal airmass along with lower dew points /30s/.
However as surface high slips south of New England Thursday...surface
winds become west-southwest and this will support temperatures warming to 75 to 80 and
potentially climbing into u70s and l80s by Friday. Warm weather
continues Sat with highs in the l80s away from the South Coast. In
addition with south-southwest surface winds dew points will climb into the 50s.
Still comfortable but this will result in nightly temperatures not as cool
along with patchy fog. Sunday...tricky as potential backdoor front
impacts eastern Massachusetts and possibly Rhode Island. Not as warm early next week
given likely cloud cover...southerly flow and risk of showers.
However temperatures will still average warmer than normal.


As mentioned above dry pattern prevails Wednesday through Friday and probably
into Sat. Risk of showers increases Sunday as upstream trough
approaches along with remnant moisture offshore from closed low over
the southeast states later this week. However greatest risk of
showers appears to be early next week as upstream trough gets closer
to the region and begins to interact with deeper moisture along and
off the eastern Seaboard.


Aviation /02z Tuesday through Saturday/...
forecaster confidence levels...

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

High confidence through Tuesday night.

7 PM update...

Only change is to add low level wind shear to taf sites in eastern Massachusetts and Rhode Island for
low level southwest jet of up to 50 knots peaking around 06z tonight.
Earlier discussion below.


SW winds may bring some 20-25kt gusts through early evening...otherwise
VFR through tonight. VFR ceilings Tuesday as cold front drops through
southern New England...with scattered showers possible. May see
some MVFR ceilings near S coast Tuesday afternoon. VFR Tuesday night.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook...Wednesday through Saturday...

348 PM update...

High confidence for VFR and dry weather. Low risk for patchy fog
each night between midnight and sunrise with local IFR cigs/vsbys.


forecaster confidence levels...

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

Short term /through Tuesday/...

Tonight into tomorrow...moderate confidence. The SW flow will
slowly give way to west flow as a cold front cross the waters during
the Tuesday evening hours. With the persistent SW flow today...some
concern wind-driven seas could approach 5 feet on the ocean
waters. It is marginal...but did have enough confidence to issue
a Small Craft Advisory across the outer coastal waters. The main
risk will be rough seas...but could see a few gusts to 25 knots as
well ahead of a cold front. Conditions improve Tuesday afternoon.
Some showers...with possibly even a thundershower.

Tuesday night...winds and seas continue to diminish.

Outlook...Wednesday through Saturday...

348 PM update...

Wednesday...high pressure over the waters with tranquil/dry weather and
good visibility. High forecast confidence.

Thursday...high slips south of New England with winds becoming south-southwest.
Tranquil/dry weather with good visibility continues.

Friday...high pressure moves east of New England. Dry/tranquil weather


Fire weather... weather headlines were cancelled as wind gusts have
diminished with loss of daytime heating. Winds will not be nearly
as strong on Tuesday so no fire weather headlines anticipated.

Thursday...low risk of elevated fire weather concerns with min relative humidity
values dipping to 25 to 30 percent along with west-southwest wind gusts up to
20 miles per hour. Sustained winds will be less 10-15 miles per hour but again gusts up
to 20 miles per hour and perhaps 25 miles per hour are possible. While isolated or
widely scattered showers are possible Tuesday most of the region will
be dry with any rainfall likely less than 0.25 inches.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory until 9 am EDT Tuesday for anz250.
Small Craft Advisory until 3 PM EDT Tuesday for anz254.
Small Craft Advisory until 3 PM EDT Tuesday for anz255-256.


near term...Frank
short term...Belk
long term...nocera
fire weather...staff

National Weather Service Glossary of Abbreviations