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Area forecast discussion 
National Weather Service Taunton Massachusetts
711 am EDT Tue Oct 25 2016

west to northwest winds will continue to bring unseasonably cool
but dry conditions across the region through midweek. Some of the
coldest air of the season will push across the region Wednesday
into Thursday. Low pressure will track across the region Thu into
early Friday and will be accompanied by a cold rain...possibly
heavy at times and gusty winds along the coast. A period of snow
and sleet is likely at the onset across the interior. A drying
trend develops Fri in the wake of the low, but blustery northwest
winds develop. Another round of showers is possible sometime over
the weekend.


Near term /until 6 PM this evening/...

7 am update...

Not much change from previous forecast. Cold but dry northwest flow
continues across New England. Storm Prediction Center mesoanalysis indicates 850 temps
currently -5c to -6c across the area at 7 am with -9c upstream
just across the New York/Vermont Canadian border. Thus robust cold air
advection for late Oct with 850 mb temps anomalies running around
-2 Standard deviations colder than climo.

Winds will increase later this morning as solar heating increases
blyr mixing. This will only exacerbate the chilly conditions.
Expect a mix of sun and clouds in this flow regime. Previous
discussion below.


Low pressure at the surface and aloft continues to spin across the
Maritimes with west-northwest flow in place. Strong 850 mb cold air advection
in place on the northwest flow aloft, with temps falling back to -5c to
-8c through midday before leveling off. Also noting an 850 mb jet of
30-35 kt to pass across the region by mid-late morning. Lapse
rates will increase up to 10c/km through h85, will see low level
mixing increase. This will bring gusts up to 25-30 mph, though
may be higher across the higher inland terrain.

Will still see good downsloping on the northwest flow, so expect skies
to be mostly sunny, though clouds may linger across the east
slopes of the Berkshires as well as near the mass/New Hampshire border
through late morning. Some diurnal clouds may develop away from
the coast.

As the low across the Maritimes start to slowly shift east this
afternoon, winds will diminish from west-E, though will remain gusty
across Cape Cod and the islands. The winds will also slowly veer
to a more northerly direction toward sunset, which will allow for
low clouds to form across the warmer ocean waters near and east of
Cape Cod. Some question as to whether some ocean effect showers
may develop toward sunset as well. Rap and 4km NAM BUFKIT
soundings signaling some ocean effect precip may develop on the
Outer Cape. The big question will be whether the winds shift to a
more northerly direction to allow the ocean effect precip to work
in, or if it remains more northwest and keep it offshore.

With the excellent cold air advection in place, will be a very
chilly day today. Expect highs only in the lower-mid 40s across
the higher inland terrain, ranging to around 50 along the coast.


Short term /6 PM this evening through 6 PM Wednesday/...

North-northwest winds will drop off, but not completely diminish except
possibly the low inland valleys tonight. However, with the cold
air in place, temperatures will plummet. Expect temps to fall
below freezing away from the coast, but should hold in the upper
30s to mid 40s along the immediate coast.

Some of our inland areas have not experienced a killing freeze
yet, but should tonight. Have issued freeze warnings for those

Another question for tonight will be whether frost will form.
Noting relative humidities up to 75 to around 90 percent after
midnight in the areas where the freeze will take place. Can not
rule out some patchy frost, especially where the winds drop off
after midnight.

Will also ocean effect clouds across portions of Cape Cod as well
as Nantucket. There will also be a low chance for some showers
there. Have only carried slight chance pops mainly for the Outer
Cape and Nantucket.


Any leftover clouds and isolated showers across the Outer Cape
should end by mid morning, though clouds will linger there through
most if not the remainder of the day. Otherwise, high pressure
will slowly push into the region, allowing for lighter north-northwest winds.
Skies will average out mostly sunny, though high clouds will
filter in from the west during the afternoon. It will remain chilly
though with highs in the 40s to around 50, mildest along the
immediate South Coast.


Long term /Wednesday night through Monday/...

Updated at 423 am...


* coldest temperatures of the season possible Wed ngt/Thu morning

* cold rain and wind Thu/Thu ngt W/snow and sleet likely at the
onset across the interior

* blustery with a drying trend Fri

Wednesday night...

1034 mb high over Quebec will nose southward into New England
providing one of the colder nights this season. 850 temp anomalies
are about -2 Standard deviations colder than climo by days end Wed.
This cold/dry airmass will combine with light winds and mostly clear
skies to allow temps to plummet with sunset Wed evening. Northerly
flow over Cape Cod and the islands will preclude temps from free
falling given SSTs still in the upper 50s to low 60s. In addition
this air/sea temp difference on northerly flow will likely yield
ocean effect clouds and limit temps from being as cold as across the
interior. Any ocean effect showers on Wed will diminish as
subsidence inversion lowers Wed night with surface high cresting
over New England. Also some uncertainty on exact timing of mid/high
clouds arriving into western portions of CT/MA. This will impact
temp forecast. Otherwise just a cold/dry night with diminishing
winds. As for mins...used a blend of the colder MOS guidance to
derive low temps.

Thursday into Friday...

Interesting setup with cold airmass lingering over the region early
Thu in response to 1035 mb high over Quebec. Meanwhile robust
northern stream short wave energy diving southeast into the Great
Lakes/Ohio Valley. Differences in deterministic guidance with 00z ec
colder than 00z GFS on the front end with airmass over the region
early Thu. This results in the ec driving the baroclinic zone/storm
track farther southward. In addition ec is stronger with jet energy
diving into the Great Lakes/Ohio Valley and also mergers energy
quicker than GFS...although not as robust as its prior 12z run. This
results in mid level flow digging farther southward to our
latitude...which would delay warming in the mid levels. In addition
this also results in cyclogenesis developing farther south than the
GFS...with ec forming secondary low along the South Coast. This
scenario would linger low level cold air longer across the interior.
Both gefs and eps ensembles provide support for the deeper/colder
solution of the European model (ecmwf). Thus will blend the stronger/colder European model (ecmwf)
solution into this forecast. However not expecting a high impact
event here given system is progressive and doesn/T really intensify
until it moves northeast of the region into coastal ME and Gulf of
ME. So for now expecting a period of snow and sleet Thu at the onset
across northwest CT/MA...possibly as far east as the Worcester Hills
with a risk of a minor accumulation across the higher terrain of the
east slopes of the Berkshires.

Otherwise...with mid level low tracking west-northwest of the region
mid level warming overspreads the entire region with a changeover to
all rain by late in the day. For the remainder of the region a cold
rain is expected and possibly heavy at times given strong jet
dynamics and moisture advection. Could also have a period of brief
strong onshore winds Thu ngt across coastal eastern Massachusetts as secondary
low intensifies over Rhode Island/southeast Massachusetts before exiting into Gulf of ME.

System is fairly progressive so should see a drying trend Fri along
with brisk northwest winds on the backside of the low.

Weekend... models differ on next bundle of northern stream energy.
Good agreement that there will be a period of showers sometime this
weekend. GFS is of lower amplitude with progressive system and risk
of showers late Sat into Sat night. European model (ecmwf) more dynamic with risk of
showers Sat night thru Sun night.

Early next week...uncertainty on timing of departing system sun/Mon.
However thereafter both deterministic and ensemble guid suggest
pattern deamplifying next week...suggesting not as cold as this week.


Aviation /11z Tuesday through Saturday/...
forecaster confidence levels.

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

Updated 7 am...

Not much change from 06z and 09z tafs. Any cigs will be in the VFR
range. Main issue today will be gusty west-northwest winds from late morning
into the afternoon. Earlier discussion below.


Short term /through Wednesday/...high confidence.

Today...VFR. Mainly few-scattered clouds at 5-7kft across NE mass and
Outer Cape cod through midday. West-northwest winds gusting up to 20-25 kts
across higher terrain and coastal terminals.

Tonight and Wednesday...mainly VFR. May see MVFR ceilings move into
Outer Cape cod and Nantucket with north-northwest winds around or after 00z
through 14z-15z. Low risk of isolated showers.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Wednesday night through Saturday/...moderate confidence.

Updated 423 am...

Wednesday night...

VFR and diminishing north winds.

Thursday into Friday...

IFR-LIFR likely. Initial snow/ice pellets possible with potential accompanying
low level wind shear transitioning to -ra/rain with embedded +ra, possible thunderstorms and rain mostly
S/se. Blustery S/southeast winds. Gusts up to 30 kts along the immediate
shoreline terminals. Improving Friday with winds turning out of the


Brief period of VFR before conditions return low-end VFR to MVFR
with another chance of -ra/ra.


forecaster confidence levels.

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

Short term /through Wednesday/...high confidence.

Northwest winds will continue to gust up to 25-30 kt today, then
gradually diminish tonight. Seas will remain up to 5-8 ft. Small
craft advisories remain in effect.

Winds and seas will diminish below small craft criteria along the
near shore waters tonight, but will linger on the outer waters
into Wednesday.

Outlook /Wednesday night through Saturday/...moderate confidence.

Wednesday night...

North winds diminishing. Vsby may lower in rain and snow showers

Thursday into Friday...

Rain on the increase through Thursday, moderate to heavy at times
with the possibility of thunderstorms. S/southeast winds strengthening
ahead of a deepening area of low pressure across the region. Seas
building 8 to 10 feet the height of which will be on Friday, slowly
dropping off thereafter as winds turn out of the west behind a cold
front but remain breezy.


Breezy west winds continue as there is a brief lull in the weather.
Seas remain above 5 feet on a good chunk of the waters as winds
increase once again along with wet-weather late Saturday into
Saturday night.


Box watches/warnings/advisories...
CT...freeze warning from 2 am to 9 am EDT Wednesday for ctz003.
Massachusetts...freeze warning from 2 am to 9 am EDT Wednesday for maz006-007-
Rhode Island...freeze warning from 2 am to 9 am EDT Wednesday for riz001-003-
Marine...Small Craft Advisory until 2 am EDT Wednesday for anz232.
Small Craft Advisory until 8 PM EDT this evening for anz230-
Small Craft Advisory until noon EDT Wednesday for anz231.
Small Craft Advisory until 1 am EDT Wednesday for anz237.
Small Craft Advisory until 9 am EDT Wednesday for anz235.
Small Craft Advisory until 6 PM EDT Wednesday for anz250-254-
Small Craft Advisory until 8 am EDT Wednesday for anz251.
Small Craft Advisory until 2 PM EDT Wednesday for anz256.


near term...nocera/evt
short term...evt
long term...nocera

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