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Area forecast discussion 
National Weather Service Taunton Massachusetts
429 am EST Thursday Jan 29 2015

Synopsis...
high pressure over New England will move east this afternoon and
evening. A clipper will move into the Great Lakes tonight with a
secondary low developing along the southern New England coast and
moving into the Gulf of Maine Friday into Friday evening. This will
bring a period of snow later tonight and Friday...which will
continue into Friday night for parts of the region. Blustery and
very cold conditions are expected this weekend. Another storm may
bring snow to the region Sunday night and Monday.

&&

Near term /until 6 PM this evening/...
ocean effect clouds over the cape and islands are gradually
eroding and will clear out by daybreak. Otherwise...a frigid
morning across southern New England with temperatures several degrees below zero in some
of colder spots.

High pressure builds over new eng today...then moves to the east
during the afternoon. Sunshine will give way to increasing high
clouds this afternoon...especially west new eng as high level
moisture moves in ahead of a middle level shortwave. With light
winds...expect a nice recovery in temperatures after very cold start.
Maxes will reach the upper 20s to low/middle 30s.

&&

Short term /6 PM this evening through Friday night/...
tonight and Friday...

Digging shortwave from the upper lakes will move southeast and phase with
another impulse moving out of the Ohio Valley to form a negative tilt
trough along the new eng coast on Friday. Primary low lifts NE into
northern New York tonight while secondary low develops near the southern New England
coast Friday associated with the middle level shortwave and height falls
moving to the coast. European model (ecmwf) is furthest south with the secondary
low and as a result has more quantitative precipitation forecast than the other models. The track
of the 700 mb low will be critical to where heavier snowfall sets
up.

Deepening moisture and increasing middle level lift will result in a
period of snow developing across southern New England later tonight into Friday.
However...southerly flow ahead of the primary low will likely warm
the boundary layer enough for a mix or changeover to rain late
tonight into Friday along the immediate S coast and especially
cape/islands.

The 700 mb low tracks across southern New England which suggests heavier snow will
set up across northern areas...mainly north of the Mass Pike with
lighter snow to the south. Through Friday...generally looking at
2-3 inches north of the Pike with 1-2 inches to the
south...except less than an inch near the South Coast.

Expect gradual improving conditions in the CT valley during the
afternoon...with gusty northwest winds developing by late in the day.

Friday night...

Middle level trough closes off just south of the southern New England coast as coastal
low intensifies in the Gulf of Maine. As mentioned above...European model (ecmwf)
is furthest S with the surface low and thus is most bullish on
brining a period of heavier snow...mainly to north/NE Massachusetts. We used a
multi model blend of quantitative precipitation forecast as a basis for snow accumulate. Models are
in agreement the middle level low moves into the Gulf of Maine with
a band of snow in the comma head rotating into the eastern half of
southern New England. Expect an additional inch or 2 for central and east Massachusetts...with
locally higher amounts possible across NE Massachusetts. Will have to watch
this area for the potential of higher accumulate per European model (ecmwf).

We decided on a Winter Weather Advisory for areas north of the
Mass Pike in north/NE Massachusetts where heaviest snow expected...for the period
from midnight tonight to Friday night. Current thinking is total
accumulate through Friday night will be 4-6 inches north/NE Massachusetts with locally
higher amounts possible. Low probability that warning will be needed for
NE Massachusetts per European model (ecmwf)...but confidence not high enough so we opted for
an advisory.

Turning much colder Friday night as gusty northwest winds develop with
deepening low pressure in the Gulf of Maine. Dangerously cold wind
chills of 10 to 20 below zero in higher terrain of central and west
Massachusetts...with 5 to 10 below in the coastal plain. Wind chill
advisories will likely be needed for higher terrain in central
and west Massachusetts.

&&

Long term /Saturday through Wednesday/...
* snow eastern areas Friday night diminishes as low exits the area
* Arctic air invades New England this weekend on brisk northwest winds
* coastal storm possible Sun night-Mon, but low confidence

Overview...low pressure center is expected to be off the Maine coast
Friday night. Snow is most likely eastern areas...especially coastal
areas closer to this low such as Boston and points north. The
snow is forecast to gradually wind down during the night Friday night
as the low pulls away.

Arctic air will usher into New England behind this departing low for
the weekend with blustery northwest winds and frigid wind chills. Winds
chill advisories may be needed Friday night.

A more vigorous shortwave dives into the eastern states Sun night
and Monday. Models continue to struggle with regards to the
amplitude of the trough and the corresponding surface low and track.
The latest 28.12z operational runs of the GFS and European model (ecmwf) now are more
progressive and show a weaker surface low and well east of the
benchmark. However both models did just the same several days
before our recent blizzard...so we cannot have any degree of
confidence with either a hit or a miss this far out in time. We
will continue to use a model blend including their ensembles as
there is a high degree of spread amongst them.

High pressure will build into the region Tuesday-Wednesday as the
shortwave/low moves east with high pressure taking over...bringing
quiet weather middle week. Yet another chance of snow or a wintry
mix enters the picture by Thursday. An active wintertime pattern
indeed!

&&

Aviation /08z Thursday through Monday/...
forecaster confidence levels...

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

Short term...through tonight...high confidence.

Today...VFR. Increasing clouds above 10 k feet in the afternoon.
Light wind

Tonight and Friday...ceilings lower overnight to MVFR/IFR in
occasional snow. The snow may mix or change to rain along the
immediate S coast and especially the cape/islands late tonight
and Friday. Snow diminishes Friday afternoon in the CT valley but
continues across east new eng. Winds shift to northwest during the
afternoon. Gusts to 25-30 knots and VFR ceilings developing in the CT
valley by middle/late afternoon.

Kbos taf...high confidence...but lower confidence on exact timing
of snow and lower cigs/vsbys.

Kbdl taf...high confidence...but lower confidence on exact timing
of snow and lower cigs/vsbys.

Outlook /Friday night through Monday/...

Friday night...low confidence. VFR west. Possible IFR to start
for eastern locales...but with improvement expected overnight.

Saturday-Sunday...high confidence. VFR. Gusty northwest winds
25-35 knots Saturday...lighter winds Sunday.

Sunday night-Monday...low confidence. Coastal low track highly
uncertain. Just way too early to have any confidence on VFR or IFR
this period.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...high confidence.

Today...high pressure builds over the waters with diminishing winds
becoming light and subsiding seas below Small Craft Advisory.

Tonight...increasing southerly winds expected ahead of low pressure
moving through the Great Lakes...but wind gusts should remain below
Small Craft Advisory.

Friday...southerly winds will shift to west then northwest during Friday
afternoon...with gusts to 25-30 knots developing across Rhode Island coastal
waters by late afternoon.

Outlook /Friday night through Monday/...moderate confidence Friday-
Sat...low confidence sun-Mon.

Friday...low pressure will cross the waters. Expect reduced visibilities in
snow. Expect winds to shift to northwest and increase Friday night...with
gales possible over the waters. Freezing spray will likely develop
Friday night.

Saturday...northwest gales expected with potential for freezing spray. High
Seas Forecast...10-12 feet offshore waters. Winds will begin to
diminish Sat night with a corresponding lowering of seas.

Sunday...winds and seas at Small Craft Advisory levels early
Sunday...but will diminish through the day.

Sunday night-Monday...much will depend on strength and track of a
possible coastal low so take the official forecast of winds/seas
during this period with a grain of salt. A low closer to the coast
would spell a significant impact to mariners...while an
offshore/weaker track would have much less impact. Too early to
say either way...so went with a model blend.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...Winter Weather Advisory from midnight tonight to 6 am EST
Saturday for maz004>007-014-026.
Rhode Island...none.
Marine...Small Craft Advisory until noon EST today for anz250-254.
Small Craft Advisory until 10 am EST this morning for anz255.

&&

$$
Synopsis...kjc
near term...kjc
short term...kjc
long term...99
aviation...kjc/99
marine...kjc/99

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