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Area forecast discussion 
National Weather Service Taunton Massachusetts
1256 am EST Thursday Jan 29 2015

high pressure over the eastern Great Lakes will build over New
England tonight and Thursday...then move east Thursday evening.
This will bring very cold air for tonight and then moderation on
Thursday. An Alberta clipper will move east from the plains and
bring a chance of snow Thursday night through Friday night. Very
cold conditions linger through the weekend. Another storm may
bring snow to the region Sunday night and Monday.


Near term /until 6 am this morning/...
1250 am update...
ocean effect clouds still locked in across the cape and islands
but clouds are beginning to south and expect gradual clearing
trough daybreak. Otherwise...skies are clear. Good radiational
cooling will result in very cold temperatures with lows dropping below
zero in the colder spots in west Massachusetts and east Massachusetts. Will make a few
modifications to low temperatures.


Short term /6 am this morning through 6 PM Friday/...
Thursday...high pressure overhead and low dewpoints should result
in a dry weather day. As the high moves offshore...moisture from
the next system will start streaming in at high levels. The
afternoon should feature increasing/thickening high clouds which
may dim the sun. Temperatures at 950 mb will be around -5c and
would support surface maximum temperatures either side of 30f. Cape Cod and
islands may inch a tad higher to the middle 30s.

Thursday night and Friday...

We continue to watch disturbances in both the northern and
southern streams which are expected to phase by Thursday and
evolve into an elongated trough over the eastern USA by Friday.
The primary low actually races toward the Great Lakes Thursday
night. But the southern upper jet curls around the elongated
trough and extends its left exit region either over or just south
of southern New England. This should support a coastal development
off our coast on Friday. A more northerly development would focus
low level lift and precipitation farther north...a more southerly
development would bring things farther south. The GFS suggests the
northern solution...the European model (ecmwf) and ggem develop the secondary
southeast of Nantucket.

We have opted more toward the southern development. This would
support roughly 0.20 to 0.30 inches of precipitation during Thursday night
and Friday. Thermal profiles mostly favor snow...but with some
potential for rain mixing in midday before the secondary develops
and pulls colder air in. This suggests snow accumulations of 2-5
inches with the the eventual need for a Winter Weather Advisory
when the storm gets closer.


Long term /Friday night 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 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


Aviation /06z 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. Some rain may mix in along the immediate S coast
and especially the cape/islands late tonight and Friday morning. Snow
diminishes Friday afternoon but lingering across portions of east Massachusetts.
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.


forecaster confidence levels...

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

Short term/tonight through Friday/...high confidence tonight and
Thursday...moderate confidence Thursday night and Friday.

10 PM update...dropped Small Craft Advisory for anz256 as seas have dropped below 5

Tonight...diminishing northwest wind. Diminishing freezing spray
potential. Still rough seas with 5-7 feet on the outer waters as
well as parts of Cape Cod Bay and Massachusetts Bay. We will keep
the Small Craft Advisory in effect for these waters through the
part or all of the night.

Thursday...high pressure builds over the waters. This should bring
light wind which will allow seas to subside. A Small Craft
Advisory will linger into the morning on the outer waters east of

Thursday night-Friday...low pressure from the Midwest will
redevelop over the coastal waters Friday. Snow will move in after
midnight and through the morning Friday with reduced visibility.
South winds will slowly increase with gusts to 20 knots by Friday
morning. Winds will then shift to northwest Friday afternoon with
potential for 30 knot gusts by evening.

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 went with a model blend.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory until noon EST today for anz250-254.
Small Craft Advisory until 4 am EST early this morning for
Small Craft Advisory until 6 am EST early this morning for


near term...kjc
short term...wtb
long term...gregoria

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