Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
246 am EST Thursday Mar 5 2015

Synopsis...
a front will stall south of New England overnight. Low pressure
will push along the front with another round of snow overnight into
Thursday...mainly across southern CT...RI...and southeast Massachusetts. High
pressure will build in for Friday through this weekend...bringing
dry conditions with colder than normal temperatures. A couple of
weak cold fronts may slip through with widely scattered snow showers
Saturday night and Monday.

&&

Near term /until 6 PM this evening/...
130 am update...

Cold front has made its way toward the coast and at 1 am stretched
from near Marshfield Massachusetts to Groton CT. Temperatures were slowly
falling behind it...now below freezing in the Berkshires.
However...dewpoints were really falling with readings in the upper
teens and lower 20s ushering in much drier air into northern and
western Massachusetts. Hence the sharp cutoff of precipitation expected on
the northern edge.

Tough forecast because satellite imagery shows a very moist
continuous feed from the Gulf to southern New England. Thus...the
precipitation...which will be changing over to snow by daybreak...
should continue for most of the day today along the South Coast of
Rhode Island and Massachusetts. This could amount to a good deal of snow. But...farther
to the north it now looks like Boston...Worcester..and Springfield
may not receive any snow. New wpc graphic confirms this thinking.

For those wondering about bos snowfall record...we need 1.9
inches to tie 1995-96. Our latest forecast has about 0.7 inches at
bos but this may not even pan out.

&&

Short term /6 PM this evening through 6 PM Friday/...
focus for steadier snowfall will be over southeast New England Thursday
morning with rapid drying from northwest bringing clearing to interior by
afternoon. Expect additional 2 to 4 inches during day across S
coastal Rhode Island/Massachusetts and Cape Cod/islands with less than inch as far north as
Mass Pike. Definitely colder day ahead with highs only in 20s
except near 30 on cape and islands.

Clearing sets in across all of region Thursday night as system heads
farther out to sea and high pressure builds in. Another shot of
bitterly cold air arrives with lows from about 5 below to 5 above
across interior to teens closer to coast.

&&

Long term /Friday night through Wednesday/...
big picture...

Broad trough over the eastern USA during the weekend with below
normal contour heights over New England. This feature flattens
during next week with contour heights returning to near normal or a
little above. This suggests cooler than normal weather over the
weekend trending closer to normal during the week.

The weather-supporting features will be guided by weak shortwaves in
the flow. As such...confidence is low in the timing of these
shortwaves. To minimize this...we used a blend of model data.

The dailies...

Friday night-Saturday...

High pressure moves offshore Friday night setting up a west-
southwest flow across New England. Another northern stream shortwave
dives south from northern Canada to the Great Lakes Saturday and New
England Saturday night. Limited jet support within the northern
stream while high pressure across the south blocks any inflow of
moisture into the northern system. Expect an increase in sky cover
Saturday and maybe some isolated snow showers.

Sunday through Wednesday...

Same story every couple of days. Another northern shortwave and
surface cold front may bring scattered or isolated snow showers.
High pressure in place to our south will again block inflow of any
significant precipitation. An inverted trough south of the high and along the
Gulf of Mexico suggests that the moisture is there to be
tapped...just that it is being pushed east out to sea to our south.

So this is a generally dry period with a moderating trend on
temperatures.

&&

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 Friday/...moderate confidence.

Pockets of IFR persist across portions of Cape Cod and the
islands. VFR with isolated MVFR ceilings elsewhere.

MVFR/IFR spreads north in light snow toward daybreak...probably as
far north as kijd-sfz-kpym...mainly due to visibility. Light rain changes to
sleet and snow closer to S coast after 09z where LIFR expected
through daybreak Thursday. VFR ceilings farther north and west. MVFR ceilings also
spreading from the Berkshires into western Massachusetts and western CT
between 06z and 09z.

Conditions slowly improve Thursday from northwest to southeast...with Cape Cod and
islands last to improve 16z-20z.

Expected general snow accumulations...
bos/baf/bdl/bed/orh...little or no snow
pvd...2 inches
fmh/hya...3-4 inches
ack...5-7 inches

Kbos taf...high confidence.

Kbdl taf...high confidence.

Outlook...Friday night through Monday...moderate confidence.

VFR. Brief MVFR ceilings/visibilities possible Saturday in widely scattered
snow showers.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...moderate confidence.

Maintaining Small Craft Advisory on outer waters and Block Island/Rhode Island sounds
primarily due to seas through Thursday or Thursday night.

Cold front approaching the coast as of 1 am. It will drops S
overnight with wind shift to northwest and possibly a few gusts to 25 knots.
Spotty light rain will give way to sleet and snow toward daybreak.

Snow should mainly affect S coastal waters Thursday before heading
offshore Thursday night. High pressure building in to region may bring
period of 25kt northwest wind gusts Thursday night...mainly on outer waters.

Outlook...Friday night through Monday...moderate confidence.

Friday...north winds below 25 knots. Seas less than 5 feet.

Saturday...increasing southwest wind with frequent gusts to 25 knots
possible in the afternoon and evening. Seas build to 3-5 feet on the
outer waters. A Small Craft Advisory may be needed.

Sunday-Monday...winds below 25 knots. Seas generally below 5
feet...although occasional 5 foot seas possible on the outer waters.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...Winter Storm Warning until 7 PM EST this evening for maz023-
024.
Winter Weather Advisory until 7 PM EST this evening for
maz020>022.
Rhode Island...Winter Storm Warning until 7 PM EST this evening for riz008.
Winter Weather Advisory until 7 PM EST this evening for
riz003>007.
Marine...Small Craft Advisory from 5 PM this afternoon to 7 am EST
Friday for anz231-251.
Small Craft Advisory until 6 am EST Friday for anz235-237.
Small Craft Advisory until 10 am EST Friday for anz250-254>256.

&&

$$
Synopsis...wtb/gaf
near term...gaf
short term...gaf
long term...wtb
aviation...wtb/gaf
marine...wtb/gaf

National Weather Service Glossary of Abbreviations