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Area forecast discussion 
National Weather Service Taunton Massachusetts
1014 am EST Thursday Mar 5 2015

Synopsis...
a cold front will stall south of New England while weak low
pressure travels along the front today. This will bring snow to
southern portions of the forecast area through the day. 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/...
1015 am update...updated the snowfall forecast to up the snow
amounts within a stronger band that set up basically along the 195
corridor between Providence and the cape. This may allow this area
to get close to or possibly even reach 3 inches just north of the
advisory area...however confidence is low that this will occur or
that the area will be large enough to warrant adding zones to the
Winter Weather Advisory. Will keep headlines as they are.

The northern edge of the snow is very tight despite radar
reflectivities. Dewpoints have already crashed into the single
digits across much of southern New England. The northern edge of
the snow based on observations runs roughly from Willimantic
Connecticut...to Providence Rhode Island and Plymouth
Massachusetts.

Otherwise...updated temperatures as well to account better for
the falling temperatures.

Previous discussion...

Tough forecast because satellite imagery shows a very moist
continuous feed from the western Gulf of Mexico to New England.
Thus...the precipitation should continue for much of the day
today along the South Coast of Rhode Island and Massachusetts. However...farther to the
north where the drier air is moving in...it now looks like
Boston...Worcester..and Springfield may not receive any snow. A
few flurries at best.

After the mild day yesterday...today will feel much colder.
850 mb temperatures will be plunging to temperatures will be
falling from near 0c this morning to -15c by evening. Surface
temperatures will drop into the 20s and may hold steady for a
while during the day before plunging tonight.

Northwest winds may be initially gusty this morning behind the
front but am not expecting it to be a windy day.

Model quantitative precipitation forecast is quite consistent for southern Rhode Island and S coastal
Massachusetts...with totals between 0.50 and 0.75 inches...some of which has
been in the form of rain and sleet. Still do get computations of
2 to 5 inches along the south coasts of Rhode Island and Massachusetts and 4 to 6
inches over the islands...from Block Island eastward to
Nantucket. Will keep the Winter Weather Advisory in place from
southern Rhode Island eastward to Cape Cod. Big question has been whether to
lower the Winter Storm Warning to an advisory for the islands.
Technically one needs an average of 6 inches. However...since we
do have very close to those amounts...have decided to leave the
warning in place as well. One could argue that there will be some
additional impact of a layer of ice as the rain freezes with
falling temperatures.

&&

Short term /6 PM this evening through 6 PM Friday/...
clearing sets in across all of region tonight as system heads
farther out to sea and very strong high pressure builds into the
Ohio Valley and appalachian region. Clear skies and northerly
winds will spell another bitterly cold night. Winter is not over
yet. Overnight low temperatures will range from from about 2 below
to 5 above across the interior...to the teens closer to coast.

NAM seems to be capturing the magnitude of the cold air over the
ocean waters the best with 925 mb winds up to 25-30 knots and swannam
showing seas building to 4 to 6 feet over the eastern Massachusetts waters.
Surface winds could have gusts to 20-28 knots over the waters.
Have issued a freezing spray advisory for the northeast Massachusetts
coastal waters for tonight.

A sunny but cold day is forecast for Friday as high pressure
centered over Delaware-Maryland-Virginia ridges northeastward across southern New
England. Highs only in the 20s with light winds.

&&

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 /15z 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 today. High
confidence tonight and Friday.

IFR and MVFR conditions in light to occasionally moderate snow
across southern portions of the region...mainly south of a line
from hfd-sfz-tan-ghg. These conditions persist most of the day.
VFR to occasional MVFR ceiling north of that line.

Skies begin to clear from northwest to southeast late this afternoon...reaching
Cape Cod and Nantucket this evening. Clear skies expected later
tonight through Friday.

Expected general snow accumulations today...
bos/baf/bdl/bed/orh...no accumulation.
Pvd...2 inches
fmh/hya...3-4 inches
ack...4-6 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.

Small craft advisories have been extended into middle-morning on
Friday for the outer waters. A Small Craft Advisory is in effect
for mass Bay and Ipswich Bay and for Block Island/Rhode Island sounds
through tonight. Seas will build to 5 to 6 feet over the outer
waters and even into a portion of Cape Cod Bay as well as Block
Island/Rhode Island sounds.

A freezing spray advisory has been posted for the waters east of
Cape Ann and east of Boston for tonight. Temperatures in the teens
may combine with northerly wind gusts to 20 to 28 knots to create
moderate freezing spray which could be a danger to mariners.

A cold front was moving off of Cape Cod as of 3 am and it will be
exiting the coastal waters early this morning...then stall as low
pressure travels along the front. Rain will change to sleet and snow
toward daybreak. Snow will continue across the southern coastal
waters through much of the day before heading offshore tonight.

Strong high pressure builds into the region from the west and this
may cause a period of 25 knots northwest to north wind gusts tonight...mainly on
the eastern outer waters.

Friday...north winds begin to shift to the southwest. Winds below
25 knots. Seas less than 5 feet.

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

Friday night and Saturday...increasing southwest wind with
frequent gusts to 25 knots possible by Sat 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.
Freezing spray advisory from 8 PM this evening to 5 am EST
Friday for anz250-251.

&&

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

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