Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Taunton Massachusetts
925 PM EDT Friday Mar 14 2014
a cold front will move across the region Saturday and will be
preceded by mainly rain showers very late tonight and Saturday
morning. Mild conditions Saturday will be replaced by below normal
cold Sunday and especially Monday as Arctic high pressure builds to
the north. A coastal storm is expected to pass far enough offshore
Monday to spare the region a winter storm. A cold front will bring
more precipitation Wednesday and Thursday.
Near term /until 6 am Saturday morning/...
925 PM update...
Dry weather will persist through much of the night...but middle level
cloudiness will continue to increase out ahead of an approaching
shortwave. Developing low level jet of 50 knots along with a burst
of elevated instability should allow a band of mainly rain showers
to develop very late. Expect this band of showers to sweep across
the region between 4 am and 10 am. While the activity should be
short lived in a given location...feel most locations will probably
see a brief period of rain showers so will run with likely probability of precipitation.
As for ptype...warming boundary layer will result in mainly rain
showers. However...initially dry air may cause soundings to go
isothermal for a time across the higher terrain of southwest
New Hampshire/western Massachusetts resulting in a brief period of wet snow. Any
accumulations would be a dusting to less than 1 inch. Given
southerly winds at the surface...appears any freezing rain threat is
a low probability but it can/T be completely ruled out. Will
continue to monitor but no plans for any advisories at this point.
In terms of temperatures...given increasing low level jet readings will
remain steady or slowly rise overnight. In fact...much of the
coastal plain should already have temperatures at 40+ by daybreak Saturday.
Short term /6 am Saturday morning through Saturday night/...
expect a band of light rain showers to be moving through eastern
New England during the first part of the morning...then skies will
become ptsunny by midday as the column dries out. There is enough
low level moisture for broken cumulus in the afternoon with most cloud
cover in the interior. It will be a mild day with increasing
west winds and afternoon sun allowing temperatures to reach low/middle 50s
in the coastal plain and 40s over the interior higher terrain.
West wind gusts to 25-30 miles per hour expected to develop in the afternoon.
cold front moves offshore followed by a decent shot of cold air
advection. It will be dry with a period of gusty northwest winds. Min
temperatures will be in the 20s...except teens northwest.
Long term /Sunday through Friday/...
big picture... Sunday starts with closed upper low over eastern
Canada and a ridge along the West Coast...and seperate
northern/southern streams in the eastern USA. Early week...the low
ejects through Labrador and the western ridge breaks down. This
leaves US in a progressive and changeable flow through the week.
Of interest to New England are two shortwaves. One in the southern
stream races south of New England Monday. One in the northern
stream moves through late in the week...with model differences on
Sunday... Arctic high pressure north of the Great Lakes extends into
New England Sunday with cold dry air. Dewpoints are forecast in the
single numbers...possibly below zero in spots. Mixing heights are
forecast to reach up to 900 mb and may reach a little higher. Temperatures
at 900 mb would support maximum surface values of 25-30...climbing a little
higher would support 28-35. Will stay close to model concensus for
now. But some concern that maximum temperature forecast may be 3-4f too warm
especially in Rhode Island/southeast mass. Winds at the top of the mixed layer are
forecast at 25-30 knots...which is higher than model gust forecast.
We bumped gusts up to near 25 knots.
Sunday night-Monday... southern stream low pressure moves across the
deep south Sunday night and reaches the coast late at night. Surface
high shows no sign of retreating north and the upper flow remains
progressive. In line with this...the GFS and European model (ecmwf) carry the storm
out to sea and mostly south of southern New England. Model quantitative precipitation forecast
fields do bring the 0.01 inch contour to the islands south coasts of
Rhode Island and mass...but with the bulk of precipitation out to sea. We will maintain
cloudy skies. But we have backed off on the extent of probability of precipitation in the
forecast from late Sunday night through Monday with slight chance
values in northern CT and northern Rhode Island...and chance probability of precipitation along the South Coast.
High pressure shifts south Monday night and brings a clearing trend
to the region Monday night.
Tuesday... high pressure in place with mostly clear skies and dry
air. Temperatures at 925 mb of -6 to -8c should support maximum surface temperatures in
Wednesday-Thursday... northern stream shortwave moves through the
plains Tuesday and generates a surface low and cold front that lift
through the Great Lakes on Wednesday. Southwest winds will increase
ahead of the low/cold front...with a low level jet of 45-55 knots at
2000-5000 feet above the ground. This jet will ride over the colder
surface air over New England and produce clouds for Wednesday-
Thursday as well as an increasing chance of rain or snow. The
trailing cold front crosses New England sometime Thursday...but
model differences of 18 hours in the timing of cold frontal passage. We will
forecast chance probability of precipitation for the period from Wednesday afternoon through
Thursday. Temperatures should be a little milder each day with values
around seasonable levels.
Friday... high pressure builds with mostly clear skies and drier
air. Temperatures will cool from Thursday...but should remain near or just
below seasonable levels.
Aviation /01z Saturday through Wednesday/...
low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Short term...through Saturday night...moderate confidence.
Tonight into Saturday...moderate confidence. VFR first half of
tonight. A period of MVFR conditions expected from west to east
08-15z as scattered rain showers move through. Local IFR
possible. There may also be some wet snow or pockets of freezing
rain across northwest Massachusetts and SW New Hampshire. Conditions improving to VFR Sat
afternoon with west wind gusts to 25-30 knots developing.
Sat night...VFR. High confidence.
Kbos terminal...moderate confidence in taf. A period of MVFR
possible Sat morning in a few showers.
Kbdl terminal...moderate confidence in taf. A period of MVFR
possible late tonight into early Sat in a few showers.
Outlook...Sunday through Wednesday...moderate confidence
Sunday...VFR with northwest winds gusting to 25 knots. Winds
diminish Sunday evening.
Monday...low pressure offshore remains mainly offshore but may clip
our South Coast. VFR north of the Mass Pike. MVFR ceilings possible to
the south. MVFR ceilings and visibilities possible along the South Coast and
Wednesday...conditions may start the day VFR but should lower to
MVFR in ceilings during the afternoon/evening. MVFR/IFR visibilities possible
Wednesday night. Increasing southwest winds at 2000 feet with 40-50
knots possible late in the day...and potential for low level wind
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Short term /today through Saturday night/...high confidence.
Small Craft Advisory conditions will persist through Sat night.
SW wind gusts to 25-30 kts expected tonight into Saturday associated
with a low level jet across the waters. Winds will shift to the
west Sat afternoon. Winds shift to northwest Sat night and gusts to
25-30 kts will continue with good cold air advection.
Outlook...Sunday through Wednesday...moderate confidence.
Sunday...west to northwest winds may gust near 25 knots at
times...especially off Cape Ann. Seas will linger at 5-6 feet on the
outer waters. A Small Craft Advisory may be needed.
Sunday night-Monday... winds will shift to north or northeast as low
pressure passes well offshore. Winds will gust 20-25 knots off the
eastern mass coast...and 25-30 knots off the Rhode Island and mass south
coasts. A Small Craft Advisory may be needed. There is a low
probability that a Gale Warning may be needed for a portion of the
Tuesday... lingering 25 knot winds south of mass and Rhode Island...otherwise
winds and seas will be less than small craft thresholds.
Wednesday...southeast winds less than 25 knots. Seas may build to 5-
6 feet by Wednesday evening and night.
Marine...Small Craft Advisory until 8 PM EDT Saturday for anz230>237-