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Area forecast discussion 
National Weather Service Taunton Massachusetts
440 am EDT Friday Oct 31 2014

dry and seasonable conditions will continue today as high pressure
moves across northern New England. A developing coastal storm
will move up the coast Saturday and pass offshore Saturday night
and early Sunday. High pressure builds over the eastern U.S. For
early next week. One or two cold fronts may cross southern New
England Wednesday and Thursday.


Near term /until 6 PM this evening/...
area of low to middle level clouds remain across central and eastern
areas at 07z...though noting some clearing across the CT valley as
well as along the S coast on latest infrared satellite loop. NAM and GFS
BUFKIT soundings indicating that the 5-6kft ceilings may break up
briefly around middle to late morning before redeveloping as NE winds
bring in increasing low level moisture during the afternoon...
again across central and eastern areas.

Low pressure moves southeast out of the Great Lakes...then secondary
development begins off the middle Atlantic coast. Looks like most of the
deep moisture with the cyclogenesis will remain S of the region so
have kept a dry forecast going. May see some sprinkles and patchy
drizzle develop late in the day along the East Coast...but not enough
to mention at this point.

Expect temperatures to only rise to the upper 40s across the higher
inland terrain...then mainly in the 50s elsewhere with the
freshening east-NE winds especially during the afternoon.


Short term /6 PM this evening through 6 am Saturday/...

Tonight...short range models appear to be in better agreement in
the development of not one but two centers of low pressure as 500 mb long
wave trough digs across the southeast U.S. Noting two strong upper level
jets moving around the base of this digging trough...the first
90-100 knots 300 mb jet axis works NE overnight. This will help
intensify the first low off the middle Atlantic coast around 12z Sat.

Area of rain will work steadily northward...especially around or
after midnight. Will also see NE winds increase along the coast
with gusts up to 25-30 knots...highest along the S coast...Cape Cod
and the islands. Best shot for precipitation will be across Rhode Island/east Massachusetts.

Expect overnight lows to range from the upper 30s over SW New Hampshire to
between 45 and 50 along the coast.


Long term /Saturday through Thursday/...
big picture...
deep amplitude troughs on both coasts Saturday with a ridge in
between. Shortwave moving through the eastern trough generates a
cutoff upper low with two jet streams...a northern stream along
the Canadian border and a southern stream moving with the short
wave. The pattern shifts east during the week with the ridge
building over New England. The pattern then transforms to a more
zonal flow. Remains of the Pacific coast trough move across New
England midweek.

Colder than normal heights with the eastern trough this weekend.
Heights increase to normal or a little above normal by midweek.
This points to a colder than normal weekend...trending to normal
temperatures by midweek.

31/00z guidance suite remains in decent overall agreement. There
also remain some differences with track...intensity and timing. At
this point it appears snowfall is mostly off The Table away from a
very brief period late Saturday night across the higher terrain.
Even will not amount to much. Favored a blend to smooth
over some of the more minor differences. This resulted in very
good continuity with the previous forecast.

The dailies...

coastal storm continues to be indicated for Saturday and early
Sunday. Support comes from two sets of forcing mechanisms...
suggesting a two-part event. Initial forcing comes from right
entrance region of northern stream jet Saturday morning. This will
send a coastal wave of low pressure past southern New England
during the day Saturday.

The second forcing comes from left exit region of jet supporting
a potent shortwave rounding the base of the eastern trough late
Saturday/Saturday night. Even so...most of the frontogenetic
forcing with each segment is focused offshore into the Maritimes
and Maine. The western edge of this forcing should extend into
southern New England with the first...and possibly the second...of
the segments. We expect rain Saturday and Saturday night with
highest probability of precipitation over Cape Cod and the islands...lesser values north
and west.

Strong pressure gradient at the surface and a 50 knot low level
jet will contribute to windy conditions. The strongest winds will
be over the eastern/southeast waters. Strongest land winds will be
over the Outer Cape and islands...diminishing farther west. Have
featured 45 knots for the strongest winds and 20-25 knots in the

A coastal storm will pass US in pieces Saturday and later
Saturday noted above. Expect precipitation to diminish
west to east after midnight and end on the Massachusetts East Coast after
sunrise Sunday morning.

Temperatures through most of this storm should remain favorable
for all rain. As the winds shift from northeast to northwest
Saturday night...colder air will be drawn in which could change
the last showers over to snow across the higher terrain. Any
accumulations should not be much more than a trace...where it
snows at all.

Drier air Sunday will bring clearing skies. Cold advection will
promote mixing through at least 850 mb. Winds in this layer will
be 35 to 40 expect northwest gusts to at least the
lower end of this range. Winds diminish Sunday night as the storm
moves farther away.

high pressure builds over the region. Monday should be sunny as
this high moves overhead. Mixing will again bring increased wind
gusts during the afternoon. Winds in the mixed layer are expected
around 30 knots with potential for a little stronger speeds. Winds
will diminish with sunset.

This high pressure moves offshore Tuesday. This will make room
for a warm front to swing past. Sufficient lift and moisture to
support middle and high clouds...but the best warm frontal lift will
remain to our north and west so expect at least some sun through
the day.

low confidence on midweek weather. At least one trough in the
zonal flow will swing across the region during this time. GFS and
European model (ecmwf) are hinting at one on Wednesday...but showing a more
substantial trough passing on Thursday. The forecast will have
clouds and low-end chance or slight chance probability of precipitation.


Aviation /08z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /through tonight/...

Through 12z...mainly VFR. Local MVFR-IFR visibilities in patchy fog in
normally prone areas.

Today...high confidence. VFR. Any leftover MVFR visibilities in patchy
fog will improve by 14z.

Tonight...moderate confidence. Conditions deteriorate through the
night to MVFR-IFR from south to north with lowest conditions along
the coast. Expect light rain along the S coast and into southeast Massachusetts
around or after midnight...moving into the remainder most of the
region toward daybreak.

Kbos...high confidence in taf.

Kbdl...high confidence in taf.

Outlook...Saturday through Tuesday...moderate confidence.

Saturday-Sunday...IFR ceilings and MVFR or IFR visibilities in periods of rain
Saturday and Saturday night. VFR and drier weather move in from west
to east early Sunday. Northeast winds Saturday gusting 35-45 knots
on the cape and islands and 25-35 knots across the coastal plain.
Winds shift to north Saturday night and northwest Sunday. Gusts 40-
45 knots on the cape and islands...with 25-35 knots elsewhere across
southern New England.

Monday...VFR. Daytime wind gusts will increase to near 30 knots
inland and 35 knots cape and islands...diminishing toward evening.

Tuesday...VFR with increasing high clouds.


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...winds and seas remain below small craft criteria. Winds
will veer to east-NE during the day and begin to pick up. Gusts up to
20 knots reach the southern outer waters by late in the day. Seas
remain below 5 feet.

Tonight...E-NE winds increase with gusts up to 25-30 knots. Small
crafts remain in effect for most of the waters...but not quite
there for Boston Harbor and mass/Ipswich bays. Seas will also
build especially on the southern open waters during the night.

Outlook...Saturday through Tuesday...moderate confidence.

Saturday...strong potential for high end gales...with low
potential for storm force winds. On the outer waters...expect
gusts to at least 45 knots.

Expect rain with increasing northeast winds. Gale force gusts
expected on most of the waters. Right on the edge of gale force
winds in Boston Harbor and Narragansett Bay. Gale watches posted
for all waters. Kept it simple for now...but will definitely need
to refine the timing for the near shore waters with later

Sunday...rain moves off to the east. Winds shift northwest with
gale force gusts up to 45 knots. Expecting these winds to diminish
below gale force Sunday night. With the wind shift...rough seas
will transition farther offshore with diminishing seas closer to
shore. Gale warnings will likely linger into the evening hours.

Monday...gusty northwest winds with wind gusts approaching gale
force again during the day. Winds diminish toward evening. Seas
will linger at 5-9 feet...especially on the outer waters. Small
Craft Advisory is likely...low end chance that gales may be needed
on some of the waters.

Tuesday...winds and seas should remain below Small Craft Advisory


Tides/coastal flooding...
astronomical high tides are rather low Saturday evening and again
early Sunday morning. However...strong northerly winds and high
seas will have the potential to result in minor coastal flooding
and beach erosion along the eastern Massachusetts coast...particularly the
north side of Cape Cod and Nantucket Harbor during both high tide

The main uncertainty revolves around when and how strong the
winds/seas will get. The models seem to be showing two pulses of
wind with two waves of low pressure. The first one appears to be
Saturday evening with the second one Sunday morning. The potential
continues for wind gusts up to 50 knots and seas building to 20
feet across the open waters east of Massachusetts. The trend of
the 12z guidance has been to show the strongest winds/highest seas
with the Saturday evening pulse. Will have to wait and see how the
models trend...but still feel both high tide cycles are at risk
with a 1 to 2 foot storm surge.

Areas of greatest concern appear to be the north side of Cape
Cod...such as Sandwich...Barnstable...Dennis...Brewster and
possibly Eastham. Other typical hot spots will be Salisbury and
Plum Island...Hull...Scituate and perhaps Sandwich Harbor and
Nantucket Harbor. Again...the main concerns will be minor coastal
flooding as well as beach erosion.


Box watches/warnings/advisories...
New Hampshire...none.
Rhode Island...none.
Marine...gale watch from Saturday morning through late Sunday night for
Small Craft Advisory from midnight tonight to 6 am EDT
Saturday for anz231>234-250.
Small Craft Advisory from 8 PM this evening to 6 am EDT
Saturday for anz235-237-254>256.


near term...evt
short term...evt
long term...wtb
tides/coastal flooding...Belk

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