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Area forecast discussion 
National Weather Service Taunton Massachusetts
458 PM EST Tuesday Dec 1 2015

the bulk of a more steady rainfall will arrive into this evening
as low pressure moves along the southeast New England coast.
Another low pressure tracks over our region Wednesday and
Wednesday night...yielding a second round of rain which may be
heavy at times. As the low intensifies as it pushes to the
Maritimes on Thursday...drier but cooler and blustery conditions
move in. High pressure then takes over...with dry and seasonable
weather from Friday into early next week.


Near term /until 6 am Wednesday morning/...
a low pressure was developing off the middle Atlantic coast early
this afternoon. This low pressure will move northeast...but remain
mainly south of our region tonight. Expecting a more steady
rainfall to move into southern New England this evening and
overnight. The northward extent of this rainfall will be heavily
dependent on exactly how close to our region this middle Atlantic low
pressure tracks to our region. Most of the 01/12z guidance tracks
this low pressure just south of Nantucket. The European model (ecmwf) had the
slowest forward motion.

Expecting this low pressure to be well east of Cape Cod and
Nantucket toward daybreak. This would mean widespread rain
becoming more showery toward daybreak for most of southern New
England. Although...there could be lingering pockets of drizzle.
Areas of fog also likely to develop...some of which could be
locally dense. Kicked the tires on a dense fog advisory. Not
convinced at this time dense fog will be widespread enough to
warrant one. This potential will need to be monitored overnight.

As for temperatures...shallow cool air will likely remain
entrenched across the we remain in the northwest
quadrant of the passing low pressure. That said...modest southerly
flow higher up will keep temperatures nearly steady...or slowly
rising...through tonight.


Short term /6 am Wednesday morning through Wednesday night/...
another low pressure will approach southern New England Wednesday
evening and night. The big difference is this one will be more of
a direct hit. After a brief lull during the morning
hours...another round of widespread rainfall should arrive during
the afternoon and evening hours.

As mentioned by previous forecasters...guidance continues to
advertise a very moist airmass...with precipitable water values
of 2-3 Standard deviations above climatology. As such...cannot
rule out periods of moderate to heavy rainfall. No flooding
concerns with this event...other than typical nuisance
street/Highway flooding. Heaviest rainfall will begin to wane from
west to east after midnight Thursday...behind a cold front
crossing our region.

Since this low pressure will be farther north...expecting
temperatures to be well above freezing into Thursday morning for
most of the region. Temperatures during most of this period should
not follow typical diurnal patterns. Temperatures will most
likely not drop much until well behind a cold front crossing our
region Wednesday night.


Long term /Thursday through Tuesday/...

* drying trend moves in during Thursday...and looks to continue into
Monday as large high pressure takes over
* seasonably cool temperatures into the weekend with slightly milder
readings late this weekend into early next week
* low chance for some light rainfall moving in during next Tuesday

Overview and model preferences...
medium range guidance continues to signal highly amplified upper
level pattern across the northern tier states into Canada as split
steering flow remains dominant through this timeframe. Noting
generally good agreement through this weekend...then appears that
the models try to deamplify the upper ridge across eastern Canada
early next week. Timing of this pattern change and its effects on
surface features causing increased model solution variance beyond

Low pressure and associated front push into the Maritimes during Thursday.
Large surface high pressure develops late this week...which will sit
across the region into at least Monday as blocking high pressure
remains over the middle Atlantic. Some question noted with a small 500 mb
cold pool meandering somewhere from the Middle Atlantic States to
possibly as close as SW CT/southeast New York underneath the surface ridge.
This may cause problems with diurnal cloudiness especially across
the west...but for now have gone with partly cloudy skies through
the weekend. Some question with movement of moisture starved 500 mb
short wave in the northern stream...but appears this should remain
north of the region than a wind shift with weak surface front.

Beyond Monday...models handling the departure of the high
differently...with the European model (ecmwf) pushing it offshore to our east while
the GFS pushes it east faster while developing low pressure with the
remnant upper low off the middle Atlantic coast then tries to push it north.
Needless to say...with this being so far out...did not play too
much into the sensible weather but did mention slight chance probability of precipitation
mainly Tuesday night.

Used a blend of available guidance for this forecast through
Sunday...then transitioned over to ensemble blend for early next
week with the timing differences.


Thursday...high confidence.
As low pressure pushes into the Maritimes during will
intensify. This will cause west-northwest winds to become gusty as good low
level mixing /up to 900 hpa/ moves across beginning around midday
into Thursday night. Noting 850 hpa jet up to 40-45 knots and 1000 hpa jet
at 35-40 knots. Should see gusts up to 25-30 knots...highest across the
inland terrain...and may reach around 35 knots on the Outer Cape and
Nantucket into Thursday evening. Pressure gradient relaxes as high pressure
moves east out of the Ohio Valley so winds will diminish during the
evening. Highs will range from the Lower-Middle 40s across the higher
inland terrain to the Lower-Middle 50s across the coastal plain.

Friday through Monday...high confidence.
High pressure will expand across the northeast build Friday and
remain across the region into early next week. Dry conditions will
prevail. Do note a weak short wave moving along in the northern
stream flow...but with the high amplification looks like most of
the energy and moisture will remain north of the region during the
late Sunday or Sunday night timeframe. Likely just a wind shift
with this feature. After near normal temperatures through Saturday...
readings will rise to around 5-8 degrees above normal Sunday into

Tuesday...low to moderate confidence.
A lot of questions during this timeframe with breaking down the
upper level ridging across eastern Canada into the northeast.
Models handle this quite differently...with the GFS taking the
remnant cutoff 500 mb low sitting across the middle Atlantic and developing
low pressure that begins to move north. However...the European model (ecmwf) moves the high
pressure into the Gulf of Maine...with a developing S-southeast wind that may
cause light precipitation to develop. Ironically...while different
mechanisms in place...may see some precipitation develop late Tuesday/Tuesday
night. With such a difference in model solutions...only mentioned
slight chance probability of precipitation at this point.


Aviation /22z Tuesday through Sunday/...
forecaster confidence levels...

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

Short term /through Wednesday night/...

Through 00z...moderate confidence. VFR conditions dominate.
MVFR...with some IFR conditions...arrives from the southwest late
this afternoon. Main uncertainties with this forecast is timing.

Tonight...moderate confidence. Widespread low end MVFR to IFR
conditions in low clouds and fog. Its possible that some of the
fog may be locally dense for a time...resulting in vlifr
conditions. Periods of showers possible through the night...but
steadiest rainfall should occur this evening.

Wednesday...high confidence. Low pressure tracks over southern
New England. Periods of heavy rain and fog reducing visibility.
Expecting mainly MVFR with local IFR conditions.

Wednesday night...cold front crosses the region...resulting in
only modest improvements from west to east very late. Areas closer
to the South Coast should see the biggest
lingering low level moisture could still mean IFR conditions in
fog and stratus farther north.

Kbos terminal...high confidence in trends. Moderate confidence in

Kbdl terminal...high confidence in trends. Moderate confidence in

Outlook /Thursday through Sunday/...high confidence

Thursday...high confidence. Mainly VFR. May see leftover MVFR
ceilings early. West-northwest winds gusting to 25-35 knots. Low chance of 40 knots
gusts on the Outer Cape and Nantucket.

Friday-Saturday...high confidence. VFR. May see patchy late night
fog with brief local MVFR-IFR visibilities late Friday night.

Sunday...high confidence. VFR.


forecaster confidence levels...

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

Short term /through Wednesday night/...moderate to high confidence.

Tonight...low pressure approaching from the south will allow
easterly Small Craft Advisory wind gusts of 20 to 30 knots to
develop across portions of the southern coastal waters this
evening. Seas will also build above small craft thresholds across
all outer waters and western sounds. Another concern will be areas
of fog developing...which may be locally dense for a time.

Wednesday...another low pressure tracks over southern New England.
Periods of moderate to heavy rain and fog reducing visibility.

Wednesday night...a cold front crosses the waters very late. South
winds shift to west. Rough seas linger across the outer coastal

Outlook /Thursday through Sunday/...high confidence

Thursday...moderate to high confidence. Low pressure tracks into the
Maritimes and intensifies into a gale center. Expect west-northwest winds
gusting to 35 knots...with low risk of a few gusts to 40 knots. Seas
build up to 10 feet on the outer waters Thursday afternoon. Have issued
gale watches from midday Thursday into Thursday night for most of the open
waters. Winds should begin to diminish overnight Thursday night.

Friday...leftover northwest winds gusting to 25 knots Friday morning...then
diminishing. Seas will also subside.

Saturday and Sunday...winds and seas below small craft levels.
May start to see west winds gusting close to 25 knots Sun night on the
outer waters east and S of Cape Cod.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...gale watch from Thursday afternoon through late Thursday night
for anz231-232-235-237.
Small Craft Advisory until 1 am EST Wednesday for anz232>234.
Gale watch from Thursday afternoon through Thursday evening
for anz233-251.
Small Craft Advisory until 5 PM EST Wednesday for anz235-237.
Gale watch from Thursday morning through late Thursday night
for anz250-254>256.
Small Craft Advisory until 11 am EST Thursday for anz250-254-
Small Craft Advisory until 11 am EST Thursday for anz256.


near term...Belk
short term...Belk
long term...evt

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