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Area forecast discussion 
National Weather Service Taunton Massachusetts
400 am EST Friday Feb 27 2015

high pressure slowly building in from the west will bring dry but
unseasonably cold weather into Sunday morning. A low pressure system
will bring a period of snow late Sunday into Monday. Another
storm is likely Tuesday into Wednesday...with precipitation types


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

Sprawling high pressure from the Central Plains will result in dry
but unseasonably cold temperatures today. High temperatures will only be
in the 20s...but rather light winds will make it more tolerable then
some of our recent cold waves. A moisture starved shortwave will
approach the region from the west this afternoon. Moisture and
forcing is extremely limited so not expecting any precipitation...but
we will see a scattered to broken of clouds mixed with sunshine at


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

Large high pressure will continue to build in from the west. Skies
will become mostly clear along with light wind. The result will be
an excellent night of radiational cooling over the deep snow pack.
Low temperatures will bottom out between 5 and 15 below zero across the
normally coldest outlying locations...while other locations see
low temperatures in the single digits to around 10 above.


High pressure will remain in control of the region. Sunny skies
will allow for high temperatures to rebound into the middle to upper 20s
Sat afternoon. Winds will once again be rather it will
feel a bit more tolerable by afternoon with the help of the late
February sun angle. Nonetheless...these high temperatures will still be
about 15 degrees below normal.


Long term /Saturday night through Thursday/...
* high pressure Saturday night into Sunday
* cold front brings snow Sunday night into Monday
* another storm possible Tuesday...ptype less certain

Overview and model preferences...
noting little change in the overall pattern through the long term
with nao/ao remaining primarily negative. The biggest chance is in
the pna which looks to trend negative under a negative epo.
Therefore..this is slightly different than the overall pattern
across noam during the snow blitz period. At odds primarily is a
split flow regime and their merger /or lack thereof/ across the
eastern half of the Continental U.S.. the first wave to watch arrives via the northern
stream Sun night into Monday...manifesting as low pressure through southern
Canada and a cold frontal passage across New England. The second
may be a result of phasing of these two streams as waves move
through...which is likely why models have been struggling to
settle on a solution for the surface and low level features.
However...given this does involve the southern stream...will likely see
more moisture and higher latent heat release resulting in a
stronger system. Models are trending warming in the low-middle
levels...however with a deep snowpack in place and some ageostrophic
drainage flow possible...will need to watch for mixed p-type
issues. In any case...a blend of warmer deterministic European model (ecmwf) and
GFS with the cooler members from both ecens and gefs will show the
potential range. Will use this blend for the remainder of the
forecast as well.


Sat night into sun...
dry weather prevails as 1030+ hpa high pressure crests across the region
early sun. Overnight mins are likely to dip into the single digits
blow and above zero under the weak winds and deep snowpack.
Moderating temperatures under weak warm advection sun...but highs are
still likely to be below normal...mainly in the 30s.

Sun night into Monday...
low pressure will pass through northern New England...allowing a cold
frontal passage Sun night into Monday through southern New England. Noting
moderate isentropic lift in advance of the front...along with middle
level f-general associated with the frontal passage itself. These two sources of
lift look to act just below /but also somewhat within/ the peak
dendrite zone and thermal profiles in the lower levels are all cold
enough for snow. Therefore...given quantitative precipitation forecast values range from about 0.2
inches to about 0... level snowfalls are likely. It is
likely that accumulation will have begun before...and continue
during the Monday morning commute.

Monday night into Tuesday...
another brief ridge of high pressure moves over the region. Fast
moving embedded within confluent flow aloft. Low level thermal
profiles support temperatures remaining below normal.

Tuesday night into Wednesday night...
as mentioned above...and noted by the previous forecaster...there
remains a fair amount of uncertainty with yet another low pressure
system passing to the northwest. With the potential for phasing of the
streams is difficult to determine exactly where the low
pressure will move or whether a second low will form. Any slight
adjustment is likely to make significant changes in the thermal
profiles...but the recent trends suggest middle level warming with 850 mb
temperatures likely exceeding 0c throughout much of southern New England. With
deep snowpack...this is likely to lead to mixed precipitation types and a
potential for icing. It could start as snow even the
warmest of the available guidance begins cold enough for snow at
the first quantitative precipitation forecast onset. Given this does seem to have some connection
to the southern stream...the infusion of moisture with precipitable waters
potentially 2-3 Standard deviations above normal suggests that warning
level snow is not out of the question for areas that maintain snow
longer...with some ice accretion. Will need to continue to watch
this storm as we approach. Heavy rain not out of the question
either if a full change over is allowed /the further southern reaches
have the best chance of this/.

Late next week...
once again it/S dependent on whether each of the streams phase.
If they do possible the low pressure/frontal system will be
rather slow moving and may linger into Thursday potentially. In any appears another intrusion of Arctic air will impact the
region toward the end of the week.


Aviation /09z Friday through Tuesday/...
forecaster confidence levels...

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

Short term /today through Saturday afternoon/...

Today and tonight...high confidence. A scattered to broken deck of
middle level cloudiness is expected into early this evening. While
conditions will generally be VFR...brief bouts of MVFR ceilings will
probably occur.

Saturday...high confidence. VFR

Kbos taf...high confidence. VFR.

Kbdl taf...high confidence. VFR.

Outlook...Saturday night through Tuesday...

Saturday night into Sunday...high confidence.
Mainly VFR. Ceilings slowly diminish during the day on sun.

Sun night into Monday night...moderate confidence.
A cold frontal passage will bring about accumulating snowfall at
area terminals. Expecting 2-5 inches at this time. Periods of
IFR/MVFR likely with gusty northwest winds on Monday...20-30 knots at times.

Tuesday...high confidence.
Mainly VFR.


forecaster confidence levels...

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

Short term /today through Saturday afternoon/...high confidence.

Today through Saturday afternoon...high pressure will continue to
build in from the west. This will keep wind gusts generally under
20 knots through Sat afternoon. However...will need to continue
small craft advisories for hazardous seas across our outer-waters
into early Sat morning. This is for 3 to 6 foot seas as a result of
left over easterly swell.

Outlook...Saturday night through Tuesday...

Saturday night into Sunday...high confidence.
High pressure over the waters. Winds and seas generally below Small
Craft Advisory criteria.

Sun night into Monday night...moderate confidence.
A cold front crosses the waters on Monday. This will bring a
period of snow /mixing with rain on the South Coast/. Expect
southerly winds and building swell Sun night into early Monday...with
Small Craft Advisory conditions likely. However after the frontal
passage and winds shifting to the west-northwest gale force winds possible.

Tuesday...moderate confidence.
Conditions improve but small craft advisories are likely to


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory until 6 am EST Saturday for anz250-


near term...Frank
short term...Frank
long term...doody

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