Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 270326
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1026 PM EST Sun Feb 26 2017

.SYNOPSIS...
High pressure centered south of New England brings dry weather
through Monday. Milder air moves back into our region Monday,
then lingers through much of this week. A couple of weather
systems will bring periods of wet weather Tuesday into Wednesday
night. Colder air returns late this week into next weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

High pressure centered along the Mid Atlantic coast remains over
the region through morning. Winds are diminishing and will
continue to diminish overnight.

Based on 10 pm temps and dew points, we lowered min temps by a
couple of degrees. Min temps range from the upper teens to mid
20s, with a few coastal and urban centers near 30. Otherwise,
no changes to the forecast.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...

Continued quiet weather. Roughly 1030+ high pressure prevailing
off the Mid-Atlantic, S of New England, slowly moving E.
Persistent S/SW flow as forecast models suggest deep boundary
layer mixing up to H8 given the milder airmass aloft and
expected mostly clear conditions with some increasing mid- to
high-cloud late from the SW. Within the modest SW to NE gradient
flow, daytime mixing will lead to the mix- down of faster
momentum and drier air to the surface. Another dry day on tap
with SW wind gusts up around 20 to 25 mph, stronger over the
S/SE coast with gusts up to 30 mph possible. Leaned with the
warmest of temperature guidance considering: 1) deep boundary
layer mixing of warming air aloft, 2) abundant sunshine, and
lastly 3) bare ground over much of S New England. Highs around
the low to mid 50s. Can not rule out low-lying locations of the
Merrimack River Valley to nudge near 60 degrees.

Monday night...

Perhaps the chance of a spotty shower by morning. The SW-NE
gradient tightening out ahead of low pressure emerging along the
lee of the Rockies, some initial mid-level vortmax energy
emerges from the H5 trough situated across the W CONUS.
Invocation of a lifting warm front along which we see initial
over-running moisture with higher theta-E values creeping into
our region during the morning lending to moistening of the low-
to mid- level column, there is some measure of weak lift that
may result in a spot shower. Aside, at a minimum, continued
increasing and thickening clouds with continued S flow. Given
the blanket of clouds, leaning somewhere between the mean to
warmer end of temperature guidance with lows fluttering around
the mid- to upper-30s. Coolest spot in N/W MA. Thinking slight
chance PoPs as a consensus of model forecast guidance has us
mostly dry with only higher theta-E creeping in out of the SW by
morning, and lift is rather weak, mostly isentropic. Focus of
PoPs over SE New England.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...

* Above average temperatures for most of this week
* Widespread showers possible Tuesday through late Wednesday
  night
* More seasonable conditions return Friday into Saturday

Overview...

26/12z guidance continues to show rather good agreement on the
overall pattern through Friday. That said, there are the
typical discrepancies in the timing and amplitude of shorter
wavelength features toward the end of this week. Since these
sorts of details are usually less predictable at this time
range, still prefer a consensus approach.

Details...

Tuesday...High confidence.

High pressure to our south will move slowly offshore. This will
result in an increasing southwest flow, which means good
overruning, with increasing clouds, and eventually rising
temperatures. While not close to the record warmth late last
week, still expecting temperatures well above normal.

The greatest risk for precipitation will be toward the south
coast, where moisture should be deeper. Depending upon the
timing, it`s possible for some wet snowflakes to fall during the
morning along and north of Route 2. Low confidence in that
happening.

Presence of a strong low level jet Tuesday night should lead to
either steady or slowly rising temperatures overnight.

Wednesday into Thursday...Moderate confidence.

Main weather producer will occur Wednesday into Thursday. Still
some  uncertainty on the timing and location of the surface
low.

Our region should remain in the warm sector of a low pressure
moving through the Great Lakes. Strong southwest winds aloft
are likely to bring an unseasonable amount of moisture our way.
This expecting plenty of clouds. Rainfall amounts however are
generally expected to be less than one half inch for most of our
region.

Convective instability will be the wildcard. Most convective
indices are rather marginal. However, if we could get some low
level instability to go along with the wind shear, then a few
thunderstorms may develop. This has been consistent, weak signal
the past couple of days. By no means is this a lock, but will
keep the mention of isolated thunderstorms in the forecast.

Still have high confidence that at least some precipitation
will fall, and temperatures will be above average Wednesday
into Wednesday night.

Cold front will sweep through early Thursday morning, resulting
in drying conditions with falling temperatures falling through
the day. Strong cold air advection likely to mean gusty west to
northwest winds.

Friday and beyond...Moderate confidence.

26/12Z GFS remains the model with the strongest hint of a
clipper-like low pressure passing by to our south Friday
morning. The other models are neither as aggressive, nor as
humid. Favored the drier consensus solution for now. This will
be something to watch over the course of this week.

High pressure remains to our south next weekend. After a period
of more seasonable temperatures Friday and Saturday, it appears
we get back into more of a warmup next Sunday.

Good mixing and cold air over the ocean may result in ocean
effect snow showers next weekend, before another clipper system
possibly approaches towards late Sunday.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Short Term /through Monday Night/...

Overnight...High confidence.

VFR. SKC. Winds become light out the W while gradually turning
out of the SW.

Monday...

VFR. Increasing SCT-BKN mid to high level CIGS late. S/SW winds
around 240 becoming breezy through the day with 20-25 kt gusts,
strongest over the high terrain and along the coast, dissipating
into the evening hours.

Monday night...

VFR. Cigs becoming BKN-OVC, lowering to low-end VFR with a risk
of MVFR over S-coastal terminals. Light S flow around 5-10 kt.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday into Wednesday...Moderate confidence. Periods of -RA
through the period will result in MVFR/IFR conditions. Cannot
rule out LIFR in fog during the overnight hours.

Thursday...Moderate confidence. VFR conditions from west to
east during the morning. Blustery westerly winds are possible.

Friday...Moderate confidence. Mainly VFR, with MVFR possible
toward the south coast, including the Cape and islands.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Monday Night/...High confidence.

High pressure along the Mid Atlantic coast builds over the New
England coastal waters. Diminishing winds turning from the west
and eventually southwest. Small Craft Advisories will end on
the nearshore waters by 1 am while continuing on the outer
waters into Monday night.

Outlook /Tuesday through Friday/...

Tuesday...Moderate confidence. Improving conditions across the
waters as high pressure passes southward. Warm frontal passage late
Tuesday could drop vsbys in rain and fog.

Wednesday into Thursday...Moderate confidence.  Approaching system
from the west will push a cold front through on Thursday, increasing
both seas and winds during this period. Heavy rain and a few
thunderstorms are possible, lowering vsbys. There is the
potential for southerly gales across the waters Wed night, and
northwesterly gales on Thursday behind a cold front.

Friday...Moderate confidence. Gusty west winds continue. Small
Craft Advisories likely will be needed for some of the coastal
waters.

&&

.FIRE WEATHER...
Dry and blustery conditions will persist on Monday pushing
minimum relative humidity values at or below 30 percent for a
good portion of interior Southern New England as southwesterly
flow gusts up around 25 mph.

Considering in the last 24 to 36 hours much of Western and
Central MA and CT saw around 0.50-0.75" of liquid, with around
0.10-0.25" to the east, there`s some concern of potential fire
weather conditions over Northeast CT, RI and Eastern MA as
temperatures warm into the mid to upper 50s.

&&

.HYDROLOGY...
Rising water levels, partly from weekend rain but also from
snowmelt in Northern New England. There is still plenty of
water moving downriver from the snowpack. We will need to
monitor water levels across southern New England for a while
this week.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ231>235-237-
     251.
     Small Craft Advisory until 1 AM EST Tuesday for ANZ250-254.
     Small Craft Advisory until 10 PM EST Monday for ANZ255-256.

&&

$$
SYNOPSIS...Belk/Sipprell
NEAR TERM...WTB/Belk/Sipprell
SHORT TERM...Sipprell
LONG TERM...Belk
AVIATION...Belk/Sipprell
MARINE...Belk/Sipprell
FIRE WEATHER...
HYDROLOGY...


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