Area Forecast Discussion
Issued by NWS Boston, MA

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453
FXUS61 KBOX 271052
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
652 AM EDT Mon Mar 27 2017

.SYNOPSIS...
High pressure over Marine will retreat into the Maritimes, but
provide cool weather across southern New England today. A warm
front will approach the region during this time and result in
periods of rain with areas of freezing rain across the high
terrain. Wet weather continues Tue and Tue night as low pressure
tracks over or near the region. Although Tue should be milder
than Monday. High pressure brings dry but chilly weather Wed and
Thu. More unsettled weather is possible late Fri into Sat.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

7 AM Update...

First batch of precipitation continues to move across the region
this morning. Biggest concern is the freezing rain and icing
potential. Temperatures across Western MA and even in the hills
of CT are at or just below 32F. The heavier precip has allowed
for the profile to cool a degree or two increasing the icing
potential. A few obs have reported either Freezing rain or UP
this morning. Webcams were temps are at or below 32F show wet
pavements so believe a glaze of ice is on surface that are
untreated this morning. This will result in hazardous travel for
the morning commute.

Closely watching the CT valley where the winds have turned to
the north. This will result in cold air drainage and the temps
may drop to 32F within the next hour. Still feel the SPS in
those locations is still valid and thus will hold off on
expanding the advisory.

Did however expand the freezing rain adv as hi-res guidance
including the HRRR and RAP keep temps hovering near 32F into the
late morning hours. Felt 10 AM was a good start and will let day
crew reevaluate.

Aside from these updates, the rest of the forecast remains on
track.

Previous Discussion...
Continuing to monitor progress of main area of precipitation
toward southern New England. Temperatures at elevations about
700 feet and higher were near freezing, so will continue the
Freezing Rain Advisory this morning. Low dew point depressions,
so additional cooling is possible with the main area of
precipitation arrives. Temperatures still expected to rise above
freezing by 8 AM, ending the threat of freezing rain.

A warm front will try to push north into southern New England
later today. A low pressure moving along this front will prevent
it from completely doing so. This will provide a focus for
periods of widespread rain.

Not much sunshine today, but temperatures should be near normal.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Tonight...

Abundant clouds linger. Lots of low level moisture in the lowest
3,000 feet above the ground in the wake of a low pressure moving
offshore. As previously mentioned, cannot completely rule out
some patchy drizzle. Still not expecting temperatures to fall
much, even with a weak cold front moving through.

Tuesday...

Not a lot of sunshine anticipated, despite southern New England
getting into the warm sector of a low pressure in southeast
Canada. Max temperatures should be above normal, in the upper
40s and 50s. Could be warmer if clouds and rainfall are delayed
until late in the day. Low risk of a isolated thunderstorm or
two toward the south coast due to elevated instability.

&&

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

* Showers linger Tuesday night as cold front passes through
* Cooler but dry weather for Wed and Thurs
* Unsettled weather returns Friday into Saturday

Pattern Overview...

00z Model consensus continues to show an active weather pattern
for  the period. Split flow aloft will continue through the
period with a few shortwaves moving through the flow. Partial
phasing of the two streams will occur across the Great Lakes and
Northeast on Tuesday. This will result in the development of a
low pressure system east of the region late Tuesday into
Wednesday. High pressure and upper level ridge will follow
Thursday into early Friday. The next upper level low/trough
deamplifies as it moves into the mid/upper ridge axis across the
eastern U.S. A coastal low is forecast to develop and quickly
move east in the aforementioned region of this phasing. The
spread has decreased for this timeframe but the still question
in strengthen and location of this system will determine p-types
and qpf amounts.

Details...

Tuesday Night...High confidence.

Weak shortwave will move over the region on Tuesday with surface
low  pressure over Northern New England. Along the cold front,
guidance develops a secondary low pressure system just south of
southern New England by Tuesday night. This wave of low pressure
will bring showery weather Tuesday evening into the overnight
hours. Cannot rule out some isolated thunder with this system as
TT increase above 50 and LI`s drop below 0. This is strongest
in the conservative EC.

Precip chance will quickly come to an end from west to east
during  the overnight hours as CAA takes a hold of the region.

Wednesday into Friday...High confidence.

Trough overhead as upper level low deepens as it moves towards
the  Canadian Maritimes. This puts the region in northwest flow
through the period resulting in dry but breezy conditions.
Clouds may be stubborn on Wed over the Cape and islands given
northerly flow across the waters. In fact could have some ocean
effect rain/snow showers over the outer Cape! Despite cold
advection, the environment should be well mixed, so max
temperatures will be close to normal.

Northwest flow continues on Thursday with an area of high
pressure  building in New England. Anticipate increasing
sunshine and lighter winds. Dry and seasonable conditions should
persist through Friday with high pressure in control.

Friday night into the weekend...Low confidence.

Split flow remains over the region with the next southern stream
wave interacting with the northern stream. Still some model
spread in this system leading to a low confidence forecast. The
EC has become more progressive with this approaching coastal low
developing it over 1-95 while the GFS keeps the system
suppressed. The UKMET is more inbetween the two systems, but the
GEFS and EPS continue to show the system south of SNE. Overall
a chilly rain with potential for wet snow/sleet at times on the
northern portion of the precip shield. All guidance suggest
system should be or moving offshore by Sunday, thus drying trend
possible second half of the weekend.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Short Term /through Tuesday/...High confidence.

Today...FZRA risk diminishes by mid-morning. Otherwise, -RA/RA
with MVFR- LIFR cigs with light E winds initially turning SE and
increasing.

Tonight...RA diminishing, however IFR-LIFR cigs remain. Could
see areas of -DZ. Light winds.

Tuesday...MVFR conditions likely in areas of rain and fog, with
a trend lowering to IFR as frontal boundary and surface low
approach. Low risk for thunder toward the south coast.

KBOS TAF...Not expecting any FZRA impacts at the terminal with
E onshore flow. Lowering MVFR down to LIFR this morning.

KBDL TAF...Not expecting any FZRA impacts at the terminal, as
temperatures remain above freezing.

Outlook /Tuesday Night through Friday/...

Tuesday night...High confidence. MVFR conditions within any passing
rain showers with improving cigs to VFR by the morning hours. Low
risk for thunder across the south coast.

Wednesday into Thursday...High confidence. Gusty N/W winds
Wednesday with VFR conditions into Thursday.

Friday...Moderate confidence.  VFR and dry to start but likely
lowering to MVFR or possibly IFR Fri night in rain/wintry precip.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Tuesday/...Moderate confidence.

Today...Warm front will lift across the waters, resulting in an
increasing east to southeast flow. Rough seas across the
eastern outer coastal waters are more likely than the southern
outer waters. Continued the Small Craft Advisories for those
waters. A few gusts to 25 kt are also possible across Cape Cod
Bay and Nantucket Sound. Have less confidence across those
waters, so did not expand an Advisory there. That will need to
be monitored as the day progresses.

Tonight...A weak frontal boundary sweeps the waters, with light
west winds developing. This will allow seas to subside and Small
Craft Advisories to conclude.

Tuesday...Light south winds with frontal boundary north of the
region. Vsby reduced at times in rain and fog.

Outlook /Tuesday Night through Friday/...

Tuesday night...Moderate confidence. winds becoming northeast late
Tue night as front slips south and wave of low pres tracks along the
front south of New England. Vsby reduced at times in rain and fog.

Wednesday into Thursday...High confidence. Gusty north winds near
Wednesday into early Thu then diminishing as high pressure builds
into the area later Thu.

Friday...High confidence. Quiet weather with high pressure over the
area early Fri. However increasing east-southeast winds Fri night as
low pres approaches from the west. Also vsby lowering in rain and
fog Fri night.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Freezing Rain Advisory until 10 AM EDT this morning for
     MAZ002>004-008-009-012-026.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ250-254.
     Small Craft Advisory until 11 PM EDT this evening for ANZ255-
     256.

&&

$$
SYNOPSIS...Belk/Dunten
NEAR TERM...Belk/Dunten
SHORT TERM...Belk
LONG TERM...Dunten
AVIATION...Belk/Dunten
MARINE...Belk/Dunten



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