Area Forecast Discussion
Issued by NWS Boston, MA

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607
FXUS61 KBOX 271848
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
248 PM EDT Mon Mar 27 2017

.SYNOPSIS...
Damp 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 expected late Fri into Sat. High
pressure builds in Sunday into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
3 PM Update...

Back end of the Rain is approaching the coast - reaching the
Boston Metro by 4 PM. Last of the rain clears the Cape by 00Z.

HRRR continues to appear overdone with shower develop late this
evening. There is a small feature seen in the GOES 16 Water
Vapor channels over the NY City Metro, but with only one shower seen
on Radar near KHPN. Thus, will keep POPs low for the passing
shower possibility.

One unknown is the extent of dense fog overnight. WFO BOX will
look into this more this evening, but with calm winds and plenty
of moisture, fog does appear likely.

Lows above freezing all locations in the mid to upper 30s.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Tuesday...Over-running with light rain or drizzle. Temps near
50 for highs. Warm front south of Long Island with plenty of
mixture keeps it cloudy and damp. POPs of likely to
categorical, but the key here is for light rain which I was able
to get into the grids.

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 /WEDNESDAY THROUGH MONDAY/...
No significant changes at this time.

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...

12z 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 in between 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 /19Z MONDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

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

This afternoon...Rain ending. IFR cigs with light winds.

Tonight...IFR cigs remain. Fog develops overnight. 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.

KBOS TAF...IFR.

KBDL TAF...IFR.

Outlook /Wednesday through Saturday/...

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.

Saturday...Moderate confidence. MVFR or possibly lower in rain/wintry mix.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

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 this evening.

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 /Wednesday through Saturday/...

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...None.
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...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...



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