NWS Technical Forecast Discussion

FXUS61 KBOX 271433

Area Forecast Discussion
National Weather Service Taunton MA
Issued by National Weather Service Upton NY
1033 AM EDT Mon Mar 27 2017

Rain ending and cool across southern New England this afternoon
as a weak wave of low pressure tracks across the region. 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.


10 AM Update...
Rain across central MA and CT moving ENE at 30 KT. Dual Pol
Correlation Coefficient (CC) shows mixed phased PCPN in the
5-10 KFT layer - thus reflectivity is showing bright banding.

METAR and mesonet data show SFC temps are now at or just above
freezing. ZR advisory will expire at 15Z on schedule.

Diffuse warm front shows up in the SFC analysis over SE MA with
weak low pressure over the NY City area. This weak wave of low
pressure rapidly track to east of Boston by mid-afternoon. Rain
thus ends from west to east and expecting a cloudy, but dry
evening commute.



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.


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.



* 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.


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.


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.

Today...-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...LIFR lowering to IFR in rain.

KBDL TAF...IFR lowering to IFR.

Outlook /Wednesday 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.


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.

Today...Warm front will lift across the waters, resulting in an
increasing 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 /Wednesday 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.





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