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FXUS61 KBOX 201752

Area Forecast Discussion
National Weather Service Boston/Norton MA
152 PM EDT Wed Jun 20 2018

Dry weather is expected today as high pressure builds across 
New England. Showers are likely tonight south of the Mass Pike
as low pressure passes south of New England. High pressure from
Canada brings dry weather Thursday and Friday. A cold front 
them brings a chance of showers at times this weekend, followed 
by dry weather early next week.



200 PM Update...

Trends in the forecast remains on track for today. Generally
zonal flow aloft as a southern wave pushes through the flow.
This wave will spin up a low pressure system over the Great
Lakes and track towards the region tonight. Surface high
pressure is beginning to move offshore. This has allowed for the
sea breeze to wash out and temperatures along the eastern
coastline to begin to warm into the 80s. 

One thing to watch is the approaching cold front well to the
north of the area. This front will determine where the low will
travel along. Latest runs in the guidance continues to push the
precip shield farther north than prev runs. This would suggest 
that the front has slowed up a bit. Models have not accurately 
predict the ongoing precip across upstate NY. Thus may 
introduce some sprinkles or light showers late this afternoon or
early evening. Not expecting anything heavy as temp/dewpoint 
spread is still large with still some dry air introduced in the 
profile per Bufkit soundings. 



00Z model suite remains in pretty good agreement with the 
approach of low pressure out of middle Appalachians. Noted that 
the models are trending a bit further S with the low pres as the
H5 long wave trough across the NE U.S. into Labrador and 
Newfoundland tends to flatten at its base S of New England. 

The low moves off the NJ coast around 09Z or so with a rather 
sharp northern extent of the precip shield. Looks like the best 
chance for showers will occur across N CT/RI into S coastal Mass
where likely POPs are in the forecast. The higher QPF amounts 
area also suppressed to the S, so expect maybe 0.1 to 0.2 
inches, possibly a bit higher on the islands. Looks like 
conditions should remain mainly dry, but can't rule out a few 
brief showers possibly as far N as the Mass Pike. 


Leftover showers along S coastal areas should push offshore by
midday, though there is some timing issues amongst the model
suite during this timeframe. Leaned toward the somewhat faster
GFS/GGEM timing. Skies should become mostly clear during the
afternoon, though a few clouds may linger across Cape Cod and
the islands.

It will be a cooler day on Thursday along the Mass E coast as 
winds become E-NE by around midday or early afternoon. Temps
there will only top off in the mid 60s to lower 70s, coolest on
the outer Cape and Nantucket, ranging to the lower 80s across
the CT Valley.



* Dry and seasonable on Friday
* Unsettled weather for this weekend
* Dry weather early next week


20/00Z guidance continues to show improved agreement in the mid
level pattern from earlier cycles. This agreement still breaks
down in some of the finer details Saturday night into Sunday,
but not to the point where confidence is lost in the overall

High pressure should move offshore, opening the door for a low
pressure to move through the Great Lakes into the Saint Lawrence
valley. This trajectory will force both the warm and cold fronts
of this system across southern New England sometime this
weekend. At this time, expecting an increasing risk for showers
late Friday night into Saturday, peaking about Saturday evening,
then diminishing into Sunday. A secondary cold front should
cause showers to linger later Sunday. This weekend still doesn't
look like a washout. Another high pressure should return with 
dry weather early next week.

Not seeing any major deviations from normal temperatures for 
this period. Perhaps a bit cooler than normal Saturday,
depending upon timing of a warm front and amount of sunshine.


Forecaster Confidence Levels...

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

Short Term /through Thursday/... High confidence. 

Before 00z...VFR. Sea breeze is beginning to washout this 
afternoon. Southwesterly winds will pick up with gusts between 
15-20 kts. A sprinkle across the western terminals is possible. 

Tonight...Mainly VFR. MVFR across the south coast in showers and
fog. Southwest winds will flip to a more northwest by morning.

Thursday...VFR. Lingering showers along the south coast between
12-15z. MVFR cigs improve to VFR during the day but around 4-7
kft. A spot showers across the interior is possible as winds are
out of the east. 

Thursday night...VFR to start but with northeast flow believe
low levels will saturate dropping cigs and vsbys to MVFR

KBOS Terminal...High confidence in TAF. Ongoing sea breeze looks
to washout between 16-19z. 

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Sunday/...Moderate confidence.

Friday: VFR. 

Friday Night: VFR. Slight chance SHRA.

Saturday: Mainly VFR, with areas MVFR possible. SHRA likely.

Saturday Night: Mainly VFR, with local IFR possible. Chance
SHRA, isolated TSRA.

Sunday: Mainly VFR, with local MVFR possible. Chance SHRA.


Forecaster Confidence Levels...

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

Short Term /through Thursday/...High confidence. 

Today and Tonight...Light W winds early today shift to SW, up 
to 15-20 kt on the eastern waters late today. May see gusts up 
to 25 kt late this afternoon into this evening on the eastern 
outer waters, where seas may briefly build up to 4 ft. Small 
Craft Advisory has been issued. Winds may gust up to 20 kt on 
the lower end of Narragansett Bay into Buzzards Bay with locally
choppy seas this afternoon. Reduced visibility in showers and 
patchy fog tonight mainly across the south coastal waters.

Thursday...N-NW winds early Thu will shift to E-NE by midday 
Thu with gusts up to 20 kt possible. Leftover reduced visibility
along S coastal waters through midday Thu, then improving. 

Outlook /Thursday Night through Sunday/...Moderate confidence.

Thursday Night through Friday: Winds less than 25 kt. 

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers. 

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Rain showers likely. 

Saturday Night: Winds less than 25 kt. Local rough seas. Rain
showers likely, with isolated thunderstorms. 

Sunday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain showers.





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