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Area Forecast Discussion (AFD)

Issued by Boston / Norton, MA (BOX)

                            
000
FXUS61 KBOX 210202
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1002 PM EDT Sat Apr 20 2019

.SYNOPSIS...
Scattered showers persist tonight especially across eastern New
England, but should diminish in areal coverage Sunday afternoon
and night as low pressure drifts south of the region. This low 
will lift north again allowing numerous showers to redevelop 
sometime Monday and continue into Monday night before ending 
early Tuesday. A few brief showers are possible Tuesday night 
into early Wednesday, but there may be a better chance for more
widespread showers late next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
10 PM update...

Numerous showers streaming northward from the ocean and 
impacting SE MA this evening. PWAT and low level jet axis 
persists across eastern MA so expect occasional showers,
briefly heavy to move north across this area before shifting to
Cape/Islands overnight as LLJ/PWAT axis moves east. An isold 
t-storm also can not be ruled out.

Across western New Eng, there will be a few showers lifting
north across the region through 06z based on latest radar 
trends showing showers lifting north from south of Long Island. 

Areas of fog will mainly be along the south coast, where high 
dewpoint air for this time of year continues to move over the 
relatively cold ocean. Low temperatures by daybreak should only 
drop into the middle to upper 50s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Sunday and Sunday night...
Cutoff H5 low pres will linger across the mid Appalachians 
Sunday will slowly spin to the mid Atlc coast Sunday night. 
This will keep a general, moist S-SE wind flow in place. GEFS 
ensembles continue to signal a 1-2 SD above normal moisture 
plume across the region through this timeframe. Most of the 12Z
model suite also signaling a developing surface low pres E of 
the Delmarva coast, which looks to shift northward late Sun 
night. 

In the meantime, with weak lift in place, the QPF will 
generally be about 0.25 inches or less, but may be higher 
across Cape Cod and the islands with the onshore flow in place.

With the onshore flow in place temps will run around 5 degrees 
lower than on Saturday, mainly in the mid 50s to mid 60s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights ...

* Numerous showers develop sometime Mon and continue into Mon 
  night before ending early Tue

* A few showers possible Tue night/early Wed, but a better
  chance for widespread showers by the end of next week
  
* Temps are uncertain but a wide variety in readings from the
  coast to the interior may exist at times given onshore flow

Details...

Weakening closed upper level low will be lifting northeast 
across New England Mon into early Tue. The result will be 
periods of showers developing sometime Monday, which will 
continue into Monday night before ending early Tue. Dry weather 
follows, but a fast moving shortwave may bring a few brief 
showers Tue night into early Wed. However, a better shot for a 
period of widespread showers might be at the end of next week 
with a stronger shortwave.

As for temperatures, they are quite tricky much of next week 
dependent on wind direction and cloud cover. Overall, we may see
a wide variety in temperatures from the coast to the interior 
at times with the potential for a few periods of onshore 
flow/sea breezes.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

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

Tonight...
MVFR to IFR conditions persist overnight across eastern New
England with LIFR conditions near the south coast.
Meanwhile...improvement to VFR may occur across portions of
western MA/northern CT as drier air works in from the west. Bulk
of the showers overnight will be across eastern New England.

Sunday... 
Areas of IFR-LIFR CIGS/VSBYS through mid morning especially 
across eastern areas, then should slowly improve to mainly VFR. 
May see MVFR CIGS lingering across central and eastern areas. 

Sunday night...
Mainly VFR conditions. Sct SHRA across central and eastern
terminals shift slowly W overnight, with local MVFR-IFR
conditions, lowest along the coast.

KBOS terminal...Moderate confidence in TAF

KBDL terminal...Moderate confidence in TAF.  

Outlook /Monday through Thursday/...

Monday: Mainly MVFR, with areas VFR possible. Breezy. Chance
SHRA.

Monday Night: Mainly MVFR, with areas IFR possible. Chance
SHRA.

Tuesday: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.

Tuesday Night: Mainly MVFR, with areas VFR possible. Chance
SHRA.

Wednesday: Mainly MVFR, with areas VFR possible. Breezy. Chance
SHRA.

Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy. 
Slight chance SHRA.

Thursday: Mainly VFR, with areas MVFR possible. Breezy. Slight
chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

Tonight...
S winds gusting to between 25 and 30 kt early, then should 
diminish through the night. However, seas remain AOA 5 ft across
the open waters as well as the near shore southern waters, so 
Small Crafts will continue. Reduced visibility in areas of fog, 
below 1NM over the open waters.

Sunday and Sunday night...
S-SE winds around 10 kt. Seas remain AOA 5 ft mainly across the
open waters. Reduced visibility through midday Sunday, then
improving before lowering again during Sunday night. Scattered
showers. 

Outlook /Monday through Thursday/...

Monday through Monday Night: Winds less than 25 kt. Areas of
rough seas. Chance of rain showers. 

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

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers. 

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

Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers. 

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

&&


.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ232>234.
     Small Craft Advisory until 10 PM EDT this evening for ANZ230.
     Small Craft Advisory until 4 AM EDT Sunday for ANZ231.
     Small Craft Advisory until 3 PM EDT Sunday for ANZ236.
     Small Craft Advisory until 6 AM EDT Monday for ANZ235-237-250-
     254>256.
     Small Craft Advisory until 6 AM EDT Sunday for ANZ251.

&&

$$
SYNOPSIS...Frank/EVT
NEAR TERM...KJC/Frank
SHORT TERM...EVT
LONG TERM...Frank
AVIATION...Frank/EVT
MARINE...Frank/EVT
TIDES/COASTAL FLOODING...