458 
FXUS61 KBOX 142010
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
410 PM EDT Wed Oct 14 2020

.SYNOPSIS...

High pressure will result in dry weather tonight into Thursday along 
with an unseasonably mild and breezy Thursday afternoon. Rain develops 
on Friday as a frontal system stalls across New England with 
locally heavy rainfall Friday night into early Saturday as a 
coastal storm moves through. Improving conditions expected 
Saturday afternoon, then mainly dry and seasonable conditions 
Sunday into Wednesday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

410 PM Update...

A ridge of high pressure in control will result in continued 
tranquil weather tonight. Temperatures will drop fairly quickly 
after sunset given light winds and mainly clear skies. Model cross 
sections indicate there will be a period of scattered high thin 
cloudiness overnight, but that will not really impact temperatures. 
Low temps will bottom out in the 40s across most of the region.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...

* Sunny, Breezy and Unseasonably Mild Thursday

Thursday...

High pressure will move east of our region on Thursday. This will 
allow for an unseasonably mild southwest flow of air into the 
region. Model cross sections are quite dry, so expect sunny skies 
and SW flow with 850T around +12C will result in an unseasonably 
mild afternoon. High temperatures should reach the middle 70s in 
many locations. It will also become quite breezy by afternoon given 
a modest southwest low level jet and good mixing. We expect 
south to southwest wind gusts of 25 to 35 mph by afternoon.

Thursday night...

A surface cold front to our northwest will push southeast Thu 
night and be located across interior southern New England by 
daybreak Fri. Southwest flow aloft will continue and low level 
moisture be on in the increase. This should result in the 
development of some low clouds and probably a few showers as 
well after midnight. Low temps will be milder only dropping into
the upper 40s and 50s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...

Highlights

* Rain returns Fri with locally heavy rainfall possible Fri night 
  into early Sat
* Improving conditions Sat afternoon
* Mainly dry and seasonable weather Sun into Wed

Friday into Saturday...

Robust mid level trough across the Gt Lakes expected to amplify and 
become neg tilted as it sweeps across New Eng on Sat. Strong 
synoptic forcing combined with modest PWAT plume will bring 
widespread beneficial rain to SNE. A period of heavy rainfall likely 
Fri night into early Sat as strong shortwave energy moves through 
with a deepening coastal low tracking near the 40N/70W benchmark as 
impressive height falls develop off the coast. 

Still some timing differences among the models but confidence is 
high in widespread beneficial rainfall. Expect periods of rain to 
develop during Fri as cold front stalls across eastern New Eng. Rain 
on Fri will be focused along and west of the boundary where deep 
moisture plume develops. This suggests the steadiest rain on Fri 
will be confined to much of the interior to near the I-95 corridor 
with more spotty light rain across SE MA and Cape Cod. 

Rain heavy at times is expected Fri night, initially across western 
New Eng then shifting east late Fri night into early Sat. Impressive 
dynamics with right entrance region of upper jet combined with 
strong mid level frontogenesis moving west to east will bring the 
heavy rainfall to SNE. The rain Sat morning will be focused in 
eastern New Eng with improving conditions from west to east during 
the afternoon. Rainfall amounts should average 1-2 inches with 
locally higher amounts. The heaviest rainfall is expected to be in 
the interior with lighter amounts across SE New Eng but the axis of 
heavy rainfall may shift. The other concern for Sat is the potential 
for gusty NW winds behind the storm, but the latest ECMWF has backed 
off on rapid deepening of the low pres and subsequent strong winds. 

Temps: Highs should reach well into 60s Fri and possibly near 70 
east of the front which will be mainly across SE New Eng, with 50s 
in the interior. Highs saturday mainly in the 50s. 

Regarding coastal flood potential, there is a low risk of minor 
splashover for the Fri night tide cycle as a result of the 
increasing astronomical tides. But this would be the worst case 
scenario as winds and waves not expected to be significant which 
will limit surge. Another round of minor splashover is possible for 
the Sat midday high tide which gets to 11.9 ft in Boston

Sunday through Wednesday...

Broad longwave trough sets up across the upper Midwest and Great 
Lakes with subtropical ridge off the SE US coast. Mainly dry weather 
expected although a few showers are possible at times in the 
interior as series of shortwaves lifts to the north, but better 
chance of showers will be to the north and west. Mainly seasonable 
temps expected, but it could be warmer than forecast Tue/Wed as 
ECMWF is more aggressive building the subtropical ridge north along 
the coast toward midweek. ECMWF ensembles offering low probs of 70+ 
degree temps Tue/Wed. GFS keeps the polar jet further south which 
suppresses the ridge.  

Tides: Astronomical tides peak at 12.1 ft in Boston Sunday and 
Monday afternoon which may result in minor splashover.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

18z Update...

Tonight...High Confidence. VFR conditions with winds becoming
light and from the SW.

Thursday...High Confidence. VFR conditions. SSW wind gusts of 20 to 
30 knots developing by afternoon.

Thursday night...Moderate confidence. VFR conditions during the
evening, but some MVFR ceilings may develop after midnight and
there probably will be a few showers too. Light SW winds.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Friday through Monday/... 

Friday: Mainly MVFR, with areas VFR possible. Chance RA, chance
SHRA.

Friday Night: Mainly MVFR, with local IFR possible. Breezy. RA.

Saturday: Mainly VFR, with areas MVFR possible. Windy with
gusts up to 30 kt. Chance RA.

Saturday Night: VFR. Breezy. 

Sunday through Monday: VFR. 

&&

.MARINE...

Tonight...High confidence. High pressure in control will keep 
winds/seas generally below SCA thresholds.

Thursday and Thursday night...High confidence. Modest LLJ will 
result in SSW wind gusts of 20 to 30 knots developing by afternoon 
and continue into the evening. SCA headlines posted for all our 
waters with rough and choppy seas expected as well. Wind gusts 
should diminish a bit as the SW LLJ lifts northeast of our region.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain. 

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Rain. 

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Chance of rain. 

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. 

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. 

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Monday: Winds less than 25 kt. Seas up to 5 ft. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM Thursday to 2 AM EDT Friday for 
     ANZ231>235-237-251.
     Small Craft Advisory from 10 AM to 8 PM EDT Thursday for 
     ANZ230-236.
     Small Craft Advisory from 8 AM Thursday to 5 AM EDT Friday for 
     ANZ250-254>256.

&&

$$
SYNOPSIS...Frank/KJC
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...KJC
AVIATION...Frank/KJC
MARINE...Frank/KJC