Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 171925
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
325 PM EDT Wed Aug 17 2022

.SYNOPSIS...
Low pressure will lift north into Maine late tonight through 
Thursday with seasonably warm and dry conditions. Very warm 
weather with above normal temps returns Friday and Saturday, 
followed by increasing humidity for the first half of next week.
Generally dry weather is expected through the weekend with the 
best chance for scattered showers and a few thunderstorms mainly
sometime Tuesday into Wednesday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
More sunshine and warmer temps under cold pool aloft have 
contributed to less than 500 J/kg of SBCAPE resulting in 
scattered showers moving southward across the interior. These 
diurnal showers expected to linger into the evening but will 
dissipate soon thereafter with loss of heating. Meanwhile, an 
area of more stratiform light rain on the western edge of the 
mid level low will remain mostly to the north but a few light 
showers could spill into NE MA through early evening as the low
drifts NW from the Gulf of Maine. 

Expect improving conditions overnight with partial clearing 
developing from S to N as the mid level low moves northward with 
gradual drying developing in the column. Lows will range from the 
upper 50s to lower 60s. Gusty NNW coastal winds early evening 
will diminish and become W. 

&&

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

A pleasant late summer day for SNE as the mid level low lifts N 
through Maine and eventually into the Maritimes toward evening. 
Mid/high clouds may linger into the morning, especially across 
northern MA but trend will be for increasing sunshine although some 
diurnal cu will develop given cooler temps aloft. 850 mb temps 12-
13C with a modest westerly breeze and downsloping supports highs 80-
85, a bit cooler higher terrain. Humidity levels will be comfortable 
with dewpoints in the 50s. 

Thursday night...

The mid level low continues to lift north through the Maritimes with 
surface high pres building in from the west. Expect clear and light 
winds supporting decent radiational cooling. Lows will drop into the 
50s, except 60-65 near the coast and urban centers.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights...

* Dry through Saturday with warmer temperatures but relatively 
  comfortable humidity. 

* Humidity will be on the rise to start the new work week with 
  periodic shower and thunderstorm chances, mainly Tuesday and 
  Wednesday. 

Details...

Friday and Saturday...

A nice, if warm, end to the work week and start to the weekend for 
southern New England beneath rising mid level heights and high 
pressure at the surface. Normal high temperatures for the 3rd week 
of August are in the low 80s and we'll be several degrees warmer 
than that both Friday and Saturday (in the upper 80s) as low/mid 
level temps rise on SW flow around the high. These features will 
keep things dry and relatively comfortable despite the heat thanks 
to relatively low dewpoints. Friday will feel the least humid with 
dewpoints in the 50s inland, low 60s along the coast. By Saturday 
low 60s move inland, closer to the mid/upper 60s along the south 
coast. 

Sunday through Wednesday...

By the latter half of the weekend and first half of next week our 
next mid level shortwave approaches from the Great Lakes, and this 
will introduce our next appreciable chance of some rain showers. 
There remains uncertainly as to how quickly this trough traverses 
the area given significant timing differences among the global 
guidance, but it would appear that Tuesday and Wednesday are the 
best shot at widespread rain at this time. Ahead of this, warmth and 
moisture surges into southern New England on increasing southwest 
flow. Low confidence in just how high dewpoints will be Sunday into 
Monday, but by Tuesday into Wednesday as the system moves through 
dewpoints should rise back into the 70s. Temperatures each day will 
hover right around the mid 80s. 

The only other chance of rain to mention, though a low probability, 
is for mainly the south coast, associated with a coastal system 
passing well offshore late Saturday into Sunday. While most guidance 
keeps it well enough offshore that we remain dry, ensembles indicate 
a 20-40% chance of seeing some rain as far north as the south coast 
of RI and MA.

&&

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

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

18z TAF Update...

Through 00z...

Generally VFR cigs with areas of MVFR over Cape/Islands.
Scattered showers moving south across the interior. N wind 
gusts to 25 kt over Cape/Islands and portions of E MA coast. 

Tonight... High confidence. 

VFR cigs with sct evening showers, improving overnight.
Diminishing wind becoming W. 

Thursday and Thursday night... High confidence. 

VFR. W winds 10-20 kt during the day diminishing during the
evening. 

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Friday through Monday/...

Friday through Saturday: VFR. 

Saturday Night through Sunday Night: VFR. Slight chance SHRA.

Monday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

A modest low level jet will bring some 25-30 kt gusts to the eastern 
outer waters through early evening, then gradual diminishing wind. 
W/SW winds Thu will average 10-20 kt diminishing further Thu night. 
SCAs will continue into the evening for wind and/or seas but 
dropping off overnight for all but the eastern outer waters where 
SCA seas will persist through Thu.

Outlook /Friday through Monday/...

Friday through Friday Night: Winds less than 25 kt. 

Saturday: Winds less than 25 kt. Slight chance of rain showers,
isolated thunderstorms. 

Saturday Night: Winds less than 25 kt. Slight chance of rain
showers. 

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers. 

Sunday Night through Monday: Winds less than 25 kt. Slight
chance of rain showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT this evening for MAZ007-015-
     016-019-022-024.
RI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ230-
     232-256.
     Small Craft Advisory until 4 AM EDT Thursday for ANZ231-251.
     Small Craft Advisory until 8 PM EDT this evening for 
     ANZ233>235.
     Small Craft Advisory until 2 PM EDT Thursday for ANZ250-254-
     255.

&&

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