Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 071107
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
707 AM EDT Thu Jul 7 2022

.SYNOPSIS...
Slightly cooler than normals temps today followed by more
seasonable temps tomorrow. May be a few showers with a weak
frontal passage Friday afternoon. High pressure delivers a 
period of beautiful summer weather this weekend into early next 
week, with warm days and cool nights, along with comfortable 
humidity. A cold front brings the next chance for widespread 
rains around Tuesday or Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
700 AM Update: 

Adjusted winds/wind directions to better show the anticipated
development of onshore winds (sort of a synoptic gradient/sea- 
breeze hybrid). Overall no significant changes and have
otherwise incorporated current observations and blended into the
forecast. Shaping up to be a pleasant Thursday under high
pressure - enjoy!

Previous discussion:

Today

Surface high pressure shifts east of the region today. This will 
support a south/southeasterly flow into southern New England. With 
flow off the cooler ocean waters, expect temps to be around or 
slightly below normal for early July with high temps topping out in 
the mid 70s along the coast and upper 70s to low 80s across the 
interior. Dewpoints generally in the upper 50s will support 
comfortable humidity levels. Expect increasing cloudiness during the 
afternoon hours, especially across the western areas.|

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Tonight

Mainly zonal flow in the mid and upper levels will support another 
night of quiet weather. Boundary layer winds becomes more 
southwesterly overnight. This will allow dewpoints to come up a bit 
before sunrise. Nonetheless, a comfortable evening with lows 
bottoming out in the upper 50s to low 60s.

Tomorrow

Temperatures and humidity climb back up tomorrow as low-level 
southwesterly flow prevails over southern New England. Expect more 
seasonable temperatures with highs in the low to mid 80s. Weak 
surface front will push through the region during the mid to late 
afternoon. This will support a wind shift to the northwest by 
tomorrow evening. Can't rule out a few isolated to scattered showers 
as this front slides through the region. Both deep layer moisture 
and synoptic forcing will be lacking, thus not expecting any 
widespread or persistent precipitation with the frontal passage.

&&

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

* Lengthy stretch of pleasant, tranquil summer weather with plenty 
  of sun, low humidity and dry weather Sat thru Mon.

* Turning warmer and more humid into midweek ahead of a cold front 
  passing through either later Tues or into Wed.

Details:

Friday Night:  

Cold front from the daytime hrs Fri will get more of a southeastward 
push Fri evening into our coastal waters from a shearing-out 
shortwave moving into northern New England. Short-lived period of 
higher moisture could support continued generally light rain showers 
but the frontal boundary more or less passes SE with little fanfare. 
Decreasing clouds from NW to SE and a SW to N/NE wind shift for the 
remainder of the evening, with lows in the mid 50s to mid 60s, 
mildest south, coolest north/northwest.

Saturday through Monday Night: 

Continued generally strong multi-model consensus in a Canadian-
origin anticyclone and related ridging/subsidence governing 
conditions across SNE through much of this period. As much as 2.5 
sigma PWAT anomalies support dry weather with comfortable humidity 
levels ideal for any outdoor plans. It is worth noting the 00z/7th 
NAM generates a decent slug of QPF into interior CT, RI and SE MA, 
well north of a sfc low over the mid-Atlantic region but view this 
as an outlier compared to good consensus for dry weather across the 
global models/ensemble means. 

Thus for the weekend, expect full sun and rather deep mixing during 
the daytime with modest NW to NEly breezes and good radiational 
cooling at night. Highs mid 70s to lower 80s, with lows in the 50s 
to near 60. As high pressure settles into the waters south of SNE on 
Mon, ensuing warm advection pattern should bring warmer temperatures 
(upper 70s-mid 80s) and SWly breezes.

Tuesday and Wednesday:

Surface frontal system with weak low pressure will be the focus in 
this period, but did note more variation across the guidance with 
regard to the timing. The progressive GFS supports a frontal passage 
around Tues-early Tues night; on the other hand the ECMWF supports a 
frontal passage closer to Tues evening into part of Wed. Thus given 
more solution spread in timing carried Chance-level PoP for 
showers/t-storms into at least the first part of Wed. Given 
amplification of the Intermountain West heat ridge in this period, a 
hedge toward the slower ECMWF idea might seem more appropriate but 
still plenty of time to sort through the timing over the next few 
days. Pending timing of the frontal passage, Tues into Wed would 
feature elevated humidity levels and summerlike temperatures in the 
middle to upper 80s.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels:

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

12z TAF Update: 

Today: High confidence. 

VFR. Outside chance at MVFR across the ridgelines of the
Berkshires later in the day. Most of the FM groups in TAFs are 
essentially wind direction changes. Winds trend from N to NE/E 
and eventually SE/S as the day moves on.  

Thursday night...moderate confidence for VFR except MVFR across
CT into western-central MA, dry weather and light S-SE winds. 

Friday...VFR. Light south/southwest winds.

KBOS...High confidence in TAF. N winds trend NE/ENE 14-16z
before becoming SE/S late in the day. 

KBDL...High confidence in TAF. 

Outlook /Friday Night through Monday/...

Friday Night through Sunday Night: VFR. 

Monday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Friday...High confidence

Calm conditions expected over the coastal waters over the next 48 
hours. Seas range from 1 to 2 feet in the near-shore zones and 2 to 
3 feet in the outer zones. Light south/southeast winds today and 
tonight. Winds becoming more southwesterly during the day Friday.

Outlook /Friday Night through Monday/... 

Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Nocera/Chai
NEAR TERM...Loconto/RM
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Loconto/RM
MARINE...Loconto/Chai