Lexington Weather

Lexington, Massachusetts, USA

56°F
6/9/2023 8:34pm 
  • Lexington Conditions: Clear
  • Temperature: 55.8°F / 13.2°CColder 0.5°F than last hour.
  • Dew Point: 54.1°FDecreased 0.6°Fsince last hour.
  • Relative Humidity: 94
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 29.68 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.22 in
  •   

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 090553
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
153 AM EDT Fri Jun 9 2023

.SYNOPSIS...
Scattered mainly diurnally driven showers are expected again
Friday and Saturday. The activity will be most numerous on
Friday with a few thunderstorms with small hail possible too. 
Temperatures will continue to run cooler than normal. A brief 
pattern change occurs Sunday and possibly lingering into Monday,
bringing drier and warmer conditions to the region. Then the 
next frontal system may bring widespread rain to the region 
around Tuesday.

&&

.NEAR TERM /UNTIL 5 AM THIS MORNING/...

155 AM Update...

Mostly clear conditions and light winds have led to patchy fog
across the region. Otherwise, dry weather prevails along with
chilly temps mainly from the upper 40s to lower 50s, mid to
upper 50s for Boston. 

&&

.SHORT TERM /5 AM THIS MORNING THROUGH 6 PM SATURDAY/...

Highlights...

* Numerous showers & scattered t-storms develop Fri 
* Small hail possible with the strongest storms
* High Fri mainly in the 60s

Details...

Friday...

Another piece of shortwave energy will drop down into southern 
New England from the main closed upper level low to our north on
Friday. This piece of energy will be stronger than the one 
impacting the region this afternoon/evening. Therefore...when 
combined with the diurnal heating showers should be more 
numerous than today. In addition...mid level lapse rates will 
also be steeper on the order of 6.5-7.5 C/KM. While instability 
will be limited given an abundance of clouds and highs only in 
the 60s...we should be able to muster 300-600 J/KG of Cape. This
should be enough to result in scattered thunderstorms. Given 
the steep mid level lapse rates and 700T are around -4C...small
hail is possible with the strongest storms especially with 
surface temps only in the 60s. We can not rule out a rogue 
marginally severe t-storm or two given such cold temps 
aloft...but mainly just sub-severe storms with small hail. 
Activity may develop initially along the terrain and also on a 
pseudo backdoor cold front/narrow low level convergent zone.

Lastly...lingering smoke from the Canadian Wildfires will be
focused mainly near and south of a Hartford to Providence line
according to the HRRR/RAP simulations. Air Quality alerts 
continue into Friday to cover this scenario.

Friday night...

The showers and scattered t-storms should dissipate during the
evening with the loss of diurnal heating. Still enough shortwave
energy wrapping around to support a few spot showers during the
overnight hours but most of this time will probably be dry. We 
will need to watch for some low clouds and fog patches 
developing especially across the eastern half of the region 
overnight. Overnight low temps will bottom out mainly in the 
upper 40s to the lower 50s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

Highlights

* Warmer this weekend with more showers on Saturday, and drier 
  weather on Sunday

* Unsettled weather returns early next week as a new area of low 
  pressure moves over The Northeast

Significant changes finally expected to take hold during this 
portion of the forecast. Large-scale omega block should finally 
break down towards Sunday, which would permit the persistent mid 
level cutoff of this week to finally get picked up in the mid level 
flow and pushed out over the North Atlantic. This is expected to 
give us a little bit more than one day of dry weather, before we 
will have to contend with another low pressure arriving from the 
Great Lakes. At least this one should be moving, albeit not likely 
very quickly. Have average confidence in the details into Tuesday, 
then below average confidence thereafter. 

At this point, looking for a drying trend late Saturday through 
Sunday, and perhaps into Monday morning.  Increasing risk for 
showers and thunderstorms late Monday into Tuesday. While a cold 
front should pass across southern New England by Wednesday, will 
still need to deal with a mid level cold pool, leading to more of 
what we saw this week: lingering showers with a low risk for 
thunderstorms. Trending drier towards late next week.

Near to below normal temperatures expected Saturday, followed by 
near to slightly above normal conditions the rest of this period.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels:

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

06z update...

Thru 12z...high confidence.

VFR/MVFR vsbys in patchy fog with isolated IFR. Otherwise,
mainly VFR cloud bases along with dry weather. Light WNW
trending NNW toward sunrise. 

After 12z...moderate confidence. 

VFR/MVFR in patchy fog with isolated IFR at sunrise slowly
improves to VFR. Dry weather then scattered to numerous showers
and thunderstorms develop this afternoon. A few storms may
contain small hail and gusty winds. Mainly VFR but brief MVFR
possible in the stronger storms. Light WNW winds become locally
onshore. Any vsby restriction due to smoke should be confined to
the south coast of MA/RI. 

Friday night...moderate Confidence.

The scattered showers and a few t-storms should wind down Friday
evening. It does appear that MVFR-IFR ceilings/vsbys may 
develop across the region Friday night as a result of the 
cooling boundary layer and lingering low level moisture. Areal 
extent/coverage of these potential low clouds and fog patches is
somewhat uncertain...but greatest risk will be across central 
and eastern sections of our region. Winds will be light/calm.

Saturday...moderate confidence. 

Light NW winds but becoming locally onshore. VFR/MVFR in the
morning will trend toward VFR cloud bases. Chance of scattered
showers and thunderstorms after 15z especially across eastern
MA. Lower risk across CT into western MA and a drying trend late
in the day. 

KBOS Terminal...Moderate Confidence in TAF. Mainly VFR but a
period of MVFR possible this morning and then again in the
afternoon in scattered showers/thunderstorms. Small hail and
gusty winds possible in the strongest storms. Light WNW predawn
wind becomes north after sunrise then NE and finally east this
afternoon. 

KBDL Terminal...High confidence in TAF. Main concern will be the
potential for a few t-storms within the vicinity of the terminal
Friday afternoon/early evening. A few of the stronger storms may
contain small hail and gusty winds. 

Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday: VFR. 

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.

Tonight through Friday night...High Confidence.

Closed upper level near the Quebec/northern New England will
continue to remain nearly stationary into Friday night.
However...weak pressure gradient at the surface will keep
winds/seas well below small craft advisory thresholds. Main
issue for mariners will be reduced vsbys at times across our 
waters. A bit of that may be from overnight fog...but greater 
risk will be from Canadian forest fire smoke in the southern 
waters.

Outlook /Saturday Night through Tuesday/...

Saturday: Winds less than 25 kt. Chance of rain showers. 

Saturday Night through Sunday: Winds less than 25 kt. 

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

Monday: Winds less than 25 kt. Chance of rain showers.

&&

.FIRE WEATHER...
Latest HRRR/RAP model simulations keep most of the near ground 
level smoke from the Quebec fires near and south of a Hartford 
to Providence line on Friday. This a result of the near ground
level smoke wrapping all the way around from the southwest. Air
Quality alerts have been extended for Friday into CT & RI to 
cover this scenario.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until 1 PM EDT this afternoon for CTZ002>004.
MA...Air Quality Alert until midnight EDT tonight for MAZ020>024.
RI...Air Quality Alert until midnight EDT tonight for RIZ001>008.
MARINE...None.

&&

$$
SYNOPSIS...Belk/Frank
NEAR TERM...Frank/Nocera/KP
SHORT TERM...Frank
LONG TERM...Belk
AVIATION...Belk/Frank/Nocera/KP
MARINE...Belk/Frank
FIRE WEATHER...
      

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