Lexington Weather

Lexington, Massachusetts, USA

89°F
8/8/2022 6:01pm 
  • Lexington Conditions: Clear
  • Temperature: 88.5°F / 31.4°CColder 3.6°F than last hour.
  • Dew Point: 74.3°FDecreased 0.9°Fsince last hour.
  • Relative Humidity: 63%Increased 5.0% since last hour.
  • Wind: Wind from W W 1 mph, 10-min avg: 3 mph, gust: 12 mph
  • Barometer: 29.79 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.00 in
  •   
Southeast Middlesex County, MA - Heat Advisory
 - SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 021029
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
629 AM EDT Tue Aug 2 2022

.SYNOPSIS...
Becoming hot, muggy, with brief widely scattered showers and 
isolated thunderstorms develop ahead of an approaching cold 
front Tuesday afternoon. Dry and very warm again Wednesday 
albeit noticeably cooler along portions of the immediate coast. 
This will be followed by near record high temps and oppressive 
humidity Thursday some of which may linger into Friday. The 
threat for scattered showers and thunderstorms increases Friday 
and may persist at times this weekend into next Monday, but a
washout is not expected. Above normal temperatures continue as 
well, but not at the potential record breaking levels of 
Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

630 AM Update

Forecast remains on track this morning. Muggy start to the day
with dewpoint and air temperatures in the mid and upper 60s
respectively. GOES night time microphysics reveals areas of low
stratus across portions of the interior this morning. Latest
observational trends have shown this cloud layer lifting
gradually. Expect this trend to continue as the morning
progresses. No significant changes to the near-term forecast. A
hot muggy day remains in store. See previous discussion for
additional details.

Previous Discussion

Rather expansive area of stratus was located over 
the eastern 2/3 of southern New England this morning. This 
stratus should dissipate rather quickly after sunrise, only to 
be replaced with higher clouds later today.

Expecting another rather warm and humid day today, with the 
risk for some showers and a few thunderstorms as a cold front 
approaches. Given the timing of this front, these are more
likely across the western half of southern New England. There is
not a lot of shear to organize to modest CAPE values of
1,000-1,500 J/kg. Thus, not expecting a widespread severe
weather event today, but cannot rule out a strong storm or two.
These storms should weaken after sunset.

Expecting max temperatures to be about 5 degrees higher today
due to a persistent southwest wind ahead of a cold front. This
will also lead to much higher dewpoints. At this time, thinking
we will stay just under the threshold for a Heat Advisory, but
it will be close. This will need to be monitored by the day
shift, as a subtle increase of only a degree or two in either 
temperatures or dew points from the current forecast could make
all the difference. If you must work outdoors today, please
drink plenty of fluids and take frequent breaks out of the sun.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
A cold front will move offshore late this evening and overnight,
leading to less humid conditions Wednesday. A few locations
across eastern MA could also be slightly cooler, with seabreezes
developing by afternoon. Across the interior, max temperatures
should be similar to today.

Once showers dissipate this evening, rain-free weather should
persist through Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights

* Potentially record setting heat on Thursday with heat indices
  over 100.

* Oppressive humidity Friday with scattered showers and 
  thunderstorms Friday afternoon.

* Above normal temperatures continue this weekend

Thursday and Friday

Deep southwest flow is forecast to advect an anomalously warm 
and humid air mass into southern New England for Thursday and 
Friday. Temperatures at 850 hPa are expected to rise above 20 
Celsius on Thursday. With persistent 15-20 knot southwest winds 
expected in the boundary layer, we can expect diurnal mixing to 
850 hPa which will support high temperatures in the upper 90s to
perhaps 100 degrees across much of interior southern New 
England. Lower temperatures forecast across southeastern MA and 
the south coast in the upper 80s to low 90s. Dewpoints in the 
upper 60s to low 70s will result in heat indices in the low 100s
at some locations. Heat advisory headlines are likely at this 
time. Dry air in the mid-levels will keep the region dry on 
Thursday afternoon, but a spot shower/thunderstorm Thursday 
night can't be ruled out across the western zones.

Deep southwest flow continues into Friday and supports surging 
dewpoints into the low to mid 70s. Temperatures remain above 
normal, but increasing cloudiness Friday afternoon should limit 
high temperatures to the upper 80s and low 90s. Nonetheless, the
oppressive humidity will have us flirting with heat advisory 
criteria with heat indices in the upper 90s likely. 

Weak upper-level disturbance and surface frontal boundary moves
across the region late Friday. This will bring the potential 
for a few thunderstorms and some much needed rainfall across 
portions of southern New England. Weak boundary layer winds and 
PWATs close to 150 percent of normal will be supportive of 
locally heavy downpours. Not expecting any severe storms to 
develop as both deep-layer shear and synoptic forcing for ascent
will be very limited.

This Weekend

Southwest flow continues to support above normal temperatures 
this weekend. No strong signals for advisory level heat this 
weekend, but still hot with highs in the upper 80s to low 90s. 
Dewpoints remain elevated in the low to mid 70s making for some 
very uncomfortable sleeping weather. Can't rule out a few 
isolated convective showers or thunderstorms during the 
afternoon.

Next Week

Consensus among long-term models and ensembles if for the 
southwest flow pattern and above normal temperatures to continue
into Monday. Beyond Monday there is a signal for a frontal 
passage early next week that would bring the next opportunity 
for substantial rainfall.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels:

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

Today...High confidence.

Mainly VFR conditions with a scattered to broken deck of diurnal 
CU. Widely scattered brief showers and perhaps a few isolated 
thunderstorms develop this afternoon, which may result in 
brief/localized lower conditions but areal coverage/duration 
should be limited. SW winds 10-15 knots.

Tonight and Wednesday...High confidence. VFR.

KBOS...High confidence in TAF. Moderate confidence in timing
dissipation of stratus.

KBDL...High confidence in TAF. 

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR. 

Thursday: VFR. Breezy. 

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

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

Friday Night: Mainly MVFR, with areas VFR possible. Chance
SHRA, slight chance TSRA.

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Monday evening into Tuesday night...High confidence.

Poor visibility early this morning will improve during the day.
A cold front brings another chance for showers and slight 
chance for thunderstorms this afternoon and early evening. A
cold front will move across the waters tonight, with fair
conditions expected Wednesday.

Outlook /Wednesday Night through Saturday/... 

Wednesday Night through Thursday: Winds less than 25 kt. 

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, slight chance of thunderstorms. 

Friday Night: Winds less than 25 kt. Chance of rain showers,
slight chance of thunderstorms. 

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

&&

.CLIMATE...
August 4th daily record maximum high temperature.

BOS - 96F [1928]
ORH - 95F [1944]
PVD - 98F [1944]
BDL - 96F [1944]

August 4th daily record maximum low temperature.

BOS - 76F [1930] 
ORH - 72F [2002] 
PVD - 74F [2010] 
BDL - 74F [2006]

&&

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

&&

$$
SYNOPSIS...Belk/RM
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...RM
AVIATION...Belk/RM
MARINE...Belk/RM
CLIMATE...
      

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