Lexington Weather

Lexington, Massachusetts, USA

85°F
8/8/2022 7:30pm 
  • Lexington Conditions: Clear
  • Temperature: 84.9°F / 29.4°CColder 2.4°F than last hour.
  • Dew Point: 74.1°FIncreased 0.5°Fsince last hour.
  • Relative Humidity: 70%Increased 6.0% since last hour.
  • Wind: Wind from S S Calm, 10-min avg: 1 mph, gust: 9 mph
  • Barometer: 29.80 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 012350
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
750 PM EDT Mon Aug 1 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 AM TUESDAY MORNING/...

745 PM Update...

Weak surface wave south of Nantucket was in the process of
departing the region. This was taking the last of the lingering
light showers across the Cape/Islands out to sea. Dry weather
will persist overnight. In the wake of the departing weak low
pressure system...surface winds will shift to the southwest 
keeping bulk of the low clouds across RI/SE MA from advancing 
much further north overnight. In fact...may it see improvement 
towards daybreak in these locations. It will remain muggy 
tonight, which may lead to localized patchy ground fog in the
typically prone locations late. Lows will mainly in the 60s to 
near 70.

&&

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

Highlights... 

* Becoming hot, muggy, with some scattered garden variety t'storms 
  ahead of an approaching cold front. 

A surface low over the northern Great Lakes region moves northeast 
into the Saint Lawrence River Valley. Out a head of the trailing 
cold front southwest winds are 8-12 kt with gust to 15-18 kt near 
the immediate coast. Temperatures throughout the day reach 88-92 
degrees with an apparent temperature of 92-95 degrees. Dew points 
are back in the low 70s for the most part and upper 60s across the 
northern border. There will be some cooler spots, coast and east 
slopes of the Berkshires, there temperatures are in the low to mid 
80s. A cold front moves across the region between 18z and 02z with 
isolated thunderstorms possible.

Forecast soundings off the HRRR show plenty of instability with on 
average 1500 J/kg of MUCAPE, but next to no shear. We have healthy 
surface to 3km lapse rates of 8.0C/km, but as always the mid level 
lapse rates are less than ideal, around 5.5C/km. At this time SPC 
has much of the region in general thunder for Tuesday afternoon, 
primarily looking at garden variety storms with a low chance for an 
isolated strong or severe storm. PWATs are 1.5 inches which is near 
normal for early August, so a few heavier downpours aren't out of 
the question. We need the rain, though it will be isolated. In 
addition, localized strong wind gusts are a possibility tomorrow as 
well given DCAPE values are around 1000. 

Post cold front wind direction becomes west/northwest which will 
temporarily help dry out the atmosphere and reduce dew points to the 
low 60s. Temperatures though will remain mild with lows in the mid 
and upper 60s to low 70s at the urban centers.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...

Highlights...

* Dry & Very Warm Wed but noticeably cooler along the coast

* Near Record High Temps Thu between 96-101 Degrees along with Heat 
  Indices in the 100 to 104 degree range

* Heat & Humidity linger Fri with scattered showers/t-storms possible

* Still above normal temps this weekend into Mon but not record 
  breaking; with the risk for a few showers/t-storms at times
 
Details...

Wednesday...

A somewhat drier and a bit less humid airmass will be ushered into 
the region behind Tuesday/s cold frontal passage; but it still will 
be quite warm away form the immediate coast. A weak ridge of high 
pressure will provide plenty of sunshine and dry weather. We still 
expect high temps to top out in the upper 80s to near 90 in many 
locations. The weak pressure gradient will allow for sea breeze 
development and noticeably cooler high temps along portions of the 
immediate coast; compared to Tuesday. 

Wednesday night...

The weak ridge of high pressure moves east of the region Wed night. 
Dry weather will persist given the lack of any real synoptic scale 
forcing. Low temperatures will mainly be in the 60s.

Thursday...

All the guidance is in very good agreement in pumping a very 
anomalous airmass into southern New England. 850T are depicted to 
rise to between +21/+22C across most of the region. Good mixing with 
plenty of sunshine should support near record high temps in the 96 
to 101 degree range across much of the region. Oppressive heat 
indices of 100 to 105 degrees are expected and Heat Advisories will 
be needed for many locations. Low risk for approaching Excessive 
Heat Criteria, but thinking is dewpoints will not be quite high 
enough. Temps will be a few degrees lower towards the south coast 
with a modified marine airmass, but still hot. The lack of synoptic 
scale forcing/deep layer moisture will result in mainly dry weather 
on Thu. However, we can not rule out a few showers/t-storms working 
into our western zones late Thu/Thu night.

Friday...

The actual surface cold front will cross the region sometime on 
Friday. The latest guidance seems to have trended with a slower cold 
frontal passage on Friday, so a decent shot much of the region see/s 
high temps break 90 again. In fact, dewpoints may pool in the 70 to 
75 degree range. So even though temps may be several degrees lower 
than Thursday; Heat Indices of 95 to 100 degrees are certainly 
possible particularly for southern areas. Decent shot Heat Headlines 
will need to be continued into Fri. Would not be surprised if these 
numbers even have to be increased too with later forecast packages 
if this front continues to slowdown. 

The other issue on Friday will be scattered showers and 
thunderstorms with the actual cold front. Localized heavy rainfall 
will be possible too given relatively weak wind fields and Pwats of 
2+ inches. 

This Weekend into Monday...

The EPS/GEFS guidance continue to indicate above normal height 
fields across the region. This will favor above normal temps 
persisting, but not to the levels we are expecting on Thu. But we 
certainly may see high temps in the 90+ degree range at times. There 
also will be the risk for a few showers/t-storms with a frontal 
boundary/shortwave or two, but not a washout. Timing is quite 
uncertain at this point, but guidance tends to be favoring Sat and 
Mon as a better chance for the activity at this point.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...

Forecaster Confidence Levels:

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

00Z update...

Tonight...Moderate confidence.

MVFR-IFR conditions mainly in low clouds will generally remain 
across RI/SE MA tonight. Light SE-S winds will shift to the SW,
which should keep the low clouds from advancing much further
northwest than their current location. Otherwise, expect VFR
conditions outside some localized fog patches.

Tuesday...High confidence.

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

Tuesday Night...High confidence.

VFR. NW wind 5-8 kt. 

KBOS...Moderate confidence in TAF.

KBDL...High confidence in TAF. 

Outlook /Wednesday through Saturday/...

Wednesday through Wednesday Night: VFR. 

Thursday: VFR. Breezy. 

Thursday Night: VFR. Breezy. Slight chance SHRA, isolated TSRA.

Friday: VFR. Chance SHRA, chance TSRA.

Friday Night: Mainly VFR, with local IFR possible. Chance SHRA,
chance TSRA.

Saturday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, slight chance TSRA.

&&

.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.

Surface low pressure moves over coastal waters tonight with chance 
showers and low stratus clouds. Poor vsbys conditions develop 
overnight into the early hours of Tuesday. Short wave provides a
secondary chance for showers for the waters south of Block 
Island to Nantucket. Vsbys improve during the day with SW wind 
10-15 kt and near shore gust to 20 kt. Seas generally 2 to 4 
feet. Cold front brings chance showers and slight chance thunder
Tuesday afternoon and early evening. Post cold front wind 
direction becomes northwest at 8-12 kt. 

Outlook /Wednesday through Saturday/... 

Wednesday 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, isolated
thunderstorms. 

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

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

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

&&

.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...Gaucher/Frank
NEAR TERM...Frank
SHORT TERM...Gaucher
LONG TERM...Frank
AVIATION...Gaucher/Frank
MARINE...Gaucher/Frank
CLIMATE...Simpson
      

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