Lexington Weather

Lexington, Massachusetts, USA

86°F
8/8/2022 7:14pm 
  • Lexington Conditions: Clear
  • Temperature: 85.8°F / 29.9°CColder 2.2°F than last hour.
  • Dew Point: 73.6°FDecreased 0.2°Fsince last hour.
  • Relative Humidity: 67%Increased 4.0% since last hour.
  • Wind: Wind from SSE SSE 2 mph, 10-min avg: 2 mph, gust: 15 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 030229
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1029 PM EDT Tue Aug 2 2022

.SYNOPSIS...
Heat and humidity will be the main weather story right through the 
weekend and into early next week. The heat and humidity will peak on 
Thursday and Friday with near record high temperatures and 
oppressive heat indices as well. The greatest potential for showers 
and thunderstorms will be on Friday with even some localized heavy 
rainfall possible.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Atmosphere has quieted late this evening, with only an isolated
shower still hanging on around Willimantic, CT. Expecting this
shower to continue to dissipate as it moves east. Mainly dry
conditions for most the rest of tonight. A cold front across
central southern New England will continue to move offshore
overnight. While low temperatures will not be much different
from last night, we will get into less humid air by daybreak.

745 PM Update...

Isolated thunderstorms have impacted a small portion of the 
region in association with a cold front working towards the 
I-95 corridor early this evening. While most of the region 
remained dry...a strong t-storm was working across far eastern 
CT and into the NW RI border. It has pulsed up at times and the
outflow was now surging well ahead of it. This should result in
a weakening trend, but perhaps some brief 45 mph wind gusts are
still possible.

Otherwise...we should see the remaining isolated activity
dissipate over the next 1-3 hours as diurnal heating dissipates
coupled with weak mid level lapse rates. The cold front should
approach the Cape Cod Canal towards midnight. This will keep 
the risk for any low clouds and fog confined to mainly parts of 
the Cape and especially Nantucket.

While it will remain quite humid tonight across far southeast
New England...a bit drier air will push in from the northwest 
behind the cold front elsewhere especially toward daybreak. Low 
temps will be in the 60s to near 70. Localized patchy ground fog
is possible in the typically prone locales late, but should be 
limited as drier air gradually works in from the northwest.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
330 PM Update:

Wednesday through Wednesday Night: 

High pressure ridges into SNE as cool front moves offshore. Still 
will be quite warm but northerly flow as well as heating/mixing of 
drier air aloft should support lower to middle 60s dewpoints for 
most. So a little less humid, but plenty of sun and 850 mb temps in 
the mid teens C range should support highs at least as warm as today 
with mid 80s to low 90s in the interior and coastal plain. Should 
see local sea-breezes develop which will keep coastal areas a couple 
degrees cooler. Winds will shift from N/NW to S/SW as high pressure 
moves offshore later in the day. 

Dewpoints rise again back to uncomfortable levels (upper 60s/low 
70s) later Wed aftn into Wed night. As indicated by several guidance 
sources and the 12z HREF, developing fog/stratus near the South 
Coast/Cape and Islands looks to expand northwestward; it's not clear 
how far north and west fog may make it but could expand at least to 
the I-95 corridor and potentially into eastern CT/southern Worcester 
County. Lows mid/upper 60s to lower/mid-70s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...

* Oppressive Heat & Humidity Thu and Fri with Heat Headlines Posted

* Heat Indices in 100 to 105 degree range Thu & Fri

* Main threat for showers & thunderstorms will be Fri with localized 
  heavy rainfall possible 

* Heat and humidity continue this weekend into early next week 
  with a few showers & thunderstorms possible 

Details...

Thursday and Friday...

Excellent model agreement in oppressive heat and humidity for both 
Thursday & Friday. The 500 MB height fields are on the order of 590 
to 594 DM which is outside the ECMWF climatological database. That 
is an excellent signal for an anomalous weather event; in this case 
being oppressive heat & humidity. 850T will be on the order of +19C 
to +21C over this time period along with southwest flow. 

Plenty of sunshine Thursday with good mixing should yield near 
record high temps in the 96 to 101 degree range. Dewpoints well into 
the 60s should bring Heat Indices on the order of 100 to 105 degrees.
By Friday...the surface cold front will be dropping down from the 
north. While high temps may end up a few degrees lower than Thu;
the dewpoints will be higher as moisture should pool along the 
cold front likely in the 70 to 75 degree range. High 
temperatures should still come up well into the 90s and it is 
not out of the question that a few spots hit 100 on Friday. 
Heat Indices should be on the order of 100 to 105 degrees. Given
the above we have opted to issue Heat Advisories for our entire
region...except for the Cape and Islands. We eventually may need
to include the Cape in the Heat Advisory for Friday. Lastly, 
given the potential for those very high dewpoints Friday...a 
few spots may see Heat Indices on the order of 105 to 107 so an 
upgrade to an Excessive Heat Warning is not out of the question.
Either way oppressive heat and humidity is on tap for the 
region.

Dry weather should prevail for much of Thursday given lack of 
synoptic scale forcing/deeper moisture. However, a few showers & 
t-storms can not be ruled out late Thu across our western 
zones. However, the main threat for scattered showers and 
thunderstorms will be on Friday as the cold front drops south 
into our region. The severe weather threat will be rather 
limited by weak wind fields. However, Pwats of 2+ inches coupled
with a slowing frontal boundary may result in localized heavy 
rainfall.

This Weekend Into Early Next Week...

Upper level ridging will remain anchored off the mid-Atlantic coast. 
This will result in continued above normal height fields and 
temperatures as well. In addition...this setup will result in quite 
a bit of humidity too. Highs in the upper 80s to the middle 90s 
along with humid conditions may result in the need for additional 
Heat Headlines. Perhaps some relief arrives by Tuesday. There also 
will be the potential for a few showers/t-storms at times, but not 
expecting a washout with dry weather dominating.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels:

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

Tonight: High confidence. 

VFR, except for a period of LIFR conditions across Nantucket, 
and perhaps parts of the Cape, ahead of a cold front. Either 
way should see a windshift. Otherwise, any of these low clouds 
and fog should dissipate across Nantucket toward daybreak as 
winds shift to the WNW behind this front.

Wednesday and Wednesday Night: High confidence. 

VFR with expected sea-breezes for the coastlines about 15-17z. 
Otherwise, winds become WSW 4-8 kt late. 

Continued VFR for most, though re-developing mist/fog and
stratus for the evening for at least the Cape and Islands but
also possible towards SE MA and PVD. S/SW winds 4-8 kt.

KBOS...High confidence in TAF. 

KBDL...High confidence in TAF. 

Outlook /Thursday through Sunday/...

Thursday: VFR. Breezy. 

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

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

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

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

Saturday Night: Mainly VFR, with local MVFR possible. Breezy. 

Sunday: Mainly VFR, with areas MVFR possible. Breezy. Slight
chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Overall high confidence. 

Winds and seas to stay at sub-SCA levels through the period. 

SW winds near 20 kt late today shift to W and decrease early 
tonight, then becoming NW around 10 kt. Biggest concerns for
tonight are potential for isolated/scattered thunder early 
tonight, then fog with significant reduction in visibility 
overnight near the south coastal/nearshore waters. 

NW winds 10 kt shift to onshore with sea-breeze development Wed 
afternoon; then will trend S/SW Wed night with fog re-developing. 

Seas 3 ft or less all waters.

Outlook /Thursday through Sunday/... 

Thursday through Thursday Night: Winds less than 25 kt. 

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

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

Saturday: Winds less than 25 kt. 

Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. 

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers, isolated thunderstorms.

&&

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

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

August 4th daily record maximum low temperatures...

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

August 5th daily record maximum high temperatures...

BOS - 100F [1955]
ORH - 96F  [1944]
PVD - 100F [1944]
BDL - 101F [1955]

August 5th daily record maximum low temperatures...

BOS - 76F [1938]
ORH - 73F [1938]
PVD - 77F [1938]
BDL - 76F [1938]

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     CTZ002>004.
MA...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     MAZ002>021-026.
RI...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     RIZ001>007.
MARINE...None.

&&

$$
SYNOPSIS...Frank/Loconto
NEAR TERM...Belk/Frank/Loconto
SHORT TERM...Loconto
LONG TERM...Frank
AVIATION...Belk/Frank/Loconto
MARINE...Frank/Loconto
CLIMATE...Staff
      

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