Old Res Weather

Lexington, Massachusetts, USA

39°F

4/24/2024 11:36pm

Lexington Conditions: Clear
Temperature: 38.7°F / 3.7°C
Dew Point: 21.6°F
Relative Humidity: 50%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.16 in Rising Slowly
Visibility: 10 miles
Rain Today: 0.00 in
UV Index: $VPuv None

Southeast Middlesex County, MA - Freeze Warning
- SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 222315
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
715 PM EDT Mon Apr 22 2024

.SYNOPSIS...
A ridge of high pressure will result in dry weather through
Tuesday with pleasant days and chilly frosty nights, along 
with elevated fire weather potential. Widespread showers and 
perhaps an isolated thunderstorm will develop Wednesday as a 
cold front moves into the region, followed by drying and 
unseasonably chilly temperatures Wednesday night. Large high 
pressure will build into the region Thursday through Saturday 
bringing dry weather with moderating temperatures Friday and 
Saturday. The next chance of showers will be Saturday night into
Sunday as a frontal system approaches.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Clear skies and diminishing wind will set the stage for very 
good radiational cooling. Expecting dew points to rise from the 
teens overnight, but it will take a while to do so. Thinking 
patchy frost will remain a concern, so the Frost Advisory 
continues. Can see a scenario where some of our usual effective 
radiators could get below freezing where the frost/freeze 
program has begun. However, also thinking these freezing 
temperatures will not be widespread enough to warrant an upgrade
to a Freeze Warning. That possibility will need to be watched 
this evening.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
High pressure moves off the Eastern Seaboard for Tuesday and
Tuesday night. Dry weather continues Tuesday with a persistent 
southerly wind. This should result in near normal temperatures 
for late April through Tuesday night.

Our next chance for showers is anticipated to be late Tuesday
night as a front approaches from the west. It is more likely
these showers will impact the western half of southern New
England by the Wednesday morning commute.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Points...

* Widespread showers Wed and possibly an isolated t-storm, then 
  drying and cold Wed night with freezing temps

* Dry Thu through Sat. Cool Thu then milder Fri-Sat

* Chance of showers Sat night and Sun

Wednesday and Wednesday night...

A robust mid level trough and cold front will swing through New Eng 
Wed afternoon. Ahead of the front, a modest low level jet will 
transport PWATs 0.75-1" into SNE. Modest forcing for ascent combined 
with increasing deep layer moisture will result in numerous showers 
moving through Wed morning into early afternoon, then fropa will be 
followed by drying late in the day from west to east. Cold pool 
aloft assocd with the mid level trough will steepen mid level lapse 
rates with 7-8 C/km lapse rates in the 700-500 mb layer and Total 
Totals rising into the 50s. Not much SB instability present, but 
decent forcing combined with steepening mid level lapse rates 
suggest potential for a few t-storms. 

Very dry post-frontal airmass moves in Wed night with PWATs dropping 
to near 0.10". Rapid clearing Wed night with gusty NW winds in the 
evening diminishing overnight. Cold night for late April with 
widespread lows in the 20s in the interior and low 30s near the 
coast. Frost/Freeze headlines will likely be needed. 

Thursday through Saturday...

Large high pres builds into New Eng Thu and persists into Sat 
bringing dry weather with sunny days and clear nights. Below normal 
temps Thu with freezing temps likely again late Thu night interior, 
then temps gradually moderate Fri and Sat to near seasonable 
normals. 

Regarding fire weather conditions for Thu, it will be rather dry 
with RH values dropping to 20-30 percent, but winds will be less of 
a concern as the high pres builds in with winds generally less than 
15 mph. 

Saturday night into Monday...

Mid level warm front moves into the region Sat night followed by the 
surface warm front Sunday. Moisture is increasing which will lead to 
chance of showers, although forcing for ascent is limited as upper 
ridge builds into the region. Then mostly dry for Monday but will 
have to watch a potential backdoor front. Above normal temps 
expected Sun-Mon but how warm it gets will be dependent on cloud 
cover and location of the surface boundary. Interesting that GEFS 
and ECMWF ensembles both have moderate to high probs of >70F and 20-
30% probs of >80F for next Mon. Wide range in temp outcomes for Sun 
and especially Mon with the warmer outcomes dependent on backdoor 
front remaining to the north which is uncertain at this time.

&&

.AVIATION /23Z MONDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

00z TAF update...no changes

Through Tuesday...High confidence. 

VFR. Light S winds develop overnight increasing to 10-20 kt Tue
afternoon.

Tuesday Night...High confidence.

Mainly VFR through the night. MVFR/IFR cigs should develop from
west to east across the western half of southern New England
after midnight. -SHRA increasing from west to east as well.

KBOS TAF...High confidence in TAF.

KBDL TAF...High Confidence in TAF. 

Outlook /Wednesday through Saturday/... 

Wednesday: Mainly MVFR, with local IFR possible. Breezy. SHRA
likely.

Wednesday Night through Thursday: VFR. Breezy. 

Thursday Night through Friday Night: VFR. 

Saturday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Tuesday Night...High Confidence.

High pressure moving off the Eastern Seaboard tonight into
Tuesday will result in rather light winds and seas across the
waters. Good visibility. Increasing risk for showers late
Tuesday night. Increasing south winds may lead to rough seas
across the outer coastal waters late Tuesday night. However, do
not have enough confidence in the timing for a Small Craft
Advisory at this time.

Outlook /Wednesday through Saturday/... 

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers. 

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. 

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Thursday Night through Saturday: Winds less than 25 kt.

&&

.FIRE WEATHER...
Tuesday...

There will be elevated fire weather concerns Tuesday. Given 
that we are in a pre-greenup and a very dry atmosphere is in 
control, expecting minimum afternoon relative humidities to 
drop to between 20 and 30 percent. Winds will be from the south
with some gusts again of 15 to 20 mph.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Frost Advisory from 11 PM this evening to 7 AM EDT Tuesday for 
     CTZ002>004.
MA...Frost Advisory from 11 PM this evening to 7 AM EDT Tuesday for 
     MAZ013-016>023.
RI...Frost Advisory from 11 PM this evening to 7 AM EDT Tuesday for 
     RIZ001>008.
MARINE...None.

&&

$$

SYNOPSIS...Belk/KJC
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...KJC
AVIATION...Belk/KJC
MARINE...Belk/KJC
FIRE WEATHER...Belk