Old Res Weather

Lexington, Massachusetts, USA

52°F

4/25/2024 7:12pm

Lexington Conditions: Clear
Temperature: 52.2°F / 11.2°C
Dew Point: 26.6°F
Relative Humidity: 37%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.29 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 251458
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1058 AM EDT Thu Apr 25 2024

.SYNOPSIS...
Expansive high pressure system builds in across the northeastern 
United States through the end of the work week with sunny days and 
chilly overnights. Unsettled pattern sets up for Sunday into early
next week with shower chances. Temperatures turn milder but there
is a good deal of uncertainty as to how warm Sun/Mon are.

&&

.NEAR TERM /THROUGH TONIGHT/...
1057 AM Update: 

Well, today is April 25th and weatherwise, it's about a perfect
a day weatherwise as one could reasonably ask for, with high
pressure overhead supplying abundant sun. You'll need a light
jacket though with highs in the 50s, especially near the coast 
as sea-breezes get going look for highs in the mid to upper 
40s. 

Very dry air aloft should cause dewpoints to plummet into the
single digits through mixing, especially in the interior.
RHs thus could drop to around 15 percent but winds are light. 
Seabreezes near the coast should bring in higher dewpoints (mid 
20s). Blended in some of the WRF-ARW dewpoints which are quite
low into the official forecast to bring dewpoints down some into
the late morning to mid afternoon peak mixing period.

Previous discussion:

Highlights: 

* Sunny, but slightly cooler than what is average for late April.

* Another chilly night ahead which has prompt a re-issuance of a 
  Freeze Watch for many of the same locations, in addition to the 
  Cape and Islands. 

A quiet and sunny day ahead with surface high pressure moving down 
from the northwest and transporting a much drier and cooler airmass 
over southern New England. While the day starts off in the upper 20s 
and lower 30s, Freeze Warning remains in effect through 8AM, it
will warm into the middle 50s for most locations, though coastal
towns will be cooler due to an onshore wind, here the temperatures
are in the upper 40s. Otherwise, winds are light and from the 
northwest. 

PWATs are very low, less than 0.2 inch in most cases - this allows 
for lower dewpoints this afternoon, which are in the single digits 
north and low teens to the south - minimum RH values are upper teens 
and middle 20s. 

Given the dry atmosphere, temperatures late this afternoon should 
drop a bit faster - many spots fall below 40 degrees by midnight. As 
we go into the overnight these light and variable winds become calm 
which sets up for a night of good radiational cooling. Nighttime low 
temperatures drop into the 20s and low 30s, while interior sections
of northern Massachusetts may drop as low as the upper teens. Did
leaned on the colder MOS guidance for these overnight lows. 
With that said, have opted for a Freeze Watch for for much of 
southern New England where the Freeze/Frost program is active, 
this includes eastern Massachusetts, Cape Cod, Martha's 
Vineyard, and Nantucket. All of Rhode Island, with the exception
of Block Island, and northern Connecticut, with the exception 
of Litchfield County. Our neighboring WFO OKX did include their 
zones along our boundary in Connecticut for your awareness. Day 
crew will assess the guidance and make a final decision on 
whether or not a Freeze Warning or Frost Advisory is needed. 
Stay tuned! 

Lastly, could be area of patchy fog in prone radiator locations as 
temperatures will fall close to the dewpoint temperature.

&&

.SHORT TERM /FRIDAY/...
Highlights: 

* Mostly sunny and slightly warmer than Thursday. Coastal locations 
  likely experience onshore winds which keep temperatures a bit 
  cooler than interior communities. 

There are no big changes to Friday, high pressure holds strong 
across the northeast while mid-level ridge noses into southern New 
England. The atmosphere remains fairly dry again, supporting another 
mostly sunny day. There are height increases and subtle WAA at 850mb 
and think afternoon high temperatures will be 3 to 5 degrees warmer 
with many locations reaching the upper 50s and low 60s. Given the 
high pressure with little winds aloft, do think there will be a good 
chance an onshore wind develops again, with speeds less than 10 mph 
and keeping those communities by the coast cooler in the low 50s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Key Points...

* Dry weather through Saturday.

* Scattered showers Saturday night become more hit-and-miss Sunday 
  into Monday; more widespread rain chances on Tuesday and 
  maybe a thunderstorm. 

* Warming trend through next week but there remains a good deal of 
  uncertainty as to how warm temperatures will be. 

Details...

Friday night and Saturday will be dry under the influence of high 
pressure as a mid level ridge builds overhead. Southern New England 
will remain on the northern periphery of an east coast ridge through 
at least Monday. A warm front extending from a low pressure lifting 
from the Great Lakes into Quebec will move through kicking off some 
scattered showers Saturday night but lack of strong forcing and 
rising heights aloft will keep rainfall amounts from a few 
hundredths to a few tenths. The chance for hit-and-miss showers 
continues Sunday and Monday as we remain on the periphery of the 
ridge and another passing low, but most areas will be dry much of 
the time. The more significant chance for showers comes around 
Tuesday as a low passes to our northwest and moist southerly flow 
kicks in ahead of it with a subsequent cold front. Guidance is so 
far keeping the best instability to our west in NY but but still 
plenty of time for changes, so can't rule out some thunderstorms, 
especially in western MA/CT.

As for temperatures, radiational cooling will contribute to a cold 
start to the weekend (in the low to mid 30s) before mild southerly 
flow kicks in and temps moderate each day. A pesky back door cold 
front may yet ruin party (i.e. keep 70s out of the forecast) at 
least for eastern SNE on Monday though a tight gradient is likely 
from west to east. Low confidence temperature forecast at this time. 
By Tuesday, however, stronger southerly flow kicks in ahead of the 
cold front and odds of upper 60s/low 70s are good.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Today...High confidence. 

VFR. Light winds, with local sea breezes developing by 14-15Z. 

Tonight...High confidence. 

VFR. Light and vrbl winds. Chance of patchy fog in areas that 
radiate. 

KBOS TAF...High confidence.

VFR. Sea breeze likely develops between 14-15z. 

KBDL TAF...High confidence.

Outlook /Friday Night through Monday/... 

Friday Night through Saturday: VFR. 

Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

Sunday: Mainly VFR, with local IFR possible. Breezy. Slight
chance SHRA.

Sunday Night through Monday: Mainly VFR, with local MVFR
possible. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Friday...High Confidence.

Surface high pressure sets up over the waters with light winds and 
diminishing seas - Small Craft Advisory continues for the outer 
waters do to rough seas, but is expected to fall below 5 feet by the 
end of today. Tonight and Friday features dry and tranquil boating 
conditions with gusts less than 15 knots and seas are 2 to 3 feet. 

Outlook /Friday Night through Monday/... 

Friday Night through Saturday: Winds less than 25 kt. 

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

Monday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Freeze Watch from late tonight through Friday morning for 
     CTZ002>004.
MA...Freeze Watch from late tonight through Friday morning for 
     MAZ007-014>024.
RI...Freeze Watch from late tonight through Friday morning for 
     RIZ001>007.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ250-
     254>256.

&&

$$

SYNOPSIS...BW/Dooley
NEAR TERM...Loconto/BW/Dooley
SHORT TERM...Dooley
LONG TERM...BW
AVIATION...Loconto/BW/Dooley
MARINE...Loconto/BW/Dooley