Old Res Weather

Lexington, Massachusetts, USA

54°F

4/25/2024 6:46pm

Lexington Conditions: Clear
Temperature: 54.1°F / 12.3°C
Dew Point: 26.4°F
Relative Humidity: 34%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.28 in Steady
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 241927
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
327 PM EDT Wed Apr 24 2024

.SYNOPSIS...
A cold front moves off the coast by this evening followed by 
unseasonably cold conditions tonight. High pressure dominates 
Thursday through Saturday with dry weather and gradually moderating 
temperatures. Unsettled pattern sets up for Sunday into early next 
week with shower chances at times but turning milder.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Scattered convective showers along the cold front moving across
SNE this afternoon. The cold front has pushed east of the CT 
valley and will move across the region this afternoon and off 
the coast by early evening. Sunshine and surface heating below 
steep mid level lapse rates contributing to SBCAPES 200-500, and
low level lapse rates are impressive as well at 8-9 C/km. 
Scattered convective showers will move across the region through
the afternoon, and an isolated t-storm or 2 is possible given 
marginal instability and steep lapse rates. Shower activity will
be brief, not lasting much more than an hour in any location, 
but a brief downpour and small hail is possible. 

Rapid clearing develops this evening behind the front as PWATs 
crash. Cold advection maximizes this evening with NW gusts to 20-25 
mph, and up to 30 mph along the coast, then diminishing overnight. 
Low temps forecast tricky as cooling will be from advection this 
evening, then radiational cooling late tonight as winds diminish. 
Still expecting lows mid/upper 20s interior, coldest NW MA, with 
lower 30s near the coast, but mid 30s Cape/Islands where winds will 
stay up through the night. Freeze watch was converted to Freeze
warning and expanded along the entire coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
Thursday and Thursday night...

High pressure will be in control with very dry airmass in place. 
Expect full sunshine Thu and clear skies Thu night. Winds will be 
light which will promote developing sea breezes by afternoon along 
the coast. Cooler airmass Thu as 850 mb temps bottom out at -2 to 
-4C. Highs will be in the mid-upper 50s but upper 40s along the 
immediate E MA coast where onshore winds develop. Very dry airmass 
with dewpoints well down into the teens Thu will result in RH values 
dropping to 15-25 percent, but winds will be light. 

&&

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

* Warming trend through the middle of next week.

* remaining dry Friday and Saturday.

* Low chance for showers Saturday then again Tuesday and Wednesday.

Friday and Saturday...

Upper level ridge and surface high pressure remains centered over 
the region through Saturday. With subsidence aloft and very dry mid 
level air, skies look to remain clear with very little clouds until 
late Saturday afternoon when high clouds ahead of a short wave move 
in. This will help moderate day time temperatures into low to mid 
60s Friday and mid to upper 60s Saturday. With a weak pressure 
gradient, local sea breezes will occur Friday and possibly again 
Saturday. However, winds begin to increase out of the south Saturday 
afternoon, which could keep a true sea breeze from forming along the 
east coasts. 

With the clear skies and weak winds Friday night, there will be very 
efficient radiational cooling setting up. low temps should drop near 
freezing in the typical cold spots of NW MA, and some low lying 
spots in SE MA. Otherwise lows drop into the mid to upper 30s across 
the rest of SNE. Upper level ridge axis passes to the east by 
Saturday night with some warm air advection ahead of the next 
shortwave trough. This will lead to increased cloud cover and and 
isolated to scattered showers. Lows stay warmer Saturday night in 
the upper 30s to low 40s. 

Sunday and Monday

The center of the high pressure drops south to the Carolinas, but 
the upper level ridge axis continues to stretch north in SNE. Being 
at the top of the ridge axis, weak vort impulses, along with warm 
air advection aloft bring high clouds and low chances for isolated 
showers both Sunday and Monday. High temperatures Sunday and Monday 
will be very dependent on the possibility of a back door cold front 
working in. Latest GFS and EURO is bringing that back door cold 
front through Sunday keeping temperatures in the low 60s. However, 
if that cold front stays offshore Sunday, temperatures could easily 
top the low to mid 70s. Given the uncertainty and run to run 
inconsistency, blended warmer NBM guidance with cooler CONSALL 
guidance. High temps will be warmer Monday regardless, but latest 
guidance has also trended temperatures back from the upper 70s to 
low 80s, down to the low to mid 70s due to the back door cold front. 
Again used a blend of the NBM and CONSALL guidance for Monday 
afternoon. 

Tuesday and Wednesday

Upper level ridge axis again moves offshore to the east, but this 
time, a weakening shortwave trough moves through the region. Given 
this is a week out, stuck with NBM for precip chances, which shows 
30-40% chance for showers. This seems reasonable given the weak 
forcing from the weakening trough. A cold front looks to move 
through behind the trough which could bring an isolated 
thunderstorms with it. Stuck with the NBM for high temperatures on 
Tuesday as southerly flow should kick out the back door cold front 
from Sunday and Monday. Highs should reach the mid to upper 70s, 
with a 30-40% chance at 80F in the CT river valley. Highs begin to 
trend cooler wednesday and beyond in the mid 60s to low 70s.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Through 00z...

VFR, but a brief shower or isolated t-storm possible with brief
lower conditions as area of scattered showers move across SNE 
through 22z. SW winds shifting to NW 18-22z from W to E. Gusts 
to 25 kt. 

Tonight...High confidence.

VFR with rapid clearing. NW gusts to 25 kt along the coast,
diminishing after 06z. 

Thursday and Thursday night...High confidence. 

VFR. Light winds, with local sea breezes developing by
afternoon.  

KBOS TAF...High confidence.

Brief convective showers possible 20-22z as the cold front moves
through, but VFR persists. Low risk for thunder but not enough
confidence to include in TAF. Wind shift to NW after FROPA with
gusts to 25 kt, diminishing after 06z. Sea breeze develops
15-17z Thu. 

KBDL TAF...High confidence.

Brief convective showers possible through 20z as the cold front
moves through, but VFR persists. Low risk for thunder but not 
enough confidence to include in TAF. Wind shift to NW after 
FROPA with gusts to 20 kt, diminishing after 00z. 

Outlook /Friday through Monday/... 

Friday through Friday Night: VFR. 

Saturday: VFR. Breezy. 

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

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

Sunday Night: VFR. Slight chance SHRA.

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. 

Tonight through Thursday night...High Confidence.

A period of NW wind gusts to 25-30 kt developing this evening behind 
the cold front, but diminishing overnight. SCA for all waters. 
Northerly winds 10-15 kt Thu morning becoming light Thu 
afternoon/night. Onshore winds develop near the coast Thu afternoon 
as sea breezes develop.

Outlook /Friday through Monday/... 

Friday 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 Warning from 2 AM to 8 AM EDT Thursday for CTZ002>004.
MA...Freeze Warning from 2 AM to 8 AM EDT Thursday for MAZ007-
     014>021.
RI...Freeze Warning from 2 AM to 8 AM EDT Thursday for RIZ001>007.
MARINE...Small Craft Advisory until 4 AM EDT Thursday for ANZ231-251.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT 
     Thursday for ANZ232>235-237.
     Small Craft Advisory until 2 PM EDT Thursday for ANZ250-
     254>256.

&&

$$

SYNOPSIS...KJC/KP
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...KP
AVIATION...KJC/KP
MARINE...KJC/KP