Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 150611
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
211 AM EDT Mon Apr 15 2024

.SYNOPSIS...
Showers end overnight, along with gradual clearing. Dry and
seasonably mild Monday through Wednesday. Another unsettled 
pattern develops late this week, with near normal temperatures
and a few chances for rain Thursday into next weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1005 PM Update: 

Low pressure near the Poconos in northeast PA will continue to
ride ENE along an elongated frontal boundary from its center
northeastward into Southern New England through late tonight.
This should gradually shift the effective frontal boundary
southward into the southern waters as time goes on tonight.
Though we had a few lightning strikes in CT a few hours ago, the
bulk of convective activity has remained well to the southwest.
Radar showing a fractured line of scattered showers located just
south of the Route 2 corridor, which will slowly progress 
southeast toward the southern coastal waters thru midnight.
That will likely be the extent of it though over much of the
land with dry weather for the 2nd half of the overnight, 
however it is possible we could see a rogue, garden-variety TS 
develop over the southern waters (perhaps near MVY/ACK?) early 
overnight per the HRRR and 18z/14th NAM-3km guidance. Rain amts
probably won't amount to much more than a tenth of an inch as
showers should be passing and of generally light intensity.

Though the frontal boundary will be slowly sagging southward for
the 2nd half of the night well into the waters, cloud cover
could be a little slower to erode especially if the boundary
slows down. Did bump cloud cover up somewhat across the southern
half of Southern New England thru the pre-dawn hrs, essentially
a slower erosion of cloud cover. Further inland though, most
areas should trend mostly clear by overnight/pre-dawn period. 

Previous Discussion...

A disorganized frontal wave will traverse over the Northeast 
this afternoon and evening with scattered showers and a perhaps 
a few thunderstorms. Latest SPC meso-analysis reveals no 
significant surface based CAPE over southern New England within 
the warm sector of the wave of low pressure moving through the 
region. However, steep mid-level lapse rates are contributing to
elevated instability that could support a few rumbles of thunder 
across western MA/CT and possibly over some locations near the 
south coast this evening. Areas along and north of I-90 are
forecast to be in the cool sector, thus not expecting any
thunderstorm activity north of that mark. Any remaining showers 
and thunderstorms are forecast to clear to the south and east 
around or just before midnight. Thereafter we can expect gradual
clearing with winds shifting to the west/northwest. Low temps 
bottom out in the low 40s across northwestern MA and mi to upper
40s elsewhere.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Tomorrow

A dry surface cold front pushes through the region during the
day tomorrow. This will support dry conditions and
west/northwest winds throughout the day. Skies will be clear to 
start which will allow surface temps to warm to the upper 60s to
near 70 in some locations by the mid-afternoon hours. After a
sunny start, we will begin to see increasing diurnal cu during
the afternoon thanks to steep low- level lapse rates from cooler 
air aloft. Overall a warm/dry afternoon. Warmest temps will be 
focused in the CT River Valley and over southeastern MA where 
downsloping from WNW winds should help temps over achieve.

Tomorrow Night

Very quiet tomorrow night. Clear skies and light west/northwest  
winds. There is some question as to whether or not the
atmosphere decouples overnight. This will govern how far
temperatures are able to fall with radiational cooling. Will
have a better idea by tomorrow, but for now have leaned on a
blend of CONSMOS and NBM for low temps in the low to mid 40s on 
Tuesday morning.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights:

* Broad trough settled over the region for much of the upcoming  
  week, with a brief period of mid level ridging in the Tuesday-
  Wednesday timeframe

* Near to above normal temperatures, with an unsettled pattern 
  developing late this week

Based on the latest guidance suite, still have the greatest
confidence in the forecast details into early Wednesday. After
then, there is little consistency with the timing and amplitude
of some synoptic features, leading to low confidence in the 
forecast details. Kept a broad period of unsettled weather from 
late Wednesday into Saturday, but not expecting this to be a 
total washout this entire time. Expecting it will be a couple 
more days before these details come into better focus. All that 
said, there has been a consistent signal for near to above 
normal temperatures through this portion of the forecast.

High pressure dominates our weather Tuesday into Wednesday.
Thinking we could get through most of Wednesday dry, especially
across the eastern half of southern New England. Just a low risk 
for some showers during the afternoon farther west. More likely 
to see rainfall arrive some time Wednesday night into Thursday 
as a low pressure moves into the Great Lakes, with a secondary 
low pressure possibly developing toward the Mid Atlantic coast. 
This should move offshore Friday, with a lingering cold front 
into Saturday. A large high pressure over the northern Plains 
states should become more of a factor in our weather some time 
Sunday.

Moisture is not particularly impressive, so not expecting a lot
of rainfall during the second half of this week. This should be
a good thing, by permitting area waterways a chance to drain 
further.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

06z TAF Update: 

Through 12z Monday: High confidence in TAF/trends, though
moderate on fog coverage. 

VFR for most TAFs; however IFR-LIFR visby mist/fog is ongoing 
at BAF where winds were light/calm. We could see fog developing 
at BED and perhaps BDL thru daybreak but this is still a bit 
uncertain. SW winds around 10-15 kt for southeast MA/Cape 
airports; otherwise winds become light westerly for the 
remaining airports.

Today: High confidence. 

Mainly VFR, with any sub-VFR fog that developed overnight to 
trend VFR shortly after 12z as W/WNW winds start to increase. 
Will see SCT-BKN VFR decks today (bases 045-070, on the higher 
end of that range in aftn). 

With a light pressure gradient to start, winds are a little 
tricky/nuanced. Light W winds begin the morning before the 
increase in WNW speeds/gusts; that could put a period of brief 
sea- breezes at south-coastal sites (SWlys) and at BOS (SElys 
4-7 kt between 14-16z indicated with TEMPO). Anticipate after 
16z that winds become WNW and increase to around 10-15 kt with 
gusts 20-25 kt all areas, strongest over the terrain.

Tonight: High confidence.

VFR. Outside chance at a shower affecting ACK late
tonight/midnight. WNW winds continue but slacken to around 5-8 
kt.

Tuesday: High confidence. 

VFR mainly SKC. NW winds increase to 8-12 kt with gusts to 20
kt starting mid-morning and continuing til sundown.

KBOS TAF...High confidence in TAF. VFR with SCT 050 bases. Could
see a possible sea-breeze develop around 14-16z but would be
brief as prevailing WNW gradient wins out after 16z, with 
WNWlys 10-14 kt with gusts in the low-20s kt range.

KBDL TAF...High confidence in TAF. Mainly VFR. There could be a
brief period of IFR BR/BCFG near the airport early this morning
but will dissipate shortly after sunrise as W/WNW winds increase
to around 10 kt.

Outlook /Tuesday Night through Friday/... 

Tuesday: VFR. Breezy. 

Tuesday Night: VFR. 

Wednesday: VFR. Slight chance SHRA.

Wednesday Night: VFR. Chance SHRA.

Thursday: VFR. Breezy. Chance SHRA.

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

Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight

Some showers and possible a rumble of thunder possible over the 
south coastal waters before midnight tonight. Otherwise, expect 
gusty southwest winds to diminish as winds shift to the
west/northwest overnight. Sustained speeds fall to 5 to 10 knots 
by tomorrow morning with gusts less than 20 knots. Seas begin to
subside but remain high enough to warrant Small Craft Advisory  
headlines for the outer marine zones.

Tomorrow and Tomorrow Night

Seas continue to subside to sub-Small Craft Advisory criteria by 
tomorrow evening. Otherwise, expect relatively quiet conditions 
over the coastal waters with modest 10-15 knot west/northwest 
winds. 

Outlook /Tuesday Night through Friday/... 

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

Tuesday Night through Wednesday: Winds less than 25 kt. 

Wednesday Night: Winds less than 25 kt. Slight chance of rain
showers. 

Thursday through Friday: Winds less than 25 kt. Seas locally
approaching 5 ft. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for 
     ANZ232>235-237-250.
     Small Craft Advisory until 8 PM EDT this evening for 
     ANZ254>256.

&&

$$

SYNOPSIS...Belk/RM
NEAR TERM...Belk/Loconto/RM
SHORT TERM...RM
LONG TERM...Belk
AVIATION...Loconto/KS
MARINE...Loconto/KS