Lexington Weather

Lexington, Massachusetts, USA

39°F
3/2/2024 8:49am 
  • Lexington Conditions: Mostly cloudy
  • Temperature: 39.2°F / 4.0°CWarmer 1.6°F than last hour.
  • Dew Point: 33.3°FIncreased 0.9°Fsince last hour.
  • Relative Humidity: 79%Decreased 2.0% since last hour.
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 30.45 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.00 in
  •   

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 021128
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
628 AM EST Sat Mar 2 2024

.SYNOPSIS...
Low pressure approaches our area today, bringing periods of 
rain this afternoon into tonight. Mostly cloudy but dry weather
returns Sunday, and perhaps into Monday, with mild 
temperatures. Remains unsettled through much of this upcoming 
week, but with considerable uncertainty in timing rain chances 
and intensity. Temperatures remain mild.

&&

.NEAR TERM /THROUGH TONIGHT/...
7AM Update

Radar starting to show showers popping up along the warm 
frontal LLJ boundary where there is likely some elevated 
instability. The stratiform rain associated with the low is 
starting to work into western CT with rain and low clouds a bit
ahead of schedule. Sped up POP's this morning to account for 
this. Otherwise the forecast remains on track.

Previous Discussion...

Reasonably good model consensus, so used that as the basis 
for this forecast update. High pressure will remain centered 
over the North Atlantic today, but will also provide a little 
resistance to rainfall moving into southern New England for a 
time this morning. Eventually though, a low pressure moving 
along the East Coast will be too close to maintain the dry 
weather, especially during this afternoon. Rainfall amounts in 
the latest guidance have come up from the guidance 24 hours ago.
Still not looking like much rainfall during the day today, 
generally around one quarter inch.

Thickening and lowering clouds this morning. Temperatures may be
just low enough where there is a low risk for some snow or
freezing rain should isolated showers be able to make it into
western MA right around daybreak.

Despite the clouds, persistent southerly winds should result in
above normal temperatures.

&&

.SHORT TERM /SUNDAY/...
Low pressure should pass by near the Cape and islands later
tonight into Sunday. Thus, the heaviest rainfall is expected
across RI and southeast MA. Some question on the timing of the
precipitation leaving. Thinking right now that most of the 
rainfall is offshore by daybreak Sunday, but some of the
guidance is lagging the consensus timing. Meaning there is the
possibility for the end time to slow down from the current
forecast.

No cold air to speak off, so not concerned about anything other
than rainfall. Total rainfall for this event expected to range
from about 0.25 towards NW MA, up to around 1.50 towards the
South Coast.

Above normal temperatures continue.

&&

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

* Periods of wet weather with above normal temperatures through 
  Wednesday

* Unsettled weather Thursday into the weekend, but uncertainty 
  remains high.

Monday 

The low slowly moves offshore to the east Monday and begins to 
weaken while a high pressure stretches down from Canada into 
SNE. Soundings show the column above 850mb drying out
significantly with weak subsidence aloft. NE flow behind the low 
will keep low level moisture around and could lead to sporadic 
light drizzle. However models have begun to show a dry layer 
around 925mb which could keep things drier Monday. Either way, 
Monday will feature more clouds then sun with highs in the upper
40s to low 50s in the east, and low to mid 50s in the west.


Tuesday - Wednesday

Upper level flow becomes southwest with a weak disturbance
moving through Tuesday into Wednesday. Another weak coastal 
low will accompany the weak upper level disturbance, but the 
timing of the coastal low is still uncertain at this time. The 
ECMWF is more progressive bringing it through Tuesday. The GFS 
and Canadian are slower, bringing it through Tuesday night into 
Wednesday. There remains a large amount of spread in QPF totals 
with ensembles 25th - 75th percentiles ranging from 0.01 to 0.80
inches. High Tuesday have trended cooler only in the low 50s 
now due to continued cool ENE flow. Highs on Wednesday are more 
uncertain. If surface winds become westerly this could allow for
some afternoon sun and highs to reach the low 60s. However, if 
the surface winds remain ENE, then highs will stay in the low to
mid 50s.

Wednesday night - Friday

A southern stream shortwave trough looks to intensify as in
exits to the NE from the southern U.S. At the same time, a 
northern stream trough passes to the north over Canada. This 
brings a stronger coastal low to the area sometime between 
Wednesday night and Friday. Confidence in this portion of the 
forecast remains low due to large spread in guidance along with 
large run to run variability. Given the high uncertainty, won't
speculate on how exactly this storm system evolves, but 
something to keep an eye on as we head into next week.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

Today...High confidence in trends, moderate on exact timing.

VFR to start. Conditions deteriorate to MVFR/IFR as rain 
spreads into the region, roughly 12-15Z across western and 
central MA, along with CT. Should see precip spread into eastern
areas roughly 14-18Z. Not out of the question there are LIFR 
conditions late this afternoon and evening as heavier rainfall 
arrives. Winds out of the SSE/SE at 5-10 kts with gusts of 20-25
kts across SE MA. 

Tonight...Moderate confidence.

IFR to LIFR conditions with rain. Could see gusty SE winds
across eastern terminals. Based on the current track of this low
pressure, a S low level jet of 55-65 kt should impact RI and SE
MA. Have LLWS in the forecast. More uncertain about the LLWS
across parts of CT and central MA. While the magnitude should 
be less, the vector difference should be greater.

Sunday...Moderate confidence.

Mainly IFR to start, with some improvement to MVFR during the
afternoon from W to E. Rainfall may linger a little longer than
currently forecast across eastern MA during the morning. Winds
shifting to the N as a low pressure moves farther offshore.

KBOS TAF...High confidence in TAF through this morning. 
Moderate for the rest of the TAF.

VFR with light rain showers possible this morning. Steady rain
then reaches the terminal this afternoon with MVFR CIGS.
IFR/LIFR with moderate rain this afternoon/evening. Rain ends
after 08z but IFR/LIFR CIGS stick around.

KBDL TAF...High confidence in TAF.

VFR with light rain this morning, becoming moderate rain this
afternoon. CIGS become MVFR with the rain, and drop to IFR this
evening through the rest of the TAF period. 

Outlook /Sunday Night through Wednesday/...

Sunday Night: Mainly VFR, with areas MVFR possible. 

Monday: Mainly VFR, with areas MVFR possible. Slight chance RA.

Monday Night: Mainly VFR, with local MVFR possible. Chance RA.

Tuesday: Mainly MVFR, with local IFR possible. Breezy. Chance
RA.

Tuesday Night: VFR. Breezy. Slight chance RA.

Wednesday: Mainly VFR, with local MVFR possible. Chance RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Overall high confidence in the forecast. 

Looking at a period of gusty S to SE winds late this afternoon
into tonight, along with some rough seas. Winds shift to the N
and diminish Sunday, but rough seas will take longer to 
subside.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. 

Monday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain. 

Monday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain. 

Tuesday: Winds less than 25 kt. Seas up to 5 ft. Rain likely. 

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain. 

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 7 PM this evening to 7 PM EST Sunday 
     for ANZ232>235-237-250.
     Small Craft Advisory from 8 AM to 3 PM EST Sunday for ANZ251.
     Small Craft Advisory from 4 PM this afternoon to 7 PM EST 
     Sunday for ANZ254>256.

&&

$$

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

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