Lexington Weather

Lexington, Massachusetts, USA

63°F

4/16/2024 6:18pm

Lexington Conditions: Few Clouds
Temperature: 63.3°F / 17.4°C
Dew Point: 34.5°F
Relative Humidity: 34%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.00 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 101246
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
846 AM EDT Wed Apr 10 2024

.SYNOPSIS...

Increasing cloudiness today with developing light rain showers
mainly for this afternoon into tonight. Fog, low clouds and
drizzle are expected tonight, along with another period of
splashover on the eastern Massachusetts coastline. Overcast with
high moisture levels are expected for Thursday, along with
periods of showers. Cold front brings another dose of rain and 
wind to the region late Thursday night and Friday. Unsettled but
seasonably mild conditions through the weekend accompanied by 
brisk winds. Dry and mild to start next work week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

845 AM Update...

* Increasing clouds today with highs mainly in the lower to 
  middle 60s this afternoon away from the immediate coast

* Generally dry weather prevails for most of the day with just a
  few showers possible across the distant interior 

Plenty of sunshine to start the morning across most of southern
New England. This coupled with a relatively dry airmass in pre-
greenup was allowing temps to quickly jump. We are thinking that
areas inland from the coast...many locations should see high
temps reach the lower to middle 60s. We can not even rule out a
few upper 60s depending on the solar insolation. Meanwhile...southeast
flow will keep highs generally in the middle to upper 50s along
the immediate coast.

We do expect more in the way of clouds as the day progresses 
especially across interior southern New England. Bulk of the
forcing for organized precipitation though will remain well to
our west. Therefore...generally dry weather will prevail much 
of the day outside perhaps a few brief showers in northwest MA. 
After 3-4 pm we may see a few showers slide further east...but 
activity should be relatively light and scattered. 

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...

330 AM Update:

Tonight:

The warm advection burst of showers from the later-aftn hrs moves 
offshore early tonight. Thereafter we get stuck in a pretty weak sea 
level pressure pattern, with strong warm and moist advection taking 
place. PWATs actually rise to 1-1.25" which is above normal for mid-
April along with a building thermal inversion. Indication for weak 
surface ridge over interior ME/NH and extending into central MA 
favors light NE to E sfc flow. Dewpoints also surge into the mid 40s 
to near 50. This is a pretty textbook pattern for low clouds, 
fog/mist and periods of drizzle across a wide cross section of SNE. 
It isn't clear how low visibilities in fog might get, and it looks 
as though in some model soundings that there's enough albeit very 
shallow mixing that could keep visbys from reaching low levels. But 
the potential exists for fog to become locally dense and later fog 
statements/possible dense fog advisories can't be ruled out. Kept 
PoPs fairly low (20% or less), with better chances for measurable 
precip toward daybreak and mainly across western MA/CT closer to the 
periphery of a stronger warm front. 

The persistent easterly flow combined with still-elevated tides 
could bring another round of splashover or very minor coastal 
flooding for the overnight high tide in eastern MA. Of the two 
tides today, the astro tide overnight tonight is the higher one
(11.68 ft MLLW). Coastal flood statements may be needed 
tonight.

Lows tonight mainly in the 40s to low 50s, which are close to what 
forecast dewpoint temps project to be.

Thursday: 

Warm, moist advection regime continues into SNE on Thursday, 
although underneath a continued overcast with a continued strong 
thermal inversion. In the midst of continued overcast and areas of 
mist/fog, a stronger wavy warm front trailing from a potent low 
pressure over the OH Valley looks to spread another round of light 
rains to our area on Thurs, lifting northeastward through the 
day. Best chance for rains lies mainly from central MA/northwest
RI westward (around 50-70% PoP); lesser chances for eastern MA 
but couldn't rule out showers here either. Warm frontal boundary
lifts into interior northern New England during the 
midafternoon hours, with a dryslot of sorts bringing a relative 
decrease in rain chances. The approach of stronger height 
falls/mid-level diffluence and SE upglide against the Berkshires
then brings PoP toward Likely to lower Categorical levels 
across interior western MA/CT by early evening. Here too, rain 
amts still look on the light side. 

Though it will be overcast all of Thurs, dewpoints in the lower to 
mid 50s will make it feel somewhat humid by mid-April standards. 
Continued onshore flow, overcast with periods of cloud cover 
limiting mixing will probably keep highs only in the 50s, although 
925 mb temps in the +10 to +13C range would argue for a lot warmer 
but we just won't mix through the strong inversion.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Key Points...

* Most potent front of the week brings gusty winds and moderate 
  rainfall to southern New England Thursday night and Friday 

* Unsettled through the weekend with a few chances for light 
  precipitation both days

* Drier and warmer conditions develop early next week 

Thursday night into Friday...

Low pressure currently located across the mid-south moves northeast 
deepening as it interacts with trough dropping south from Canada 
into the Great lakes before continuing to move northeast into 
Ontario on Friday. Resulting cold front will drive increased 
moisture advection on southerly flow as PWATS climb to near an inch 
and a half. Limited instability, with CAPE around ~100J/kg, may be 
enough to generate a rumble of thunder or two, but not expecting 
widespread thunderstorm activity with the front. 

Heaviest precipitation should start after 00Z Friday and will be 
enhanced by a near parallel to the front LLJ of 70 to 75kt and warm 
cloud depths approaching 11,000ft. System appears to be progressive, 
wrapping up between 12-18Z from west to east, which will help subdue 
rain totals a bit. Ensembles are in quite remarkable agreement 
regarding precipitation totals, with all three "heavy hitters" (the 
GEFS, ECMWF, and CMC) highlighting a 60-80% chance of 1" of rain 
across CT and a max of 10-20% chance of 2" across the same area with 
lesser totals further north and east. Given S/SE flow, all guidance 
appears to highlight upslope enhancement across the hills of 
northwestern Connecticut, just to the west of our CWA. While our 
area certainly doesn't NEED another dose of 1-2" of rain, the 
current forecast calls for some respite for RI and southeastern MA, 
which may mitigate river flooding concerns a bit. While we currently 
do not see the need for a flood watch, later shift may elect to 
hoist River Flood Watches, especially if we see the axis of heaviest 
rain shift east into Rhode Island. 

While the 925mb jet appears quite robust, there will be a pretty 
decent inversion that looks to strengthen with warm air building in 
aloft. Given cool SSTs in the 40s, anticipating it will be quite a 
struggle for winds to mix to the surface. Per usual, the NBM is 
showing it's high wind gust bias, continuing to forecast winds  as 
high as twice the magnitude of other guidance, such as the GFS and 
Canadian deterministic models. Took a conservative approach and cut 
winds using a blend of CONSRAW and NBM10th, which still highlights 
the potential of near 40kt gusts along the coast. A wind advisory 
may be considered by later shifts if winds trend upwards over the 
coming days. 

Coastal flooding chances look to be limited to Narragansett Bay 
given prolonged southerly/southeasterly flow, but the timing of 
highest surge remains uncertain, with the PETSS guidance showing up 
to 2.5' coinciding with HIGH tide, and the SFAS highlighting the 
greatest surge will coincide with LOW tide. At this point, it 
appears that at worst, some minor coastal flooding impacts could 
affect Fox Point in Providence, with splashover along the south 
coast. 

Saturday and Sunday...

Low pressure to our north and cyclonic flow will yield shower 
activity Saturday before drier conditions establish late Saturday 
and Saturday night. Unfortunately, another trough digs out of Canada 
for Sunday and Sunday night, which will bring another chance for 
rain Sunday afternoon and evening. Fortunately, neither day appears 
to be a washout, and with temperatures warming through the weekend, 
there should be ample opportunity for residents of southern New 
England to get out and enjoy the spring temperatures!

Saturday will be quite breezy as flow shift to the west/west-
northwest behind departing cold front. 925mb jet between 25-35kt 
should be able to efficiently mix on downsloping flow, with gusts to 
30kt possible across the entire region. Winds will subside slightly 
but not completely on Sunday. 

At present, trough/rain looks to dig south of our area by Monday 
morning, setting up for a mainly dry and mild start to next week. 
Temperatures look to warm into the mid to upper 60s and given the 
pre-greenup foliage state, would not be shocked to see temps 
overachieve and reach for 70F across the interior both Monday and 
Tuesday.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...

Forecast Confidence Levels:

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

12z TAF Update: 

Today: High confidence. 

VFR initially, though with lowering cloud bases. Could be an
isolated shower or two across NW MA in the morning hrs, but
should be largely dry. Better chances for scattered showers 
occurs after 18z Wed from west to east. Ceilings deteriorate to
MVFR around 00Z Mainly east winds 5-10 kt, becoming SE around 
10 kt by afternoon; speeds decrease later in the day.


Tonight: High confidence in trends but moderate on timing and
fog/visbys. 

Deterioration to IFR-LIFR between 03 and 06Z. Any scattered 
showers move offshore by 02z, with areas of drizzle, fog/mist 
and stratus for the evening and overnight. Indicated visbys 1/2 
to 2 SM in fog but could be periods of 1/4SM visby at times. 
Winds lighten early and and become NE speeds under 5 kt.

Thursday: Moderate confidence. 

IFR to LIFR categories continue, with at least stratus and 
fog/mist around. Warm frontal showers mainly focused for 
western airports thru 20z, but can't be ruled out anywhere. 
Winds become SE to S winds, speeds increasing around 10-15 kt by
late Thurs. 

KBOS TAF...High confidence in TAF. VFR thru most of today. Winds
thru 17z will likely vary between ENE and ESE around 5-8 kt 
before becoming steadily SE by aftn around 10-12 kt. Lowering 
ceilings to MVFR levels after 20z with SCT -SHRA, but lower 
flight categories (IFR-LIFR) tonight with stratus and mist.

KBDL TAF...High confidence in TAF. VFR most of today with SE
winds 4-8 kt. Ceilings then deteriorate to MVFR and IFR tonight
with stratus and mist.

Outlook /Thursday Night through Sunday/... 

Thursday: Mainly IFR, with areas MVFR possible. Breezy. Chance
RA, areas FG.

Thursday Night: Mainly IFR, with areas MVFR possible. Windy
with gusts up to 35 kt. SHRA, isolated TSRA.

Friday: MVFR/IFR conditions possible. Strong winds with areas
of gusts up to 40 kt. SHRA likely, isolated TSRA.

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

Saturday: Mainly VFR, with areas MVFR possible. Windy with
gusts up to 30 kt. Slight chance SHRA.

Saturday Night: VFR. Windy with areas of gusts up to 30 kt. 

Sunday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

335 AM Update:

** Gale Watch In Effect Thursday Night into Friday **

Overall high confidence.

Winds and seas to remain below SCA levels through Thursday. 
Persistent period of E/SE winds continues, with speeds around 
10-15 kt through tonight. For Thursday, winds become SE to S and
increase to 15 to 20 kt later in the day. Seas through the 
period mainly 4 ft or less on the outer waters. 

Periods of light rain showers develop this afternoon, but what
may restrict visibility to a greater degree is developing fog
tonight, fog which may continue into a good part of Thursday.
Another period of light rains is expected again on Thursday.

Outlook /Thursday Night through Sunday/... 

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain, patchy fog. Local visibility 1 nm
or less.

Thursday Night: Low risk for gale force winds with gusts up to
40 kt. Areas of rough seas. Chance of rain showers. 

Friday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Rain showers, isolated
thunderstorms. 

Friday Night: Moderate risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Rough seas up to 12 ft. 

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 11 ft. 

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. 

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from late Thursday night through Friday evening for 
     ANZ230>237-250-251-254>256.

&&

$$

SYNOPSIS...Loconto/KS
NEAR TERM...Frank
SHORT TERM...Loconto
LONG TERM...KS
AVIATION...Loconto/KS
MARINE...Loconto/KS