Old Res Weather

Lexington, Massachusetts, USA

50°F
3/28/2024 11:24am 
  • Lexington Conditions: Light rain, Mist, Overcast
  • Temperature: 49.6°F / 9.8°CWarmer 0.1°F than last hour.
  • Dew Point: 47.7°FIncreased 0.2°Fsince last hour.
  • Relative Humidity: 93
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 29.94 inFalling 0.03  inHg/hr Falling Slowly
  • Visibility: 1½ miles
  • Rain Today: 0.64 in
  • UV Index: $VPuv None
  •   
Southeast Middlesex County, MA - Flood Watch
 - SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 211732
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
132 PM EDT Thu Mar 21 2024

.SYNOPSIS...

Dry conditions for today and Friday. Though southern New England is 
located between two pressure systems and will experience strong 
west/northwest gusts through this evening, before diminishing on 
Friday. Due to the dry and gusty conditions today, all of southern 
New England is placed under elevated fire weather concerns. A 
more active weather pattern then evolves for Friday night into 
the weekend. A strong frontal system may bring the risk for 
minor accumulating snow in the interior late Friday night, but 
transition to widespread soaking rain Saturday into Saturday 
evening, capable of poor drainage flooding and rises on rivers 
and streams. Drying out Sunday into early next week but 
temperatures will average below normal with persistent onshore 
flow.

&&

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

* Second day of spring features gusty winds, below normal highs, and 
  elevated fire weather concerns. 

Main weather concerns today are the gusty winds and low values of 
relative humidity, leading to elevated fire weather concerns for 
this afternoon. First off, southern New England is placed between 
two pressure systems, a building high over the Ohio River Valley and 
a deepening low across northern Maine. Forecast soundings based on 
BUFKIT continue to show a deep and well-mixed boundary layer to 
850mb. Wind gusts today will be in the neighborhood of 30 to 40 mph, 
with the potential of nearing 50mph for towns along the east slope 
of the Berkshires. In collaboration with NWS Albany we continued our 
Wind Advisory for western Massachusetts, which includes Berkshire 
County, as well as the western most of the following counties; 
Franklin, Hampshire, and Hampden. 

With a well-mixed boundary layer we are able to transport the low 
dewpoint temperature to the surface, which is in the single digits. 
And because of that, our minimum relative humidity values are 25 to 
35 percent. And after speaking with our fire weather partners and 
neighboring WFOs, we have agreed to issue a special weather 
statement (SPS) for elevated fire weather concerns for today. You 
can find more information regarding fire weather are the bottom of 
the AFD. 

While there will be a fair amount of sunshine, temperatures this 
afternoon will struggle to reach the 40 degree mark. In fact, those 
living along the coast will have the better chance of recording a 
high temperature of 38F to 42F, areas west of I-95 are generally in 
the middle to upper 30s this afternoon. It is also important to 
consider the gusts, it will allow it to feel as if it were in the 
teens and 20s. Brr, never fun talking about wind chills when the 
calendar reads spring.

&&

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

* Gusty wind and below normal temperatures this evening into the 
  overnight hours. 

* Sunny, light wind, and potentially a renewed fire weather threat 
  for Friday. 

Overnight: High pressure moves in from the west and will help ease 
the tight pressure gradient force over southern New England, thus 
allowing winds to drop off. Gusts diminish, 15 to 25 mph, by the end 
of the night. Continued CAA overnight will result in below normal 
low temperatures, forecast ranges from the teens across the interior 
and the 20s over the coastal plain. 

Friday: An 1030+mb area of high pressure settles over the northeast 
and allows for wind speeds to become light. Expecting a mainly sunny 
day due to the dry airmass, though this will lead to a second day of 
low values of relative humidity. It is possible an SPS for elevated 
fire weather concerns could become needed if our partners deem it 
necessary. The good news, winds are light, less than 15 mph from the 
west/southwest. Afternoon high temperatures are a few degrees warmer 
than today, generally expect highs in the low 40s.

&&

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

Highlights: 

* Minor snow accum possible late Fri night into early Sat in 
  the interior

* Widespread rain, heavy at times Sat into Sat evening capable of 
  minor urban and poor drainage flooding and some river flooding

* Trending drier for Sun into early next week, but blustery with 
  below normal temps

Friday Night into Saturday Night... 

Potent northern stream trough moves into New Eng with enough 
interaction with southern branch to bring a plume of anomalous PWATs 
northward into SNE. Meanwhile southern stream low pres is forecast 
to lift northward along the mid Atlc coast Sat then track south and 
east of Nantucket Sat night. Inverted trough extending north from 
the low pres combined with coupled upper level jet structure will 
result in strong forcing for ascent, acting on anomalous moisture to 
bring heavy rainfall to SNE Sat into Sat evening. 

Initial warm advection and deepening moisture ahead of the 
approaching mid level trough will result in precip developing from 
west to east mainly after midnight Fri night. The column is cold 
enough to support a few hours of snow north and west of I-95 
corridor where a coating to one half inch is possible before snow 
changes to rain. Snow will persist longer further in the interior, 
with 1-3 inches possible north of the Route 2 corridor in far 
northern MA, especially over the higher terrain. Snow will change to 
rain here Sat morning and there could also be a period of freezing 
rain during the snow to rain transition. 

The bigger impact from this storm will be the heavy rainfall during 
Sat into Sat evening which will be focused along and to the west of 
the surface boundary/inverted trough. The heaviest rain will 
initially be focused across the interior during Sat but shift to the 
SE New Eng late Sat and especially Sat evening as low pres tracks 
south of Nantucket. Deterministic and ensemble guidance suggesting 
potential for 1.5 to 3 inches of rainfall. However, where this axis 
of heaviest rainfall sets up remains uncertain. GEFS and CMC 
ensemble probs of 2+ inches favor areas south of the MA Pike while 
ECMWF ensembles have heaviest rainfall in the interior. Still need 
to iron out these details but the heavy rainfall may lead to areas 
of minor urban and poor drainage flooding. In addition, MMEFS 
probabilistic hydrographs based on the GEFS are indicating high 
probs (70-80 percent) of minor flood for the Pawtuxet and Wood River 
basins in RI, with 30-40 percent probs of moderate flood. 

Rain will be ending from west to east Sat night as colder air begins 
to move back into the region. If cold air comes in quicker it is 
possible rain could change to a period of snow before ending, mainly 
interior where some minor accum are possible. But this is a low 
confidence forecast at this time.

Regarding potential for coastal flooding Sat, it is looking like a 
rather low risk at this time. Along the south coast, the tide in 
question is the Sat evening high tide. Providence would need a 2.5 
ft surge to reach minor flood, and we are currently forecasting a 1-
2 ft surge. No concern along the E coast for the Sat and Sat night 
high tides.

Sunday into Wednesday...

Deterministic guidance continues to trend drier for Sun into early 
next week as ocean storm remains well offshore with high pres 
building to the north. However, ensemble guidance still showing low 
probs for measurable QPF across SE New Eng Sun-Mon so we continued 
low pops in the grids. Still a chance that a piece of moisture could 
wrap around the low pres and back in across SE New Eng sometime Mon 
or Tue so will have to watch this. The shower chances increase again 
toward midweek as a shortwave approaches from the west. Persistent 
onshore flow will keep temps below normal. 

Not expecting any coastal flooding issues for the east coast Sun 
into early next week as forecast surge is much less than what is 
needed to reach minor flood.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...

Forecast Confidence Levels:

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

Through 00Z...High confidence

VFR with strong W to WNW winds at 15-25 kts. Gusts of 30-40 kts
gradually ease to 25-35 kts by this evening.

Tonight...High confidence.
 
VFR with winds out of the WNW to NW at 10-20 kts, with gusts of
20-30 kts for most of the night. Anticipate that the gusty winds
cease by roughly 08-12Z. 

Friday... High confidence. 

VFR with NW winds at 5-10 kts shifting to the W by late morning.
Should continue to shift to the SW by the afternoon. Increasing
mid/high clouds during the afternoon.

Friday Night...High confidence in trends, moderate in exact
timing.

VFR to start, but will have conditions deteriorate as
precipitation spreads in. Should see MVFR to IFR after 06Z with
light snow to start for most. Will stay as snow across the
higher terrain, but transition over to all rain elsewhere fairly
quickly. 

KBOS TAF... High confidence in TAF. 

VFR with WNW winds at 20-25 kts through the day and winds
gusting 35 kts. Should ease tonight, but still will be gusty 
until the Fri AM push. Winds shift to the SW Fri afternoon.

KBDL TAF...High confidence in TAF. 

VFR with WNW/NW winds 15-20 kts and gusts 30 kts through the 
day. Winds ease tonight, but still remain gusty until the Fri AM
push. Winds shift to the W/SW Fri afternoon.

Outlook /Saturday through Monday/...

Saturday: Mainly IFR, with areas MVFR possible. Windy with
gusts up to 35 kt. RA.

Saturday Night: Mainly VFR, with local IFR possible. Strong
winds with local gusts up to 40 kt. Chance RA, slight chance
SN.

Sunday: VFR. Windy with gusts up to 35 kt. 

Sunday Night: VFR. Strong winds with local gusts up to 40 kt.
Slight chance RA.

Monday: VFR. Windy with gusts up to 35 kt. 

&&

.MARINE...

Forecaster Confidence Levels:

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

Today through Friday... High Confidence. 

Dry conditions throughout this period. A Gale Warning continues for 
all waters, with the exception of Narragansett Bay through this 
evening. Today, west/northwest gusts up to 40 knots with increasing 
seas between 5-8 feet near shore, and 8-11 feet off shore. Friday 
the wind becomes west/southwest with gust below 25 knots and 
diminishing seas. 

Outlook /Friday Night through Monday/...

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

Friday Night: Winds less than 25 kt. Chance of rain. 

Saturday: Low risk for gale force winds with gusts up to 35 kt.
Areas of rough seas. Rain. Local visibility 1 to 3 nm.

Saturday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 14 ft. Rain. Areas of visibility
1 to 3 nm.

Sunday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Slight chance of rain. 

Sunday Night through Monday: Moderate risk for gale force winds
with gusts up to 40 kt. Rough seas up to 13 ft. Slight chance
of rain. 

&&

.FIRE WEATHER...

Elevated fire weather concerns today and also potentially into 
Friday. Today offers a combination of gusty NW winds between 35
and 50 mph and lowest RHs around 20-35 percent. In addition, 
rainfall received on Wednesday were less than 0.2 inches.

In collaboration with our neighboring WFOs and state partners, a 
special weather statement for Elevated Fire Weather Concerns goes 
into effect from 11am to 8pm .  

For Friday, NW to W winds are lighter but RHs project to be lower in 
the upper teens to 30 percent range. Will reassess with incoming 
guidance before coordinating with our fire weather partners over the 
coming days.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 8 PM EDT this evening for MAZ002-008-009.
RI...None.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ230.
     Gale Warning until 2 AM EDT Friday for ANZ231>235-237-250-251-
     254>256.
     Small Craft Advisory until 2 AM EDT Friday for ANZ236.

&&

$$

SYNOPSIS...KJC/Dooley
NEAR TERM...KJC/Dooley
SHORT TERM...Dooley
LONG TERM...KJC
AVIATION...BL
MARINE...KJC/Dooley
FIRE WEATHER...Dooley
      

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