Old Res Weather

Lexington, Massachusetts, USA

38°F
3/29/2024 8:56am 
  • Lexington Conditions: Light rain, Overcast
  • Temperature: 37.9°F / 3.3°C 
  • Dew Point: 36.1°F 
  • Relative Humidity: 93
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 29.62 in Steady
  • Visibility: 8 miles
  • Rain Today: 0.41 in
  • UV Index: $VPuv None
  •   

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 232319
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
719 PM EDT Sat Mar 23 2024

.SYNOPSIS...
Heavy rain today, exiting by midnight. Drying out Sunday into early 
next week but rather windy along the coast, especially Cape and 
Islands.Cooler with breezy to gusty northeast winds Monday and 
Tuesday, and chances for light rain showers expanding westward 
from the offshore waters. Building rough seas are likely Monday 
and Tuesday over the southeastern waters. It remains unsettled 
through mid to late in the week, with rain chances returning 
Wednesday night into Thursday, and a better chance around late 
Thursday and into Friday. Temperatures trend above normal for 
mid to late in the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
715 PM Update: 

Storm system bringing several potential weather related concerns
underway. Specific sections follow:

Hydro/Heavy Rain: Period of heaviest rain is now underway 
across Southern New England, having moved northward from 
southeast NY and southern CT. Hourly rain rates have been as 
much as a half inch per hour in these bands of moderate to heavy
rain. In fact Windsor Locks has broken its daily rainfall 
record for March 23rd, and we'll have a final record report sent
later this evening as rain continues to fall. While there are 
numerous gaged rivers and smaller streams/creeks experiencing 
rises, so far these have been within bank, but rivers and 
streams are expected to continue to experience rises. The area 
where we are most concerned for the heaviest rainfall totals 
lies roughly near or just east of the I-84 corridor in CT, into 
Kent/Providence Counties in RI and adjacent portions of southern
Worcester, Bristol, Norfolk, and southern Middlesex Counties in
MA. Mesoanalysis shows a substantial axis of 925-700 mb 
moisture flux convergence oriented in these counties, focused by
a sfc inverted trough which lies along or just east of the I-95
corridor. Rather fortunately, obs and near-term models are 
showing the eastward progression ending sooner:
around 10 PM or so for western MA/CT, and around midnight for
central/eastern MA and RI, and around 2 AM for the Cape and
Islands. Flood Watch remains valid.

Winter Weather: Will note though there could be some additional
pockets of light FZRA in the hills in northwest MA as precip 
begins to decrease and colder air rushes back in on NW winds, so
will keep the Winter Weather Advisory going for this as some of
these locations have seen ice accretions of a quarter to four- 
tenths of an inch. 

Strong Southeast Winds: Specific to the Wind Advisory for 
southeast MA, southern RI and the Cape and Islands...gusts so
far have been borderline, with peak gust speeds in the 40-45 mph
range. Per regional Doppler velocity profiler data, strongest 
low- level jetcore is just about crossing our southeastern 
waters now, so likely only another couple hrs before winds flip
to N/NW and the risk for wind gusts capable of minor damage 
ceases. Had considered cancelling the Wind Advisory with this
update but will leave up for now. Possible that this could be
cancelled in the next hour or so before its slated expiration.

Coastal Flooding: Fox Point tidal gage indicating a 2.17 ft
storm surge as of 706 PM as SE winds have increased, bringing a
total water level of 6.15 ft, just under a foot below minor
flood stage. With high tide set to occur in another hour or so,
it's looking like we'll reach Minor flood stage but likely not 
into the Moderate range. Will leave Coastal Flood Statement as
is.

Previous discussion:

The low bringing us all this rain is currently centered over the 
Delmarva, poised to lift into our offshore waters and slide along 
the south coast then over the Cape Cod canal this evening and 
overnight. The excessive rainfall is the result of a strengthening 
low level jet coinciding with moist inflow off the Atlantic combined 
with large scale ascent thanks to placement beneath the entrance 
region of a 150 kt upper jet. This sets up a good pattern for heavy 
rainfall, with HREF guidance indicating the period of heaviest rain 
being generally 4pm-10pm with potential for as much as 1-2 inches in 
3 hours for a brief period from coastal CT to RI to southeast MA. 
The Flood Watch remains in effect for some river flooding and the 
potential for urban/poor drainage flooding as well. The previously 
mentioned low level jet kicks in in earnest this evening with gusts 
to 40-50 mph. The cold front then drops through and colder air 
filters in on the back end. However, dry air also quickly moves in, 
so any changeover back to snow should be very brief with little to 
no impact. Rain comes to an end from west to east between 10pm and 
2am. Winds quickly shift to the northwest and remain gusty 
overnight, gusting 25 to 35 mph.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Sunday will be dry but blustery thanks to our placement between a 
strong low well south over the Atlantic and high pressure over the 
Great Lakes. This also produces winds out of the northeast which 
will serve to keep moisture (clouds) over eastern MA, potentially 
into RI and even eastern CT tomorrow. Further west expect even more 
sun. Winds gusting 25 to 35 mph will make highs in the upper 30s 
feel more like upper 20s/low 30s. The gradient only tightens 
overnight as the storm passes closer to SNE and this will mean 
deteriorating conditions on our southern and eastern waters with 
wind gusts to 35 to 45 kts and seas of 12-14 ft.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights: 

* Temps near or slightly cooler than normal Mon and Tue, with 
  northeast breezes/gusts. Light showers offshore expanding westward 
  Mon night/Tue? 

* Likely very choppy, rough seas over southeast waters Mon and Tue.

* Remains unsettled mid to late week with chances for rain Wed 
  night/Thu and a better chance Thu night/Fri. Temps trend 
  near/above normal.

Details:

Monday and Tuesday: 

Rather prolonged period of onshore NE flow, with a tightening 
pressure gradient driven by a 1040 mb high pressure area over 
northeast Quebec and a nearly vertically-stacked but strong coastal 
low over 35N/68W lat/lon vicinity. Sfc ridge axis from the high is 
expected to extend southward through the mid-Atlantic states and 
Carolinas, though it tends to weaken as we move through time. With 
that said, there remains considerable disparity on when this ridge 
axis starts to weaken, which would influence the northward return of 
showers and how far west any showers may extend. 

The tightening NE pressure gradient will bring stiff NE winds to 
eastern and especially southeastern portions of Southern New 
England. NE gusts around 35 to 45 mph take place over eastern and 
southeast MA and RI and around 20-30 mph inland. Though this wind 
will bring a bit of chill, the persistent NE gradient and stable 
fetch region seem more likely to bring some impact for marine and 
coastal interests, with building seas and winds gusting to gale 
force. Rough, choppy seas building to 12-14 ft are expected and 
though it's not beach season, could be some surf/beach erosion 
issues along east-facing shorelines, especially Cape and Islands. 

With the stated uncertainty in how any offshore moisture/related 
showers expands landward and further inland, kept PoP lower than the 
high-chance NBM values; GFS would favor a shutout entirely, although 
some consensus in the GEM/ECMWF in showing westward-spreading and 
light rain showers Mon aftn along the coast, then further inland 
into Tue/Tue night. PoPs will need adjusting, either up or down, as 
we move through time, but rain amts look light and wouldn't be 
necessarily impactful.

Despite slowly rising 925-850 mb temps, a limited mixing depth and 
more clouds further south and east will likely favor slightly below 
normal high temps and slightly above normal low temps for each day. 
Overall a pretty chilly, raw couple days are likely with the NE 
breezes, especially nearest the coast. 

Wednesday through Friday Night: 

Ridging aloft between the distant/offshore coastal low and a broad 
upper trough over the east-central CONUS weakens considerably early 
Wed. The broad trough gradually shifts eastward and sends a couple 
periods of rain showers to our area. One focused period looks to 
take place Wed night/early Thurs as a cool front moves east. Then a 
somewhat better chance later Thurs into Fri as the cool front stalls 
offshore and induces low pressure near the Carolinas to move NNE 
into the mid-Atlantic and coastal New England. PoPs were highest in 
this latter period in the 45-60 percent range, higher east. Still 
uncertain in some of the details and how quickly rain would shift 
eastward/offshore, but the mid to late week period looks pretty 
unsettled. 

Temps trend near to above normal, with highs in the upper 40s/low 
50s and lows in the mid/upper 30s.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

18Z update...

This afternoon...High confidence in trends. 

Rain will pick up in intensity after 20Z across CT then heavy 
rain spreads NE into RI and portions of central and eastern MA 
this evening. Southeast winds gradually increase throughout the 
day ranging from 10 kt across the interior to 15 to 20 kt over 
the coastal plain. A strong low level jet will likely increase 
winds across Rhode Island and southeast MA between 21z and 03z, 
gusting as high as 35 to 40 knots. 

Tonight...High confidence in trends. Moderate in timing. 

IFR/MVFR cigs improve to VFR returns as precip gradually ends  
from west to east from 02Z to 09Z. Rain lingers a bit longer 
over The Cape/Island terminals likely tapering off between 04 
and 07Z with VFR returning. Winds strengthen after 00Z behind a
surface cold front. 15 to 25 knot sustained northwest winds 
with gusts up to 35 knots. 

Sunday...High confidence. 

VFR. Strong winds with local gusts up to 40 kt.

Sunday night...High confidence. 

VFR. Northeast winds 15 to 20kts, gusting to 30 kts just
offshore. 

KBOS TAF...RA becoming heavy this afternoon with IFR 
conditions. Rain ends late this evening around 04z. Gusty 
southeast winds as well, nearing 30 knot gusts around 00z 
through 02Z/03Z. Shift from southeast wind to northerly wind by 
03z tomorrow with improving CIGS to MVFR.

KBDL TAF...Rain for the rest of today with IFR to LIFR 
conditions. Rain becomes heavy this afternoon and through this 
evening, ending after 00z. Light northeast wind will become 
northerly after 00Z and gusting 20 to 25 knots, and improving 
CIGS to MVFR.

Outlook /Monday through Thursday/...

Monday: VFR. Strong winds with local gusts up to 40 kt. 

Monday Night: Mainly VFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt. 

Tuesday: Mainly VFR, with local IFR possible. Windy with gusts
up to 35 kt. 

Tuesday Night: Windy with areas of gusts up to 30 kt. Chance
RA.

Wednesday through Wednesday Night: Chance RA.

Thursday: Breezy. Chance RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

* Gale Warning in effect for all waters Saturday and continues
  into Sunday

Tonight: A cold front moves over the waters tonight. Winds 
become even stronger out of the north/northwest with 30 knot 
sustained winds for most of the marine zones. Wind gusts from 30
to 40 knots. Seas increase to 10 to 13 feet over the outer 
coastal waters, and 6 to 10 feet for the nearshore waters.

Sunday: Low pressure system to our north will continue northerly
gales with gusts to 40 knots. Seas on the outer waters are
greater than 12 feet, near shore waves are 6 to 10 feet. 

Sunday night: Low pressure passing to our south will increase
gusts and seas. NE winds 20-35 kts gusting 35 to 40 kts with
seas increasing to 12-14 ft. 

Outlook /Monday through Thursday/...

Monday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 15 ft. Slight chance of rain. 

Monday Night: Moderate risk for gale force winds with gusts up
to 45 kt. Rough seas up to 14 ft. Slight chance of rain. 

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

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 12 ft. Slight chance of
rain. 

Wednesday: Winds less than 25 kt. Rough seas up to 9 ft. Chance
of rain. 

Wednesday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain. 

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

&&

.TIDES/COASTAL FLOODING...
There is some concern for Narragansett Bay during the high tide this 
evening but confidence has grown that th core of the jet stays 
just to the east and so the surge will likely be limited to 
1.5-2 ft which will keep water levels below flood. A Coastal
Flood Statement is in effect. The worst case scenario is for 
pockets of minor flooding.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Sunday morning for CTZ002>004.
MA...Flood Watch through Sunday morning for MAZ005>007-009-011>024.
     Winter Weather Advisory until 11 PM EDT this evening for 
     MAZ002>004-008-010-026.
     Wind Advisory until 11 PM EDT this evening for MAZ017>024.
RI...Flood Watch through Sunday morning for RIZ001>008.
     Wind Advisory until 11 PM EDT this evening for RIZ004>008.
MARINE...Gale Warning until 2 PM EDT Sunday for ANZ230>235-237-251.
     Gale Warning until 2 AM EDT Sunday for ANZ236.
     Gale Warning until 8 PM EDT Sunday for ANZ250-254>256.

&&

$$

SYNOPSIS...Loconto/BW
NEAR TERM...Frank/BW
SHORT TERM...BW
LONG TERM...Loconto
AVIATION...Loconto/BW
MARINE...
TIDES/COASTAL FLOODING...KJC
      

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