Old Res Weather

Lexington, Massachusetts, USA

51°F
3/28/2024 12:43pm 
  • Lexington Conditions: Light rain, Mist, Overcast
  • Temperature: 50.5°F / 10.3°CWarmer 0.3°F than last hour.
  • Dew Point: 48.6°FIncreased 0.4°Fsince last hour.
  • Relative Humidity: 93
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 29.93 inFalling 0.02  inHg/hr Falling Slowly
  • Visibility: 2 miles
  • Rain Today: 0.73 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 221959
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
359 PM EDT Fri Mar 22 2024

.SYNOPSIS...
Active period of weather arrives late tonight through Saturday 
night with heavy rain, flooding, wintry weather, and marine 
hazards. Drying out Sunday into early next week but rather windy
along the coast, especially Cape and Islands. Below normal 
temperatures will prevail. The next chance of rain will be 
Wednesday and Thursday as another frontal system approaches.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...


Tonight/early tomorrow

First half of the night is quiet across the region with some 
increasing cloud cover and light winds ahead of a robust low-
pressure system that will move over the region tomorrow. Active 
weather begins to settle over southern New England during the early 
morning hours as a surface warm front associated with a deepening 
low-pressure system begins to lift over the region. Temperatures on 
the north side of the warm frontal boundary will be well below 
freezing. As warmer air aloft overruns the cooler air in place, 
we'll begin to see precipitation develop in the form of light snow 
showers across western MA and CT. As the warm nose edges further 
north, a melting layer develops between about 850 and 900 hPa. With 
surface temps remaining at or below freezing, this will support a 
freezing rain profile for north/northwest Hartford county, western 
MA, and northern Worcester county. Based on latest suite of ensemble 
guidance, freezing rain may begin as early as 5am  across western 
MA/CT and continue through 09 to 10 am when surface temps will begin 
to rise above freezing and allow a changeover to rain. Prior to the 
changeover, substantial ice accumulations from a few hundredths of 
an inch to a tenth of an inch or more will be possible. For this 
reason, a winter weather advisory remains in effect for the 
aforementioned areas expected to experience freezing rain. Winds 
increasing out of the southeast to 10 to 15 knots during this period 
as well.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...


Tomorrow

By mid-morning tomorrow, surface temps will have increased to above 
freezing across southern New England. This will result in any 
remaining frozen precipitation changing over to rain. From there on 
out, the rest of tomorrow is a complete wash out. A coastal low 
develops and moves off the mid-Atlantic coast before tracking over 
or just southeast of The Cape/Islands. An impressive region of 
frontogenesis develops across southern New England by early 
afternoon and will support a period of heavy rainfall that may 
result in urban, small stream, or poor drainage flooding. Latest 
HREF run paints a swath of 2 to 4 inches of rain across CT, RI, and 
southeastern MA with the heaviest rainfall between roughly 2pm and 
8pm. While confidence in a significant rainfall event is higher than 
normal, even subtle changes in the storm track could result in the 
axis of heaviest rainfall lifting north or south, so there still 
remains a bit of uncertainty at 24 hours out. Given the relatively 
wide goal post for the axis of heaviest rainfall, a flood watch is 
in effect for the southern and eastern forecast areas. Only northern 
Worcester county, Franklin, and Hampshire counties are excluded. In 
addition to small stream flooding, some larger area rivers in 
southern RI are at risk for flooding as well (see Hydro AFD 
section). Temperatures range from upper 30s to low 40s across the 
interior/northwest areas tomorrow, with more mild temperatures in 
the upper 40s to low 50s across southeastern MA and RI. 

Tomorrow Night

Surface cold front associated with the low-pressure system moving 
over southern New England pushes through the region tomorrow 
evening. This brings precipitation to and end for most of the region 
from west to east between about 8pm and 2am. Clearing and strong 
northwest winds from 15 to 25 mph will follow the cold front. Precip 
lasts a bit longer over The Cape/Islands tapering off between 
roughly midnight and 4 am. Temps dive into the low to mid 20s across 
the interior/northwest areas and upper 20s to low 30s across 
southeastern MA/RI prior to sunrise on Sunday. 

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...

Highlights: 

* Mostly dry Sun into Tue, but blustery with below normal 
  temperatures. Quite windy over the Cape/Islands

* Increasing risk of wet weather Wed into next Fri. Temperatures 
  trending back above normal late next week.

A broad mid level trough is expected to morph into a mid level 
cutoff over the North Atlantic early next week. This should trap the 
surface low pressure beneath it, and keep it lingering offshore of 
southern New England. Still some uncertainty in just how far 
offshore this low pressure will wind up being. At present, thinking 
the latest NationalBlend (NBM) deterministic solution is on the 
pessimistic side of the envelope. Maintained a faster departure of 
clouds and rainfall Sunday.

High pressure over eastern Canada is expected to nudge into our 
region for Monday and Tuesday, leading to mainly dry and partly 
cloudy conditions across most of our region. The exception to that 
will be across far eastern MA, and especially the Cape and islands. 
Thinking clouds may linger longer there, along with a few showers 
Sunday morning. Will possibly need a Wind Advisory at some point 
Sunday into Sunday night into Monday. It's marginal still, so not 
very high confidence. With all the other ongoing headlines, will 
wait until confidence increases before issuing such a headline.

The weak high pressure should maintain dry weather MOnday and 
Tuesday, but also bring in colder air with a persistent N to NE 
wind. Eventually though, this high pressure should break down and 
move farther offshore. That will open the door for a slow-moving 
front to impact southern New England late next week, most likely 
some time from late Wednesday into Friday. It should not be a total 
washout, but looking at the prospect of a prolonged period of 
unsettled weather. Will need to monitor the impact of any additional 
rainfall on our creeks, streams and rivers, which should still be 
recovering from the rainfall this weekend.

Temperatures should trend warmer mid week, and likely return to 
above normal temperatures Thursday into Friday.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

18Z update... 

Through 00Z... High Confidence

VFR. Increasing mid-high clouds from 080-120. Steady 5 to 10
know westerly winds weakening and becoming light southwest by
00Z.

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

VFR through about 06Z with light southwesterly winds becoming
more south/southeasterly. Conditions begin to deteriorate after
06Z as precip associated with a surface warm front lifting over
southern New England begins to support MVFR ceilings and light
precip. Frozen precip will be an issue at the western terminals
(BDL/BAF/ORH). A brief period of -SN followed by -FZRA will be 
possible beginning as early as 08Z. Elsewhere, any precip will
be limited to -RA, but likely will be closer to or after 12Z
before precip reaches the eastern terminals.

Tomorrow...High confidence in trends. Moderate in timing.

-FZRA pay persist at BDL/BAF/ORH through as late as 14Z, but
 will changeover to rain thereafter with surface temps rising
 above freezing after sunrise. MVFR cigs/vsbys deteriorate to 
 IFR by 18Z as rain overspreads the region. Rain picks up in 
 intensity after 18Z and remains steady through 00Z. Southeast 
 winds gradually increase throughout the day ranging from 10 
 knots across the interior to 15 to 20 knots over the coastal 
 plain.

Tomorrow Night... High  trends. Moderate in timing.

IFR/MVFR cigs improve to VFR returns as precip gradually ends 
from west to east from 00 to 06Z. Rain lingers a bit longer over
The Cape/Island terminals likely tapering off between 06 and 
09Z with VFR returning to this area between 09 and 12Z. Winds
strengthen after 00Z behind a surface cold front. 15 to 25 knot
sustained northwest winds with gusts up to 35 knots. 

Outlook /Sunday through Wednesday/...

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

Sunday Night through Monday: VFR. Strong winds with gusts up to
45 kt. 

Monday Night: Mainly VFR, with local MVFR possible. Strong
winds with areas of gusts up to 45 kt. 

Tuesday: Mainly VFR, with areas MVFR possible. Windy with gusts
up to 35 kt. 

Tuesday Night: Mainly VFR, with areas IFR possible. Windy with
local gusts up to 30 kt. Chance SHRA.

Wednesday: MVFR/IFR conditions possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight

Quiet marine conditions through about midnight tonight. Thereafter, 
winds begin to increase out of the southeast ahead of robust low 
pressure system with sustained winds of 20 knots and gusts up to 25 
knots by sunrise.

Tomorrow

Conditions deteriorate rapidly tomorrow as a strong low-pressure 
system moves over southern New England. Steady 20 knot southeast 
winds persist with gusts up to 35 knots possible, especially over 
the southern Marine Zones. Seas gradually increase from 4 feet early 
in the day to 6 to 9 feet by tomorrow evening. Near-shore eastern 
zones stay a bit lower with 4 to 6 foot seas. A gale watch is in 
effect through Monday morning.

Tomorrow Night

A cold front moves over the waters tomorrow night. 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 marine zones and 6 to 10 
feet for the near-shore zones. 

Outlook /Sunday through Wednesday/...

Sunday: Moderate risk for gale force winds with local gusts up
to 45 kt. Rough seas up to 15 ft. 

Sunday Night through Monday: gale force winds with gusts up to
45 kt. Rough seas up to 15 ft. Slight chance of rain showers. 

Monday Night: Moderate risk for gale force winds with gusts up
to 45 kt. Rough seas up to 15 ft. 

Tuesday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 13 ft. 

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 10 ft. Slight chance
of rain showers. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 2 AM to noon EDT Saturday for 
     CTZ002.
     Flood Watch from Saturday morning through Sunday morning for 
     CTZ002>004.
MA...Winter Weather Advisory from 2 AM to noon EDT Saturday for 
     MAZ002>004-008>011-026.
     Flood Watch from Saturday morning through Sunday morning for 
     MAZ005>007-009-011>024.
RI...Flood Watch from Saturday morning through Sunday morning for 
     RIZ001>008.
MARINE...Gale Watch from Saturday afternoon through Monday morning for 
     ANZ230>237-250-251-254>256.

&&

$$

SYNOPSIS...Belk/RM
NEAR TERM...RM
SHORT TERM...RM
LONG TERM...Belk
AVIATION...Belk/RM
MARINE...Belk/Dooley
      

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