Area Forecast Discussion
National Weather Service Boston/Norton MA
130 PM EDT Mon May 13 2024

.SYNOPSIS...
Mainly dry conditions today and turning milder with more 
seasonable temperatures as high pressure builds to the south. A
warm front will bring scattered showers tonight followed by 
warm weather Tuesday, but a few showers are possible in the 
interior during the afternoon. A coastal storm lifting NE from 
the middle Atlantic coast may bring showers and cooler 
temperatures Wednesday, and unsettled weather could linger into 
Thursday as the low pressure is slow to depart. High pressure 
returns Friday then another system may bring more rain next 
Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update: 9:30AM 

Areas of patchy fog in western Massachusetts and northwest 
Connecticut have lifted, now wall-to-wall sunshine across 
majority of southern New England thanks to surface high 
pressure. Temperatures already are in the middle and upper 50s
and are on track to reach the upper 60s and low 70s away from
the coast. Forecast remains in good shape with no changes. 

See previous forecast discussion below. 


Shortwave ridging moves into New Eng today with surface high 
pres south of New Eng. Dry air in the column to start the day 
will result in lots of sunshine this morning, then clouds will 
increase during the afternoon as warm advection increases ahead
of an approaching warm front. A modest low level jet transports
higher PWATs into New Eng from the west during the afternoon 
which may lead to a few showers in western MA mid-late 
afternoon, otherwise dry weather today. The S-SW flow will bring
a milder airmass into SNE as 925 mb temps increase to 10-12C. 
Highs should reach the upper 60s to lower 70s, but cooler along 
the immediate coast where sea-breezes develop.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Tonight...

Warm front will be moving into SNE tonight with PWATs 
increasing to 1-1.25". Deepening moisture plume ahead of the 
front moves across the region 00-06z which will bring scattered
showers, especially north of the Pike where best forcing sets 
up. Then dry slot moves in behind the front 06-12z so shower 
activity will exit to the north and east overnight. S-SW winds 
and higher dewpoints advecting into the region will result in a 
milder night with lows upper 40s to lower 50s. 

Tuesday...

Warm sector airmass overspreads SNE on Tue with warm and somewhat 
more humid airmass. Some stratus is possible across northern MA to 
start the day, otherwise expect partly to mostly sunny skies with 
clouds increasing later in the afternoon. 925 mb temps increase to 
15-17C supporting highs 75-80, perhaps a few lower 80s in the 
interior valleys, but 60s near the south coast due to increasing S-
SW flow. Dewpoints will be climbing through the 50s. It will become 
breezy with soundings suggesting gusts to 20-30 mph in the 
afternoon. 

Marginal instability across the interior which may lead to a few 
convective showers developing mid-late afternoon, but better chance 
of showers and t-storms will be to the north and west where better 
moisture and instability closer to a frontal boundary.

&&

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

* Rain possible Wednesday with showers lingering into Thursday

* Mainly dry Friday, then unsettled wet weather returns for the 
  weekend.

* High temps remain seasonable with onshore flow

Wednesday

Shortwave trough exits out of the Ohio River Valley and passes just 
south of SNE.  With the best forcing to the south, this has caused 
models to trend the associated surface low further south. This shift 
south has been a trend with guidance over this time range in the 
last week. Wouldn't be surprised if models keep shifting the low and 
QPF south over the coming days. With the shift south, Ensemble QPF 
probs have decreased significantly. Probs for 1 inch of rain is now 
less then 10% and for 0.5 inches less then 30%.  High temps drop 
back into the mid to upper 60s with 850mb temps dropping back to +7C 
along with showers and thick cloud cover around much of the day. 

Thursday and Friday

Guidance has trended slower kicking out the shortwave as it tries to 
cutoff over the mid Atlantic coast due to downstream blocking. This 
has resulted in rain chances lingering into Thursday before an 
abnormally dry airmass and NW flow kicks in for Thursday afternoon 
into Friday. High temps both days should reach the upper 60s to mid 
70s with mainly sunny conditions and onshore flow. The only wrench 
in a nice pleasant end to the week is if the cutoff stalls just 
south of the region which would bring cooler temps, cloudy skies, 
and more rain. Winds Thursday could become gusty up to 35mph 
esspically near the coasts as the surface low passes offshore to the 
east. 

Next Weekend

Another shortwave trough exits the Great Lakes Saturday into Sunday. 
Guidance remains quite spread on the timing and amplitude of this 
shortwave. There will likely be rain sometime over the weekend, but 
its too early to pin down exact timing and how much will fall. Highs 
over the weekend look to remain seasonable in the upper 60s to mid 
70s with onshore flow.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

Through 00z...High confidence.

VFR, 4-7k ft CIGs. A rouge shower is possible in far western MA
and NW CT, otherwise dry runways. Sea-breeze along the coast
will continue until 23z/00z, from there wind shifts to the
south. Elsewhere, winds are south to southwest 10 to 15 knots. 

Tonight...High confidence.

VFR. Scattered showers are possible across northern MA, with at
times briefly lower VFR CIGs 3-5k ft. Winds are south to
southwest 5 to 10 knots.

Tuesday...High confidence.

VFR. A few convective showers possible across interior MA and
northern CT during the afternoon. Steady southwest winds with
gusts developing in the afternoon 20 to 25 knots. 

Tuesday Night...Moderate confidence. 

VFR to start, becoming MVFR/IFR heading later into the night
with increasing rain chances from west to east. Southwest winds
8 to 12 knots early, becoming south 5 to 10 knots. 

KBOS TAF...High confidence in TAF. 

VFR. Sea-breeze continues this afternoon, becoming a southerly
wind after 23z. A brief shower or two is possible overnight, opt
to include a PROB30 for -SHRA between 07z/09z. For Tuesday, most
of the daylight hours are dry, breezy southwest winds with gusts
20 to 25 knots. Rain chances increase Tuesday night.  

KBDL TAF...High confidence in TAF. 

VFR. Light south-southwest winds today and into tonight.
Increasing wind speeds Tuesday with gusts 20 to 25 knots
possible. Dry for most of Tuesday as well, rain arrives after
00z. 

Outlook /Tuesday Night through Friday/... 

Tuesday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA.

Wednesday: Mainly MVFR, with areas IFR possible. Breezy. SHRA
likely.

Wednesday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA.

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

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Tuesday...

Increasing S-SW winds this afternoon into tonight with gusts to 20 
kt at times over nearshore waters. SW gusts to 25 kt Tue, 
especially eastern MA waters where SCA will likely be needed.

Outlook /Tuesday Night through Friday/... 

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers. 

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

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of rain showers.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Chance of rain showers.

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&