Area Forecast Discussion
National Weather Service Boston/Norton MA
640 AM EDT Sun Apr 28 2024

.SYNOPSIS...
Warm but unsettled conditions today with a few chances of 
widely scattered showers through early Monday. Mainly dry and 
warm temperatures on tap for Monday, except it's considerably 
cooler along portions of the immediate coast. A backdoor cold 
front will bring cooler temperatures Tuesday and Wednesday 
before it warms up again by late in the week. The greatest risk 
for a period of showers will be later Tuesday into Wednesday. 
Next period of unsettled weather arrives around Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Numerous showers across southern New England into northern New York 
early this morning, in northern New York there is enough instability 
for rumbles of thunder. These showers are associated with a warm 
front that is slowly making its way across the northeast states. 
Would not be shocked if a couple make it to western Massachusetts or 
northwestern Connecticut. Otherwise, showers east of the CT River 
will diminish shortly after sunrise.

Surface high pressure which gave us wonderful conditions over the 
past couple of days is shifting south along with surface pressure 
falls. Today features more clouds than sunshine. WAA increases PWATs 
across southern New England, well above an inch in most cases. 
Aloft, mid-level ridge with pulses of energy provides enough lift to 
keep the clouds about and a few hit-and-miss showers. An isolated 
rumble of thunder is not out of the question for areas furtherest 
north and west where a some breaks in the clouds may allow for a few 
hundreds units of CAPE. Window for these showers are between 22z and 
03z, does look to be more sct'd in nature. Will say there are some 
discrepancies in the CAMs this morning, most notably the ARW, which 
shows more widespread light to moderate rains with potential for 
embedded thunder into southern Connecticut. 

Given higher PWATs, higher humidity is on tap today, dewpoints are 
increasing through the 40s and 50s. This is most noticeable since the 
previous two days have featured dewpoints in the 20s and 30s. Highs 
this afternoon climb into the upper 60s and lower 70s away from the 
coast. Perhaps a few mid 70s in the mid CT River Valley. The coastal 
plain, areas south of Boston to Providence area in the mid 60s. The 
immediate south coast will be the coolest do to the onshore winds, 
from the southwest, keep temperatures in the mid 50s to 60
degrees.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
A mild night ahead, many locations are in the lower and mid 50s, at 
the coast temperatures are slightly cooler in the upper 40s and low 
50s. Deep southwest flow and overcast sky cover helps maintain these 
temperatures. Any lingering showers exit the region between 03z and 
06z. Do think there will be areas of coastal fog that develops, many 
VSBY guidance show potential of widespread fog and/or low stratus. A 
wind shift to the north-northwest around dawn should help to advect 
lower dewpoints, this should help to cut down on the duration of the 
fog. That said, a later shift in the wind could prolong the fog 
across southeast Massachusetts and Rhode Island. 

Clouds to start Monday, mid-level ridging is nearly over New England 
by afternoon should promote cloud cover to gradually thin. Otherwise 
a warm afternoon away from the coast. While coastal towns are in the 
upper 50s and lower 60s, just a few miles inland temperatures 
quickly climb into the 70s! Further inland, mid and upper 70s are a 
good possibility. In fact, NBM has 20-30 percent probabilities of 
80F across the lower CT River Valley, Springfield to Hartford. What 
will be tricky, how far inland does the sea breeze make it. If the 
guidance shows the sea breeze to be a bit strong it could mean the 
forecast highs will need to be lowered. In addition, if clouds 
remain stubborn and don't thin out enough, it could lead to cooler 
temperatures as well. Something to keep in mind heading into
Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Points...

* Periodic rain chances through the week, first late Tue/Wed then 
  again on Friday. 

* After a warm start to the week temps cool Tue/Wed before warming 
  back up late week. 

Details...

Tuesday and Wednesday...

Tuesday a weak surface low pressure moves into SNE and this in 
conjunction with the high to the north will push a backdoor cold 
front through the region taking those 70s we enjoyed on Monday out 
of the forecast for two days. Highs will be limited to the 60s 
(inland) and 50s (along the coast) each day. A mid level shortwave 
moves out of the Great Lakes Tuesday night bringing a round of light 
rain to the region overnight into Wednesday. The best forcing from 
divergence at 300 mb and upslope orographics will place the bullsey 
for the largest rainfall totals over northern/central MA and areas 
further to our north and west. 

Thursday through Saturday...

Mid level ridging then builds in for the latter half of the week 
leading to a warming airmass (highs back into the 70s!) and dry 
weather. The trend in the guidance over the last 24 hours has been 
to slow the advancement of our next disturbance, now looking more 
likely to bring unsettled weather for sometime over the weekend but 
as early as Friday night. GEFS ensemble guidance is more excited 
about the possibility of measurable rain Friday night than the EPS; 
for now sticking with a blend and low POPs.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

Today... High confidence. 

MVFR/IFR conditions early in the morning. Improving cigs after 
16z, trending VFR some time after 18z/20z. Lower cigs may linger
later into the afternoon for terminals on Cape Cod & Islands
into the late afternoon. Winds are southwest 8 to 12 knots. 

Tonight... Moderate confidence.

Generally VFR away from the Cape and Islands where patchy fog
will develop. Winds are southwest to start, transitioning to 
the west-northwest across the interior by daybreak. 

Monday... Moderate confidence. 

VFR, mid-level clouds across western terminals 050-070k ft.
Northerly winds for most, but do expect a sea breeze for 
eastern Massachusetts, east-northeast winds along the north and 
south shore of Boston. Sea breeze may be strong enough to reach 
KPVD with a east-northeast wind. 

KBOS TAF...High confidence in TAF. Scattered showers possible 
between 08Z and 12Z. MVFR develops behind diminishing showers 
for the better part of the morning. VFR at times later this
afternoon, before returning to MVFR/IFR overnight.

KBDL TAF...High confidence in TAF. Scattered showers through
09z, becoming MVFR shortly after. VFR conditions later this
afternoon along with a low chance of a brief afternoon shower.
Trending back to MVFR tonight.
Outlook /Monday Night through Thursday/...

Monday Night: Mainly VFR, with areas MVFR possible. Slight
chance RA.

Tuesday: Mainly MVFR, with areas VFR possible. Chance RA.

Tuesday Night: Mainly MVFR, with local IFR possible. Chance RA.

Wednesday: Mainly VFR, with local IFR possible. Chance RA.

Wednesday Night: Mainly VFR, with local MVFR possible. 

Thursday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Monday... High confidence.

Generally tranquil boating conditions expected through Sunday
outside of a few rounds of widely scattered showers overnight
tonight and tomorrow evening. Onshore breeze across the eastern
waters will subside quickly this evening giving way to primarily
south/southwest winds for Sunday. Some patchy fog possible
Sunday night into early Monday morning. Dry conditions with mix
of clouds Monday afternoon along with northerly winds 10 to 15
knots. Seas mainly 3ft or less all waters.

Outlook /Monday Night through Thursday/... 

Monday Night: Winds less than 25 kt. Slight chance of rain. 

Tuesday through Wednesday: Winds less than 25 kt. Chance of
rain. 

Wednesday Night through Thursday: Winds less than 25 kt.

&&

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

&&