Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 241122
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
722 AM EDT Tue May 24 2022

.SYNOPSIS...
More seasonable and less humid conditions continue into
Wednesday. The weather becomes more unsettled Friday through the
Memorial Day weekend, with a chance of showers or thunderstorms
each day.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
725 AM update...

Sprinkles from a mid level cloud deck were exiting the islands
early this morning. Northeast winds had gusted past 20 mph but
they were settling down as high pressure moves southward toward
the region.

Previous discussion...

A high pressure centered over southeast Canada will be the
primary driver for our weather today. Expecting a generally
easterly flow through much of today, leading to below normal
temperatures along the coast, with near normal temperatures
towards the western 2/3 of southern New England. Comfortable
humidity continues.

A low pressure passing us by well to our south will spread some
mid and high level clouds for a time this morning. There is only
a risk for a few sprinkles towards the south coast and southern
coastal waters, but it will not amount to much, if anything at
all reaches the surface.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
The center of this high pressure should move slightly southeast
tonight into Wednesday. This will maintain the relatively quiet
weather across our region. However, winds will shift to a more
southerly direction for Wednesday, leading to slightly higher
temperatures with just a few periodic clouds. Not expecting a
strong synoptic flow, so local seabreezes will likely establish.
The main change there would be more of a southeast wind is
spots.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights...

* Turning more unsettled with a chance of showers or a
  thunderstorm Friday through Sunday.

Overview

The ECMWF is now more in line with the GFS and Canadian models
regarding the evolution of a closed upper low over the Midwest
on Thursday. It now looks like it will slowly progress eastward,
but not reaching New England until Sunday, then moving off the
coast. Previously, the ECMWF was the fastest in launching this
feature northeastward and out of the country by Sunday.
This slower movement will keep a risk of showers and a few
thunderstorms across our region from Friday through Sunday.
But the Memorial Day Weekend will not be a washout. We will just
have to keep one eye to the sky and be careful with outdoor
activities.

The operational GFS run keeps this upper low over the Northeast
early next week, but the GEFS ensemble mean shows it exiting
the coast. So, thinking is that a high pressure ridge will build
aloft over the region from Monday through the middle of next
week, which will start a significant warming trend.

Details

Wednesday night and Thursday...

Dry and seasonable weather as high pressure off the coast still
maintains control. Winds turn southerly. Lows within a few
degrees of 50. Highs 70 to 75 away from the coast.

Thursday night through Friday night...

On deeper southerly flow, dewpoints surge into the mid and upper
50s late Thursday night, leading to patchy dense fog, especially
along the south coast. A few light showers possible toward
morning.

On Friday, an upper low moves into the Ohio Valley and surface
low pressure inches closer to New England from New York state.
S-SSW flow will become somewhat gusty...up to 20-25 mph. Highs
in the mid and upper 70s away from south-facing coasts, where it
will be cooler. If we get some sunshine, a few spots could touch
80 degrees. Dewpoints will climb into the lower to mid 60s.
There could be a few showers or an isolated thunderstorm, but
the greatest probability will be Friday night.

Memorial Day Weekend (Saturday and Sunday)

A lot will depend on the proximity of upper level low pressure.
It appears that it will slowly meander from the Ohio Valley to
New England. This will keep skies varying from partly cloudy to
cloudy and there could be a chance of a shower or thunderstorm
at any time, but most likely in the afternoon or evening each
day. Seasonable temperatures with highs each day in the 70s.

Memorial Day...

If the upper low moves eastward as expected and high pressure
builds in aloft, Monday will be dry with high temperatures
warming to 75 to 80, except 60s on the Cape and Islands.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Today through Wednesday...High confidence. VFR with dry weather
and relatively light winds. Onshore winds both days, but more of
a seabreeze along the east coast Wednesday.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR.

Thursday: VFR. Breezy.

Thursday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.

Friday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, chance TSRA.

Friday Night: Mainly VFR, with areas MVFR possible. Breezy.
SHRA likely, chance TSRA.

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

&&

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

High pressure should move from southeast Canada today, across
the eastern coastal waters tonight into Wednesday. This will
maintain relatively light winds and seas with go visibility.
Some chances for gusts up to 20 kt this morning.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.

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

Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain showers.

Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Rain showers likely.

Saturday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain showers.

&&

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

&&

$$
SYNOPSIS...Belk/GAF
NEAR TERM...Belk/GAF
SHORT TERM...Belk
LONG TERM...GAF
AVIATION...Belk/GAF
MARINE...Belk/GAF


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