Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 251119
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
719 AM EDT Wed May 25 2022

.SYNOPSIS...

High pressure will bring seasonable and less humid conditions through
Thursday. Becoming more unsettled Friday through Saturday as a
cold front approaches and slides through the region. This will
bring showers and perhaps a few thunderstorms. Drier on Sunday
into early next week with increasing warmth.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

715 AM Update...

No changes in the latest update. Have just brought things in
line with the latest observations.

Previous discussion...

Core of a high pressure moves southeast across the Maritimes
today. This will mean another day of dry conditions with
relatively low humidity. Winds will be more southerly today
synoptically, but expecting local seabreezes to develop along
the east coast, leading to lower temperatures there due to more
onshore flow. Overall though, most locations will be warmer
today, but still close to normal temperatures for late May.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...

High pressure over the North Atlantic still pretty much in
control of our weather tonight and Thursday. Dry weather
continues with near normal temperatures. Southerly flow
increases slightly, making it less likely for seabreezes along
the east coast.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...

Highlights

* Near to above normal temperatures throughout the extended.
  Possible return to summer warmth early next week.

* Next shot for showers and thunderstorms comes Friday through
  Saturday. May be a bit breezy at times especially across
  eastern areas during this timeframe.

Thursday night through Saturday...

A cutoff low will be situated over the Mid Mississippi River
Valley Thursday night. The cutoff will rotate and lift
northeastward into the OH Valley by late Friday. The trough
lifts into the eastern Great Lakes/Mid Atlantic by late
Saturday. Ahead of the incoming trough/cutoff will have subtle
shortwaves lift into the eastern Great Lakes Thursday night
through Friday. Will be well within the warm sector for much of
this timeframe with a pre- frontal trough sliding into the
region on late Friday. The trailing cold front works its way
into and through much of the region on Saturday.

Did reduce precip chances Thursday night into early Friday as
the NBM seems a bit hot with shower activity well ahead of the
upper forcing. At this point appears to be more of a low
cloud/stratus/drizzle signal given the S/SSW flow advecting warm
and moist air into the region. Could be enough low level
convergence to eek out an isolated shower or two. Low temps
range from the mid to upper 50s.

Risk of showers and perhaps a few thunderstorms comes later on
Friday mainly for the interior as a prefrontal trough lifts in.
Will see PWATs surging to roughly 1.5 inches, which is AOA the
90th percentile per SPC Sounding Climatology for CHH. Not out of
the question there are heavier showers, but the best
forcing/instability is just west of our region. Risk for more
widespread showers and perhaps a few thunderstorms comes Friday
night through Saturday as the cold front is moving through. Not
anticipating a washout at this point, but there will be showers
around for much of this period. Could perhaps see a few rumbles
of thunder on Saturday, but this is provided we can see some
breaks of sunshine.

Lastly, bumped up wind speeds/gusts through much of this period
as we have a 30-40 kt 925 hPa SSW low level jet sliding through
across the region. This will make it a bit breezy at times,
especially across eastern areas. May actually need to bump up
gusts a bit more in future updates, but just nudged things in
the right direction. Better chance for the stronger winds on
Friday as we will have more sunshine to work with, which will
allow for a deeper boundary layer. Bumped high temps to the 75th
percentile of guidance, which results in widespread 70 degree
readings with some low 80s across NE MA.

Sunday through Tuesday...

Lots of uncertainty in the Sunday timeframe at this point in
time, but confidence increases for early next week per WPC
Cluster Analysis. Main source of uncertainty on Sunday is
regarding the cutoff lifting into or through southern New
England. Have stuck with the NBM, but may actually be a bit too
high based on WPC Cluster Analysis. Out of the 100 members 77
are a dry solution, closest to the latest ECWMF. This lifts
the trough offshore and builds a ridge into the central/eastern
Great Lakes, which puts a high over us. The wetter solution,
which accounts for 23 members most closely resembles the latest
GFS. This keeps the cutoff/trough over southern New England
through Sunday, which brings us chances for rain showers. This
also would result in much cooler temps than currently advertised
given flow would be onshore. Again have leaned on the NBM, which
is warmer and perhaps a bit too wet given how many dry members
we have.

As for Monday/Tuesday confidence in the forecast increases as a
ridge builds into the OH Valley and the central/eastern Great
Lakes. This should result in dry and quiet weather with
increasing temperatures, though this will depend on the location
of the surface high and associated low level winds. There are
some indications we could still have some onshore flow per the
latest GFS and cooler solutions on WPC Cluster Analysis. For
now, have stuck with the NBM, which brings increasing
temps/humidity into early next week. May have fairly widespread
80s with perhaps some 90s for highs on Tuesday.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...

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

Today and Tonight...High confidence.

VFR with high pressure in control. Will have some mid/high
clouds in place with light winds. Seabreezes expected to develop
between 14-16Z for most locations. Flow becomes more southerly
late this afternoon into the evening. Wind generally less than
10 kts.

Thursday...High confidence.

VFR with increasing mid/high clouds. Should see cloud bases
between 5-10 kft. Winds out of the S at 10 kts with gusts of
15-20 kts during the afternoon.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Thursday Night through Sunday/...

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

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

Friday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA, isolated TSRA.

Saturday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, isolated TSRA.

Saturday Night: VFR. Slight chance SHRA, isolated TSRA.

Sunday: VFR. Slight chance SHRA.

&&

.MARINE...

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

High pressure maintains a firm grip through Thursday. This will
maintain relatively light winds and seas with good visibility.
Increasing south winds tonight could lead to rough seas across
portions of the eastern outer coastal waters by Thursday
evening.

Outlook /Thursday Night through Sunday/...

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Slight
chance of rain showers.

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

Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Chance of rain showers,
isolated thunderstorms.

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain showers, isolated
thunderstorms.

Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers, isolated thunderstorms.

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

&&

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

&&

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


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