Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 040717
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
317 AM EDT Tue Oct 4 2022

.SYNOPSIS...
Persistent low pressure south of New England will generate
gusty northeast winds and periods of rain Tuesday into
Wednesday. 1-2" of rain can be expected across RI and southeast
MA, with localized higher rain totals may result in urban and
poor drainage flooding. Less rainfall is expected across CT into
western-central MA. Dry and much warmer weather arrives
Thursday and lingers into Friday. Then a cold front crosses the
region Friday night, ushering in dry, but blustery and cool
weather for the weekend. Dry weather is likely into Columbus
Day, along with moderating temperatures and less wind.

&&

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

315 AM Update...

Dry mid level air that prevented most returns on radar from reaching
the ground overnight will gradually saturate this morning, leading
to spotty, but expanding, shower activity during the late morning
and early afternoon hours. Showers will begin in Earnest this
afternoon, first across our southeast zones before gradually moving
north and west. Most guidance keeps our far northwest zones
primarily dry, but steady showers are likely to develop across
southeast MA and coastal RI.

Gusty northeast winds will persist again today, between 20 and 30
kt. The 925mb jet centered around the low will gradually begin to
shift to out southwest, over Long Island and the mid-Atlantic. While
the highest winds shift to our south/southwest, gusts to between 30-
40kt cannot be ruled out, especially across our southern waters.

While high temperatures will remain much below normal, warm air will
begin to advect in the  low and mid levels around the occluded low.
By late Tuesday afternoon, 925mb temperatures will warm to between 7
and 9 C. While deep mixing is not expected given the WAA regime,
warmer mid level temperatures should prohibit much of the region
from dropping below the mid to upper 50s for daytime highs.
Additionally, overnight lows did not dip as low as expected thanks
to robust cloud cover, so temperatures will be starting out a few
degrees above the previous forecast.

&&

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

315 AM update...

The heaviest rain of the short term period is expected after sunset
Tuesday through Wednesday. While there is still uncertainly
regarding how much precipitation will fall, ensemble guidance
suggests that a healthy 1-2" of precipitation is likely across
southeast MA, with amounts tapering off further north and west.
With PWATs around 1.5", as remnant tropical moisture from Ian
rotates around the low to our south, there is potential for this
system to generate locally higher rain totals, which could
result in poor drainage and urban flooding during the Wednesday
morning commute. Some guidance even hints a non-zero chance for
3"+ 6-hour precipitation totals.

As we have seen several times over the past few months, a convective
complex well offshore be causing some of the most aggressive
guidance, like the NAM3km, to overestimate rainfall totals (HREF
ensemble max totals hint at a bullseye of 5"+ across SE MA). While
5"+ rainfall totals may be an overestimate, there is evidence that
localized heavier totals are substantiated, as a more barcoclinitic
environment, given the more robust "fall-like" temperature gradient,
should provide a mechanism for this system to tap into the potential
to generate some beneficial rainfall totals.

The low level jet will continue to shift further to our southwest,
allowing winds to finally relinquish their gusty grip on us by late
in the day Wednesday. While winds will still remain breezy, they
should drop to between 15-20kt across most regions.

Overnight low temperatures Tuesday night will remain in the upper
40s and low 50s thanks to significant cloud cover and precipitation.
Temperatures will finally warm to near 60 by late Wednesday
afternoon across Cape Cod and the CT River Valley.

&&

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

315 AM update...

Highlights...

* Showers continue into at least Wed evening

* Dry Thu and Fri, along with a big warmup, with highs in the low to
  mid 70s

* Blustery and cool Fri night, Sat & Sun, then moderating with less
  wind Columbus Day

Details...

Wednesday night...

Closed low remains south of New England Wed night, along with a
conveyor belt of anomalous PWATs up to 1.5 inches (leftover moisture
from remnants of Ian), circulating across SNE. This occluded low and
its TROWAL precip shield, will slowly pull away from the region
overnight Wed. However, showers should be fairly widespread in the
evening and can`t rule out a few heavier downpours given anomalous
moisture and instability aloft along the leading edge of the dry
slot. Moist NNE flow will keep temps fairly uniform, with lows in
the mid to upper 40s, except 50-55 along the coast given NNE flow.
Breezy in the evening, then NE winds diminish as low level jet
slowly erodes.

Thursday...

Drying trend as short wave ridging advects across the area. This
will support abundant sunshine and much warmer temps, as remnant
warm air aloft from departing occluded low, mixes down supporting
highs in the low 70s away from the coastline. Weak high pressure
overhead will promote seabreezes, keeping the shoreline in the 60s.
Still very pleasant given light winds and abundant sunshine. The
only wrinkle maybe clouds slow to depart Cape Cod and the Islands,
with a better chance of afternoon sunshine.

Friday...

Remaining mild across SNE ahead of approaching northern stream short
wave and attending cold front. Mild start to the day give SW flow
Thu night. Depending on timing of FROPA, could see temps fall late
in the day across western MA/CT. Given timing issues, most likely
warmest temps will be across eastern MA, where low to mid 70s are
expected, about 5-8 degs warmer than normal. Expecting a dry FROPA
given the lack of prefrontal moisture. Modest SW wind 10 to 20 mph.
Partial sunshine thru mid/high clouds. Overall, a very pleasant
early Oct day, with mild temps. Becoming blustery and much cooler
Friday night, as post frontal airmass overspreads the region and
accompanied by robust CAA.

Holiday Weekend...

Dry WNW flow aloft this period. Blustery and cool Sat, then
moderating temps Sunday and especially Monday/Columbus Day, as mid
level flow becomes more zonal, yielding less wind.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels:

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

06Z Update...

Tuesday...Moderate confidence.Ceilings will vary from IFR to
VFR across southern New England with IFR conditions expected
across far southeastern MA and the Islands beginning mid-day. A
mostly dry start to the day will lead to scattered showers by
about 14Z along the south coast. As precipitation moves
northward during the day, so too will IFR ceilings. VFR likely
to prevail across far northwest areas that remain dry. Northeast
winds continue to gust between 20 and 30 kt during the day
Tuesday. Isolated gusts to 35 kt possible across the Cape and
Islands.

Tuesday night...Moderate confidence

Steadier precipitation expected Tuesday night as IFR conditions
prevail across much of the region. VFR ceilings will deteriorate
to MVFR across the far northwest interior as precipitation
continues to pivot northward. Gusty northeast winds continue
overnight, again between 20 and 30kt; highest across coastal RI
and the Islands.

Wednesday... Moderate confidence

Persistent precipitation will extend into Wednesday, especially
across eastern MA and RI; the heaviest precipitation of the
period may be observed Wednesday morning. IFR conditions persist
across eastern MA and RI much of the day. Ceilings across the
interior will improve from MVFR to VFR as the day wears on.
Gusty NE winds will finally begin to subside late Wednesday as
winds fall back to between 10 and 20 kt.

KBOS Terminal...Moderate Confidence in TAF.

Periods of VFR, MVFR and IFR possible Tuesday morning before
IFR conditions develop thanks to increased shower activity. IFR
to persist from about 16Z Tuesday through the end of the period.
Rain develops around the same time, becoming more widespread
overnight Tuesday into early Wednesday. Gusty NE winds, between
20-30 kt expected.

KBDL Terminal...High Confidence in TAF. VFR ceilings becoming
MVFR as showers develop on Tuesday. IFR conditions possible in
the heaviest showers. Gusty NE flow through the period, with
gusts between 20-30kt expected.

Outlook /Wednesday Night through Saturday/...

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

Thursday through Thursday Night: VFR.

Friday through Saturday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

315 AM update...

Low pressure centered to our southwest continues to generate gusty,
gale force conditions across the southern waters as winds gust over
35 kt. Elsewhere, NE winds continue to gust between 25 and 30 kt.
Persistent NE flow allows waves to grow to between 7-10 ft outside
bays and harbors. Conditions will be hazardous to pleasure
craft through at least Wednesday evening.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain.

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

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday: Winds less than 25 kt.

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     ANZ231>237-250-251-254.
     Gale Warning until 8 PM EDT this evening for ANZ255-256.

&&

$$
SYNOPSIS...Nocera/KS
NEAR TERM...KS
SHORT TERM...KS
LONG TERM...Nocera
AVIATION...Nocera/KS
MARINE...Nocera/KS


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