389
FXUS61 KBOX 231907
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
307 PM EDT Sat May 23 2026
.WHAT HAS CHANGED...
No major changes with expectation of a soggy Sunday across much of
Southern New England. A narrow swath of heavier rain is possible
near the South Coast, and if heavier rain develops in this corridor,
the potential exists for ponding or localized street flooding in
more urban areas.
&&
.KEY MESSAGES...
- Rain gradually moves eastward late this evening. Soggy and
cool Sunday, steady moderate rain in all areas and localized
downpours possible, especially the RI/MA South Coast. Rain
pulls offshore Sunday night with slow warming, but with areas
of fog and drizzle into Monday morning.
- Wet to start Memorial Day, drying out through the day. Above
normal temperatures for the middle of next week before
trending closer to normal late next week. A couple periods of
showers possible.
&&
.DISCUSSION...
KEY MESSAGE 1...Rain gradually moves eastward late this evening.
Soggy and cool Sunday with steady moderate rain in all areas and
localized downpours possible, especially the RI/MA South Coast.
Rain pulls offshore Sunday night with slow warming, but with
areas of fog and drizzle into Monday morning.
Sfc ridge of high pressure is still maintaining itself for most
of Southern New England, with regional radar mosaic as of
Saturday afternoon showing a distinct NW to SE cutoff in light
rain trailing from roughly Watertown NY through Westerly RI
south and west. Only measurable rain so far per METARs has been
near Hartford. This precip shield will be slowly advancing
eastward, making its greatest eastern inroads after midnight.
Onset of light rains into eastern MA and RI should take until
the early pre-dawn hours. Nighttime cooling with be slow under
overcast and east flow but some wet-bulb cooling once rain
arrives should bring lows in the 40s to low 50s.
Sunday is a soggy, cool day with steady rain bringing a welcomed
and much needed rainfall to Southern New England. A southeast
low-level jet of 40-45 kt should help lead to favorable moisture
convergence (PWATs rising to around 1.4-1.7", approx 2 standard
deviations above late-May PWAT climatology); there are
indications in the higher- resolution solutions showing a swath
of potentially heavy downpours in southern RI into the RI/MA
South Coast, Cape and Islands during the afternoon. Could be
some ponding in some of the more urbanized locations such as
Newport, Fall River and New Bedford. Left low probs for a rumble
or two of thunder in the forecast but I`m not really bullish on
thunder prospects as lapse rates are poor, CAPE is minimal, and
K indices are around 30 units. Winds will increase especially
in eastern/southeast MA to around 20-25 mph in gusts, but will
become NE late in the day into the evening and lighten up as
rain begins to move offshore late in the day to early in the
evening. With steadier rain all day and onshore winds, daytime
temperatures Sunday aren`t likely to go very far, in the upper
40s to mid 50s.
Temperatures slowly rise through low-level warm advection Sunday
evening as steadier rain pulls offshore. Even though
temperatures will be slowly warming into the 50s overnight, a
light northeast drainage flow wedges southwestward from interior
ME/NH Sunday night. BUFKIT profiles show a layer of low-level
RH about 3000-5000 ft thick from the near-surface with drier air
aloft across interior Southern New England into the coastal
plain. So while steadier rain ends, this is a profile that is
rife for development of mist, fog and areas of drizzle for
Sunday overnight into the early morning of Memorial Day. PoPs
decrease into the Chance range, reflective of more
intermittent/showery activity or drizzle.
Storm total rainfall through early Monday ranges from 0.75" to
1" north of the Mass Pike, to 1-2" of rain for CT-RI-SE MA,
with a stripe of locally higher amounts up to 2.5" from Newport
to New Bedford where I`ve added a mention of heavy rain at times
wording in the zone forecast. Of note is the the 12z SPC HREF
localized probability-matched-mean QPF, often considered a
reasonable worst- case, which shows amounts in that RI/MA South
Coast corridor up to 4.5 inches. If values that high were to
materialize, then we could have to monitor for street flooding
and river/stream/creek rises, but it would take more convective-
enhanced rates to see values that high, which is not a favored
outcome.
KEY MESSAGE 2...Wet to start Memorial Day, drying out through
the day. Above normal temperatures for the middle of next week
before trending closer to normal late next week. A couple
periods of showers possible.
The mid level synoptic pattern next week will be more of a
little dance between the Bermuda High and a cutoff over
southeast Canada and the Maritimes. The Bermuda High is
projected to shift west and south over the course of next week,
permitting the mid level cutoff to move towards the Maritimes
from southeast Canada. There remains considerable uncertainty
with how quickly this cutoff will move east after Wednesday,
leading to below normal confidence in the details late next
week. For this forecast, thinking we`ll see above normal
temperatures Tuesday into Wednesday, which looks to be our
warmest day. Temperatures should then trend towards near to
slightly below normal temperatures for late next week.
Rainfall-wise, we will still be dealing with lingering showers
for Memorial Day. Expecting drier conditions to overspread
southern New England from NW to SE during the day. By afternoon,
the risk for showers should be confined to the Cape and
Islands. Even there, dry weather should arrive by evening.
Thinking there will be two more periods of concern for
precipitation. The first of these should be with a cold front
Wednesday, which could lead to the possibility for mainly
afternoon showers and thunderstorms. A pool of colder air aloft
could lead to another round of showers for Friday. This is part
of the uncertain timing of the colder air late next week, so
confidence is low in this outcome.
&&
.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update:
Through 00z Sunday: High confidence.
BKN/OVC VFR high clouds for most of the TAFs; exception is BDL
with OVC VFR ceilings to go along with light -RA. E/SE winds
5-10 kt.
Tonight: High confidence in TAF/trends but moderate on timing.
Mainly VFR through midnight/05z, with VFR -RA at BDL continuing.
Rain shield then begins to spread slowly eastward, and as
steadier rains develop, expect categories to deteriorate to
sub-VFR levels. MVFR visby RA with MVFR- IFR ceilings at BDL,
and deteriorating eastward with onset of light rain 07-10z,
becoming steadier shortly thereafter. SE winds increasing to
around 8-12 kt.
Sunday: Moderate confidence.
MVFR to IFR ceilings, steady light to moderate rain with
visibilities3-5 SM. Localized downpours mainly for TAFs S/E of
I-95 in the afternoon. SE winds around 10-15 kt with gusts
20-25 kt, becoming E/ENE for the eastern TAFs in afternoon.
Sunday Night: Moderate confidence.
MVFR-IFR in steady rain moving off the east coast around 03-06z.
Clearing of steadier rain then brings widespread IFR-LIFR with
drizzle, mist and fog with light NE winds.
KBOS...High confidence in TAF. VFR, east winds become SE around
10 kt by 00z Sunday. Onset of RA not likely until at least 08z,
becoming a steadier light rain with MVFR more likely after 10z.
KBDL...High confidence in TAF. VFR light -RA prevails thru
03-05z, then becoming steadier with MVFR visibilities and
ceilings becoming MVFR-IFR. SE winds around 5-10 kt.
Outlook /Sunday Night through Thursday/...
Memorial Day: Mainly VFR, with local IFR possible. Chance SHRA.
Monday Night through Tuesday Night: VFR.
Wednesday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.
Wednesday Night through Thursday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Far from ideal boating conditions expected this weekend. SCAs
take effect tonight on most waters with SE winds becoming
15-25 kt tonight, then increasing to 25-30 kt on Sunday. Seas
will be building to 4 to 8 ft (higher southern waters) tonight,
then build to the 6 to 10 ft range by Sunday into Sunday night.
Areas of rain will reduce visibility to around 3 miles.
Rain moves offshore early Sunday night, with winds easing and
becoming ESE to S around 10-15 kt. Seas will still remain
elevated at 5-7 ft through Sunday night, thus SCAs continue
into most of Monday to allow for seas to subside. Although rain
comes to an end, fog and drizzle is likely to develop Sunday
night on the waters, with locally dense fog possible.
Outlook /Sunday Night through Thursday/...
Memorial Day: Winds less than 25 kt. Rough seas up to 9 ft.
Chance of rain showers.
Monday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Tuesday: Winds less than 25 kt. Seas up to 5 ft.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
Wednesday Night through Thursday: Winds less than 25 kt. Seas
locally approaching 5 ft. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 5 AM Sunday to 2 AM EDT Monday for
ANZ231.
Small Craft Advisory from 2 AM Sunday to 5 AM EDT Monday for
ANZ232>235-237.
Small Craft Advisory from 5 PM Sunday to 8 PM EDT Monday for
ANZ250.
Small Craft Advisory from 8 PM this evening to 8 PM EDT Monday
for ANZ254>256.
&&
$$
DISCUSSION...Belk/Loconto
AVIATION...Belk/Loconto
MARINE...Belk/Loconto
NWS BOX Office Area Forecast Discussion
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