BOX issues Area Forecast Discussion (AFD) at Mar 4, 6:06 AM EST
104
FXUS61 KBOX 041106
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
606 AM EST Tue Mar 4 2025
.SYNOPSIS...
Warming trend with increasing southerly winds takes place today
and into Wednesday. A frontal system brings a period of soaking
rains, southerly breezes and possible coastal splashover in the
south coast Wednesday night into early Thursday. Then a strong
but dry cold front brings more seasonable temperatures, but also
a period of strong northwesterly wind gusts Thursday night
through Friday. Trending drier and slightly cooler than normal
for the weekend into early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
600 AM Update:
Ended up increasing sky cover starting around the mid morning
timeframe. Leading edge of mid-level warm front over central NY
is leading to a stream of overcast midlevel cloud deck across a
good portion of the northern mid-Atlantic region. RAP model
soundings seem to be handling this layer of moisture the best
and suggests it is shallow enough that we should see more of a
partly to mostly cloudy look as it moves eastward today. Chilly
start to the day, but even despite the cloud cover, warming
temps into the 40s develop by the afternoon in the face of
incresasing warm advection on breezy southerly winds.
Previous discussion:
High pressure well south of the region begins to push out to sea,
allowing southerly return flow to start pushing out the cold air
from the last couple of days. Strong WAA will bring temps aloft at
850mb from -14C this morning to 0C this evening. Even if skies turn
mostly cloudy from the strong WAA, high temperatures will rebound
into the mid-to-upper 40s to low 50s with the sun. Southwesterly,
925mb LLJ of 20-30 knots will clip portions of southern and eastern
SNE. Gusts of 15-25 should mix down to the surface, with gusts of
30mph possible if skies remain mostly sunny. With rising heights
aloft, not expecting any precipitation with the WAA.
Despite increasing winds aloft to 30-50 knots, the nocturnal
inversion will keep winds at the surface light at 10-20mph. Cloud
cover will increase overnight ahead of the potent shortwave over the
Great Lakes. With continued WAA and less than ideal radiational
cooling conditions, overnight lows stay mild in the upper 30s to low
40s. Rain showers could start to move into western MA and CT
towards daybreak on Wednesday, but the bulk of the QPF moves in
after sunrise.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
430 AM Update:
Key Messages:
* Steady, windswept downpours develop late Wed night into the Thurs
AM commute. Minor ponding of water possible but main impact will
be for a difficult Thurs AM commute from reduced visibility.
* Splashover to minor coastal flooding possible RI/MA South Coast
around the early Thurs AM high tide.
* Well above normal temps Wed night and Thurs.
Details:
We start to enter into a more active weather pattern starting the
latter part of Wed, as a mature Plains cyclone and its associated
cold front/frontal occlusion approach and cross Southern New England
Wed night into early on Thurs. This portion of the discussion will
discuss potential hazards associated with this frontal system -
which include a period of downpours Wed night into the Thurs AM
commute that could make for difficult travel, breezy to gusty
southerly winds, and splashover to minor tidal flooding on south-
facing coastal roads/bays late Wed night/early-overnight Thurs.
Increasing cloudiness on Wed but with a rather mild low-level
airmass advecting in on increasing southerly winds. Not much diurnal
heating with cloud cover in abundance, but temps will rise given the
strong warm thermal advection, boosting highs in the 50s, with upper
40s/near 50 along the immediate southern coast given the cooler
water temps just offshore. Most of the area should be cloudy but
generally dry Wed AM, however at least intermittent to steadier
light rains then start to develop/move in slowly from eastern NY Wed
aftn. Conditions then start to deteriorate Wed night with
increasing rains and gradually strengthening southerly winds.
Steady Moderate to Brief Heavy Rains...
Buoyed by advection of a elevated precipitable water plume (maxing
out around 1.1-1.3") on SSW 850 low-level jet of 65-70 kt, expect
moderate to briefly heavy rain to develop. We expect the heaviest of
the rains to fall between about 03-11z Thurs from west to east
before moving offshore. Synoptic and mesoscale pattern recognition,
featuring an influx of a seasonably-robust PWAT plume
parallel to the cold front, could favor localized downpours in
portions of the Berkshires, northern CT, RI and into
southeastern MA. This is also reflected in GEFS/EPS probs of 24
hr rainfall over an inch, which are high (60-90%) in that
described area, with lower probablities north and east of that
general area. Latest rain forecast calls for rain totals around
1 to 1.4 inches. Confidence in exact rain totals is lower to
moderate, and will need to reassess the HREF suite of rain total
probabilities once we get into that range within the next day.
Latest MMEFS guidance using the NAEFS QPF input show within-
bank rises in most watersheds in response to this rain; while
areas of urban and poor drainage ponding could develop, the risk
for widespread flooding is quite low to nil at this time.
Reduced visibility in downpours certainly could lead to a
difficult Thursday morning commute, with RI and central/eastern
MA being most susceptible as the heaviest rain is more likely to
arrive during the peak morning travel period. Rain moves
offshore by Thursday mid- morning.
Gusty Southerly Winds...
We mentioned the southerly low-level jet maxing around around 65-70
kt around 850 mb moving in late Wed night into early Thursday,
almost in lockstep with the heavier rains. Although we do have some
robust 6-hourly pressure falls 6-9 mb, it looks as though the core
of this jet will be locked above what most models depict is a
gradually strengthening inversion. The advection of slightly cooler
water temps may also limit mixing to an extent, too. Southerly wind
gusts increase into the 25 to 40 mph range after midnight and
continue into early Thurs until frontal passage shifts the winds to
more of a SSWly direction and the southerly jetcore passes to our
east. Higher gusts 40-45 mph possible over the Cape and Islands.
While it will be rather breezy, and will reassess once we get into
the range of the mesoscale guidance, the chances for the southerly
winds becoming strong enough to support the potential for minor wind
damage seems pretty low at this time. More on this in the long-term
section, but an even stronger period of gusts seems more likely in
the colder NWly flow for Thurs night into Fri.
Coastal/Tidal Flooding on South Coast...
Stevens Institute and P-ETSS guidance shows gradually increasing
storm surge in the face of the sustained southerly winds Wed,
peaking around 1.5 to 2 ft range early Thurs morning near or just
after the ~1240 AM high tide with astro tides at Fox Point around
4.58 ft MLLW and New Bedford 3.82 ft MLLW. Current total water level
forecasts suggest potential for at least splashover, which is what
the official forecast calls for. This could be conservative and I do
wonder if the forecast surge values are running a little bit low. It
wouldn't take much - either an earlier arrival to the peak surge or
higher surge values - to bring some of our Narragansett/Buzzards Bay
gages to minor flooding categories. Minor coastal flooding seems to
be an absolute worst case. Potential exists for a coastal flood
statement or perhaps an advisory.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Key Messages:
* Period of strong northwest wind gusts Thurs night and Fri. Wind
headlines likely.
* Still monitoring potential storminess late in the weekend, but may
pass too far offshore for any impacts. Trending colder by the
weekend into Monday.
Details:
Thursday:
Conditions to then trend dry with rapid decreases in wind speeds by
mid-morning Thurs as frontal occlusion pulls away. Overcast skies
should also trend toward partly cloudy conditions by the afternoon,
which will allow for temps to rise back into the 50s before the
arrival of a strong but generally dry cold front. This feature will
flip winds to the northwest and becoming increasingly gusty thru
sundown as strong cold advection ensues, however the winds won't
necessarily start to howl until Thurs night.
Thursday Night through Friday:
Although this period is dry with a cooldown in temps, the main story
in this forecast period is that of gusty to strong northwesterly
winds. Strong cold advection will lead to a very well mixed
atmosphere even at night, and a NWly low level jet of 50-60 kt
develops Thurs night and continues into mid-afternoon Fri before
rapidly diminishing. Expect gusts in the 35-55 mph range
starting early Thurs evening, with strongest gusts around
Worcester County and into the Berkshires/CT Valley region. A
second surge of gusts is likely on Fri in the lower elevations
once daytime mixing gets going. Wind advisories seem likely to
be needed at least for the higher terrain areas and may gust up
to near high wind criterion Thurs night; it is a little more
borderline regarding wind headlines in the lower elevations but
nonetheless very close. This is also a somewhat longer period of
stronger wind gusts, which won't really ease up until later Fri
aftn as the low level jet weakens. Otherwise, mostly sunny and
quite dry/well mixed, with highs in the upper 30s to mid 40s,
but the wind will make those readings feel quite a bit colder.
The Weekend into Monday:
Although earlier iterations of the GFS and the GEFS were indicating
potential storminess around the weekend as a southern stream trough
skirted across the southern tier of states, its 00z suite has now
backed off on this potential toward the more suppressed ECMWF/GEM
depictions. There are still a few GEFS members which bring this
system close enough to Southern New England where it will still need
to be watched, but for now, forecast will call for reinforcing
colder air for the weekend into Monday, with prevailing dry weather.
Highs mainly in the 30s to low 40s.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12Z TAF Update:
Today: High confidence.
VFR. Winds increase from the SW today, gusting 20-25 knots.
Tonight: Moderate confidence.
VFR, though turning MVFR/IFR especially interior sites towards
daybreak Wed. Nocturnal inversion will brings wind gusts back
down to 10-15 knots. Increasing SW 925mb LLJ at 30-50 knots will
bring wind shear concerns lasting into Wed.
Wednesday and Wednesday Night: Moderate confidence.
Conditions deteriorate to MVFR-IFR for all airports early Wed.
Increasing southerly winds with gusts 20-25 kt during the day. A
strong cold front Wed night then brings a period of 300-600 ft
ceilings and IFR-visby downpours, with increasing southerly
winds to around 25-35 kt.
KBOS TAF...High confidence in TAF.
VFR. Increasing SW winds today, gusting 20-25 knots. Wind shear
increase this evening and overnight from the SW at 40-50 knots
KBDL TAF...High confidence in TAF.
VFR today with increasing SW winds at 20-25 knots. Wind shear
increases this evening and overnight from the SW at 35-45
knots. MVFR/IFR cigs move in towards day break.
Outlook /Thursday through Saturday/...
Thursday: Mainly VFR, with local IFR possible. Windy with areas
of gusts up to 30 kt. Chance RA.
Thursday Night: Mainly VFR, with local MVFR possible. Strong
winds with gusts up to 45 kt. Slight chance FZRA.
Friday: VFR. Strong winds with gusts up to 45 kt.
Friday Night through Saturday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Tuesday Night: High Confidence.
Increasing SW winds this morning with gusts to 25-30 kt
developing in the afternoon with seas 3-5 ft. SCA in effect for
inner/outer waters and bays.
Wednesday and Wednesday Night: High confidence.
Southerly winds continue to increase through the day on Wed,
with a period of gale force southerly gusts 35-40 kt on most
waters Wed night. Seas will build to around 10-13 ft, become
increasingly rough and shorter period by Wed night, leading to
potentially hazardous boating conditions for mariners. Period of
brief heavy downpours develops Wed night into early Thurs AM,
reducing visibility.
Outlook /Thursday through Saturday/...
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 13 ft. Chance of rain.
Thursday Night through Friday: Moderate risk for gale force
winds with gusts up to 40 kt. Rough seas up to 12 ft.
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
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 from 10 AM this morning to 7 AM EST
Wednesday for ANZ230>237-250-251-254>256.
Gale Warning from 7 AM Wednesday to 11 AM EST Thursday for
ANZ230>237-250-251-254>256.
&&
$$
SYNOPSIS...Loconto/KP
NEAR TERM...Loconto/KP
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...Loconto/KP
MARINE...Loconto/KP
Source: BOX issues Area Forecast Discussion (AFD) at Mar 4, 6:06 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202503041106-KBOX-FXUS61-AFDBOX)
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