BOX issues Area Forecast Discussion (AFD) at Mar 16, 7:38 PM EDT353
FXUS61 KBOX 162338
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
738 PM EDT Sun Mar 16 2025
.SYNOPSIS...
A strong cold front will bring heavy rain and gusty southerly wind
gusts tonight into Monday morning, with rain lingering into Monday
night across SE New England. Mainly dry and mild weather returns
Tuesday into Thursday. Another frontal system will likely bring a
period of showers sometime late Thursday into Friday, possibly
changing to snow over higher elevations Friday as colder moves back
into the region. Dry and seasonable conditions follow next
weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
Key Messages:
* A period of heavy rainfall late tonight into Mon morning may
result in areas of urban and poor drainage flooding
* Heaviest rainfall will impact the Monday morning commute along the
I-95 corridor to the south coast
* South wind gusts to 45 mph possible late tonight across SE MA
and southern RI
Upper level trough moves east from the Gt Lakes tonight, then
sharpens Mon as it approaches New Eng with favorable right entrance
region of the upper jet moving across SNE. Wave of low pres expected
to develop on the cold front which will slow its eastward progress
as it moves across SNE during Mon which will keep rain going for
much of the day Monday before gradually tapering off in the west
during the afternoon.
Deep moisture plume and low level jet ahead of the cold front with
axis of highest PWATs reaching 1.25-1.50" begin to move in tonight,
with forcing for ascent increasing ahead of the upper level trough.
This will lead to widespread showers developing and moving W to E
across the region through tonight and into Mon, but rain may not
reach eastern MA until after midnight. Marginal instability to the
west weakens as it approaches New Eng, but there is some weak
elevated instability which spills into western New Eng tonight which
could lead to an rumble of thunder. PWAT anomaly 3-4SD above normal
and low level wind anomaly 2-3SD which is a strong signal for a
period of heavy rainfall. Timing of heaviest rainfall will be after
midnight in the west, and 5 am to noon from I-95 to Cape Cod. In
fact, HREF showing 30 percent probs of greater than 1" in 3 hours
along the I-95 corridor 09-12z before shifting to SE MA and
Cape/Islands 12-18z. These rainfall rates will result in the
potential for some minor urban and poor drainage flooding which will
impact the morning commute along I-95 corridor. Rain will
continue all day across eastern New Eng but should become more
scattered in the in the west during the afternoon as PWATs
decrease. However, upper level trough axis remains to the west
so at least scattered showers will continue here through the
afternoon.
We are looking at widespread total rainfall of 1-2 inches with the
potential for higher amounts somewhere from the I-95 corridor to the
south coast where low risk for localized amounts approaching 3
inches. Not expecting any river flooding with these rainfall
amounts, but combination of the rainfall and snowmelt in the upper
CT basin in northern New Eng may eventually lead to minor flooding
for some locations along the CT river toward mid week.
Strong wind potential: Winds will be increasing tonight, especially
after midnight across RI and SE MA as the low level jet moves across
the region. Low level jet peaks around 65-70 kt 06-12z. Temps will
be mild overnight holding in the mid-upper 50s across RI/SE MA which
will help to weaken the inversion somewhat and support a few hours
of 40-45 mph gusts here after midnight, which is about 50-60 percent
of the LLJ. Gusty winds will continue Mon morning over the
Cape/Islands with the low level jet overhead then diminish in the
afternoon.
&&
.SHORT TERM /MONDAY NIGHT/...
Upper level trough axis finally moves east across New Eng Monday
night. Deep moisture axis and PWAT plume will be across SE MA and
Cape/Islands in the evening with frontal wave just to east. Showers
will be ending in the west during the evening, but rain will
continue across SE New Eng Mon night before gradually tapering off
and ending overnight as the frontal wave moves offshore and drier
air moves in from the west. It may take until daybreak for rain to
end over the Cape/Islands. Lows will drop into the 30s late Mon
night and Tue morning with North winds increasing to 10-20 mph.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Key Messages:
* Drying out Tuesday under high pressure, but monitoring for river
flooding
* Another round of rain likely sometime Thursday night into Friday
morning
* Dry, but breezy and colder going into the weekend
Details...
Lingering showers push their way out to sea by midday Tuesday,
and a broad high pressure settles in behind the rain. The
majority of the associated cloud cover should begin to break up
a bit from west to east as Tuesday goes on. Winds shift more to
the north, but there is still a decent chance that temperatures
reach 55F towards the interior near the CT River Valley. Warmer
temperatures aloft (close to +10C at 850 mb) from ridging will
encourage these mild temperatures for midweek. High pressure
keeps the region dry for the rest of Tuesday into midweek;
however, we are monitoring the Connecticut River for the high
possibility of reaching minor flood stage from Northampton to
south of Hartford.
Easterly to northeasterly flow returns for Wednesday, which may
contribute to more clouds and will keep the eastern coastline of MA
cooler than the interior. South to SE flow Thursday will also advect
more moisture from over the Atlantic.
Another trough is expected to dig into the central US and move
northeast into the Great Lakes region Thursday into Friday. While
the associated surface low is likely to track northeast across
southern Ontario, most ensemble (and deterministic) guidance is
suggesting a secondary low will spin up along the cold front in the
Appalachian/Mid-Atlantic region.
With moisture being advected in Thursday, ensemble guidance
indicates about 150% of normal PWAT values ahead of the front across
southern New England for Thursday night. With the lift provided from
the cold front's passage, rain showers (and possibly snow showers in
the higher elevations) are likely to develop just ahead of the
front. As this front passes, winds during the day Friday will
increase and shift to the NW. Breezy NW winds and cooler
temperatures aloft will keep much of the region in the 40s for
Friday, with drier and colder post-frontal air Friday night possibly
bringing overnight lows down to low 30s for Rhode Island and the
South Shore and the upper 20s for interior MA and CT. Surface
temperatures looks to briefly sling shot back into the low 50s
on Saturday with southerly flow off the Atlantic under a ridge.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00Z TAF Update:
Tonight: Moderate confidence.
Ceilings are starting to deteriorate to MVFR, with IFR/LIFR
ceilings along the immediate south coast. MVFR likely to degrade
inland to IFR between 02-05z, with IFR-LIFR ceilings holding
near the southern coast. Light rains move in from 03-06z from
west to east, then becoming moderate to heavy (visbys 2-3 SM)
08-12z from west to east. Could be a rogue rumble of thunder
overnight in the heaviest rains but should be isolated if any
develops at all.
Though there have been some southerly wind gusts in the 40 kt
range at times early this evening, gusts should be more in the
25-35 kt range during overnight. Low level wind shear likely
given a 60 kt low-level jet.
Monday...Moderate Confidence.
Rain begins to taper off from west to east. Guidance is slow to
clear the rain off the east coast with showers lingering for
eastern terminals into later Monday afternoon. CIGS should
remain IFR until winds turn more westerly, but guidance may be a
bit to slow on improving CIGS behind the wind shift.
Monday Night...Moderate Confidence.
CIGS should improve to VFR across the interior if they have not
already by Monday afternoon. Eastern terminals, esspically the
Cape and Islands may see lingering MVFR/IFR CIGS. Winds begin to
shift north at 10-20 knots.
KBOS TAF...Moderate confidence in TAF.
MVFR ceilings to deteriorate to IFR thru 04-05z. Light rain
moves in around 06z, becoming moderate to heavy between 09-10z
with visbys 2SM in RA+. Rain starts to taper off to a moderate
level (3-5 SM) tomorrow afternoon, but not trending dry until
late Monday. S gusts 25-35 kt with periods LLWS thru Mon AM,
then begin to shift to SW and decrease to 10-15 kt before a
windshift to NW Mon night.
KBDL TAF...Moderate Confidence in TAF.
MVFR ceilings to trend IFR as rain moves in this evening after
02z. Rain will become heavy between 07-12z. Rain and IFR CIGS
linger into late morning to early Monday afternoon before
improving to MVFR/VFR late Monday afternoon.
Outlook /Tuesday through Friday/...
Tuesday: Mainly VFR, with local MVFR possible. Breezy.
Tuesday Night through Wednesday: VFR.
Wednesday Night: Mainly VFR, with areas IFR possible.
Thursday: MVFR/IFR conditions possible. Breezy. Slight chance
RA.
Thursday Night: Mainly MVFR, with areas IFR possible. Breezy.
RA likely.
Friday: Mainly VFR, with local IFR possible. Windy with areas
of gusts up to 30 kt. Chance RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Monday Night...High confidence.
We upgraded to Gale Warnings for tonight as low level jet ramps up
over the waters. Expect a period of marginal southerly gale force
gusts to 35 tonight, diminishing W to E Mon morning. Winds becoming
north Mon night and increasing with gusts to 25 kt overnight. Vsbys
lowering late tonight into Mon in rain and fog.
Outlook /Tuesday through Friday/...
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 10 ft. Slight chance of rain.
Tuesday Night: Winds less than 25 kt. Local rough seas.
Wednesday through Wednesday Night: Winds less than 25 kt. Seas
up to 5 ft.
Thursday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain.
Thursday Night: Winds less than 25 kt. Areas of rough seas.
Rain likely.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 10 ft. Chance of rain.
&&
.HYDROLOGY...
A slow-progressing cold front interacting with an anomalously
high moisture plume for early March will be bringing a period of
heavy downpours, perhaps with embedded thunder serving to
enhance rain rates, to Southern New England tonight into Monday.
Current rainfall forecast shows rain amounts from 1-1.5 inches
mainly north and west of Interstate 95, with the heaviest
rainfall totals forecast in RI and portions of southeast MA with
amounts here ranging from 2-2.5 inches. Although the
location/placement of where the heaviest rainfall occurs is
pretty well agreed upon, there's only moderate confidence in
rain amounts and the potential exists for up to 3" totals in
spots in sustained, slow-moving downpours.
Although this is quite a slug of rain, especially in southeast New
England, significant and/or widespread flooding are not expected at
this time. NERFC 6-hourly flash flood guidance is around 2.5-3" in
interior Southern New England, and around 3 to 5 inches in southeast
New England and we'll fall short of those thresholds. Ponding of
water and areas of minor street flooding in some of the larger urban
metro areas in southeast New England which are especially flood-
prone (Providence/Cranston, New Bedford and Fall River) could
develop Monday, although we don't expect this to rise to significant
levels.
However we'll need to keep a close eye on creeks and larger rivers
not just with the initial slug of rainfall overnight into Monday,
but also as additional/higher flows up the CT River in response to
snowmelt occurring in VT/NH take place over the next couple of days.
Within-bank rises are expected on most rivers in eastern and
southeast New England, although we could have to watch the Wood and
Pawtuxet Rivers in RI if we do get higher rainfall amounts. Further
west in the CT River Basin, latest NERFC forecasts as of early
Sunday afternoon call for several of our CT River forecast points to
rise into Minor flood stage on Tuesday (Montague MA and Northhampton
MA around 5 AM Tuesday) and Wednesday (Thompsonville CT and Hartford
CT early Wednesday morning). River flood warnings could be needed
for these rivers in the coming day(s).
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 AM EDT Monday for ANZ230.
Gale Warning from 2 AM to 11 AM EDT Monday for ANZ231-232-254-
255.
Gale Warning from 11 PM this evening to 8 AM EDT Monday for
ANZ233>237-256.
Gale Warning from 2 AM to 8 AM EDT Monday for ANZ250-251.
&&
$$
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...McMinn
AVIATION...Loconto/McMinn/KP
MARINE...KJC/McMinn
HYDROLOGY...Loconto
Source:
BOX issues Area Forecast Discussion (AFD) at Mar 16, 7:38 PM EDT----------------
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