BOX issues Area Forecast Discussion (AFD) at Mar 14, 7:56 PM EDT849
FXUS61 KBOX 142356
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
756 PM EDT Fri Mar 14 2025
.SYNOPSIS...
Increasingly mild conditions this weekend, especially away from the
south coast, with increasing wind Sunday. A strong cold front will
bring the potential for heavy rain and strong southerly wind gusts
Sunday night into Monday morning. Mainly dry and mild weather
returns Tuesday into Thursday. An approaching cold front will likely
bring a period of showers sometime late Thursday into Thursday night
followed by blustery and cooler conditions next Friday.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
240 PM update...
Surface ridging in place across SNE will shift to the east overnight
with boundary layer flow turning southerly. Nearby stratus around
Nantucket expected to expand north and west across SNE through
the night, but still some question with the inland extent. HREF
probs do suggest that stratus will overspread much of SNE overnight.
There should be a period of radiational cooling this evening before
clouds develop which makes low temp forecast a bit tricky. We
blended in the colder MAV guidance with NBM to derive low temps
which yields lows ranging from lower to upper 30s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday...
Upper level ridging across New Eng with subsidence and dry air
above 950 mb. However, will have some low level moisture below 950
mb to contend with to start the day. Low clouds expected to give
way to partly to mostly sunny skies during the afternoon as boundary
layer moisture mixes out. The exception will be near the south coast
where clouds may linger for a good part of the day. Highs will range
through the 50s, coolest along immediate south coast and
Cape/Islands where temps expected to peak around 50, and mildest in
the Merrimack valley and adjacent areas in NE MA with some lower 60s
possible furthest removed from cooling effects of southerly flow.
Boundary layer is quite shallow which will prevent increasing winds
aloft from mixing down. Modest southerly breezes 10-20 mph expected.
Saturday night...
Upper ridge axis moves to the east deepening southerly flow across
New Eng. While deeper moisture remains to the west, PWATs increase
to 0.75-1.0" overnight and this increase in moisture with modest low
level jet may lead to a few showers developing. Widespread stratus
is likely to redevelop with areas of drizzle as well. Cloud cover
with southerly flow and increasing dewpoints will result in a milder
night with lows in the 40s but rising temps into the 50s by Sunday
morning.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Messages:
* Heavy rain and windy conditions possible later Sunday through
Monday
* Drying out Tuesday bringing calmer conditions for Wednesday
* Low pressure approaches southern New England Thursday
Details...
The robust LLJ of 50-65 kts is still in play Sunday afternoon and
evening as it moves over southern New England. The jet of this
magnitude is weaker than what we typically look for when issuing
wind advisories. Still, the jet could still lead to some strong wind
gusts at the surface. The best chance for windy conditions will
likely be Sunday afternoon into the evening with better mixing
expected. By Sunday night, the arrival of steadier rain will likely
help to stabilize the column and cut back on the highest potential
gusts. We expect a period of downpours during the Sunday night
to Monday timeframe as a frontal boundary moves through
Southern New England, perhaps with some weak secondary low
pressure development along the trailing frontal boundary
indicated in some fcst guidance. Deep southerly flow with a 55
kt 850 mb jet brings an axis of elevated precipitable water axis
of 1.25 to 1.33 inches with good moisture convergence along the
frontal boundary is a synoptic pattern which tends to favor
downpours, with embedded convective elements locally enhancing
rain rates. Official forecast calls for storm-total rains
between 1-1.25" in northern MA, and around 1.25-1.5 inches for
most of interior Southern New England, with the greatest
rainfall totals of 1.75 to up to 2.5" in eastern CT, RI and
southeast MA including Cape Cod and the Islands. See the
included Hydrology AFD section for more details on the
hydrologic/river aspects.
Following this system, mid to upper level ridging builds back in
over the region, drying things out and setting up another
warming trend. Highs may once again reach the low 60s across the
region and southerly flow returns for midweek after shifting
from the NW during the day Tuesday. Low pressure over the Great
Lakes Thursday will be something to monitor as it may continue east.
Current guidance indicates a similar setup to Sunday, with a robust
frontal system pushing through the area and a narrow plume of
anomalous PWAT values along and ahead of it.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence in trends, though timing is moderate.
VFR to generally prevail, however a stratus layer lying offshore
of ACK on southwestward toward the waters south of Long Island
eventually turns landward tonight and overnight as winds become
SE 01-03z with IFR to LIFR conditions. Fog is possible as well,
but somewhat better chance for RI and SE MA where winds are
lighter. Confidence in the timing of stratus is moderate and
could come in sooner in western interior airports than further
east. Light E winds to start to trend SE to S around 4-8 kt.
Saturday: Moderate confidence.
IFR/LIFR to start; although fog disperses during the morning,
slow north to south improvement during the afternoon hours
toward MVFR-VFR, although IFR stratus may linger for much of if
not all day. S winds 5-8 kt.
Saturday Night...Moderate confidence
Increasing southerly flow will lead to IFR stratus and fog
filling back in. Expect light drizzle to form with a deeper
fog/stratus layer and dry air above 2kft. Southerly LLJ
increase to 40-50 knots will almost certainly cause LLWS as
surface winds could be less then 15 knots until day break.
KBOS TAF...Moderate confidence in TAF. VFR to start, however
IFR stratus may develop by 04z but more likely after 06z, with
IFR/LIFR mist with stratus during the pre-dawn to mid-morning
Sat hrs. Improvement likely to be slow and showed some
optimism toward SCT MVFR after 17z Sat but possible it may
linger most of the day. Light E winds currently shift to SE to S
around 4-8 kt.
KBDL TAF...Moderate Confidence in TAF. MVFR/IFR CIGS move into
tonight after ~04z. CIGS improve between 13-15z tomorrow
morning back to VFR.
Outlook /Sunday through Wednesday/...
Sunday: Mainly VFR, with areas IFR possible. Windy with gusts
up to 35 kt. Chance SHRA.
Sunday Night: MVFR/IFR conditions possible. Windy with gusts up
to 35 kt. RA.
Monday: MVFR/IFR conditions possible. Windy with local gusts up
to 30 kt. RA.
Monday Night: VFR. Breezy. Chance RA.
Tuesday through Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Saturday night...High confidence.
Light winds and seas tonight with high pres over the waters.
Southerly winds develop Sat, with increasing winds Sat night to 20+
kt overnight. Seas below SCA through Sat night but approaching 5 ft
over southern waters by Sunday morning. Vsbys reduced in areas of
developing fog tonight and Sat morning, and lowering again Sat
night.
Outlook /Sunday through Wednesday/...
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft. Slight chance of rain showers.
Sunday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 11 ft. Chance of rain.
Monday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt. Rough seas up to 11 ft. Rain. Local
visibility 1 to 3 nm.
Monday Night: Winds less than 25 kt. Rough seas up to 10 ft.
Chance of rain.
Tuesday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain.
Tuesday Night through Wednesday: Winds less than 25 kt. Seas up
to 5 ft.
&&
.HYDROLOGY...
245 PM Update:
A period of downpours is expected to develop Sunday night into
Monday in Southern New England, with latest forecast between
1-1.25" in northern MA, and around 1.25-1.5 inches for most of
interior Southern New England, with the greatest rainfall totals
of 1.75 to up to 2.5" in eastern CT, RI and southeast MA
including Cape Cod and the Islands. While forecast confidence in
the rainfall placement is moderate to high, rainfall totals are
only moderate with potential for locally higher totals if we
can see a greater coverage of embedded convection or if the
frontal boundary moves more slowly - and that could happen in a
case where we do get secondary low pressure development along
the front.
Widespread significant flooding is not expected and the rain
overall should prove beneficial in light of the spell of dry
weather we've had. However urban and poor drainage nuisance
flooding could develop, especially in some of the more urbanized
areas in eastern RI and southeast MA (including but not limited
to the Providence/Fall River/New Bedford metro areas). Could
have some difficult travel in downpours for the Mon AM commute,
especially in eastern MA and RI.
On rivers...we should see some response on the flashier urban
creeks/streams in CT, RI and eastern MA Sunday night into Monday.
While these will need to be monitored, unless we see more QPF
than currently advertised, it's unlikely these will rise to
flood stage. However we want to mention that in response to the
combo of rain Sun/Mon and upriver snowmelt moving down the CT
River, MMEFS probabilistic guidance indicates a few of the CT
river forecast points (Northhampton, Thompsonville, Hartford)
have the potential to reach into minor flood stage around
Tuesday and/or Wednesday. NERFC forecasts aren't currently
available for these forecast points since it is beyond 72 hours
in time, but these will also be monitored closely once we get
into that forecast range.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from Sunday morning through Monday morning for
ANZ230>232-250-251-254-255.
Gale Watch from Sunday morning through Monday morning for
ANZ233>237-256.
&&
$$
SYNOPSIS...KJC/Loconto/FT
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...Loconto/FT
AVIATION...Loconto/McMinn/KP
MARINE...KJC/Loconto/KP
HYDROLOGY...Loconto/FT
Source:
BOX issues Area Forecast Discussion (AFD) at Mar 14, 7:56 PM EDT----------------
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