Area Forecast Discussion Issued by NWS Boston, MA
000
FXUS61 KBOX 121838
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
238 PM EDT Fri Apr 12 2024
.SYNOPSIS...
An occluded front will sweep across the region late this
afternoon and evening, accompanied by a wind shift to the
southwest along with drier/cooler air and possibly a few
showers, especially in CT and western-central MA. It will remain
mostly cloudy tonight and Saturday, turning seasonably cool.
Generally dry Saturday night through Tuesday outside of the
chance for light shower activity late Sunday and Sunday night.
Warming trend develops with temps making a run at 70F Monday and
Tuesday. Mild but unsettled Wednesday and beyond.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
230 PM Update:
Prefrontal environment (ahead of occluded front) across SNE
featuring mild conditions with temps in the mid 50s to the lower
60s. Breezy as well with SSE winds 15-25 mph, gusting as high as
40 mph across the Cape and Islands. We let the wind advisory
expire as the low level jet as exited offshore. Ditto for the
coastal flood advisory, as high tide has past two hours ago
along with low level jet now offshore.
SPC placed western MA in a marginal risk for this afternoon, but
given very marginal instability ahead of occluded front, I think
the threat is even less than marginal. Thus, only expecting
those showers currently over southeast NY and western MA to
remain subsevere, with just isolated thunder. Hence, not much of
a concern ahead of the approaching occluded front.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/...
345 AM Update:
Tonight and Saturday:
Our weather pattern transitions to deep cyclonic flow aloft for
tonight into Saturday, with an associated pocket of low level colder
air. This will serve to keep our weather unsettled tonight into
Saturday. Though we should see more in the way of cloudy breaks in
this forecast period, all in all it is a mostly cloudy period.
Scattered instability type pop-up showers are possible on Saturday
in western New England but should be mainly dry most of the time.
Cold advection begins in earnest tonight and continues into
Saturday. So despite the cloud cover around, it should also be a
pretty blustery period, especially on Saturday where westerly gusts
around 25-35 mph should be pretty common. We could have gusts in and
around the higher terrain near 40 mph at times.
Low temperatures tonight are in the 40s with the cloud cover and WSW
breezes. Meanwhile high temps are forecast in the lower 50s for
western and central MA/CT, and the mid 50s for eastern MA and
RI.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights:
* Dry period Saturday night through Sunday afternoon before shower
chances increase Sunday evening
* Dry and mild Monday and Tuesday
* Next chance for appreciable precipitation comes mid next week
Saturday Night into Sunday
Dry period expected as any lingering day-time showers dry up as
shortwave pivots well northeast into the Canadian Maritimes
overnight. With weak mid level ridging building in from the west,
mostly dry conditions will persist through much of Sunday ahead of a
weak low pressure dropping south out of Ontario. Guidance currently
tracks the low a bit to our north, across VT/NH before moving
seaward of southern New England late Sunday night.
Guidance has come into better agreement that shower activity
associated with this low/shortwave will begin around 21Z Sunday
before diminishing between 06 and 09Z Monday morning. Emphasis
should be placed on the word "showers" as widespread, stratiform
precipitation is not expected for the region. CMC and GEFS QPF
probabilities for 0.1" of QPF are quite low, between 10 and 30% for
southeastern MA, CT, and RI, with a gradient to between 60 and 70%
across far northwestern MA. The ECMWF, which takes a bit more of a
southerly track with the low, illustrates the highest probabilities
of 0.1" across the south coast. Nonetheless, QPF probabilities of
0.5" are zero across all GEFS, ECWMF, and CMC suites. In general,
between 0.05 and 0.15" of rain can be expected; a very minor event
for our area given the deluge of water we`ve seen since the
beginning of the year.
Monday and Tuesday...
Lingering shower activity should be well seaward of southern New
England by 12Z Monday as drying WNW flow sets up across the region;
leading to clearing skies. More robust mid level ridge builds across
the northeast allowing strong WAA to develop, as 850mb temps briefly
surge to as high as 8C early Monday. Expecting temperatures to reach
well into the 60s to perhaps 70F both Monday and Tuesday.
As for winds, should see diminishing winds through the period as
925mg LLJ pulls offshore Monday morning. Winds at the top of the
mixed layer max out between 15 and 20kt by mid day Monday, with
gusts of 10-15kt possible at the surface. The NBM again shows a
terribly high bias, so cut winds significantly using CONSALL. Future
forecasters will need to remain cognizant of this NBM bias
surrounding the Patriots Day forecast. May see some increasing high
cloud cover late Tuesday ahead of our next precip maker, but all in
all it will be a great 36 hour period!
Mid-week and Beyond...
Guidance continues to trend later with our next significant frontal
passage, which now looks to impact the region late
Wednesday/Thursday; just 24 hours ago impacts were forecast to occur
late Tuesday into Wednesday. Given the delay, expected dry and mild
conditions to persist into at least Wednesday. In fact, most
guidance carries the potential for above normal temps well into late
week. Utilized NBM for this period as uncertainty still surrounds the
timing of the forecast.
&&
.AVIATION /18Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High- greater than 60 percent.
18Z TAF Update...
Thru 00z...high confidence on trends, lower on exact timing of
details.
At 18z, occluded front from NYC area northwest into NY state is
accompanied by a wind shift from SSE to SW and cigs improving
from IFR/LIFR to MVFR/VFR. This will overspread SNE between
19z-20z across western CT/MA, then arriving into eastern MA
22z-23z. Shower activity with this front should be confined to
CT and western-central MA. Mainly dry weather prevails across RI
into eastern MA. Pre and post frontal winds will gusts up to 30
kt.
After 00z: High confidence on trends, lower on exact timing of
details.
VFR cloud bases and mainly dry, but MVFR with scatterd showers
across western MA. SSW winds 15-25 KT.
Saturday: High confidence.
VFR cloud bases with just a few isolated showers possible.
However, MVFR with scattered showers across western MA. SW winds
15-25 kt, gusts up to 30 kt south coast, including Cape Cod and
Islands.
Saturday night: high confidence.
VFR, except MVFR early across western MA. West winds 15-25 kt
slowly diminishing toward Sunday morning. Dry weather prevails.
KBOS TAF...High confidence in TAF trends, but lower on exact
timing. Frontal passage/wind shift and improving to MVFR/VFR
approximately 22z-23z. Pre and post frontal winds gusting up to
30 KT at times.
KBDL TAF...High confidence in TAF trends, but lower on exact
timing. Frontal passage/wind shift and improving to MVFR/VFR
approximately around 20z. Pre and post frontal winds gusting up
to 30 KT at times. Showers til about 20z-21z.
Outlook /Sunday through Tuesday/...
Sunday: VFR. Breezy. Slight chance SHRA.
Sunday Night: Mainly VFR, with local MVFR possible. Windy with
local gusts up to 30 kt. Chance SHRA.
Monday through Monday Night: VFR.
Tuesday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
345 AM Update:
** Gale Warnings All Waters Today **
Today: High confidence.
SE to S winds increasing to 35 to 45 kt. Long southerly fetch
will build sees on the order of 8 to 14 feet over the open
waters this afternoon. Rain interspersed with areas of fog on
all waters, although the potential exists for scattered
thunderstorms on the southern waters this morning. Rain showers
then diminish in intensity and covg later this afternoon with
improving visbys.
Tonight and Saturday: Moderate confidence.
Slackening gradient brings SW winds around 20-25 kt tonight,
along with still elevated seas around 7 to 10 ft offshore.
Looking into Saturday, SCA-level SW/WSW gusts are expected on
all waters, although we could get close to Gale force gusts on
the southern waters. SCAs are likely on all waters, but outside
chance at another round of gale headlines on the southern
waters.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 10 ft.
Sunday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.
Sunday Night: Low risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Local rough seas. Chance of rain
showers, isolated thunderstorms.
Monday through Monday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.
Tuesday: Winds less than 25 kt.
&&
.TIDES/COASTAL FLOODING...
345 AM Update:
* Splashover and very minor coastal flooding on the South Coast
Fri AM
Coastal flood advisories were maintained for the South Coast.
For the South Coast, storm surge values per tidal gages have
started to increase to a greater degree, and the peak surge is
now expected to take place prior to the late Fri AM high tide.
With a 2-3 ft surge occurring before high tide, it is likely
that splashover/some overwash is the most likely outcome, with
minor coastal flooding likely an absolute worst-case per Stevens
Institute guidance.
For the eastern MA coast, although we could see storm surge
values up to 1.5 ft, the peak surge also looks to be timed just
after low tide. Coastal flooding on the eastern coast is not
expected given these conditions.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 2 PM EDT this afternoon for MAZ007-015>021.
Coastal Flood Advisory until 2 PM EDT this afternoon for
MAZ020-021.
RI...Wind Advisory until 2 PM EDT this afternoon for RIZ002>008.
Coastal Flood Advisory until 2 PM EDT this afternoon for
RIZ002-004>007.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ230>237-250-
251-254>256.
&&
$$
SYNOPSIS...Loconto/KS
NEAR TERM...Nocera
SHORT TERM...Loconto
LONG TERM...KS
AVIATION...Nocera/KS
MARINE...Loconto/KS
TIDES/COASTAL FLOODING...Loconto/KS