NWS Forecast Discussion
924
FXUS61 KBOX 130535
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1235 AM EST Wed Nov 13 2024
.SYNOPSIS...
High pressure builds into the region Wednesday. A storm system
over the Canadian Maritimes on Thursday will move westward late
this week into the weekend, bringing with it at least increasing
cloud cover but rainfall chances are more uncertain. Higher
astronomical tides this weekend could result in splashover or at
worst minor coastal flooding for eastern coastal areas. Gradual
warming trend this weekend.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
10 PM update...
Ocean effect strato-cu across the Cape/Islands expected to
persist overnight as low level moisture lingers in the boundary
layer. Otherwise clear skies across SNE. Winds still gusting to
20-30 mph but will become less gusty overnight, except along
the immediate coast. Still expecting a steady overnight which
will keep temps from falling sharply. Lows will settle into the
upper 20s for most locations, with low-mid 30s near the coast,
and upper 30s outer Cape and Nantucket.
Based on input from our state fire weather partners and meshing
expected weather conditions, we`ve opted to extend the existing
Red Flag Warning through tonight and into Wednesday for all of
Southern New England, with its expiration now set for 600 PM
Wednesday.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
Wednesday will be a pleasant, if cold, day across the region as
winds slacken compared to today with the arrival of high pressure.
Those ocean effect clouds linger over the Cape and islands through
the morning but otherwise sunny skies prevail. Given 925 mb temps in
the -1 to -2C range we can expect highs colder than today, only in
the mid to upper 40s. While winds will be less than today, gusting
to 20 mph for most, those along the immediate southeast coast and on
the water will see stronger gusts in the 25 to 35 mph range.
Wednesday night the high moves overhead allowing winds to diminish
so the low temperature forecast favored the MOS guidance which
better handles radiational cooling. Expect lows in the low to mid
20s and even the mid to upper teens for northwest and north central
MA.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights:
* Ocean storm moving westward late week into the weekend may bring
cloud cover to eastern New England, although rain chances are more
uncertain.
* Higher astro tides late this week into the weekend could result in
splashover or at worst minor coastal flooding in parts of the
eastern coastline.
* Gradual warming trend to temps thru this weekend.
Thursday through the Weekend:
High pressure both at surface and aloft will initially be in place
to begin this period, with a closed upper low well to our east over
the Canadian Maritimes. However this upper level low is still
forecast to retrograde westward for Fri into Sat, in response to
blocking over the North Atlantic as well as a complex interaction
with a weak shortwave disturbance moving off the central
Appalachians into the coastal Carolinas. This could bring the
potential for increased cloud cover and off-and-on light rains to
Southern New England Fri into the weekend, however considerable
uncertainty exists with regard to how far west this low pressure
retrogrades. Latest deterministic guidance has trended toward a
drier outcome with somewhat better chances for light rains
restricted to ME, NH and our adjacent outer waters, although
ensemble membership analyses are more mixed and would still favor at
least some light rains. I ended up walking back some of the NBM`s
Chance/low-Likely PoP toward more lower Chance, with drier
conditions for the interior. It doesn`t look as though this system
would be a heavy precip-maker if model guidance trends back toward a
western/wetter outcome.
With rising astronomical tides starting Thurs into the weekend,
peaking on Saturday at 11.96 ft MLLW at Boston Harbor, will have to
monitor the potential for tidal flooding for the east coast of MA in
this period of time. Tides will only start to rise on Thurs when
northerly flow could be enough to produce splashover on the eastern
coastline. With offshore/NWly flow becoming more favored as tides
reach their peak, that could limit how much surge portions of the
eastern coastline sees but could favor Cape Cod and MVY/ACK for
possible minor coastal flooding.
Temps will be gradually warming a couple degrees each day in this
period, but we should have some pretty chilly nights Thurs and Fri
nights. While high temps start off in the 40s on Thurs, gradually
warming into the lower to mid 50s for Fri and into the mid
50s/around 60 for the weekend, although cooler readings near the
eastern coast where cloud cover could limit insolational heating.
Early Next Week:
We get into a flatter quasi-zonal pattern for early next week. Some
potential for a progressive frontal system moving through the region
around Mon night or Tue, but this doesn`t look to produce much rain.
Temps to trend near to above normal.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update:
Today through Thursday...High confidence.
VFR, but occasional sct-bkn cigs around 4k ft over Cape/Islands
through this morning, and possibly returning over ACK overnight.
N wind 10-20 kt, gusts to 25-30 kt Cape/Islands, gradually
diminishing mid-late afternoon. N wind 5-15 kt tonight and Thu,
with gusts to 20 kt Cape/Islands.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Thursday Night through Sunday/...
Thursday Night: VFR. Breezy.
Friday through Friday Night: VFR. Breezy. Slight chance RA.
Saturday through Saturday Night: VFR. Breezy. Slight chance RA.
Sunday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Gale warning continue on all waters except Narragansett Bay for
NW-N gusts to 35 kt continuing into tonight. Winds slowly
diminish late tonight into Wednesday, but gusts to 25-30 kt will
continue Wednesday over eastern waters. Rough seas develop,
building to 8-12 ft over the eastern waters. Winds remain breezy
Wednesday night and seas remain between 6 to 9 feet.
Outlook /Thursday Night through Sunday/...
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 10 ft.
Thursday Night: Winds less than 25 kt. Rough seas up to 10 ft.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain.
Friday Night through Saturday: Moderate risk for Small Craft
Advisory winds with gusts up to 25 kt. Areas of rough seas.
Chance of rain.
Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Rough seas up to 9 ft. Chance of rain.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Slight chance of rain.
&&
.FIRE WEATHER...
645 PM Update:
Red Flag Warnings have been extended through tonight and into
Wednesday, set to expire at 600 PM Wednesday. With less RH
recovery expected tonight and continued northerly breezes,
we opted to extend the Red Flag Warning through tonight and into
Wednesday after coordination with fire weather partners.
It will be drier on Wednesday with RH values lowering to 25 to 35
percent away from the Cape/Islands. Winds will be lighter with 10-20
mph north winds expected.
Thursday, winds tend lighter overall compared to Wednesday with
winds decreasing into the afternoon. However, marginally breezy
conditions may still persist, mainly across southeast MA (Cape)
with gusts up to 25 mph. Dry conditions continue with relative
humidity values dropping in the 30 and 40 percent ranges in most
areas, locally lower in spots across central MA.
&&
.TIDES/COASTAL FLOODING...
Astronomical tides climb to near 12 ft at Boston Friday and
Saturday. With offshore low possibly retrograding back towards
New England, it would only take less than a 1 ft storm surge to
induce minor/nuisance coastal flooding.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Red Flag Warning until 6 PM EST this evening for CTZ002>004.
MA...Red Flag Warning until 6 PM EST this evening for MAZ002>024-
026.
RI...Red Flag Warning until 6 PM EST this evening for RIZ001>008.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ230.
Gale Warning until 7 AM EST this morning for ANZ231-232-250-
251-254-255.
Gale Warning until 1 AM EST early this morning for ANZ233>235-
237-256.
Small Craft Advisory until 7 AM EST this morning for ANZ236.
&&
$$
SYNOPSIS...Loconto/BW
NEAR TERM...KJC/Loconto/BW
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...KJC/Loconto/Guest
MARINE...Loconto/BW
FIRE WEATHER...Loconto/BW
TIDES/COASTAL FLOODING...Nocera
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