BOX issues Area Forecast Discussion (AFD) at Sep 12, 10:23 PM EDT801
FXUS61 KBOX 130223
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1023 PM EDT Thu Sep 12 2024
.SYNOPSIS...
Mainly dry weather and above normal temperatures expected
Friday. There is a low chance of an isolated shower or storm in
northeast MA late afternoon Friday. Otherwise, high pressure
will continue to dominate our weather through at least early
next week, maintaining dry weather and above normal temperatures
for the foreseeable future.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1010 PM Update:
No major changes needed to the going forecast. Clear skies and a
light southerly wind is allowing for good radiational cooling.
Dewpoints are a little higher than last night and we'll be
monitoring for fog development south of the Mass Pike, though
we're probably another couple hours away before we start seeing
development occur. Could need either an SPS or possible advisory
for fog but will make that final determination pending
observational trends.
Previous discussion:
As things stand at this hour, temperatures are plummeting
quickly across SE MA already in the mid 60s, but still in the
70s across western MA and CT. With surface high pressure
staying put over the region, expect another night of mainly
clear skies and radiational cooling. Overnight low once again
drop into the low to mid 50s. Surface moisture trends higher
than the previous night. Higher dewpoint air stays trapped under
a strong temperature inversion with drier mid and upper levels.
This will support potential for fog development overnight. In
additional to the usual prone spots along the CT River Valley,
HREF guidance has been consistently highlighting potential for
patchy fog in areas of the CT, RI and southeast MA, generally
south of the Mass Pike. Areas can see patchy fog with
visibilities 3-5 SM, with 1/2-1SM in spotty areas. In terms of
timing, fog may develop in the 12-2am timeframe, increasing in
coverage as temperatures continue to cool at the surface. There
is some uncertainty in how long it sticks around, but HREF means
seem to agree on it slowly improving throughout early Friday
morning (7am-10am).
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
Friday:
Once fog erodes, we'll be on track for another warm September
day Friday under surface high pressure. 850mb temperatures warm
a degree or two from Thursday supporting highs in the upper 70s
and low 80s across most spot. Southern New England stays on the
east periphery of an upper ridge Friday with a brief shortwave
trough dropping south along it in the afternoon. Overall, this
won't amount to much given limited synoptic support and
moisture. With 50-600 J/kg of MLCAPE, instability will be
sufficient enough to support a few weak showers or a stray
storm across northeast MA in the afternoon-early evening
timeframe. Given the limited support, it will be isolated and
thus resulting in a lower probability (<15%).
Friday Night:
Region remains under the influence of an upper ridge and surface
high pressure. This will likely support the set-up of ample
radiational cooling with low-level moisture trapping beneath the
subsidence inversion. This will lead to potential for fog/low
stratus overnight in similar areas as Friday night in CT, RI
and southeast MA, mainly south of the Mass Pike.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The dry weather pattern continues well into the extended forecast as
guidance agrees that an upper-level blocking ridge will keep high
pressure parked over the region. Trended high temperatures just a
bit cooler then the NBM For the weekend into early next week with
weak onshore flow, but temps should still top out in the upper 70s
to low 80s each day with clear skies. With the longer nights along
with good radiational cooling conditions, blended NBM with cooler
CONSMOS data for overnight lows through Tuesday night. The warmest
night appears to be Saturday night, where dewpoints in the upper 50s
to low 60s will keep temps in the upper 50s. Sunday and beyond,
dewpoints begin to fall back to the low to mid 50s again which will
allow overnight temps to drop down into the low to mid 50s as well.
Expect patchy radiation fog to develop each night, especially with
low level moisture getting caught underneath the subsidence
inversion due to the upper level ridge.
Looking way ahead to late next week, guidance had indicated the
upper-level ridge may start to break down, however, it is now
trending towards rebuilding the ridge back in. This should keep any
substantial precip south of SNE. NBM POPS for Wednesday and beyond
have decreased from 30% to 10%.
We continue to monitor tropical development in the eastern Atlantic
and near the SE Atlantic Coast. NHC shows several areas of possible
tropical development, along with Tropical Depression Seven. With
the blocking ridge overhead, this should steer any tropical activity
away from our region. For more information, please visit
www.nhc.noaa.gov.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight: High confidence overall, but moderate on fog
development and coverage.
Mainly VFR along and north of the Mass Pike, although should be
a better chance for radiational BR/FG across CT-RI-southeast
MA. There is potential for FG/BR to linger within the first few
hours after sunrise. Still uncertainty on exact end time, but
will likely see improvement in the 11-14z timeframe. Light SSW
winds, calm at times.
Friday and Friday Night: Moderate to high confidence.
Overnight fog could linger around CT-RI-Southeast MA until 15z,
then become VFR all airports. SSW winds 5-10 kts for most of
the terminals. A low (<15%) chance at a SHRA/TS near BED after
20z Fri until sundown, but dry conditions appear more likely.
KBOS TAF...High confidence in TAF. SE winds this afternoon 5-10
kts transitioning to SW after 22Z. For Friday, sea breeze
develops in 16-18z timeframe, similar to today with SE winds
5-10 kts.
KBDL TAF...High confidence in TAF, moderate on fog dissipation
timing. VFR through this evening. Fog is more likely after 05z
Fri. If fog develops, it may linger in the first couple of hours
of sunrise. There should be gradual improvement in the 11-14z
timeframe, likely VFR by 15z.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Mainly VFR, with local IFR possible. Patchy BR.
Sunday: VFR. Patchy BR.
Sunday Night: Mainly VFR, with areas IFR possible. Patchy FG.
Monday: VFR.
Monday Night: Mainly VFR, with local IFR possible. Patchy FG.
Tuesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Friday: High confidence.
High pressure will continue remains over the waters for the
next several days. Light winds with daily sea breezes are
expected, and seas 2 ft or less expected.
Fog may develop tonight over the southern waters and near Cape
Cod Bay, which could reduce visbys to under 1 mile. There is
also a low (<15%) chance at a thunderstorm over the northeast
waters late Friday afternoon, although dry weather should
prevail.
Friday Night:
Patchy fog possible again overnight Friday over the southern
water and near Cape Cod bay (moderate confidence). Still
uncertainty in coverage.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Winds less than 25 kt. Patchy fog. Local
visibility 1 to 3 nm.
Sunday: Winds less than 25 kt.
Sunday Night: Winds less than 25 kt. Patchy fog.
Monday: Winds less than 25 kt.
Monday Night: Winds less than 25 kt. Patchy fog. Local
visibility 1 to 3 nm.
Tuesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Mensch/KP
NEAR TERM...Loconto/Mensch/KP
SHORT TERM...Mensch
LONG TERM...KP
AVIATION...Loconto/Mensch/KP
MARINE...Loconto/Mensch/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 12, 10:23 PM EDT----------------
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