NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
000
FXUS61 KBOX 260550
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
150 AM EDT Mon Aug 26 2019
.SYNOPSIS...
Patchy low clouds over RI and SE Mass will diminish this
morning. High pressure over the Maritimes will build over
Southern New England today and maintain dry pleasant weather
through Tuesday. Possible showers Wednesday and Thursday ahead
of a cold front. Still keeping an eye on the track of a
potential tropical system offshore late this week, which could
produce high surf and dangerous rip currents along the immediate
shoreline.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Satellite imagery...nighttime microphysics and shortwave
IR...shows low clouds moving slowly southwest across SE Mass and
RI. These will continue to move across this area overnight,
spreading for a time into Northeast CT as well. A few
sprinkles/drizzle possibly in this area, but mainly dry
conditions. A few changes were made to sky cover forecast to
expand this area through 2 AM.
Clear and dry conditions across the remainder of Southern New
England overnight.
Observed temperatures at 9 PM were in the mid 50s to mid 60s.
Expect further cooling overnight, with overnight mins in the mid
40s through the 50s. This is in line with the existing forecast,
so no changes planned to the forecast.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
2 pm update...
Monday...
Looking to clear out. A continued long fetch off across the
Gulf of ME, two things: 1.) Sea-surface temperatures have
lowered a bit with the turbidity and upwelling of the waters,
and 2.) dry air advection will be quite strong and deeper within
the column compared to today and sinking. So an expectation
that low clouds will linger across New England during the
morning hours, gradually dissipating S/W with drier, subsiding
pushing S. But not ruling out scattered to broken cloud decks
given boundary layer mixing of onshore cool, moist air. Expect
cloudy issues to linger especially S-coastal New England but
lesser drizzle issues. Late Summer sun still strong while mixing
out to H85 undergoing cold air advection, around +8C, another
day of 70s throughout the interior while 60s along the E/SE
shore.
Monday night...
Becoming clear. Daytime heating concludes, dry air and high
pressure in place, looking at the boundary layer to decouple and
light winds to prevail over most of S New England albeit the
southeast. Warm air advection aloft, moisture is trapped beneath
the dry inversion just above the surface. Dense fog not out of
the question especially in areas of onshore flow and/or higher
dewpoints (notably earlier in the day with the cross-over
threshold). Lean with cooler guidance and evaluate fog based on
winds (below 3 mph) along with temperature- dewpoint thresholds
of 2 degrees or less. This as a first guess, fog seemingly will
be more prevalent.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights...
* Temperatures will remain below normal Tuesday, then will
moderate to near and above normal by late this week
* Scattered showers will move across our region sometime late
Wednesday into Thursday ahead of a cold front.
Details...
Tuesday...
High pressure will remain across the region, or at least close
by. Dry weather and below normal temperatures expected to
continue. Onshore winds will keep the immediate coastal areas
even cooler.
Wednesday through Friday...
The biggest question remaining to be answered will be how close
a potential tropical system comes to southern New England during
this time. Latest model guidance has trended ever so slightly
west, but still well within the margin of error for a forecast
this far out. Still expecting a cold front to slowly approach
from the west late Wednesday into Thursday. At this point,
expecting scattered showers with the cold front. Instability is
too poor to warrant a mention of thunderstorms in the forecast.
Rainfall chances would be significantly higher if the ocean low
pressure comes even closer to our region. Time will tell. The
most likely impact from this coastal system would be a period
of rough surf along ocean-exposed beaches.
There may be another front that might approach late this week,
but timing is very much in question.
Near to above normal temperatures should prevail during this
period.
Saturday and Sunday...
High pressure should be in control. Current forecast is for dry
weather. Above normal temperatures Saturday, with below normal
temperatures Sunday as this high pressure moves in.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday/...High confidence.
Rest of Tonight...
MVFR ceilings over RI and SE Mass as an area of clouds drifts
southwest across that area. Expect these clouds to diminish
overnight. Patchy IFR FG possible where SKC prevails in the CT
River Valley of MA as well as a few regular fog spots. VFR clear
across the remainder of Southern New England.
Today...
Any remaining MVFR ceilings over RI should dissipate this
morning. Similarly, any patchy fog from overnight should
dissipate after sunrise. High pressure over New Brunswick will
maintain east-northeast winds today with strongest winds gusting
20 to 25 kt across the South Coast and Islands. The high will
build south over our area late today, diminishing the wind.
Tonight...
High pressure over the region will bring clear skies and light
wind. Radiational cooling will bring areas of fog, especially
over the CT River Valley in Mass. and in the regular fog spots
of Srn New England. IFR cigs/vsbys in any fog.
Tuesday...
High pressure continues to bring mostly clear skies and light
wind. Thin cirrus will move in from the west, most likely over
CT and Western MA.
KBOS Terminal...
Expect FEW025 through mid morning as fragments move up from the
marine clouds across SE Massachusetts. Otherwise VFR clear with
a continued east-northeast wind up to 10 kt.
KBDL Terminal...
Lingering 2500 ft bases should remain south/east of KBDL this
morning before dissipating. VFR clear with a light ENE wind.
Outlook /Tuesday Night through Friday/...Moderate confidence.
Tuesday Night: VFR.
Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA.
Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.
Thursday Night through Friday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday/...High confidence.
E/NE winds persist through Tuesday morning. That will contribute
to an E swell and wave heights around 4 to 6 feet. Strong gusts
will taper slightly overnight, and then pick back up Monday
with gusts up to 25 kts. As high pressure builds from the N
into midweek, will see both winds and seas begin to subside.
Small Craft Advisory headlines continue for a majority of the
waters.
Outlook /Tuesday Night through Friday/...Moderate confidence.
Tuesday: Winds less than 25 kt. Seas up to 5 ft.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers. Local visibility 1 to
3 nm.
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Thursday Night through Friday: Winds less than 25 kt. Seas
locally approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for
ANZ232>234.
Small Craft Advisory until 5 AM EDT early this morning for
ANZ235-237.
Small Craft Advisory until 8 PM EDT this evening for ANZ250-
254.
Small Craft Advisory until 6 AM EDT Tuesday for ANZ255-256.
&&
$$
SYNOPSIS...Belk/Sipprell
NEAR TERM...WTB/Sipprell
SHORT TERM...Sipprell
LONG TERM...Belk
AVIATION...WTB/Belk
MARINE...WTB/Belk/Sipprell