BOX issues Area Forecast Discussion (AFD) at Aug 20, 10:01 AM EDT021
FXUS61 KBOX 201401
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1001 AM EDT Tue Aug 20 2024
.SYNOPSIS...
A departing cold front Monday morning will give way to an
extended period of dry weather. The only minor exception may be
a few isolated showers Wednesday and Thursday. Unseasonably cool
weather to begin the week, with temperatures running about 10
degs below normal through Thursday. Then temperatures rebound
to near normal Friday and Saturday, then possibly warmer than
normal Sunday into early next week.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
10 AM update...
Post frontal airmass overspreading the region with NW winds
gusting up to 20-25 mph and dew pts tumbling into the 50s. This
drier airmass is promoting sunshine to develop this morning,
but will continue to mix with diurnal clouds given cyclonic flow
aloft. Could even be a few hours this afternoon when sky
conditions become BKN-OVC. Cooler too with highs only in the
low to mid 70s, upper 60s high terrain, about 5-10 degs cooler
than normal.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Tonight those clouds will disappear with sundown setting us up for a
night of good radiational cooling if the atmosphere can decouple.
For that reason the forecast has leaned on MOS guidance, showing
lows dipping into the upper 40s and low 50s. This will be 5-10
degrees colder than Monday night and quite a bit cooler than normal
for late August in southern New England. Wednesday is similar to
Tuesday in many ways with persistent highs in the 70s and dewpoints
in the 50s. The change in the synoptic setup will be a weak
shortwave rotating through the broader trough which acts to kick up
isolated to scattered showers over the interior. However, most
locations should stay dry.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
* Mainly dry with unseasonably cool temperatures Thursday
* Warming trend Friday into the weekend
Closed upper level low and cold pool aloft remain over New England
Thursday. Northwest flow and 850mb temps only around 5C will keep
high temperatures below normal in the upper 60s to low 70s. With
cyclonic flow and cool temperatures aloft, any daytime heating will
result in diurnal cumulus and possibly a weak low topped shower. The
best chance for showers looks to be across northern MA. Further
south, soundings show a more capped environment. Either way,
Thursday will not be a washout with mainly dry conditions.
The upper level closed low finally moves out of New England Friday
to the northeast with rising heights expected behind. Winds turn
more westerly Friday into the weekend allowing for temperatures to
warm into the upper 70s by Friday, to low 80s for the weekend. With
the upper level ridge overhead and high pressure building in, the
weekend is shaping up to be absolutely gorgeous with dry weather and
clear skies. Dewpoints will be rather comfortable Friday and
Saturday in the upper 50s to low 60s, but turns more muggy on Sunday
into the mid to upper 60s.
&&
.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
15Z TAF Update - not much change from previous TAFS, NW winds
gusting up to 20 kt at times along with VFR cloud bases. Earlier
discussion below.
--------------------------------------------------------------------
Today...High Confidence.
Any fog and MVFR dissipates by 15-17Z as rain exits. VFR
elsewhere. NW winds 5-10 kts.
Tonight...High Confidence.
VFR. Light NW winds.
Wednesday...High Confidence.
VFR. NW winds 5-10 kts with seabreezes along the coast after
around 15Z.
KBOS TAF...Moderate confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: VFR.
Thursday: VFR. Slight chance SHRA.
Thursday Night through Saturday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
High confidence.
With Ernesto moving well away from the US East Coast, the swell
energy is quickly diminishing. Still some residual wave heights
that are above Small Craft Threshold, so those alerts will
remain in effect for a little while longer, but no later than
this afternoon for the further offshore marine zones. A cold
front will push across the waters early this morning, bringing
a wind shift to the northwest, but with speeds staying 15kt or
less. Those conditions will continue tonight and Wednesday.
Outlook /Wednesday Night through Saturday/...
Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ250-
254>256.
&&
$$
SYNOPSIS...BW/KP
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...KP
AVIATION...BW/KP
MARINE...BW/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 20, 10:01 AM EDT----------------
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