Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 251426
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1026 AM EDT WED MAY 25 2016

.SYNOPSIS...
An upper level ridge will bring very warm weather to most of the
region through Saturday, except for cooler temperatures at times
along the immediate coast. A backdoor cold front will bring cooler
weather to the region sometime on Sunday, but temperatures should
rebound to at or above normal by early next week. A few showers
and thunderstorms are possible Thursday night into Friday, and
again this weekend but the vast majority of this time will be dry.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
***Summer temperatures push in today across the region***

1030 AM Update...Most of the fog has cleared out across the area
with the exception of one band of fog that is hugging the south
coast of RI and moving eastward towards Buzzards Bay and the Cape.
If it continues on this trajectory without burning off, portions
of Cape Cod along the Cape Cod Canal as well as Martha`s Vineyard
and the Elizabeth Islands will see a period of fog later this
morning into early afternoon. Visibilities have been generally
about a mile with this bank of fog on land, it may be more dense
over the water. Made minor adjustments to the temperatures to ease
them back as they have not jumped up as quickly as forecast.
Otherwise, the previous forecast is on track.

Weak ridging at the surface and aloft will cross the region by
midday through the afternoon with NW winds aloft. Warm core H925
temps will push across the region, up to +19C to +22C by this
afternoon. Once skies become mostly sunny, temps will rise quickly
with excellent low and mid level mixing in place. Expect temps to
top off in the mid-upper 80s with a few spots touching 90.
However, dewpoints falling into the 40s will result in low
humidity levels.

High clouds will start to push in from the NW during the mid and
late afternoon ahead of H5 short wave across far northern New
England.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Tonight...

Most of the energy from a weak H5 shortwave trough will remain
across northern New England. NW flow keeps dry conditions across
the region tonight. The mid and upper level clouds will dissipate
overnight as SW winds shift back to W-NW and diminish. It will
remain mild, with temperatures only bottoming out from the mid 50s
well inland to lower-mid 60s across the coastal plain.

Thursday...

A cold front will slowly push S across the region during the day.
Clouds will push in from the W as the front moves in during the
afternoon. Short range models vary in their solutions, with mainly
dry conditions through the day offered by the ECMWF, but the GFS
tends to bring some moisture with a weak H5 shortwave in the W-NW
flow aloft. Have mentioned only slight chance PoPs moving into W
MA/N Central CT during the mid and late afternoon hours.

Have noted marginal instability with this system, plus another
day of warm temperatures, so have mentioned widely scattered
showers/isolated thunderstorms.

It will be another warm day, with somewhat higher dewpoints making
it feel a bit more humid. Highs will again be in the mid-upper 80s
away from the immediate coast, with a few spots possibly hitting
90 again.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights...

* Friday: Very warm w/highs mid-upper 80s northwest of BOS-PVD but
  a bit cooler across southeast MA/RI

* Saturday: Hot and a bit humid w/highs mainly upper 80s to lower
  90s away from the immediate south coast

* Sunday: Temps uncertain depending on timing of cold front, warmest
  readings likely CT River Valley w/coolest across Eastern MA coast

* A few showers/t-storms possible Thu night/Fri and again Sat/Sun
  but the vast majority of this time will be dry

* At or above normal temperatures likely return early next week

Details...

Thursday night...Shortwave energy and a burst of elevated
instability may result in a few showers/t-storms Thursday night,
mainly northwest of a Boston to Providence line. If any activity is
able to develop, it will be short-lived with the majority of the
night ending up dry. Low temps mainly in the upper 50s to the lower
60s.  May see some patchy ground fog develop late in the typically
prone locations.

Friday...Surface winds shift to the south-southwest behind the
warm front as 850T rise to around +14C. Plenty of sunshine should
allow highs to warm into the middle to upper 80s northwest of a
Boston to Providence line. Southeast of this line...a cooling
marine layer may hold highs in the upper 70s to the lower 80s.

Dry weather will dominate on Friday, but enough instability
combined with a pre-frontal trough may allow a few
showers/thunderstorms to develop across W MA/N CT Fri afternoon
and evening. Not sure if this activity gets into our region or
stays to our west, but highest risk will be across northwest MA.
Shear is rather weak so even if we see a few thunderstorms in our
western zones, overall severe weather threat is rather low.

Saturday...A hot and somewhat humid day is on tap to kick off the
Memorial Day Weekend.  850T around +16C, plenty of sunshine, and a
westerly component to the surface winds should allow for high temps
to reach into the upper 80s to the lower 90s away from the immediate
south coast. Dewpoints between 60 and 65 across most of the region
will make it feel a bit humid.

While most of the day will be dry, a few showers and
thunderstorms may develop Saturday afternoon and evening with a
pre-frontal trough and CAPE values between 1000 and 2000 J/KG.
This will be mainly to the northwest of a Boston to Providence
line. Forcing will be rather weak, so areal coverage of any
activity that develops may remain limited. Severe weather threat
also looks rather low at this time with rather weak 0 to 6 km
shear, but too early to rule out a strong thunderstorm or two
given decent instability.

Sunday...Low confidence on high temperatures given a subtle change
in timing of the backdoor cold front will make a big difference in
the exact outcome. We can say that the warmest readings will be
across the lower CT River Valley and coolest along the eastern MA
coast. Good shot though at the CT River Valley seeing high temps
reaching well into the 80s, while the eastern MA coast has
afternoon temps falling into the 60s. A few showers will remain
possible and perhaps even a couple of t-storms across the interior
if enough instability develops during the afternoon.

Monday and Tuesday...Backdoor cold front does not appear as strong
on the latest model runs.  It looks to washout across the region
early next week. GFS washes out on Monday while the ECMWF waits
until Tuesday. Probably should see the return to above normal temps
by Tue with rather warm temps aloft.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels.

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Today...High confidence. VFR conditions expected the rest of the
day, except on the Cape and Islands where fog may reduce
visibilities down to MVFR/IFR at times.

Tonight...High confidence. VFR conditions. W-NW winds 10 kt or
less.

Thursday...High confidence. VFR. Light W-NW winds, except sea
breezes possible late morning/afternoon along the coast.

KBOS TAF...Moderate to high confidence. An ESE sea breeze has
developed and is expected to continue into early afternoon.
Southwesterly winds should overcome this by late afternoon.

KBDL TAF...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Thursday night and Friday...Moderate to high confidence.  VFR
conditions likely dominate but some brief MVFR conditions possible
in a few brief showers/t-storms mainly across the interior. Also,
some patchy ground fog possible in the typically prone locations
very early Fri AM.

Saturday...Moderate to high confidence. VFR conditions likely
dominate but a brief period of MVFR-IFR cigs/vsbys possible in a
few afternoon and evening showers/thunderstorms.

Sunday...Low confidence.  MVFR-IFR conditions may develop from east
to west behind a backdoor cold front.  A few thunderstorms also
possible Sun afternoon across the interior.

&&

.MARINE...
Forecaster Confidence Levels.

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Today...High confidence.  W winds up to 10 kt will back to SW
10-15 kt this afternoon with gusts up to 20 kt on the southern
outer waters. Seas 4 ft or less. Patchy fog mainly along the south
coast will result in reduced visibilities at times.

Tonight...High confidence.  Light southwesterly winds become
westerly, gusting up to 20 kt on the southern outer waters this
evening. Seas 4 ft or less.

Thursday...High confidence.  Light W winds shifting to S in the
afternoon. Seas remain below 5 ft.

Outlook /Thursday Night through Sunday/...High Confidence.

Winds and seas will generally remain below Small Craft Advisory
thresholds through the period.  The main concerns are a period of
near-shore southwesterly wind gusts of 20 to 25 knots Saturday
afternoon which will result in some choppy seas for mariners. May
also see some brief easterly wind gusts between 20 and 25 knots on
Sunday behind a backdoor cold front.

&&

.FIRE WEATHER...
Today...Expect temperatures will rise quickly, soaring well into
the 80s to near 90 across most locations except cooler along the
immediate south coast. These temperatures will combine with
dewpoints dropping into the 40s resulting in afternoon RH values down
to between 20 and 30 percent. A few hours of westerly wind gusts up
to 20 to perhaps briefly 25 mph are anticipated. Given Tuesday`s
rainfall and marginal criteria, will fall short of needing fire
weather headlines. Many locations are close to or already at full
green-up.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024.
RI...Air Quality Alert until 11 PM EDT this evening for RIZ003-004-
     006>008.
MARINE...None.

&&

$$
SYNOPSIS...Frank/EVT
NEAR TERM...Frank/RLG/EVT
SHORT TERM...EVT
LONG TERM...Frank
AVIATION...Frank/EVT
MARINE...Frank/EVT
FIRE WEATHER...Staff



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