Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 152014
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
414 PM EDT Fri Jun 15 2018

.SYNOPSIS...
Dry weather continues this weekend with a warming trend each
day. Dangerous heat and humidity is expected Monday along with
record high temperatures. As a result heat headlines will likely
be needed. A warm front may trigger scattered showers and
thunderstorms Sunday night followed by a second round of storms
possible late Monday into Monday night, possibly lingering into
early Tue. Then turning less humid later Tue behind the
departing front. Not as hot Tue thru Thu with highs in the 80s
along with lower humidity.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Skies have started to clear out from the north as dry air is
pushed south into the region by NW winds. Light rain showers
linger along the southern coast but should be dissipating and
offshore in the next couple hours, along with the cloud cover.

Temperatures east of the Worcester hills have remained in the
upper 50s/low 60s for most of today due to northeasterly winds
and cloud cover. With clearing skies, it`s possible that some
areas may see a brief spike in temperatures before sunset.

Skies will continue to clear out across the region as
a high pressure system builds in from the southwest. Skies
should be mostly clear by midnight, which will allow for some
radiational cooling, especially across northern MA. Lows will
likely be in the low to mid 50s, and possible upper 40s at
higher elevations.

Fog may form early tomorrow morning across the Cape and Islands.
BUFKIT model soundings show an inversion overhead, but if winds
at the surface pick up it may be difficult for fog to linger.
Hi-Res models show very low probabilities of visibilities less
than 5 mi across the region.

Cannot rule out the possibility of some patchy fog in the
northern Connecticut River valley early tomorrow morning.
Current guidance is hinting at some minor visibility
restrictions.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...

Sat...
Dry and clear conditions tomorrow as a high pressure builds
into the region, keeping dew points in the 50s. The ECMWF
suggests 18z and 00z 2M temps reaching into the low to mid 80s.
It`s possible that some areas could reach into the upper 80s
given weak winds and little cloud cover.

Sat night...
Winds become westerly-southwesterly as the high pressure pushes
southeast away from New England. Given minimal cloud cover, low
dewpoints, and light winds at the surface, we could see yet
another night of radiational cooling across the interior,
dropping lows into the 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...

* Showers & T-storms possible Sun ngt & Mon ngt otherwise dry
* Dangerous heat and humidity Mon along with record high temps
* Turning less humid and not as hot Tuesday thru Thursday next week

Details...

Saturday night and Sunday...

Dry NW flow aloft over the area along with rising heights. High
pressure south of New England provides light winds. This combined
with mostly clear skies and dew pts in the 50s will support
radiational cooling with mins 55-60, very comfortable for mid June.
By Sunday warm 591 dam ridge remains to our west across the OH and
TN valleys with airmass gradually warming here in southern New
England as 850 temps climb to about +15C Sunday. Thus highs well
into the 80s are expected with a few locations in the CT and
Merrimack river valley approaching 90. Although with warm front and
warm sector airmass remaining west of New England Sunday, dew pts
begin the day in the 50s and touch 60 by days end. Thus humidity
will be tolerable.

Sunday night...

Warm front moves across the region and may trigger scattered showers
and T-storms (elevated instability) as 591 dam ridge over the OH and
TN valleys begins to move east. Given the WNW flow aloft some of the
model guidance suggest a possible MCS in the ring of fire around the
top of the ridge into New England. Although at this time range can`t
add much more detail than that and will have to monitor as Sun ngt
approaches. Warm and more humid than previous nights.

Monday...

As warm front moves east Mon morning true warm sector airmass
overspreads southern New England by midday with dangerous heat and
humidity. Both ECENS and GEFS ensembles advect +20C air at 850 mb
into the region with higher res deterministic guidance pushing
+21C/+22C at 850 mb! This will support mid to upper 90s away from
the south coast. These temps will be sufficient to break record
highs for the day. In addition this excessive heat will combine with
dew pts surging into the lower 70s which will result in heat indices
greater than 100F. Thus will likely need heat advisories for heat
indices of 100-104F with highest values in the CT and Merrimack
valleys. Thus looking at a potential dangerous heat event Monday.
The only mitigating factor that may reduce the effects of the
dangerous heat will be a gusty WSW wind of 15-25 mph that may take
some of the edge off the extreme heat. Northern stream short wave
and attending cold front enter the region late Mon/Mon night and may
trigger scattered showers/T-storms. However with prefrontal blyr
winds westerly, low level convergence will be limited and may
restrict areal coverage to isolated or widely scattered.

Tuesday thru Thursday...

Risk of showers/T-storms early Tue ahead of approaching front.
However a trend toward lower humidity and not as hot begins later
Tue behind FROPA. Still warm Tue - Thu with highs in the 80s but dew
pts lowering into the 50s, making for much more pleasant conditions.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...

Tonight...High confidence for interior, low confidence for the
Cape and Islands

VFR west of the Worcester hills. Areas of MVFR/IFR across the
eastern interior and Islands. With clearing to the south,
conditions will improve to VFR into the evening.

Possible IFR conditions early tomorrow morning across the Cape
and Islands due to fog, but will likely lift around 12z.

Sat...High confidence.
VFR across the region. Winds out of the W at or below 10 kt.
Low risk for E coast sea breezes.

KBOS Terminal...High confidence in TAF.
MVFR conditions improving to VFR into the evening. Winds E-NE.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday through Wednesday/...

Saturday Night: VFR.

Sunday: Mainly VFR, with local MVFR possible.

Sunday Night: Mainly VFR, with areas MVFR possible. Breezy.
Slight chance SHRA, slight chance TSRA.

Monday through Monday Night: Mainly VFR, with local MVFR
possible. Breezy. Slight chance SHRA, slight chance TSRA.

Tuesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...

Tonight into Sunday: Light NW winds and diminishing seas.
Slight risk for some fog development along the Cape and Islands
early tomorrow morning, but should dissipate shortly after 12z.

Saturday Night: WNW winds less than 25 kt.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kts.

Sunday Night: Winds less than 25 kt. Seas locally approaching 5
ft. Slight chance of rain showers, slight chance of
thunderstorms.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Slight chance of rain showers,
slight chance of thunderstorms.

Monday Night: Winds less than 25 kt. Local rough seas. Slight
chance of rain showers, slight chance of thunderstorms.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.

&&

.TIDES/COASTAL FLOODING...
Early morning high tides are astronomically high again early
Saturday morning, running about 12.1 ft in Boston Harbor. With
this past high tide cycle, an additional 0.8ft was observed.
Tonight, wave action offshore is lessened, but easterly flow is
expected through the day. Therefore, we could see another round
of very minor coastal flooding with the high tide Sat morning.
Once again, impacts should only be to typically prone locations,
but enough to warrant a second Coastal Flood Advisory.

&&

.CLIMATE...
With increasing heat and humidity early next week, high
temperatures may approach or exceed record levels on Monday.

Here are the record highs for Monday June 18...

Boston/BOS          94 degrees set in 1907 and 1929
Windsor Locks/BDL   95 degrees set in 1957 and 1994
Providence/PVD      94 degrees set in 1929
Worcester/ORH       93 degrees set in 1907 and 1929

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory from midnight tonight to 4 AM EDT
     Saturday for MAZ007-015-016-019-022-024.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Nocera/Correia
NEAR TERM...Correia
SHORT TERM...Nocera/Correia
LONG TERM...Nocera
AVIATION...Nocera/Correia
MARINE...Nocera/Correia
TIDES/COASTAL FLOODING...
CLIMATE...



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