514
FXUS61 KBOX 161748
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
148 PM EDT Sun Jun 16 2024

.SYNOPSIS...
High pressure will bring dry and pleasant Father`s Day.
Dangerous heat and humidity arrives on Tuesday and peak in the
Wednesday through Friday time frame. Near to record breaking
high temperatures are possible with afternoon Heat Indices
between 95 and 105 degrees. Not much relief at night with near
record breaking warmest low temperatures and heat indices still
in the 70s.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Forecast is on track with a beautiful morning in progress across
southern New England. We`re just starting to see some of those
high clouds make their way into the region, and this will
continue to filter more sun through the afternoon as clouds
increase.

Previous Discussion...

* Plenty of sunshine with highs mainly in the middle-upper 70s
  but upper 60s to lower 70s on the immediate eastern MA coast

Upper level ridge and high pressure continues to build into the
region from the west. A passing weak 500mb shortwave will bring
some high clouds and filtered sunshine to the region late in
the day. All in all, today will be another gorgeous day with
highs mainly in the middle to upper 70s...but developing sea
breezes will hold afternoon highs in the upper 60s to lower 70s
along portions of the immediate coast.. Dewpoints mainly in the
40s will make it feel very comfortable this afternoon. Winds
will also be also be light as they turn from northerly to
southerly late in the day. Sea breezes along the coast will
develop this morning into the afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight:

High pressure remains over the region leading to another night of
good radiational cooling. Clear skies and light winds will allow for
overnight lows to drop into the low 50s. The only thing keeping the
region from dropping into the 40s again is dewpoints will be on the
rise due to light southerly flow. With rising dewpoints, there could
be isolated patches of fog overnight.

Tomorrow:

Upper level ridge continues to build over the region with high
pressure still overhead. 850mb temps will be on the rise to +15C
ahead of the dangerous heat and humidity expected mid week. Winds at
the surface will also continue to increase out of the south at 10 to
15 mph, gusting 20-25 mph. This will bring high temperatures back up
into the low to mid 80s with dewpoints in the low 60s. Winds should
be strong enough to keep sea breezes at bay except near the south
coast where southerly winds will enhance the sea breeze and bring
cooler daytime temps in the 70s to southern RI and SE MA.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Points...

* Dangerous Heat & Humidity Tue through Fri...Near Record High Temps
* Excessive Heat Watch Issued...Potential for Heat Indices of 105+
* Main risk for scattered showers/t-storms Fri and/or next weekend

Details...

All the model guidance continues to be very consistent and in
excellent agreement on dangerous heat and humidity beginning
Tuesday...peaking in the Wed through Fri time frame. The models
indicate 500 mb height fields approaching 600 dm...which is rarely
seen in our region and a strong signal for the potential of record
heat. This is also supported by the NAEFS & EPS Situational
Awareness tables...which indicates several parameters outside the
models climatology. That is another strong signal for the potential
of a rare/highly unusual weather event...in this case being heat and
humidity.

The ensemble guidance supports near record highs well into the
90s...perhaps touching 100 degrees in spots. If that were to
occur...we would challenge all time record highs for the month of
June in spots. The only possible relief would be if localized sea
breeze are able to develop along portions of the very immediate
coast. Either way...the main story will be several days of dangerous
heat & humidity. Afternoon Heat Indices will reach into the 95 to
105+ degree range. There will not be much relief at night with heat
indices only dropping into the 70s.

We opted to issue an Excessive Heat Watch in the Tue through Fri
time frame for the Lower CT River Valley as well as the lower
elevations of northeast MA/Merrimack Valley away from the immediate
coast. This is where our confidence is highest in the potential for
105+ Heat Indices. This Watch might certainly need to be expanded in
later forecasts...but at the very least Heat Advisories will
eventually be needed away from the immediate south coast,
Cape/Islands.

The strong upper level ridge will tend to result in mainly dry
weather for much of the week. That being said...given near record
high temps we can not rule out mainly diurnally driven widely
scattered showers/t-storms. The main threat though for scattered
showers/t-storms will not arrive until Fri and/or next weekend
depending on when a cold front drops south into the region.

&&

.AVIATION /18Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

18z TAF Update...

This afternoon: High Confidence.

VFR. Light S winds. Localized sea breezes near the coasts.

Tonight: High Confidence

VFR, calm/light southerly winds. Low chance for patchy fog to
develop.

Monday:

VFR. Increasing southerly winds at 10-15 knots, gusting 20-25
knots.

Monday night: Diminishing SW winds 5-10 kts.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: VFR. Breezy.

Tuesday Night: VFR.

Juneteenth: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA, slight chance TSRA.

Wednesday Night: VFR. Breezy.

Thursday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today and tonight

Clear conditions and light southerly winds. Seas around 2-4
feet.

Monday:

Continued clear conditions with increasing southerly winds at
10-15 knots, gusting 20-25 knots.

Outlook /Monday Night through Thursday/...

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

Tuesday through Wednesday Night: Winds less than 25 kt.

Thursday: Winds less than 25 kt. Slight chance of rain showers,
slight chance of thunderstorms.

&&

.CLIMATE...
All Time June High Temperature Record (Daily)

BOS - 100 F (06/06/1925, 06/26/1952 and 06/30/2021)
BDL - 100 F (06/26/1952, 06/30/1964)
PVD - 98 F  (06/25/1943, 06/15/1945 and 06/30/1945)
ORH - 98 F  (06/26/1952)

Most recent day of 100 F (or greater)

BOS - 100 F (07/24/2022)
BDL - 100 F (07/21/2019)
PVD - 100 F (07/28/2020)
ORH - 102 F (07/04/1911)*

* For ORH this is the only 100+ degree day in its period of record.

Daily High Temperature Records...

June 18th

BOS - 94 F (1907 and 1929)
BDL - 95 F (1957 and 1994)
PVD - 94 F (1929)
ORH - 93 F (1907 and 1929)

June 19th

BOS - 96 F (1923)
BDL - 95 F (1995)
PVD - 94 F (1923)
ORH - 93 F (1923)

June 20th

BOS - 98 F (1953)
BDL - 97 F (2012)
PVD - 95 F (1941)
ORH - 93 F (1953)

June 21st

BOS - 96 F (2012)
BDL - 96 F (1953 and 2012)
PVD - 96 F (1941)
ORH - 91 F (Multi-Years)

Daily Warmest Low Temperatures Records...

June 18th

BOS - 72 F (1929)
BDL - 70 F (1905)
PVD - 72 F (1929)
ORH - 69 F (1905 and 1994)

June 19th

BOS - 73 F (1995)
BDL - 72 F (1929)
PVD - 70 F (1995)
ORH - 72 F (1929)

June 20th

BOS - 78 F (1931)
BDL - 74 F (1931)
PVD - 74 F (1931)
ORH - 72 F (1931)

June 21st

BOS - 80 F (2012)
BDL - 73 F (1923 and 2012)
PVD - 75 F (2012)
ORH - 74 F (1923 and 2012)

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Excessive Heat Watch from Tuesday afternoon through Friday
     evening for CTZ002-003.
MA...Excessive Heat Watch from Tuesday afternoon through Friday
     evening for MAZ003-005-006-010-011-013-014.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Frank/KP
NEAR TERM...Frank/BW/KP
SHORT TERM...KP
LONG TERM...Frank
AVIATION...Frank/BW
MARINE...Frank/KP
CLIMATE...BL/Dooley