257
FXUS61 KBOX 161920
AFDBOX

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

.SYNOPSIS...
High pressure will bring dry weather and warming temperatures
to start the week. 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 AM MONDAY MORNING/...

High level cirrus clouds continue to stream overhead as a weak
shortwave rounds the ridge. Meanwhile the radar is clear except for
one feature of note: the leading edge of the seabreeze moving north
into RI and southeast MA. More of the same quiet weather is expected
tonight under high pressure with mostly clear skies. This will allow
for some radiational cooling once again, though slightly warmer
dewpoints thanks to southerly flow will limit it a bit. Lows dip
into the low to mid 50s.

&&

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

Mid level ridging continues to build over the region which, along
with surface high pressure shifting east, will start to further warm
the airmass overhead. 850 mb temps increase from 9C this afternoon
to 16C by Monday afternoon. This translates to high temperatures in
the low to mid 80s for many. The exception will be for much of Rhode
Island and southeast MA where increasing southerly flow off the
water will hold temps in the 70s. It will feel more humid on Monday
as dewpoints increase from the 40s today to the upper 50s/low 60s.
Monday night southwest flow continues to increase dewpoints a few
degrees keeping lows quite mild, in the low to mid 60s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
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 /19Z SUNDAY THROUGH FRIDAY/...
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 /Tuesday through Friday/...

Tuesday through Wednesday Night: VFR. Breezy.

Thursday through Thursday Night: VFR. Breezy. Slight chance
SHRA, isolated TSRA.

Friday: VFR. Slight chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

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.

Monday night: Clear conditions with slowly decreasing southwest
winds 10-15 kts. Seas 2-4 ft.

Outlook /Tuesday through Friday/...

Tuesday: Winds less than 25 kt.

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

Juneteenth: Winds less than 25 kt.

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

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

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

Friday: Winds less than 25 kt. Slight chance of rain showers,
isolated 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/BW
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Frank
AVIATION...Frank/BW
MARINE...Frank/BW
CLIMATE...BL