044 
FXUS61 KBOX 172302
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
702 PM EDT Sun Jul 17 2022

.SYNOPSIS...
A frontal system will bring numerous showers and scattered 
thunderstorms Monday into Monday evening, especially in the 
interior. A few strong storms are possible along with locally heavy 
rainfall. Uncomfortable heat and humidity follows for the rest of 
week. The peak is on Thursday when it will be oppressive. A 
cold front brings us another shot for widespread showers and 
thunderstorms on Thursday. Drier weather returns Friday and 
perhaps into Saturday but the hot weather should persist.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

7PM Update

Showers and thunderstorms that flared up along the sea-breeze
boundary this afternoon have since ended. Forecast remains on
track and no changes are needed with this update. Warm and muggy
conditions expected overnight. See previous discussion for more
details.

Previous Discussion...

A few showers and t-storms continue to develop across
eastern MA into RI. Locally heavy rainfall is the primary 
threat but some hail is possible with some of the stronger 
cores. SPC mesoanalysis indicating 0-6km shear 25-30 kt which is
a bit stronger than anticipated and has resulted in a few 
stronger storms. The risk for convection will continue across 
eastern New Eng through the afternoon with sea breeze boundaries
serving as a focus for storms. 

Any leftover convection will dissipate this evening leading to a 
mainly dry night. Leading edge of convection ahead of shortwave may 
spill into western New Eng toward daybreak. It will be a humid night 
with lows in the 60s to near 70 in the urban centers. Stratus and 
patchy fog may develop along the south coast and Cape/Islands.

&&

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

An active day is in store as a potent mid level trough for mid July 
approaches from the west and acts on anomalous PWATs 2 to 2.25". It 
appears there will be 2 periods of showers and t-storms. The first 
will be in the morning with the warm front with scattered showers 
and a few t-storms lifting across mainly interior SNE although some 
activity is possible along the coast. Then a second period of 
potentially stronger storms will be possible in the afternoon 
depending on the extent of destabilization. There is some 
uncertainty with how unstable it gets Mon afternoon due to morning 
convection and expected cloud cover which could be a limiting 
factor. However, guidance is suggesting MLCAPES up to 1000 J/kg 
which would be more than enough for additional storms to develop in 
high PWAT airmass. Heavy rainfall is the primary threat with main 
focus across the interior, especially CT into interior MA. The hi-
res guidance is indicating potential for 1-2 inches of rain with 
localized amounts up to 3 inches in this region. Antecedent 
conditions remain very dry so overall flood threat remains low, 
although urban areas in CT and interior MA would be most at risk for 
flooding due to locally heavy downpours. Considerably less rainfall 
across eastern MA and RI where just scattered showers or an isolated 
t-storm is expected but not a washout.  

There is also the threat for a few strong to potentially severe 
storms if enough instability is realized as 0-6km shear increases to 
30-40 kt. Forecast soundings show sufficient 0-3km CAPE and 
increasing low level wind field/helicity which presents a low risk 
for a brief tornado given high dewpoints in the lower 70s and low 
LCLs. Always have to extra cognizant in these tropical environments 
when there is sufficient low level winds/shear. 

Cloud cover will likely limit temps to the upper 70s to lower 80s, 
but portions of eastern MA/RI could reach mid 80s or even a bit 
higher if there is more sunshine than expected given warm low level 
temps. Oppressive humidity levels with dewpoints into the lower 70s. 

Monday night...

Mid level trough passage expected Mon night. HREF CAM members are 
not especially bullish on nighttime convection. However, we expect 
some additional shower and t-storm activity with locally heavy 
rainfall possible given high PWATs and modest forcing for ascent. 
Warm and humid night with lows mid 60s to lower 70s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...

* Hot and dry Tuesday and Wednesday
* Becoming very hot and humid Thursday with thunderstorms possible
  Thursday afternoon.
* More hot/dry weather next weekend

Tuesday and Wednesday

Mid-level short-wave trough axis shifts east of southern New England 
by Tuesday morning. This will induce a deep WNW flow pattern over 
southern New England for Tuesday and Wednesday. WNW flow ushers 
drier air over the region with PWATs only around 75 percent of 
normal. This will keep skies mostly clear. Temperatures at 925 hPa 
are forecast to be around 25C which will translate to high temps in 
the upper 80s to low 90s at the surface. In addition to the heat, 
winds may be gusty at times Tuesday afternoon as well. Winds at 925 
hPa are forecast to be above 30 mph. With steep low-level lapse 
rates, we can expect some of these stronger wind gusts to mix down 
to the surface. 30 mph gusts are not out of the question for some 
locations Tuesday afternoon.

By Wednesday the pressure gradient relaxes a bit which will result 
in the gusty winds diminishing. Temperatures continue to climb with 
925 hPa temps rising above 26C. Expect high temperatures Wednesday 
afternoon to be a bit higher than Tuesday in the low to mid 90s. 

Thursday

Strong southwesterly flow develops ahead of an approaching upper-
level trough axis by Thursday. This will result in increasing heat 
and humidity. GFS is forecasting temps at 925 hPa to be near 30C! 
This would be supportive of another day with high temps in the low 
to mid 90s. What will separate Thursday from Wednesday in terms of 
heat will be the significant difference in humidity. With the strong 
southwest flow developing, surface dewpoints are expected to rise 
into the low-mid 70s. Thus as Thursday approaches, we'll be 
monitoring closely for potential heat headlines as temps/dewpoints 
of this magnitude could result in heat indices over 100 degrees. 

In addition to the heat, we'll also be monitoring Thursday for 
potential thunderstorms. The high temps and dewpoints will support 
an unstable atmosphere with CAPE values likely exceeding 1000 J/Kg. 
There is fair agreement among the global models that a cold front 
will be pushing through southern New England sometime Thursday 
afternoon. Depending on the strength of the front and the magnitude 
of deep-layer shear in the atmosphere, we may have a period of 
active weather Thursday afternoon/evening. Confidence is low at this 
time frame, but this is a day we'll be keeping an eye on as the week 
progresses.

Friday and next Weekend

Hot and dry on Friday behind an exiting cold front. Heat expected to 
continue into next weekend with more highs in the upper 80s/low 90s. 
Models are hinting at some weak upper-level disturbances that may 
produce a chance for afternoon showers/storms on Saturday and 
Sunday. No strong signals for severe weather or wash outs at this 
time.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:

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

Through 00z...

VFR, except patchy MVFR cigs over Cape/Islands with IFR 
possible at ACK.

Tonight...Moderate confidence. 

Areas of stratus likely developing over the Cape/Islands and 
portions of the south coast, but not certain how far north these
lower cigs get. Any lower cigs may be confined south of PVD- 
TAN- PYM. Elsewhere, expect VFR conditions. Scattered showers 
or an isolated t-storm may spread into western New Eng toward 
daybreak.

Monday...Moderate confidence.

MVFR/IFR cigs likely persisting along the south coast and
Cape/Islands. Elsewhere, cigs expected to lower to MVFR/IFR late
morning through the afternoon as showers and sct t-storms
develop and move across the region, but likely focused more in
the interior.

Monday night...Moderate confidence.

MVFR/IFR with scattered showers and t-storms, with some
improvement after midnight. SW gusts to 25 kt 

KBOS...High confidence in TAF. 

KBDL...Moderate confidence in TAF. 

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR. Breezy. 

Wednesday: VFR. 

Wednesday Night: VFR. Breezy. Slight chance SHRA.

Thursday: VFR. Windy with local gusts up to 30 kt. Chance SHRA,
isolated TSRA.

Thursday Night: VFR. Breezy. Slight chance SHRA.

Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Persistent SW flow through Monday night. Increasing winds late Mon 
into Mon night with gusts 25-30 kt developing as a modest low level 
jet develops. Patchy fog may reduce vsbys tonight. Scattered showers 
and t-storms possible Mon afternoon into Mon night.

Outlook /Tuesday through Friday/... 

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas up to 5 ft. 

Tuesday Night through Wednesday Night: Winds less than 25 kt.
Areas of seas approaching 5 ft. 

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers, isolated thunderstorms. 

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of rain
showers, isolated thunderstorms. 

Friday: Winds less than 25 kt. Areas of rough seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 PM Monday to 8 AM EDT Tuesday for 
     ANZ231-236-250-251.
     Small Craft Advisory from 5 PM Monday to 8 AM EDT Tuesday for 
     ANZ232>235-237-254>256.

&&

$$
SYNOPSIS...KJC/RM
NEAR TERM...RM
SHORT TERM...KJC
LONG TERM...RM
AVIATION...KJC/RM
MARINE...KJC/RM