737
FXUS63 KDLH 201736
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1236 PM CDT Sat Jul 20 2024

.KEY MESSAGES...

- Backdoor cold front today brings a chance for showers and
thunderstorms. No severe storms expected. Some fog could develop
overnight into Sunday morning.

- Hazy skies persist with smoke mostly aloft.

- Next best chance for rain and thunderstorms late Monday into
Tuesday.

&&

.DISCUSSION...
Issued at 409 AM CDT Sat Jul 20 2024

An area of upper level troughing continues to extend across much of
the eastern half of the CONUS, emanating from a cut off low near
southern Hudson Bay. This low will bring a back door cold front
marching from north to south across the area today, currently
located just north of the International Border and over far northern
Lake Superior. This cold front is expected to bring a line of
showers and thunderstorms today, most intense in the afternoon and
early evening as they are helped along by around 1000 J/kg of
MLCAPE. Shear is minimal however and severe storms are unlikely. It
will be a fairly moist and warm environment with up to 1.5" of PW,
freezing levels around 7-8kft, and surface temperatures in the low
80s. Corfidi vectors are slow, generally less than 10 knots and the
cold front should progress slowly as well. This could make for some
torrential downpours in the storms that do pop up. CAMs suggest that
under the best storms over 1.5" is possible. This will need to be
closely monitored for very localized overland flooding - if it
occurs it will not be widespread.

With the loss of daytime heating, the coverage of any showers and
thunderstorms should decrease fairly dramatically. The only shower
activity would be expected to remain along the cold front itself,
which should steadily push southward, and the best chance of any
precipitation would be along the southern edges of the CWA. Some
dense fog could develop overnight into Sunday morning. Sunday, any
re-invigoration of shower or thunderstorm activity will be kept
along and south of the front, which should limit itself to the
southern tier of our counties. Elsewhere, dry air behind the cold
front should keep much of the area fairly precipitation free.

Smoke aloft remains through the weekend, due to wildfires in Canada.
HRRR and RAP smoke output suggests a little smoke could mix down to
the surface along with our passing cold front, but concentrations
are not expected to be high.

A stouter shortwave sweeps down across the area Monday into Tuesday,
which could bring the next chance for any widespread precipitation.
There could be some stronger storms if convection timing aligns with
the best instability, and some heavy downpours could be possible
once again.

Looking ahead, our area continues to be outlooked in good chances
for above normal temperatures into early August. Some normal to
below normal temperatures could be possible mid week, but another
warm up seems likely into next weekend with highs well into the mid
to upper 80s, and possibly 90s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1235 PM CDT Sat Jul 20 2024

A weak front dropping slowly south across the region this
afternoon and evening will help generate some scattered showers
and storms around the terminals. Have put in initial estimate of
timing with VCTS groups for now, but expect to need to make
adjustments. Expect a repeat of fog again tonight, and have
included some IFR/MVFR fog at the terminals generally in the
04z-13z time frame. There may be showers that linger along the
boundary overnight, but confidence in affecting any of the
terminals is low and have left out for now. It should sag to
just south of the area by 15z, so the newer diurnally driven
convection should stay away from the terminals.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 409 AM CDT Sat Jul 20 2024

Winds turn to become northeast today, picking up behind a cold front
that pushes from north to south across Western Lake Superior today.
This could lead to some stronger gusts around 15 knots in the
afternoon, mostly for the Twin Ports, South Shore, and Apostles
area. Some afternoon thunderstorms are possible as well, which could
bring some gusty winds, small hail, heavy downpours, and lightning.
Any gusts should quiet overnight, but winds remain northeast into
Sunday as well. Some slightly stronger gusts up to 15 knots could be
possible once again Sunday as the northeast wind is reinforced by
the afternoon on shore lake breeze. We`ll see winds turn southerly
winds once again into Monday.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...None.

&&

$$

DISCUSSION...Levens
AVIATION...LE
MARINE...Levens