926
FXUS63 KDLH 202024
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
324 PM CDT Fri Sep 20 2024

.KEY MESSAGES...

-Quiet conditions are expected this evening into tonight with
 mostly clear to clear skies.

-Showers and thunderstorms develop late tonight into Saturday morning.
 Severe weather is not expected Saturday morning.

-A second round of thunderstorms are likely Saturday afternoon
 and evening, mainly over northwest Wisconsin. A few storms may
 become strong to severe, capable of producing damaging winds
 and large hail.

-Quiet and dry weather returns on Sunday and is likely to
 persist through this upcoming week.

&&

.DISCUSSION...
Issued at 324 PM CDT Fri Sep 20 2024

Compared to the active conditions that were seen yesterday, today
has been much more benign as high pressure briefly builds in a post-
frontal environment. A stratus deck that advected into the CWA
earlier this morning has been gradually scattering out this
afternoon. Expect mostly clear to clear skies overnight with low
temps cooling into the mid 40s to mid 50s. Localized areas of fog
will be possible tonight, but the potential is low (25% chance).

A strong southerly LLJ of around 35-40 knots is expected to develop
tonight ahead of approaching low pressure, which will result in WAA
and moisture advection into the CWA. Scattered showers and isolated
thunderstorms are likely to develop in the morning hours on Saturday
along a warm front, which will be lifting northward through the
area. This morning round of convection is expected to remain sub-
severe as CAPE will be minimal around 100-200 J/kg. Following the
warm frontal passage in the morning, temperatures will be warming
into the low to mid 70s on the Minnesota side of the CWA and the
upper 70s to low 80s on the Wisconsin side.

A second, stronger, round of convection is likely to develop on
Saturday afternoon along a cold front that will be sweeping through.
Ahead of this cold front, mid-level lapse rates will be increasing
to around 7-8 degC/km on Saturday afternoon. Since this cold
frontal passage will be coinciding around the time of peak
diurnal heating, MUCAPE is progged to increase into the
1500-1800 J/kg range over northwest Wisconsin by mid-afternoon.
0-6km bulk shear will also be favorable tomorrow at around 30-35
knots. These favorable convective parameters support the
potential for a few strong to severe storms in northwest
Wisconsin.

The one potential mode of failure to mention for tomorrow`s severe
weather chance is a moderately strong warm nose appearing in CAM
soundings around 750mb. This warm nose, resulting from the strong
LLJ, may limit vigorous updraft development and winnow the
potential for severe weather. SPC currently has portions of
northwest Wisconsin under a Marginal Risk for severe
thunderstorms tomorrow. Potential hazards tomorrow include
damaging winds up to 60 mph and large hail up to 1 inch in
diameter.

Following the cold frontal passage on Saturday afternoon and
evening, a quiet pattern will settle over the CWA with high pressure
building on Sunday. The only notable feature in the extended period
is a shortwave trough that will be propagating east on Monday. This
shortwave may bring a slight chance of rain to the area as a cutoff
low develops over the northern Plains and quickly dives south.
Otherwise, little to no other chances for precip are expected.
Looking out over the next 2 weeks, the Northland is favored to have
above-normal temperatures and below-normal precipitation.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1241 PM CDT Fri Sep 20 2024

Lingering MVFR cigs from this morning are expected to become VFR as
stratus scatters. There is a slight chance for fog development
tonight (25% chance), most likely in HIB. Introduced MVFR vsby in
HIB for tonight, but kept conditions VFR elsewhere. Scattered
showers with isolated thunderstorms move in Saturday morning
with conditions expected to remain VFR, except in areas of
moderate rain. Strong southerly winds aloft ahead of approaching
low pressure will likely lead to LLWS for DLH, BRD, and HYR
tomorrow morning.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 324 PM CDT Fri Sep 20 2024

Breezy southwest winds observed over western Lake Superior this
afternoon are expected to ease over the next couple hours. Winds
will be shifting to the northeast on Saturday morning with speeds
around 5 to 10 knots with gusts up to 15 knots. Scattered showers
with isolated thunderstorms will be possible on and off through the
day Saturday over the lake.

Expect another wind shift to occur on Saturday evening with winds
becoming northwesterly. A tightening pressure gradient will increase
wind gusts up to around 25 knots across much of western Lake
Superior on Saturday night into Sunday morning. Small Craft
Advisories will likely be needed. Waves will be highest on Saturday
night in the outer Apostle Islands with heights around 2-4 feet.

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...Small Craft Advisory until 4 PM CDT this afternoon for LSZ140-
     145>147-150.

&&

$$

DISCUSSION...Unruh
AVIATION...Unruh
MARINE...Unruh