802
FXUS63 KMQT 172329
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
729 PM EDT Sun May 17 2026

.KEY MESSAGES...

- Warmer than normal temperatures continue through early this
  week.

- A strengthening pressure gradient is bringing a period of
  gales to far western Lake Superior early this evening.

- Multiple rounds of showers and thunderstorms are expected tonight
  through Tuesday. Some of the storms could be severe,
  especially over the southern half of the U.P. on Monday. Heavy
  rainfall is also possible.

&&

.DISCUSSION...
Issued at 224 PM EDT Sun May 17 2026

A deep trough is analyzed digging through the Northern Rockies with
sharpening southwesterly flow across the Plains. Within this flow,
MCV is currently observed moving through Wisconsin with another
impulse over North Dakota. For our forecast area, this has resulted
in high clouds streaming into the region and light rain lifting into
Menominee/Delta counties where proximity to the MCV to the south is
smallest. Temperatures have been observed in the 40s and 50s so far,
under easterly winds in the west, and northerly central and east.

The main forecasting challenge continues to be the results of the
deep trough lifting across the Plains and its subsequent impact on
MCS development, the ongoing MCV along and just to the north of a
northward lifting warm front, and a surface low lifting northeast
through the forecast area Monday night into early Tuesday. The
ongoing MCV and a warm front are expected to lift northeast through
Wisconsin today, with the front lifting into the forecast area
tonight. This will result in showers gradually lifting into the
southern and eastern UP associated with the MCV and then
thunderstorms this evening/tonight. Instability doesn`t increase
significantly until around 0z tonight. Elevated MUCAPE eventually
builds to 1000-1500j/kg while 0-6km bulk shear builds to 40-50kts
late evening and tonight, which should sustain showers and
thunderstorms associated with any upstream development closer to the
front; however, strong to severe potential will be limited by
marginal effective shear. Should a stronger storm occur, primary
hazards will be damaging winds and hail. Latest HREF suggests the
best timing for stronger storms focuses on this evening in Menominee
County and then mainly in the west after midnight tonight. PWATs are
also expected to climb to 1-1.5 inches across the region. Model
soundings suggest a deep warm layer, with 1-1.2k feet freezing
heights. Additionally, MBE velocities suggests some training
potential. WPC positions the region within a marginal risk for flash
flooding because of the risk posed by these. Early Monday morning,
the front will lift through, positioning the forecast area within
the warm sector for the day. This will support gradual
destabilization as we warm into the upper 70s to low 80s and
dewpoints climb into the 60s. Afternoon northwesterly flow and
possible lake breeze may limit warming along Lake Superior. Latest
CAMs favor a mostly dry day, save for any diurnally, lake breeze, or
outflow (from convection well to the south) enhanced convection
occuring interior west/south-central by afternoon. Latest guidance
suggests timing for the second wave is most likely Monday
evening/overnight and will come with a better organized thunderstorm
potential and higher risk for severe weather. SPC continues to
include the CWA within their 15% risk region (slight risk), with
primary hazards being large hail and damaging winds. WPC also
continues to maintain a marginal risk for flash flooding with this
second wave.

Showers and gusty winds will linger Tuesday as the surface low and
trough aloft push through the region. Thunderstorm potential looks
to be isolated to the east in the morning. Sprawling high pressure
builds in by evening, keeping the region dry through at least Friday
morning. Daytime highs Wednesday look to peak in the 50s south and
west, and 40s north-central and east. Thursday and Friday will trend
back toward normal 60s, but the east may only top out in the 50s
both days.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 728 PM EDT Sun May 17 2026

Conditions tank at the terminals this evening as a warm front
presses into the area from the southwest tonight. As it does so,
expect SHRA and TSRA to rumble through the area, with LLWS being
seen at SAW for several hours and potentially an hour or two at IWD
and CMX as well. LIFR to near airport min conditions are projected
across the TAF sites tonight into Monday morning. As we remain under
the warm sector on Monday, we could see SHRA and TSRA redevelop over
the area throughout the day. However, chances for convection during
the day Monday are much lower (think PROB30) when compared to the
chances tonight. Expect to see some improvement in flying conditions
on Monday, especially at SAW which may get into MVFR by Monday
afternoon. However, upslope flow into IWD and CMX may keep these
terminals socked-in at LIFR cigs for the remainder of the TAF
period. Expect the E`rly winds to start out the period to veer with
time tonight, eventually becoming S`rly Monday morning and N`rly by
the end of the period Monday evening.

&&

.MARINE...
Issued at 224 PM EDT Sun May 17 2026

Guidance continues to bring a low pressure into the Great Lakes
Monday night, resulting in a tightening pressure gradient today and
cold air advection Tuesday behind the low. The former will support a
period of northeasterly gales in the western portions of Lake
Superior this afternoon and evening. Shower and thunderstorm chances
increase tonight, then linger until the low passes Tuesday morning.
The first wave comes tonight across the east and then the west late
tonight, both potentially lingering into Monday morning. Strong to
severe storms can`t be ruled out, the lack of effective shear within
the cloud layer suggests the risk is marginal. The next organized
cluster lifts through Monday night preceded by a warm and moist
airmass. This will again support strong to severe storm potential
and rainfall may be the trigger needed for overnight fog. In the
wake of the low Tuesday, a second period of gales looks possible
across eastern Lake Superior; although, ensemble guidance suggests
the probability in the east being 25% or less. Once the winds settle
Tuesday night/Wednesday, light winds are favored through at least
Friday morning.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 11 PM EDT /10 PM CDT/ this evening for
     LSZ162.

Lake Michigan...
None.

&&

$$

DISCUSSION...JTP
AVIATION...TAP
MARINE...JTP