840
FXUS63 KMQT 151921
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
321 PM EDT Tue Jul 15 2025

.KEY MESSAGES...

- Thunderstorms will progress across the western UP this
  evening. Strong to severe storms will be capable of producing
  damaging winds and large hail. Training thunderstorms may
  cause localized flash flooding.

- Sharply cooler Wednesday into Thursday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 204 PM EDT Tue Jul 15 2025

Afternoon RAP analysis and GOES satellite imagery reveal a "calm
before the storm" as morning convection has cleared the UP and sunny
skies have allowed for surface based instability to build upwards of
3000 j/kg atop 60-70 degree dewpoints. Upstream, a slow moving cold
frontal boundary has begun to redevelop convection in far western
Lake Superior. This boundary will be the focal point for strong to
severe storms this afternoon and evening as they progress eastward
across the UP. While CAM guidance doesn`t have much of a handle on
the ongoing convection in the western arm of the lake, current
thinking is this line will continue developing into the western
shorelines over the next several hours before diving south-east into
the central UP counties this evening. With increasing bulk-shear
upwards of 35-45 kts, organized convection and embedded supercell
features with the upscale growth will bring all severe weather
hazards to the table, including damaging winds and hail. Cannot rule
out a brief spin up since model soundings showing some modest
curvature in the 1-3 km range, especially in the west, though the
probability is still quite low (<2%). Guidance suggests this line
will peter out as it pushing into the central third with the loss of
diurnal instability. While not the main hazard concern, training
thunderstorms along the slow moving boundary may produce several
inches of rain under the strongest convection. This is highlighted
by both the HREF and REFS ensembles, where 6 hrly PMM shows 1-3"
across much of the west and Keweenaw by midnight. Give then more
anafrontal structure, additional showers and non-severe
thunderstorms will linger overnight.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 320 PM EDT Tue Jul 15 2025

By Wednesday morning, the cold front will have pushed south out of
the UP, ushering in a much cooler airmass. Daytime highs will be
noticeably cooler than the previous couple as northerly flow helps
cool the western half to the upper 50s and low 60s. Elsewhere across
the s-central and eastern third, temps are expected to peak close to
70. Lingering anafrontal showers and sub-severe storms will be the
rule for much of Wednesday into Thursday. 12z HREF and latest NBM
guidance suggest a 50-70% chance for an additional 0.5" through
Thursday morning across the west-central UP and Keweenaw, with
higher probabilities for at least 0.25" for the entire Upper
Peninsula. Thursday will remain on the cool side as well with this
reaching the upper 60s to low 70s, coolest in the west-central.

As the parent trough and embedded shortwaves passing through the
western Great Lakes depart east Thursday afternoon dry weather will
finally return to the region, keeping things quiet and seasonable
through Friday. A transient shortwave within the broad zonal flow
aloft may touch off some showers on Saturday before quiet/dry
conditions return Sunday into early next week. From there,
deterministic guidance varies on the timing and strength of
additional shortwaves traversing the Upper Midwest. Long range
ensembles point towards positive height anomalies building in the
eastern CONUS while slightly negative anoms fall in the PNW /
northern Rockies, leaving the Upper Great Lakes in a favored
position for passing shortwaves and active weather through mid-late
July.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 204 PM EDT Tue Jul 15 2025

Showers and thunderstorms progressing through far western Lake
Superior ahead of a cold front will continue east this evening,
impacting IWD first ~18-19z, then CMX ~21z, and eventually SAW
closer to 00z. Some storms could be strong to severe. Behind the
frontal passage, additional showers and non-severe thunderstorms are
expected to develop and linger into Wednesday. With an already moist
low-level airmass overhead, additional expected rainfall, and
cooling temperatures behind the front, cigs will lower at all sites
overnight to IFR or potentially LIFR.

&&

.MARINE...
Issued at 320 PM EDT Tue Jul 15 2025

Winds will shift northerly tonight as the cold front pushes south
over Lake Superior and stalls over northern Wisconsin. With the
stalled front in place periods of showers and thunderstorms are
expected through early Thursday morning over Lake Superior. Some of
the thunderstorms this afternoon and tonight could produce damaging
winds and large hail. Northeast winds gusting to 25kts will develop
over western Lake Superior tonight, with gusts to 20kts central and
east. Areas of fog are possible this evening and overnight with rain
falling into a moist marine airmass. Any fog that forms should
diminish on Wednesday as drier air filters into the Upper Great
Lakes. The northerly flow should help clear out much of the wildfire
smoke tonight and Wednesday. Winds will become light Wednesday night
through the weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...BW
LONG TERM...BW
AVIATION...BW
MARINE...NL