559
FXUS63 KMQT 151805
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
205 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 MONDAY/...
Issued at 313 PM EDT Mon Jul 14 2025

The low-level front continues to linger in the area Wednesday into
Thursday, with consensus supporting the surface portion of it
sagging mainly south of the area. This will result in sharply cooler
temperatures by Wednesday, with highs stuck in the 60s (and maybe
even 50s closer to the still below-normal temperatures of Lake
Superior) over most of the northern half. Additional rounds of
showers and perhaps thunderstorms are expected along the front, with
LREF and NBM guidance suggesting a 50-60% chance for an additional
0.5" of rain Wednesday through Thursday morning across the western
half of the UP. Latest 12z Euro Ensemble suggests a 50-70% chance
for total rainfall amounts >2" between Wednesday and Thursday
morning along the spine of the Keweenaw southwest across the Porkies
into far northern Wisconsin. Showers begin to wrap up Thursday
morning/afternoon, kicking off a gradual drying trend for the end of
the week as high pressure builds in the wake of this front, with
temps likely rebounding closer to normal Friday into Saturday.

&&

.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 326 PM EDT Mon Jul 14 2025

Visibility will continue to be reduced in areas of fog and wildfire
smoke into tonight. Winds will remain below 20 kts through
Tuesday. However, they will increase to 20-25 kt from the north
to northeast on Wednesday mainly across the western half of the
lake with the remainder of the lake in the 15 to 20 kt range
into Thursday. After that, light and variable winds will prevail
into the weekend. Rounds of showers and thunderstorms will be
possible, though, on Tuesday and Wednesday with the potential
for damaging winds and large hail in any storms that do form.
Plus, there is potential for fog where rainfall occurs.

&&

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

&&

$$

SHORT TERM...BW
LONG TERM...BW
AVIATION...BW
MARINE...TDUD