Munising, Michigan Weather Forecast Discussion

054
FXUS63 KMQT 161938
AFDMQT
Area Forecast Discussion
National Weather Service Marquette MI
338 PM EDT Tue Sep 16 2025
.KEY MESSAGES...
- A few showers and possibly a rumble of thunder are possible
  late tonight and Wednesday.
- Warm and humid weather through Wednesday, then more seasonable
  temperatures into the weekend.
- Areas of fog are possible again tonight over central Upper
  Michigan; fog could locally be dense along the Lake Michigan
  shores.
&&
.DISCUSSION...
Issued at 142 PM EDT Tue Sep 16 2025
GOES-East water vapor imagery and RAP analysis show a complex upper
air pattern as an omega blocking ridge over eastern North America
begins to break down with a closed low over the Carolinas and
troughs over Wyoming, southern Manitoba, and northern Saskatchewan
respectively. A minor shortwave embedded in the flow has flattened
out significantly over the western UP, ending the forcing for
isolated showers that have been near the state line this morning. At
the surface, the cold front associated with the surface low
supported by the Canadian troughs is draped over Minnesota.
That cold front will progress east over the next day, but before
it does, warm southerly flow will bring high temperatures
around the 80 degree mark today except for regions along and
upstream of Lake Michigan, where the cooler waters will help
keep highs in the 70s.
Tonight through Monday, as the features aloft all shift east, the
surface cold front drifts into the region. An unfortunately large
spread still persists in the CAMs as to the convective evolution
along the front, with the majority of models showing little to now
shower activity in the early overnight period, but the NSSL WRF
shows showers and the NAM Nest shows thunderstorms over western Lake
Superior by 03Z. With showers moving into a less energetic
environment, only remnant light showers, if any, will be present by
10Z, though some models suggest a return of some upslope-supported
fog over the central UP. Then, Wednesday afternoon, every CAM has a
slightly different timing and placement of CI, but general trends
are either a cluster or line of showers initiating across central
Upper Michigan in the mid afternoon and progressing southward
through the evening. While steep lapse rates suggest an unseasonably
high amount of available instability (mean HREF MUCAPE in excess of
2k J/kg in the interior west UP by 16Z), shear will be lacking as
soundings at ESC suggest sub-30 kt flow throughout the entire
tropospheric column around the time of CI. Thus, should
thunderstorms occur, they would be expected to be disorganized
and sub-severe. Moisture is also unimpressive as even the moist-
biased NAM soundings show little to no saturation above about
4kft. Expect a similar temperature profile on Wednesday as
today, with the exception of the far west and Lake Superior
shorelines sticking in the 70s being in the post-frontal
environment.
Through 00Z Friday, the pattern aloft will resolve by the East Coast
closed low being absorbed into large-scale troughing primarily over
eastern Canada while ridging persists in the eastern Plains and
western Great Lakes, though the ridge will be undercut somewhat by a
negatively tilted trough over the High Plains. The ensembles then
diverge in exactly how that situation diffuses, but generally the
trough will kick the blocking ridge east and the pattern will flow
again. Given that shortwaves will push occasional disturbances
through the area as ridging shifts and weakens, PoPs will be present
in much of the forecast, though differences in the details will mean
that the pattern will not be quite as rainy as the PoPs suggest as
mean LREF total QPF by 00Z next Wednesday is less than 1 inch UP-
wide. The temperature outlook looks to be above normal for lows
(LREF chances of temperatures below the normal lows of 45 is only
around 20 percent) and a little above normal for highs (LREF chances
of exceeding the normal highs of 65 is 90+%, but probability of 75+
is 30% or less).
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 142 PM EDT Tue Sep 16 2025
Primarily VFR conditions are expected during the 18Z TAF period save
for some BR/FG late tonight into Wed morning. This primarily will
impact SAW after 6Z, which has a 20-40% chance of at least MVFR vis
restrictions and a few solutions dropping down to IFR at times near
sunrise. For now, opted to only use a TEMPO group for 4SM BR between
8-12Z. Potential at IWD/CMX was too low to include mention (15-30%
chance for MVFR or lower) at this time. Otherwise, winds gradually
shift from S to SW through tonight. A cold front on Wed brings some
chances for TSRA/SHRA, but confidence in timing and development of
precip was too low to include any mention at this time. This front
also shifts winds out of the NW into the latter part of Wed.
&&
.MARINE...
Issued at 338 PM EDT Tue Sep 16 2025
Southerly winds of 20kts or less are mostly expected on Lake
Superior today, then shift to light westerlies behind a cold front
moving through the region Wednesday. Shower and thunderstorms may
move over the western and central portions of the lake tonight ahead
of the front, which may continue into Wednesday into the eastern
portions of the lake. Winds begin increasing Thursday morning from
the northeast. Guidance continues to suggest winds of 20 to 25kts
may span much of the western half of the lake into Friday night when
they become more widespread and shift to southeasterlies ahead of
the next approaching system from the west. These southeasterlies
become southerlies for the weekend, but look to remain at or below
20kts.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
DISCUSSION...GS
AVIATION...Jablonski
MARINE...GS/JTP

NWS MQT Office Area Forecast Discussion