336
FXUS63 KMQT 171920
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
320 PM EDT Tue Jun 17 2025

.KEY MESSAGES...

- Showers and a few thunderstorms are possible Wednesday, mainly
  across the central and east.

- A hot and humid airmass is expected over Upper Michigan this
  weekend into early next week. Those sensitive to heat,
  especially those without effective cooling and/or hydration,
  may be impacted.

- Hot and humid conditions will support daily thunderstorm
  chances most days this weekend and early next week.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 148 PM EDT Tue Jun 17 2025

Early afternoon RAP analysis and GOES satellite imagery reveal
decent clearing across the UP as a sfc low continues its
northeastward departure towards far southern James Bay. This feature
is dragging a weak cold front across the east UP, though mostly
sunny skies are allowing temps to climb into the low 70s to near 80
across the interior. Through the rest of this afternoon and evening,
the building mid-level ridge should keep the CWA dry with partly
cloudy skies. Peak afternoon temps will continues to climb into the
mid to upper 70s area wide and low 80s s-central. Nearby Lake
Superior, expect a nice day around 70.

The next shot at precipitation arrives late tonight through
tomorrow as a shortwave trough lifts out of the Rockies and into the
Great Lakes. Underneath the entrance region of this shortwave, an
unseasonably strong sfc low (NAEFS MSLP 10th percentile) is expected
to develop in the central Plains, tracking across the Mississippi
River Valley and into Lower Michigan by late Wednesday/early
Thursday. Ahead of this system, S to SW flow will allow ample
moisture advection and the development of rain showers; however,
despite the event being a day away, guidance is in poor agreement on
the overall system track and thus rainfall amounts. Previous 00z and
06z ensemble probability guidance and meteograms hinted at the s-
central UP receiving a localized 2-4" of rain but this signal is now
nearly gone as the latest 12z guidance has continued a southward
trend, focusing heaviest precip amounts in lower MI. 12z HREF
guidance and individual CAMs hint at a line of convection likely
aided by a lake breeze, developing across the central UP. With
MUCAPE values >500 j/kg and PWATs 0.75-1.25", locally heavy rainfall
amounts 1-2" may be realized where thunderstorms activity persists
the longest.

Otherwise, seasonable temperatures are expected with highs in the
mid to upper 70s across the interior, slightly cooler near the
lakeshores.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 320 PM EDT Tue Jun 17 2025

A cold front is expected to press southeastward, moving into the
forecast area on Thursday. This front will swing through Upper
Michigan Thursday afternoon and evening, likely resulting in
scattered showers and thunderstorms across the region. Anomalous
ridging then begins to build into the east and central CONUS coupled
with low heights out west, setting up a "Ring of Fire" pattern that
is expected to persist through much of the weekend into the
following week. A strong, long duration low level jet will enable a
continuous feed of warm and moist Gulf air into the Upper Great
Lakes. Weak perturbations embedded within the W/NW flow aloft aim to
enhance daily thunderstorms chances Friday through Sunday, though
there are some questions of whether or not enough forcing will be
realized to overcome a strong capping inversion. If we are able to
break the cap, extreme instability >2000 j/kg (particularly Sat/Sun)
coupled with marginal deep-layer shear hints at the potential for
strong to severe thunderstorm development.

Additionally, this patterns looks to setup our first real heat wave
of the year. NBM temperature guidance (which may be running a little
hot due to its spring to summer bias correction) points towards a
significant warm up come this weekend with daytime temperatures
pushing into the 90s Sat/Sun, slightly cooling overnight with low
temps in the upper 60s to around 70. If this increased temp trend in
guidance continues, 100F would not be out of the question on Sunday
where downsloping off of the higher terrain could aid in further
warming. This heat wave will be exacerbated further by a stout
increase in surface dewpoint as high as the 60s to near 70,
elevating heat indexes near or above 100F in the hottest locations.
Southerly flow off of Lake Michigan may keep the nearby lakeshore
adjacent east half in the low 80s.

Those with heat sensitivity and or a lack of cooling options may
want to consider preparing as above normal temperatures may persist
into the following week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 148 PM EDT Tue Jun 17 2025

VFR conditions should prevail through the rest of the 18z TAF period
as drier air aloft has filtered into the UP behind a departing low
pressure system. IWD has stubbornly held onto very borderline MVFR
cumulus ceilings, however, this should continue to rise and
eventually scatter out this evening. Gusty W to NW winds upwards of
20 kts may persist at all TAF sites this afternoon, especially at
SAW, but are expected to diminish this overnight as we decouple.
Another low skirts into Lower MI towards the tail end of the TAF
period bringing chances of showers and t-storms. At this time, have
opted to leave any impacts out of this TAF issuance.

&&

.MARINE...
Issued at 320 PM EDT Tue Jun 17 2025

East to southeast winds of 15-25 kts this afternoon will continue to
diminish, settling below 15 kts by Wednesday morning. This should
allow for lingering 4+ ft waves over the northeastern waters to
settle below 3-4 ft by this evening. Winds then remain light and
variable 15 kts or less through Thursday night with fairly benign
pressure patterns.

Stronger flow returns over the weekend as deeper troughing develops
to the west of the Great Lakes. This results in easterly winds
across the lake increasing up to around 20 kts at times Friday and
Saturday. Similar magnitude winds on Sunday are expected out of the
south, veering southwest to west for Monday. Thunderstorm potential
also returns over the weekend.


&&

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

&&

$$

SHORT TERM...BW
LONG TERM...BW
AVIATION...BW
MARINE...Jablonski