810
FXUS63 KMQT 190501
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
101 AM EDT Thu Jun 19 2025

.KEY MESSAGES...

- Showers and a few thunderstorms are possible, primarily over
  the central and east this afternoon and evening.

- Showers and storms return on Thursday, strongest over central
  Upper Michigan where there is a marginal risk for a few severe
  storms (5-15% chance).

- Strong to severe thunderstorms will again be possible Friday
  evening and Friday night. There is currently a slight risk for
  severe thunderstorms (15-29%).

- 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.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 322 PM EDT Wed Jun 18 2025

Afternoon RAP analysis and WV imagery show a shortwave over IA/IL,
but weak high pressure is noted over the Upper Great Lakes which has
kept us dry into this afternoon. Less cloud cover earlier in the day
quickly warmed temps well into the 70s to low 80s; cooler by the
lakeshores (upper 50s to 60s) where lake breezes have moderated
temps. While some spots may warm a bit further yet this afternoon,
increasing cloud cover is limiting radiative warming. Instability
has climbed to ~1000j/kg of CAPE. With increasing instability and
the help of the lake breezes, some shra and tsra is already ongoing.
What currently is lacking is stronger large scale lift and wind
shear. Current analysis only shows up to 30 kts of bulk shear over
the E, however guidance suggests this diminishes into tonight. Thus
shra/tsra will be unorganized and not strong. 0.15-0.3" of QPF is
fcst and there is ~25% chance (6/18 12Z HREF) for up to 0.5" in some
spots where convection is able to hold on longer. Stronger
convection with heavier downpours could mix down wind gusts up to 30
mph, despite lacking strong flow aloft given DCAPE is between 600-
900j/kg (lower to the S). The lack of well organized updrafts and
low mid level lapse rates <5.5C/km leaves little potential for hail.
With no additional lift expected after diurnal heating ends, PoPs
drop off into tonight. Temps settle into the mid 40s to near 60,
coldest N.

Thu brings additional shra with better chances for tsra as a
midlevel shortwave moves in from the NW. A strengthening LLJ
provides increasing bulk shear into Thu night and the left exit
region of an ~80kt upper level jet noses in supporting more
widespread ascent. Instability likely will be higher than today with
mean MUCAPE around 1000j/kg over the S-Central, but there are
individual models showing higher values up to ~2000j/kg. CAMs have
slightly backed off regarding the potential for a more organized MCS
developing into the S. Regardless, dry inverted-V soundings do still
support gusty winds in stronger convection and better mid level
lapse rates ~6.5C/km help support some hail potential. The SPC has a
5% chance for severe wind and over the W and Central, but the
primary focus for strong to severe tsra will be in the S-Central
where a lake breeze presses in off Lake MI. Models are otherwise hit
and miss with isolated convection into Thu night. Highs will be in
the 60s and 70s, coldest N. Temps then settle overnight into the
upper 40s to upper 50s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 432 PM EDT Wed Jun 18 2025

Anomalous ridging builds in over the Great Lakes for the weekend
into early next week, shifting E more toward the Atlantic for next
week while fairly persistent troughing holds over the W CONUS. This
pattern favors WAA to bring well above normal temps into the region
(850mb temps 20-22C), which coupled with persistent LLJ fueling the
area with Gulf moisture, supports an increasing unstable atmosphere.
A somewhat subtle shortwave on Fri, stronger PVA to the S, supports
additional shra/tsra potential during the day. Model guidance is a
bit variable on how unstable the airmass will be within the UP at
this time, but wind shear will be sufficient for a few stronger
storms if convection kicks off. The main focus of the extended will
be Fri night into Sat when a more vigorous shortwave upstream
supports convection over N MN which is anticipated to track ESE as
an MCS over the CWA along the frontal zone. Ample moisture will be
present with Tds well into the 60s to low 70s and PWATs increase to
near 1.75-2.00" late. Mid level rates also make an impressive
increase to near 8-9C/km by Sat morning! Wind shear will be high +50
kts as the strong LLJ streams into the UP and good instability will
be present with deterministic solutions reaching up to 1500-2500j/kg
and NBM probabilities of at least 1000j/kg at 25-50% across the UP,
highest SW. Strong to severe storms bringing hail up to 1" and gusty
winds up to 60mph are possible during this period, captured by the
SPC slight outlook over the W 2/3 of the UP and a marginal risk
elsewhere. Beyond this period, mid level ridging and stronger
gradient flow looks to prevent convection into the latter part of
the weekend. The active pattern does return next week as the ridge
moves toward the Atlantic.

Additionally, this patterns looks to setup our first real heat wave
of the year. NBM temperature guidance points toward a significant
warm up come this weekend with daytime temps pushing into the 90s
Sat/Sun/Mon, and only cooling overnight with low temps in the upper
60s to mid 70s. MOS guidance does point to potential for a few spots
reaching near 100F on Sun where downsloping is at play. This heat
wave will be exacerbated further by the moist atmosphere moving in
with Tds warming well into the 60s to low 70s, elevating heat
indices near or just above 100F on Sun! Southerly flow off of Lake
Michigan may keep the nearby lakeshore adjacent east half in the 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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 101 AM EDT Thu Jun 19 2025

With ample low-level moisture especially where we were able to pick
up some rainfall over the past day, patchy fog becomes a concern for
the overnight hours. Partially clearing skies will allow for
MVFR/IFR restrictions first at IWD tonight, then at CMX and SAW into
the early morning hours. After daybreak, conditions improve to VFR
while winds stay generally light and variable. However, there is a
chance for some scattered thunderstorms to develop during the
afternoon and evening hours. As exact track and timing remain
uncertain, have handled these with PROB30 groups for the afternoon.

&&

.MARINE...
Issued at 322 PM EDT Wed Jun 18 2025

The pattern in this forecast period favors mostly light winds of
20kts or less and small waves. However, multiple rounds of
thunderstorms will be possible, especially to round out the week,
which may result in stronger winds. Thunderstorm chances this
afternoon and tonight are mostly limited to near the Lake Superior
lakeshore east of Marquette this afternoon and then again
potentially by sunrise near the Arrowhead; otherwise, mostly dry
conditions are expected. The upstream showers/storms moving in from
Minnesota may hold together as they move across the lake Thursday.
By afternoon, some of the storms moving across the lake could be
strong or severe. Another wave may move across Minnesota into Lake
Superior on Friday, again with strong to severe potential, but there
is greater uncertainty in where this line of storms develops.
If it does, the afternoon into the overnight period would be
favored. If these showers/storms do move over the lake, patchy
fog should also be expected.

&&

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

&&

$$

SHORT TERM...Jablonski
LONG TERM...Jablonski
AVIATION...LC
MARINE...JTP