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682
FXUS63 KMQT 241727
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
127 PM EDT Fri May 24 2024

.KEY MESSAGES...

- An approaching low pressure system will bring a round of
  showers and a slight chance (around 20% chance) for some
  thunder to Upper MI this afternoon into early Saturday.

- There will be more opportunities for rain next week although
  model uncertainty leads to low forecast confidence on
  timing/extent.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 536 AM EDT Fri May 24 2024

Current GOES-16 Nighttime Microphysics RGB imagery shows mostly
clear skies with a small band of low to mid level clouds streaming
southeast across the Keweenaw toward Alger County. Clear skies
continue as a 1012 mb ridge builds slowly east, allowing nighttime
temperatures to decrease to the mid-40`s across the UP. Closer to
the Lake Superior shoreline, onshore flow has encouraged nighttime
lows in the high 30`s and low 40`s.

A 996 mb low, currently centered on eastern North Dakota, will move
northeast throughout the day; ensemble analysis estimates the low
will deepen slightly to 994 mb by the time it reaches the Canada-US
border around 00Z Saturday. As this mid-level trough progresses,
cloud cover will move in mid-afternoon, and gales will begin to
build into far western Lake Superior. Expect winds on Lake Superior
to peak around 20Z, reaching around 35kt sustained and gusting to
40kt, then to diminish to 20kt sustained gusting to 30kt over the
next 6 hours. Modeled radar reflectivity suggests rain showers
moving into the western UP by 20Z tonight and persisting through
early Saturday morning. Six-hour QPF`s are between 0.07 and 0.54 in
through Saturday 12Z, with most precipitation being concentrated in
Menominee and Dickinson Counties. As vorticity streamers from the
low trough pass east through the UP, models show successive bands of
rain, with the bulk of precip arriving in the early Saturday morning
hours.

Successive model runs have brought this system into the CWA more and
more slowly; so we may expect to be slowed even further as this mid-
level trough lifts into Canada. Regarding thunderstorm potential,
the 00Z HREF differs somewhat on available instability, with the
mean MUCAPE remaining below 500 J/kg until 00Z Saturday. However,
with the maximum SBCAPE values around 500 J/kg by 00Z Saturday in
the west, a few rumbles of thunder are expected, but severe weather
can be ruled out.

&&

.LONG TERM /TONIGHT THROUGH THURSDAY/...
Issued at 333 AM EDT Fri May 24 2024

Upper air pattern consists of a deep 500 mb trough on the west
coast, a negatively tilted shortwave and closed 500 mb low in the
upper Mississippi Valley 00z Sat. This shortwave heads northeast
into the upper Great Lakes 12z Sat and across Ontario on Sat night.
Upper troughing then remains over the area into 12z Mon as more
energy comes out of the west coast trough and keeps troughing over
the area. A wave of pcpn will come in tonight and move out late
tonight into Sat morning with dry weather moving in for most of
Saturday before the next system moves in for Sun. There are some
pops that could make it into the far west by Sat evening and have
slights in there to cover it. Otherwise, did not make too many
changes to the going forecast.

In the extended, the GFS and ECMWF and Canadian all show a 500 mb
trough in the Great Lakes region 12z Mon which moves to the lower
Great Lakes region 12z Tue. Ridging then moves into the northern
plains 12z Wed and into Thu. Upper troughing then moves into the
northern plains 12z Fri. Temperatures look to be near normal for
this forecast period. Only prolonged dry period looks to be Wed for
now. With troughing, does look unsettled.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
-- Changed Discussion --
Issued at 127 PM EDT Fri May 24 2024

VFR conditions prevail at all TAF sites so far, but rain showers
working into the area beginning at IWD early this evening will
result in deteriorating ceilings and -SHRA. -SHRA arrive at CMX by
00Z, and at SAW by 03Z. There is around a 25-35% chance for TSRA as
well, so VCTS remains in the forecast at all terminals. With the -
SHRA, IWD is expected to fall to MVFR with a 25% chance of IFR while
SAW and CMX are expected to fall to IFR with 20-25% chances of LIFR.
Current model guidance does not suggest LLWS at any of the TAF
sites, but some LLWS may be more prevalent over Lake Superior where
the LLJ may be stronger tonight. A quick improvement to MVFR and
then VFR is expected from west to east as showers move out after
06Z. Otherwise, expect gusty winds mainly out of the south at IWD
and CMX this afternoon and evening. Winds turn calmer behind the
passing wave tonight, shifting over to the SW.
-- End Changed Discussion --

&&

.MARINE...
Issued at 333 AM EDT Fri May 24 2024

East winds will begin to ramp up to 20 to 30 knots today in advance
of another low pressure lifting from the Northern Plains towards
Lake Winnipeg. Northeast gales to 35 knots will continue across the
far western part of the lake today. Winds over the west half
becoming southwest behind the low and the passage of its cold front
late tonight into Saturday and generally stay in the 15 to 25 knot
range. Winds decrease late Saturday behind the exiting system, then
expect light winds of 20 knots or less across Lake Superior for the
rest of this weekend as a high pressure ridge builds over the area.
Looking ahead to early next week, another system moving out of the
Plains will head towards the Great Lakes.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 8 PM EDT /7 PM CDT/ this evening for LSZ162.

Lake Michigan...
None.

&&

$$

SHORT TERM...GS
LONG TERM...07
AVIATION...LC
MARINE...07