651
FXUS63 KMQT 180729
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
329 AM EDT Sat May 18 2024

.KEY MESSAGES...

-Breezy south winds and very warm temps in the 70s and 80s today
 ahead of a cold front that will bring scattered
 afternoon/evening thunderstorms. The strongest storms may
 contain small hail.

-Borderline elevated fire weather expected this weekend with breezy
 conditions today then very dry with light winds on Sunday.

-More rain chances early to middle of next week as a series of
 disturbances moves across the area in a developing warm and
 moist southerly flow.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 346 PM EDT Fri May 17 2024

Water vapor imagery and RAP analysis show that the shortwave trof
that brought shra to the area yesterday thru last evening has lifted
across northern Ontario. In the wake of that wave, westerly flow
prevails into Upper MI. An area of sct -shra has been moving out
across western Lake Superior to the Keweenaw in an area of
waa/isentropic ascent. The -shra that have reached the Keweenaw are
really not much more than sprinkles. Elsewhere, skies cleared out
quickly in the morning, but daytime heating led to a blossoming of
cu. Stabilizing marine layer off of Lake MI and Lake Superior are
evident, preventing cu. Temps have risen into the low/mid 70s F in
the interior. Closer to the Lakes, temps range down into the 50s
with some 40s F at lakeside locations along Lake Superior.

Aforementioned waa/isentropic ascent will continue to support some
-shra/sprinkles across the Keweenaw over the next few hrs. MLCAPE
has increased to 100-200j/kg into far western Upper MI. This limited
instability may support development of a few shra/tsra late
aftn/early evening, less than 25pct chc. During the night, vigorous
shortwave that is now over nw MT will swing out to ND. While the
main low-level jet in response to this wave will develop ne thru MN
during the night, there will be a modest increase in 850mb winds
further ne across western Lake Superior this evening. The resulting
increase in waa/isentropic ascent should yield some shra/tsra later
this evening across northern portions of western Lake Superior and
possibly also nw Upper MI, mainly the Keweenaw where fcst reflects
30pct chc. Shra/tsra associated with the main 40-50kt low-level jet
developing across MN would reach western Lake Superior late tonight.
Expect min temps tonight ranging from the lower 40s on the east side
of the Keweenaw and near Lake MI to 55-60F in the southerly wind
downslope areas far w (Ontonagon/Gogebic counties).

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 325 AM EDT Sat May 18 2024

After a continued warm and very dry day on Sunday, the focus then
shifts to a couple of widespread rain events for early/mid next week
before a transition to a period of below normal temperatures by late
week.

Beginning Sunday, surface ridging and its associated much drier air
mass will take hold in the wake of tonight`s frontal passage.
Abundant sunshine and light winds will result in deep mixing into
extremely dry mid-levels during the day. For example, the 18z NAM
fcst soundings valid at 18z Sunday over several of the interior west
half sites show -30C or drier dew points at nearly 800 mb or
approximately 5 kft AGL. Fortunately, surface dew points won`t mix
that low, but by incorporating the local mixed dew point tool I did
cut back on Td values resulting in min RHs closer to 20% across the
interior portions of the cwa. The good news is light winds generally
10 mph or less should ease fire wx concerns. Lake breeze
activity should limit fire wx concerns along the shorelines due
to cooler temps in the 60s and higher RHs. Expect max temps
reaching near 80F over much of the interior west half and mid to
upper 70s over the interior east half.

Models advertise a mid-level trough amplifying over the western
CONUS early next week. Periodic shortwaves in a warm/moist sw flow
developing ahead of the western CONUS trough will bring more rounds
of showers into the area early to mid next week. The first of these
shortwaves moves through late Sun night into Monday bringing the
initial batch of showers adn isolated t-storms for early next
week. Models show this system tapping into Gulf moisture with
PWATs increasing to around 1.5 inches by midday Monday. This
increase in moisture along with increasing isentropic ascent
should lead to widespread wetting rain across much of the cwa.
Ensemble probabilities show much of the area (except maybe the
tip of the Keweenaw) with a 40-60% chance of seeing 0.5 inch of
rain from this system with the greatest chances south central.
After a period of drier weather Monday night into Tuesday
morning, the next shortwave moves through Tuesday afternoon into
Wednesday spinning up a 985-990 mb sfc low which tracks over
the far western portion of the fcst area late Tue night into
Wed. With PWAT values again increasing to nearly 1.5 inches
along with increasing isentropic ascent, PVA and upper
diffluence fcst with the shortwave, expect widespread rainfall
across the area. EPS probabilites again show a 40-60% chance for
getting half an inch of rainfall from this system with the
greatest chances southeast and west.

Despite the midweek system lifting north and east of the area,
models indicate wraparound moisture behind it could support
lingering isolated to scattered showers for late week (Thu-Fri) as
temperatures trend cooler than normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 116 AM EDT Sat May 18 2024

VFR will prevail thru this fcst period at IWD/CMX/SAW. Pcpn
associated with a cold front will move into IWD and CMX by late Sat
afternoon into early Saturday evening.  Gusty winds to 20+kt will
then set in at all sites mid to late morning on Sat.

&&

.MARINE...
Issued at 325 AM EDT Sat May 18 2024

Stable conditions will lead to light winds of generally 20 knots or
less prevailing over the lake into early next week, except for some
20-25 kt southeast gusts today over the east half ahead of an
approaching cold front. Thunderstorms are possible today into
tonight as the cold front marches across the lake. These storms may
contain small hail, gusty and erratic winds, and frequent lightning.
More thunder chances return late Sun night into Monday and then
again late Tuesday into Tuesday night as a series of disturbances
track northeast across the Upper Great Lakes region. Models and
ensembles indicate winds will ramp up Tue night into Wed as a
stronger low pressure center tracks across the western and northern
portions of the lake. Ensemble probabilities show a 40-60 pct chance
of gale force gusts to 35 knots late Tue night into Wed across
western and northern sections of the lake.

&&

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

&&

$$

SHORT TERM...Rolfson
LONG TERM...Voss
AVIATION...07
MARINE...Voss