787
FXUS63 KMQT 050856
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
456 AM EDT Sun May 5 2024

.KEY MESSAGES...

-Dry conditions expected Sun/Mon, though mostly low winds and
 antecedent rainfall should broadly limit fire concerns.
-Complex pattern setup for the midweek as multiple low pressure
 systems interact in the Midwest. Precipitation chances highest
 on Tuesday, but PoPs linger through the end of the week.
 Thunder potential highest Tuesday and Wednesday.

&&

.SHORT TERM /TODAY/...
Issued at 455 AM EDT Sun May 5 2024

Ridging/subsidence has overspread the UP early this morning in the
wake of a shortwave and associated cold front.  Thus, clearing has
commenced, and radiational cooling is rapidly dropping temperatures
across the west/southwest. As a result, forecast update will be
issued to match developing trends. In addition, patchy fog may
need to be added along the WI/MI border of that western sector
as well, will continue to monitor. For the remainder of today,
height rises will result in clear skies and plenty of sunshine
and a pleasant day with high temperatures climbing into the mid
50s to mid 60s (coolest along Keweenaw and Lake Superior
lakeshore). Ample mixing and heating will contribute to RH
values just below the 30% mark along the WI/MI border, but
antecedent rainfall will help to mitigate the threat.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 346 PM EDT Sat May 4 2024

Sunday, 500mb heights begin to rise as ridging builds over the Upper
Midwest, contrasted with troughs over Hudson Bay and the western
CONUS. The ridge over the midwest will support a 1020mb high
pressure settling over the Upper Great Lakes through late Monday.
This will give the UP as a whole its driest stretch of the last few
weeks with high confidence of no precip through at least early
Tuesday morning. The main forecast concern will be how dry the
airmass gets for Sunday and Monday, as efficient mixing and
radiative heating under clear skies will allow RHs to fall. As the
mixed layer rises to near 7kft in the interior west Sunday
afternoon, RHs look to fall just below 30 percent. Using the NBM
10th percentile of dewpoints to calculate RHs Monday gives RHs
falling to the lower 30s. With mostly light winds below 10 mph
gusting to 15 mph expected (and CAMs even suggesting a lake breeze
off of Lake Michigan) along with prior rainfall, fire weather
concerns should be fairly low.

The trough over the west becomes a bowling ball closed 500mb low as
it emerges on the other side of the Rockies Monday, negatively
tilting as it does. Height falls over the Northern Plains cause
500mb height anomalies over Montana and North Dakota to fall to -26
dam. This will support strong lee cyclogenesis, with the 12Z GEFS
showing a near-980 mb low over the Northern Great Plains. Meanwhile,
a near-120kt 300mb jet will be on the south side of the parent
trough, with divergence aloft supporting cyclogenesis further south.
Ensemble clusters bring this secondary low pressure into the Upper
Great Lakes at roughly 990s mb, but there is considerable spread as
to the interaction of these two low pressures, the timing and
strength of each, and the implications of each variable. Ensembles
vary significantly on thunder potential, with especially the 00Z
Canadian ensemble suite having multiple members with ~1000 J/kg of
SBCAPE in the afternoons of Tuesday and Wednesday, but other members
have instability never overcoming any caps. Given the uncertainty,
did not deviate from NBM PoPs, which bring up to 90% PoPs Tuesday
afternoon for much of the UP, falling off by Wednesday morning to
near 30%. PoPs never truly fall off through the week as enough
ensemble solutions have low pressure stalling near the Great Lakes
to warrant at least 15-25% PoPs into the weekend. Peeking beyond the
next week, ensembles favor ridging over the western CONUS and
troughing over the eastern CONUS, leaving the UP in a somewhat drier
northwesterly flow pattern, reflected in each CPC precipitation
outlook to favor below normal precip through the end of May.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 122 AM EDT Sun May 5 2024

Expect conditions to generally improve from MVFR to VFR early this
morning over KSAW as the low-level cloud cover continues to leave
the area. As for KCMX, some patchy FG looks to remain over the area
until after sunrise this morning. KIWD could see some patchy fog as
well; however, with low-level water vapor imagery showing very dry
air overhead, we could see conditions remain VFR throughout the rest
of the pre-dawn hours. VFR conditions remain over the TAF sites
through the rest of today.

&&

.MARINE...
Issued at 346 PM EDT Sat May 4 2024

Behind showers today, high pressure settling over the Upper Great
Lakes through Monday will cause winds to remain below 20 kt. Monday
evening, developing low pressure systems over the Great Plains will
compress the pressure gradient and cause northeasterly wind gusts to
funnel near Duluth Harbor to 20-25 kt. As low pressure approaches
Lake Superior Tuesday and into the midweek, wind gusts up to 30 kt
are forecast. There is gale potential if the low pressure tends to
be on the stronger side of guidance and the low tracks directly over
Lake Superior, but probabilities are currently only around 20% for
widespread, frequent gusts over the gale force threshold.
Uncertainty in the forecast increases greatly into the later
portions of the week, though winds are currently expected to be
around 20 kt in the wake of the low pressure.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory until 2 PM EDT this afternoon for LSZ250-
     251.

Lake Michigan...
None.

&&

$$

SHORT TERM...TDUD
LONG TERM...GS
AVIATION...TAP
MARINE...GS