883
FXUS63 KMQT 132003
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
403 PM EDT Tue May 13 2025

.KEY MESSAGES...

- Hot and dry conditions continue in the western UP through this
evening.

- Some pop-up showers and thunderstorms expected in the west half
Wednesday afternoon.

- A soaking rainfall moves over the UP Thursday into the weekend. A
Marginal (1 of 5) to Slight (2 of 5) Risk of severe thunderstorms is
expected Thursday PM.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 137 PM EDT Tue May 13 2025

GOES-East visible imagery shows clear skies over much of the UP,
save for some clouds approaching from the southeast associated with
disturbed weather across much of the eastern CONUS. 500mb RAP
analysis shows a pair of cutoff lows over the CONUS, one centered
over Paducah, KY and another over eastern OR/northern NV/southwest
ID. Ridging to the north of the eastern cutoff low is going to cause
enough subsidence to keep the UP dry for yet another day. As most
model guidance has been too low on high temperature guidance lately,
this forecast will reflect the 90th percentile of available guidance
for highs today, putting a number of areas in the west
(especially Ontonagon County) into the 90s with widespread mid-
upper 80s except for within about 20 miles of Lake Michigan and
the immediate shorelines of Lake Superior, where cooling
influence from the Great Lakes will keep highs in the 70s to low
80s (a few 60s degree highs in the Bays de Noc). Partly cloudy
skies aloft should keep RHs from bombing too much but without
the cooling influence of Lake Michigan, much of the western
third of the UP will still fall into the 20s RH range (10-20%
chance of some sub-20% RH values in typical dry spots). A
slackened surface pressure gradient (only about 5 mb across the
whole UP) and winds aloft generally sub-20 kt near the top of
the mixed layer will keep winds manageable at the surface. RHs
then recover overnight as lows across the UP fall to around the
mid to lower 50s.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 402 PM EDT Tue May 13 2025

Most significant pattern change occurs in the later portions of this
week. Aforementioned cutoff low pressure negatively tilts as it
progresses into the Northern Plains by Thursday afternoon. That
trough will wobble over the vicinity of Lake Superior Friday into
Saturday before deamplifying and shifting to the Lower great Lakes
Saturday night. By this point, broad weak ridging separates that
trough with another deep trough over the interior northwestern
CONUS, and while ensembles vary in the exact details, the
general consensus is that it will follow a similar track,
reaching the Northern Great Plains around next Tuesday. This
combination of being in the path of robust troughs aloft will
keep disturbed weather chances in the forecast for much of the
next week.

Beginning Wednesday, the eastern CONUS cutoff low will weaken and
wobble northerly, continuing to advect some cloud cover to the UP in
spite of broad ridging remaining over the area. The western UP will
be far enough away from the forcing to have less cloud cover,
allowing for destabilization throughout the day, with the 00Z HREF
showing around 500 J/kg of SBCAPE building over the western UP
Wednesday afternoon. This will allow for around 30 percent chances
of pop-up showers (with some thunder) primarily for Ontonagon and
Gogebic counties, though some 15 to 30 percent PoPs have been kept
for much of the western UP to cover some stray showers. Given a lack
of meaningful shear, these will be sub-severe, "garden variety"
thunderstorms, should any thunder occur. The QPF will be variable
depending on where exactly the showers set up, but so far the most
likely scenario is about 0.05" for the western third of the UP with
isolated pockets of around a tenth of an inch in the cores of
stronger showers. Fire weather is not expected to be a major concern
tomorrow with surface winds mainly under 10 kt sustained and
gusts under 15 kt and cloud cover helping moderate high
temperatures somewhat and keep deep mixing from messing with RHs
too much. However, if a lightning strike occurs away from a
precipitation core, that could present a wildfire risk.

PoPs then begin to ramp up Thursday afternoon into the evening ahead
of the approaching trough over the Plains. Strengthening warm
southerly flow ahead of the trough will help destabilize the
interior west once again, with 00Z GEFS/GEPS probs of 1000 J/kg of
SBCAPE by 00Z Friday up to 50 percent, though the ENS has much lower
probabilities. Shear is not overwhelming, but generally curving
hodographs (SE at surface, SSW at 700 mb, SW by 500mb) will
help organize the convection for at least a marginal risk of
severe weather. Soundings show a pretty dry HGZ, suggesting hail
might struggle to develop, but DCAPE values of around 700 J/kg
do highlight the wind threat. With the best low level shear
being displaced from the lowest LCLs, tornadoes cannot be ruled
out, but wont be the primary threat, perhaps around 5%. A more
widespread QPF footprint is expected with the Thursday PM
precip, with around 0.2 to 0.5 inches of rain expected, highest
where the stronger showers/thunderstorms go over, particularly
south-central.

A dry slot is expected to move over the area Friday morning before a
secondary round of showers moves over the UP as the system crawls
through the region. Because of how nebulous the evolution of this
system is and fairly zonal flow behind the system, spread increases
in the forecast beyond then, but NBM PoPs of 20-50% throughout
Friday PM to Saturday early PM indicate a wetter period. Troughing
over the west pushes the weak central CONUS ridge (and resulting low-
1020s mb surface high) over the UP and dry weather returns to end
the weekend and to kick off the next work week. Attention then turns
upstream to the next low pressure to eject out of the Plains, but
spread is very high in the track of such a feature at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 137 PM EDT Tue May 13 2025

SKC conditions at all TAF sites this afternoon under a dry
airmass. Low level moisture streams in from a broad disturbance
over the eastern CONUS shifting north tonight, bringing MVFR
conditions to CMX and SAW (with SAW 50 percent likely to drop
ceilings to IFR by 10Z). IWD has lower chances at MVFR, but
cannot be ruled out (20%). While some improvement in the flight
categories at CMX and SAW is expected in the late morning/early
afternoon, pop-up -SHRA with 20 percent chances of TSRA will be
in the area near IWD beginning around 18Z.

&&

.MARINE...
Issued at 402 PM EDT Tue May 13 2025

High pressure will keep sub-20 kt gusts in the forecast until
Thursday afternoon, when a low pressure passing along the northwest
shore of the Lake will ramp gusts to 25 kt, first out of the
northeast in the west half of the lake and then out of the east
across the northern extent of the lake. Winds then briefly relax
below 20 kt until post-low winds out of the northwest ramp up to 25
kt again Saturday through early Sunday. Uncertainty then grows in
regards to the next low pressure moving out of the Plains. With the
low pressure on Thursday, some thunderstorms may (15%) bring strong
and erratic winds and frequent lightning.

&&

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

&&

$$

SHORT TERM...GS
LONG TERM...GS
AVIATION...GS
MARINE...GS