777
FXUS63 KMQT 201151
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
751 AM EDT Sun Apr 20 2025

.KEY MESSAGES...

- A wintry mix late tonight through Monday night could lead to
  some slick roads for the Monday morning commute. Chances of 3+
  inches of snow are only 10-40% in the high terrain of the
  western and north-central UP.

- Rain and snowmelt will continue to lead to rises on area
  rivers and possible minor flooding on typically flood-prone
  rivers.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 508 AM EDT Sun Apr 20 2025

A swath of dry air can be seen across Upper Michigan early this
morning on water vapor imagery with surface analysis indicating 1031
mb high pressure centered over the U.P. As a result, the current
radar mosaic is quiet and will remain that way through the duration
of the short term period. Partly cloudy skies will prevail for
the majority of the day, but expect an uptick in cloud coverage
from the southwest late in the day as low pressure deepens over
the Missouri Valley. Meanwhile, high temperatures will top off
in the low to mid 50s across much of the U.P. except along the
lakeshores and Keweenaw, which will only be in the mid 40s.
Currently, ground-based obs across the forecast area are
generally reporting temperatures in the mid to upper 20s with
some outliers in the upper teens/low 20s due to significant
radiational cooling this morning under clear skies.

&&

.LONG TERM /TONIGHT THROUGH SATURDAY/...
Issued at 428 AM EDT Sun Apr 20 2025

A low pressure system around 1003mb over N MO this evening deepens
overnight to 1000mb by Mon morning over S-Central WI. During this
period, isentropic ascent/WAA and the right entrance region of an
upper level jet will support -ra overspreading the UP from the S.
Cooling aloft occurs Mon morning as the negatively tilted mid level
trough and strong low level f-gen arrive. This starts a wintry mix
of sn/pl/ra over the W and N-Central; some -fzra is also possible in
the N-Central early on Mon (50% chance). This early-mid morning
period is when the greatest lift yields the heaviest precip across
the UP, depositing 0.6-1.0" of QPF. Overall, this system brings
ample moisture noted in the NAEFS mean WV transport showing values
above the 90th climatological percentile. System QPF is expected to
range between 0.75"-1.25". The trough continues lifting NE over the
UP through the day, sending the sfc low over E Upper MI. Ra
continues over the S and E, but the wintry mix gradually transitions
over to sn from W to E through the day. Some gusty E becoming NW
winds are expected on Mon gusting up to 20-30mph. Otherwise, lows
tonight settle into the low to mid 30s with highs on Mon expected in
the upper 30s to upper 40s.

Where there still is some uncertainty yet in the fcst is how fast
the wintry mix is able to kick in and how much will actually stick
on roads and sidewalks. The GFS/HRRR are quick to begin a wintry mix
early on Mon and change p-type over to mainly sn over the W. The
HRRR is quite the extreme solution, especially with the E extent of
sn accumulations in the UP. ECMWF is similar on timing to the GFS,
but favors more of a wintry mix than pure sn. The NAM has a slower
onset of wintry mix to sn, and the CMC/RAP are even slower.
Regardless, all deterministic solutions have some sn accumulation
over the W spine of the UP with ranging totals moving E. Latest
ensemble probabilities of at least 3" of wet snow range from 0-50%
over the far W...not exactly helpful. Given the likely transition to
more widespread sn would occur after sunrise, warm sfc temps would
limit accumulations on roads and sidewalks. Thus, the NBM
probabilities of 3" or more is likely the best representation as it
shows only 10-40% chances over the high terrain of the W and N-
Central. The going fcst represents up to 1-2" of wet sn accumulation
in the high terrain of the W and N-Central, but mainly less than
0.5" over the W/N-Central. May need a SPS to account for slippery
conditions during the Mon Morning commute.

Ridging moving in from the W gradually returns dry weather to the UP
Mon night into Tue. That said, this dry period will be brief as a
shortwave and associated low pressure system over the N Plains on
Tue pivot NE sending a weak occluded front through the area. Some
-ra is possible late in the day Tue into Wed morning (30-50%
chance). Then, PoPs slowly increase to 30-50% for Thu night into Fri
as a weak low pressure system emerges off the Rockies and tracks
over the Great Lakes. There is some spread on track, however ra is
the expected p-type. Otherwise, expect warmer than normal temps for
most of the extended fcst. Highs for much of the UP rise well into
the 50s with some 60s possible near WI. The warmest day will be Wed
when some mid 60s are anticipated in the interior W. Lows generally
settle into the 30s above freezing.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 750 AM EDT Sun Apr 20 2025

VFR conditions through late afternoon/evening at which point MVFR
cigs will be possible as a low deepens over the Missouri Valley.
Will highlight initial onset of system/precipitation with a PROB30
until confidence is high enough for prevailing MVFR and eventually
IFR/LIFR by tonight. Winds will slowly shift to the east through the
course of the TAF period but won`t become strong until tomorrow
morning, especially at SAW and CMX. Sustained speeds will be above
12 kts, and gusts up to 25 kts can be expected at CMX.

&&

.MARINE...
Issued at 428 AM EDT Sun Apr 20 2025

High pressure over the Great Lakes will keep winds 20 kts or less
through this evening. Easterly winds increase to 20-30 kts by Monday
morning as a low pressure moves to Wisconsin. From there, the low
continues northeast over eastern Upper Michigan to Northern Ontario
by Monday evening. This backs winds north through the day, then
northwest Monday night. Some gale force gusts to 35 kts are possible
across the lake (20-50% chance), particularly at high observing
platforms. Winds over the far west settle below 20 kts Mon evening
with the remaining portions of the lake settling below 20 kts from
west to east through Tuesday morning. The remainder of the work week
looks to remain 20 kts or less across the lake.

Peak wave heights are expected on Monday around 4-8ft across the
lake. Waves settle below 4ft from west to east Monday night into
Tuesday.

&&

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

&&

$$

SHORT TERM...TDUD
LONG TERM...Jablonski
AVIATION...TDUD
MARINE...Jablonski