Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 252053
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
353 PM EST Thu Feb 25 2021

.SHORT TERM...(This evening through Friday)
Issued at 300 PM EST THU FEB 25 2021

A weak and fast-moving shortwave moved through this morning with a
few light snow showers. West northwest winds behind this system
produced a cloud deck around 3kft, which has been shifting east as
drier air moves in aloft. Loss of diurnal heating should allow skies
to clear quickly after sunset. I went close to a blend of raw model
guidance since bias corrected guidance seemed too cold given
southerly winds at the surface.

A low level jet develops tonight with 850 mb temperatures expected
to warm ~10C by Friday morning resulting in a sharp boundary layer
inversion. Above the inversion, LLJ winds around 50 knots should
result in increasing mid to high level clouds. These clouds will
limit surface heating on Friday so went with 60th percentile for
high temperatures. Even with cloud cover, insolation weakens the
boundary layer inversion allowing stronger winds aloft to mix down
to the surface, especially in areas where southerly winds result in
gusty downslope flow. The next shortwave trough approaches Friday
evening, but a dry air mass in place should prevent precipitation
reaching the ground until late Friday night.

.LONG TERM...(Friday night through Thursday)
Issued at 352 PM EST THU FEB 25 2021

The long-term period continues to look active. The biggest change
compared to previous forecasts has been a increase in precip chances
and potential snow amounts on Sunday as the models come into better
alignment with a stronger wave lifting through. Monday continues to
look chilly, followed by a warmup for Tuesday and beyond.

Friday night, breezy SW winds will be ongoing with some 30+ mph
gusts likely continuing in the downslope areas along the Lake
Superior shoreline, this as a 40-50 kt LLJ passes overhead. That LLJ
will be lifting off to the northeast as the night goes on, leading
to decreasing winds. However, these winds combined with overcast
skies will keep lows on the warm side. Went above the 75th
percentile of guidance for lows since the bias-corrected guidance is
likely much too cold, resulting in lows in the upper 20s for most. A
progressive short wave lifting through the area still looks to kick
off a few snow showers with the best chance being across the south
central and east. However, the strongest theta-e advection/Q-vector
forcing is consistently modeled to remain south of the area. Snow
amounts should be generally a half inch or less.

These snow showers will clear out quickly Saturday morning leading
to partial clearing by midday and temps in the upper 30s and low 40s
for highs.

By Saturday night, a positive-tilt long wave trough will be in place
across the western CONUS with a few short waves embedded within it.
One of those short waves will be riding the jet through Minnesota
and Wisconsin to the U.P. late Saturday night into Sunday and
spinning up a weak surface cyclone as it does so. This system will
have more moisture to work with than the Friday night wave will. It
also looks like there will be a stronger mid-level fgen band.
Because the pattern is progressive, this system will be in and out
quickly which means heavy snow amounts are unlikely. However, there
could end up being a fairly narrow swath of the U.P. that sees a few
to perhaps several inches of wet, slushy snow in a 6-12 hour period
Sunday morning. The exact placement of that band remains to be seen.
It`s also possible that rain mixes in south central and east as
temps rise into the 30s on the southeast side of the surface cyclone
track.

Sunday night and Monday, a northern stream wave is still expected to
drop southeastward through northern Ontario and the Upper Great
Lakes, dragging a surface cold front along with it. However, much
like yesterday, there is still considerable spread in the guidance
for just how cold temps will be on Monday. Case in point, the GFS
high at the office on Monday is 7; the EC high is 29. The NBM
interquartile range for MaxT on Monday is 14 to 27. Given the UKMET
has caved toward the warmer EC, the consistent not-as-cold signal in
multiple runs of the deterministic EC, and some bright March
sunshine reemerging in the afternoon, warmer is likely the way to
go. The NBM deterministic highs for Monday range from the low 20s
north to upper 20s south which, given the model spread, did not
alter. However even the warmer EC still has 850 mb temps getting
down to around -14 to -16 C which is cold enough to support some
lake effect snow. Although the window is short, did increase POPs
into the likely range for the NW wind LES belts of the east half on
Monday. Across the west, the combination of rising heights/drying
low levels, and lack of open water, should limit LES to much more
scattered light snow showers.

Models and their ensembles actually come back into better alignment
for Tuesday when the warmup is expected to begin. GEFS and EPS mean
850 mb temps both climb to right around 0 C with a tight clustering
between roughly -3 to +2 C. With a 40-50+ kt SW to W LLJ still
expected as well, Tuesday still looks like a breezy and warm day.
have once again raised highs above NBM deterministic guidance,
toward the NBM 75th percentile, and even a few degrees higher than
that in the traditional warm spots of the west half where a SW wind
is downslope. Should easily see 40s out there and upper 30s/low 40s
elsewhere. The onshore flow may keep the Manistique area in the mid
30s.

Above-normal temps look to persist Wednesday although there is some
indication in the models of another brief cold shot Wednesday night
and Thursday.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1245 PM EST THU FEB 25 2021

West-northwest winds behind this mornings trough are producing a
marginal MVFR/VFR lake effect cloud deck at CMX and SAW. Clouds are
expected to diminish this afternoon into this evening with VFR
conditions prevailing tonight. A strong low level jet moves into the
area late tonight into Friday morning resulting in low level wind
shear spreading west-to-east for all terminals on Friday morning.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 300 PM EST THU FEB 25 2021

SW winds increase to around 25-30 knots by Friday morning as a sfc
low shifts east to around Lake Winnipeg. A strong LLJ moves over
Lake Superior tonight through Friday allowing for winds to increase
to southerly gales by Friday afternoon, especially across the east
half of the lake. The stable marine layer should keep the strongest
winds aloft, but a 50kt LLJ over the lake Friday night could result
in some higher end gale-force gusts at higher observation platforms.
The low and LLJ move east by Saturday morning resulting in winds
diminishing below 20 knots. Winds increase to gales again on Sunday
and a lower chance on Tuesday when warming temperatures result in a
more stable marine layer.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 2 PM Friday to 3 AM EST Saturday for
     LSZ249>251-266-267.

Lake Michigan...
None.
&&

$$

SHORT TERM...EK
LONG TERM...RJC
AVIATION...EK
MARINE...EK



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