Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261105

Area Forecast Discussion
National Weather Service Marquette MI
705 AM EDT Thu Apr 26 2018

.SHORT TERM...(Today and tonight)
Issued at 431 AM EDT THU APR 26 2018

Quiet currently across Upper Michigan through there are increasing
high clouds from the west ahead of shortwave trough and cold front
poised to move through later today. Thermal ridge ahead of the front
with H85 temps pushing +5c supports highs reaching well into the 60s
scntrl ahead of the front today. Temps over west may reach mid 50s
before temps begin to drop off this aftn once front passes through.
Southwest winds ahead of front may gust over 20 mph ctntrl and RH
values still look low, 20-25 pct. Overall, seems that areas that
have now lost snow (scntrl from MMN to IMT to just south of SAW to
ESC) could be closing in on critical fire weather conditions.
Main limiting factor is lack of very strong winds. Will coordinate
with fire partners to check in on fuels to see if special weather
statement is needed to highlight the elevated wildfire potential.

Later this aftn into early this evening, weather will be quite
changeable across Upper Michigan. Once front moves through, expect
sharp wind shift from southwest to north-northwest with gusts 20-30
mph near Lk Superior. Result will be falling temps into the 40s
closer to Lk Superior late today and into the 30s by late evening.
Expect scattered rain showers mainly just behind the front as it
moves through but total rain amounts look light with just a few
hundredths at any location. As deep moisture aloft pulls out this
evneing, light rain will taper off to drizzle/sprinkles. Most of the
precip will occur over western U.P. this aftn and over central U.P.
very late aftn into early evening. Rain probably does not make it to
eastern U.P. until toward sunset this evening but it will exit
shortly after midnight. As it stands now, looks too warm near sfc
for any appreciable mixed precip with this initial precip before
midnight. If there is sufficient lift/moisture for precip over
western Upper Michigan this evening, there may be just enough
cooling for a wintry mix. Would be very light if it occurred.

Attention late tonight, well after midnight, will be on secondary
clipper system currently over far northern Saskatchewan. Main
uncertainty is how far east this system will extend into Upper
Michigan more so into Fri. Late tonight though seems that at least
far west U.P. will be affected by light snow. Best chance of minor
snow accums, maybe a coating to to a couple tenths of an inch, would
be at Ironwood toward daybreak Fri. Elsewhere, should stay generally
quiet in wake of the first system. Lows will fall back into the 20s
most locations. Could be some patchy ground fog over inland west
half depending how quickly clouds move in ahead of the late night
clipper system.

.LONG TERM...(Friday through Wednesday)
Issued at 456 AM EDT THU APR 26 2018

Models suggest that a progressive pattern will prevail as the
mid/upper level trough into the Great Lakes shifts to the ne CONUS
this weekend and a ridge builds into the cntrl CONUS downstream from
a trough advancing into the wrn CONUS. Cooler weather will move in
Fri/Sat before a substantial warming trend from Sunday into early
next week.

Friday, a compact vigorous clipper shortwave will drop se through
Upper Michigan bringing another round of mainly light pcpn. An area
of strong mid level qvector conv/fgen near the left exit of the 250-
300 mb jet along with steep 700-500 mb lapse rates of 7-8C/km will
support snow or rain showers changing to mainly rain. Although there
may be a brief period of heavier convective pcpn with this feature
overall QPF of mainly 0.10 inch or less is expected with the
greatest amounts near the WI border. Some thunder may also be
possible in the region but fcst instability to support tsra is
expected mainly from cntrl into se WI.

Saturday, high pressure building into the area will bring clearing
but northerly flow will maintain the cool air across the region and
keep highs in the upper 30s and low 40s north to near 50 south.

Sunday through Wednesday a transition to low/mid level sw flow will
bring very warm air to the norther Great Lakes with highs into the
70s by Mon/Tue. The first batch of pcpn that might develop would
be supported by the strongr 850-700 mb theta-e advection Monday.
The moisture advection pushing dewpoints to near 50 will also
provide enough instability for the mention of tsra by Tue with the
approach of a shortwave trough and cold front as low pressure
lifts to the nw of the region. There is still plenty of
uncertainty with the details of the timing of the frontal passage
and any weaker shrtwvs moving out of the plains that would impact
pcpn chances/amounts. Although some sct pcpn amounts to near 0.50
inch may be possible, the chance for any widespread heavier rain
is lower. Drier air is likely to move in Wednesday behind the
front but mild conditions will persist with highs still in the

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 703 AM EDT THU APR 26 2018

With a dry air mass remaining in place ahead of an approaching cold
front, VFR conditions will continue at KIWD/KCMX/KSAW into much of
the aftn. Cold fropa will occur w to e late aftn, followed by some
-shra/sprinkles and MVFR cigs. MVFR cigs should scatter out at
KIWD/KCMX in the evening but linger most of the night at KSAW.
Another clipper system will move into far western Upper Michigan
late tonight with a chance of snow showers developing at KIWD toward
daybreak Fri.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 431 AM EDT THU APR 26 2018

Active period with changeable stronger winds across Lk Superior into
next week. No gales are expected at this time though. Winds increase
up to 20 knots out of the southwest today ahead of an approaching
cold front crossing Lk Superior this aftn. Winds will veer to the
northwest behind the front and may see gusts reach 30 kts late this
afternoon central Lk Superior and expanding to eastern Lk Superior
through much of tonight. Winds will diminish to less than 20 kts on
Fri but could increase from the northeast to northwest at 25-30 kts
Fri night into Sat as pressure gradient tightens due to approaching
high pressure ridge and low pressure tracking over the lower Great
Lakes. Winds diminish to less than 20 kts by Sun but could increase
again by early next week, this time from the south, as a stronger
low tracks from the northern Plains to the upper Great Lakes.

Issued at 456 AM EDT THU APR 26 2018

The snow pack will continue to melt but at a slower pace mostly
driven by the sun (when not blocked by clouds). Most rivers across
Upper Michigan have seen manageable rises in water levels thus far.
Precipitation chances over the next several days look somewhat muted
(collectively less than 0.20"). However, temperatures next week will
increase dramatically with an accompanying increase in moisture,
likely leading to a rapid decrease in snow cover across the area.
There are indications of heavier precipitation toward the middle to
end of next week, though uncertainly remains on exactly where and
how much will fall. All in all, the snow pack is expected to shrink
considerably next week which may lead to minor river flooding in the
usual rivers prone to spring flooding.

Upper Michigan...
Lake Superior...
Lake Michigan...


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