Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261939

Area Forecast Discussion
National Weather Service Marquette MI
339 PM EDT Thu Apr 26 2018

.SHORT TERM...(This evening through Friday)
Issued at 339 PM EDT THU APR 26 2018

Fire wx concerns continue in the very short term but winds and RHs
have been sligly lower/higher respectively than forecast and the SPS
for Dickinson/Menominee counties should be allowed to expire at 00Z.

Surface and satellite observations indicate that the cold front is
knocking on our doorstep this afternoon, located across far western
Lake Superior. A few light showers will be possible from W to E this
afternoon and evening as the front crosses the area, but forcing
will be weak and only a few hundredths of rain will be squeezed out
of this event. Some gusty winds of 20 to 25 mph will be possible
near Lake Superior, but have lowered winds a bit overall from prev.

Patchy fog will be possible overnight for the west half dependent on
timing of cloud coverage filling back in as mid levels look quite
dry overnight. Another clipper will drop southeast out of Canada
later tonight that looks to affect the western/southern Upper
Peninsula tomorrow between about 5AM and 2PM local time.
Precipitation will likely start out as snow with post-frontal sfc
temps dropping into the upper 20s late tonight. A half an inch to
perhaps an inch of snow could accumulate, mainly on grassy surfaces,
before temperatures warm back into the lower 40s during the daytime
allowing a transition to rain. Thankfully only about 0.10-0.25" of
QPF is expected, and the cooler temperatures should limit snowmelt
some and allow some of the rivers to drain before the melt picks
back up in earnest on Sunday into next week.

.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 18Z TAFS through 18Z Friday afternoon)
Issued at 115 PM EDT THU APR 26 2018

VFR conditions continue this afternoon, but are expected to drop to
MVFR as a trough and associated sfc front approach. 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 much 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 and KCMX toward daybreak Fri. Chance for
brief vsby reductions but should stay well above IFR thresholds.
Snow will become mainly rain during the day as temps warm. At the
very end of the forecast period near 18Z Fri, Cigs may begin to
lower to near IFR levels at IWD.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 339 PM EDT THU APR 26 2018

A few periods of increased wind and wave activity will be possible
over the next several days, but no gales are expected in the
forecast period. A cold front will continue to make its way across
Lake Superior this evening. Winds will veer to the northwest behind
the front and may see gusts reach 20-25 kts through this evening in
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 north gusting to 20-30 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. Winds will
gradually shift to westerly and diminish through Wednesday.

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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