Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 260833

Area Forecast Discussion
National Weather Service Marquette MI
433 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...(Thursday night through Wednesday)
Issued at 417 PM EDT WED APR 25 2018

Thursday night, a quick moving cold front/trough will slide from the
central U.P. eastward to through the eastern U.P. Forcing along and
ahead of the system along with increased moisture will allow a light
mix of rain and snow for the system. Precipitation will be fairly
light with only a hundredth or so expected. Otherwise, overnight
lows will be in the mid to upper 20s to low 30s under partly to
mostly cloud skies.

Friday, a compact vigorous clipper shortwave will drop southeast
through Upper Michigan bringing another round of mainly light
precipitation. An area of strong mid level fgen along with steep 700-
500 mb lapse rates of 7 - 8C/km will support a rain snow mixture
over mainly the central and western portions of the U.P. in the
morning, changing to rain in the afternoon. Although there may be a
brief period of heavier precipitation with this feature overall QPF
of mainly a tenth of an inch or less is expected. In addition, the
steeper lapse rates may introduce just enough CAPE to to allow for a
lightning strike or two over the south-central Friday afternoon.

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

Sunday through Wednesday, a transition to low to mid level southwest
flow will bring very warm air to the Upper Great Lakes region with
highs into the 70s to possibly 80 by Monday and Tuesday. Dewpoints
will be low enough and temperatures warm enough Sunday and Monday to
allow for lower RH values. This may lead to increased fire danger in
locations that have lost all the snow cover, especially over the
south central U.P. and along the WI border. Moisture advection
pushing dewpoints to near 50 will then provide enough instability
for the mention of some thunderstorms Tuesday with the approach of a
shortwave trough and cold front as low pressure lifts to the nw of
the region. Exact timining and placement of any heavier or
concentrated precipitation will be based on the exact timing of any
shortwave features sliding through the area.

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 333 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 thru this
morning. Cold fropa will occur w to e during the aftn, followed by
some -shra/sprinkles and MVFR cigs. MVFR cigs should scatter out at
KIWD/KCMX in the evening.

.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 358 PM EDT WED APR 25 2018

Most rivers across Upper Michigan have seen manageable rises in
water levels thus far from snowmelt, except for more rapid rises
along the Sturgeon River near Chassell where a flood advisory has
been issued. Expect more snowmelt on Thu with temps rising into the
upper 50s and 60s ahead of an approaching cold front. A period of
light pcpn is expected Thu afternoon/evening as the front moves
through the area. After several days of little to no pcpn at the end
of this week and cooler temps which will slow snowmelt runoff,
temperatures next week will increase dramatically with an
accompanying increase in moisture, likely leading to a rapid
decrease in snow cover and rapid runoff across the area. There are
indications of possible heavier precipitation for the the middle to
end of next week, though uncertainty 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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