FXUS63 KMQT 252337

Area Forecast Discussion
National Weather Service Marquette MI
737 PM EDT Wed Apr 25 2018

.SHORT TERM...(This evening through Thursday)
Issued at 358 PM EDT WED APR 25 2018

Sunny skies under high pressure today has resulted in temp readings
this afternoon ranging from the mid 30s near the Lake Superior shore
east of Marquette in light northerly flow to lower 50s south

Sfc high pressure drifts slowly into the eastern Upper Mi tonight
and with fairly low pwats expect temps generally in the 20s. Used
the GEM bias corrected for min temps which perform best under ideal
radiational cooling conditions. Could be colder in the mid to upper
teens interior east where winds stay light all night and will likely
stay warmer into the 30s far west as southwest winds start to stir
ahead in gradient flow between the exiting high and cold front
moving toward western Lk Superior.

Thursday, similar to the scenario late Tuesday, after warming into
the upper 50s and 60s, another shortwave trough and associated cold
front will advance through Upper Michigan in the afternoon and
evening. However, since the forcing is stronger (deep layer q-vector
convergence and 850-700 mb fgen), the fcst includes higher chance
POPs/QPF, especially over the nw half. Enough colder air will move
in during the evening for some of the rain to change over to snow.

.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 00Z TAFS through 00Z Thursday evening)
Issued at 737 PM EDT WED APR 25 2018

With a dry air mass remaining in place ahead of an approaching
cold front, VFR conditions will continue at KIWD/KCMX/KSAW thru Thu
morning. Cold fropa will occur w to e during Thu aftn with some
-shra and MVFR cigs likely following fropa at KCMX/KIWD. MVFR cigs
may hold off until just after this fcst period at KSAW.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 358 PM EDT WED APR 25 2018

Light winds of 15 knots or less tonight could increase up to 20
knots out of the southwest ahead of an approaching cold front
crossing Lk Superior on Thu. The winds will veer to the northwest
behind the front and could see gusts reach 30 kts Thu afternoon
especially north central and eastern Lk Superior. Beginning
Fri...winds will generally stay blo 25 knots through the rest of the
fcst period.

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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