Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200725
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
325 AM EDT Sun May 20 2018

.SHORT TERM...(This evening through Sunday)
Issued at 327 PM EDT SAT MAY 19 2018

Latest water vapor imagery shows shortwave trough moving east
through Ontario. This shortwave has propelled a cold front into the
Upper Great Lakes region today. Temps across the northwest half of
the cwa behind the cold front this afternoon have fallen into the
40s/50s while temps ahead of the front over south central Upper Mi
remain in the lower to mid 70s. Isolated showers/drizzle linger
along/behind the front as noted on the latest radar loop.

Weather will quiet down tonight with some clouds and gusty winds to
start the evening giving way to some clearing and diminishing winds
overnight as high pressure builds in from the west. Isolated showers
will linger into the early evening over north central and eastern
sections of Upper MI but otherwise expect dry conditions tonight.
Lows will tumble into the 30s later tonight across much of the area,
and will likely dip into the upper 20s over the colder inland west
locations.

Sunday...In the wake of the cold front, another very dry air mass
will settle over the area for Sun. Based on mixing heights and dry
air aloft that can be mixed down, will continue to favor the lower
end of bias corrected guidance for dewpoints. Under abundant
sunshine, expect highs in the western interior to reach into the
lower 70s with RHs falling to 15-20pct. Fortunately, winds will be
on the lighter side which will prevent enhancement of fire wx
concerns. Will be cooler along the Great Lakes, especially Lake
Superior, where highs will only be in the mid 50s to lower 60s.

.LONG TERM...(Monday through Saturday)
Issued at 319 AM EDT SUN MAY 20 2018

Upper air pattern starts off this week with ridge over western
Canada and shortwave trough over the southwest CONUS. Flow looks
generally zonal downstream of these features including over the
Great Lakes. Generally sfc high pressure that expands across the
upper Great Lakes today will remain in place the first part of the
week. Still some hint that weak shortwave over the plains along
with increasing mid-level moisture H85-H6 could result in a few
showers Mon night over scntrl. Forcing is very weak with this
system though so may be nothing more than a few sprinkles if
precip occurs. Weak system exits east of area on Tue morning. Weak
ridging staying in place should promote lake breezes for all
areas by Tue aftn. Both Mon and Tue will feature elevated wildfire
potential due to low RH values in the 20-30 pct range inland.
Wind gusts on Mon could top out in the 13-18 mph range, strongest
over the central with enhanced southeast lake breeze off Lk
Michigan. Winds on Tue should be lighter.

By Wed, flow pattern aloft turns more northwest as troughing expands
Hudson Bay to Quebec. As sfc high pressure builds across northern
Ontario and Quebec, more dry weather will continue over Upper
Michigan. With high to the north and east of Lk Superior, northeast
winds may be enhanced closer to Lk Superior leading to temps in the
50s. However, inland toward MI/WI state line at LNL and IMT, temps
will push above 80F. Once again RH values will be in the 20-30 pct
range but winds should stay light where the warmest temps/lowest RH
values line up.

Late in the week, still looks like chances for rain will increase as
shortwave trough that begins the week over the southwest CONUS
meanders to the northern Plains and eventually heads toward the
western Great Lakes. Since high pressure over the area most of the
week moves east and troughing develops over the central Plains,
return flow should begin to bring increasing low-level moisture
northward, though will still have potential for lower RH values on
Thu over east half due to dry air lingering with departing high.
Late Thu into Fri, as low pressure deepens over the northern Plains
and moisture transport increases into Upper Great Lakes should start
to see at least chances for showers and maybe a chance for t-storms
as well. This far out, it is hard to gage if there could be stronger
t-storms, but at least based on forecast MLCAPES seems there may be
a potential, especially Sat. We will have to see if there is enough
deep layer shear around to support organized stronger storms though.

Chances for rain should continue into much of Sat as the northern
Plains low slowly crosses the Upper Great Lakes. Rain chances will
begin to diminish later in the weekend but it may take until Sun
aftn or Sun evening. Though there is decent agreement on
temperatures on Sun with 50s near Lk Superior and 70s inland, the
extent of cool down behind the low by Memorial Day is very
uncertain. Likely will depend on how far south and west the upper
level trough over eastern Canada progresses. Spread in models is
high at this point with coldest guidance suggesting highs in the 50s
inland on Memorial Day while warmest guidance shows temps in the
80s.
&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 135 AM EDT SUN MAY 20 2018

A very dry air mass is currently spreading into the Upper Great
Lakes. This drier air has already cleared out low clouds at
KIWD/KCMX. At KSAW, high IFR/low MVFR cigs will clear out in the
next hr or so per satellite imagery. With a very dry air mass
dominating, VFR conditions will prevail at all terminals today and
tonight.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 327 PM EDT SAT MAY 19 2018

Northeast to north wind gusts of 25 to 30 knots this afternoon
behind a strong cold front crossing Lake Superior. As high pressure
quickly builds in tonight expect winds to diminish blo 20 kts across
all of Lake Superior late tonight. These light winds of mostly 15
kts or less will continue through much of next week as high pressure
parks itself over the Upper Great Lakes.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...JLA
AVIATION...Rolfson
MARINE...Voss


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