Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300702

Area Forecast Discussion
National Weather Service Marquette MI
302 AM EDT Tue May 30 2017

.SHORT TERM...(Today and tonight)
Issued at 301 AM EDT TUE MAY 30 2017

Upper air pattern consists of a 500 mb closed low north of Lake
Superior with an associated trough over the Great Lakes region.
There are numerous shortwaves that will continue to rotate around
the low and the trough and will continue to bring waves of
convection to the area and be diurnally driven with the highest pops
during the strongest heating of the day. This trough and upper low
slowly move east today with two shortwaves moving through the area
this afternoon and evening. Will continue to go with persistence for
this forecast and have pops highest in the late afternoon and then
diminish them at night. Overall, did not make too many changes to
the going forecast.

.LONG TERM...(Tuesday night through Monday)
Issued at 357 PM EDT MON MAY 29 2017

Upper troughing from northern Canada to the Great Lakes dominates
into the upcoming weekend. Troughing eventually gives way to rising
heights late in the weekend into early next week. Low levels will be
influenced by sfc low over northern Ontario Tue into Tue night then
from Hudson Bay to northern Quebec Wed through Fri. Shortwaves
rotating around the upper low will continue to bring chances of
scattered showers. Swath of deeper moisture to h7 will help enhance
shower chances Tue night into Wed morning and again on Thu into Thu
evening. Chances for showers on Thu may be helped along by daytime
heating/instability and low-level convergence due to lake breezes.
May see additional showers later Thu night into Fri, but not sure on
extent of deeper moisture by that time as high pressure will be
trying to build in from the northwest, so will keep the chances low.
With the upper low in the vcnty and h85 thermal trough persisting do
expect daytime highs to stay below normal most of the week.

Coolest day of the long term will be Wed as h85 temps are progged to
be as low as 0-1c before moderating later in the day. Temps will try
to return toward normal Thu with 60s near Lk Superior and upper 60s
to mid 70s inland. On Fri, with high building out of Manitoba and
Ontario, associated north winds should keep readings cool in the 50s
near Lk Superior while temps inland rise into the upper 60s to lower

Models still struggling with extent of shortwave moving into the
upper Great Lakes for the weekend. GEM was more aggressive initially
while the GFS remains farther west with the trough over the region
this week so it keeps high pressure anchored over the area. Previous
ECMWF was not showing much rain for the weekend but latest run is
now wetter for Sat night into Sun. A lot of uncertainty so still
have low chances pops going, especially by Sun, but will not get too
aggressive with pops yet. No matter what solution verifies, still
looks like daytime temps next weekend into early next week stay on
the cool side of normal (expect highs mainly in the 50s near Lk
Superior and in the 60s inland and near Lk Michigan). Even though
it does stay on the cool side for daytime temps, pattern does not
appear to yield any significant chances for near freezing temps
or frost.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 117 AM EDT TUE MAY 30 2017

Low pres over northern Ontario will dominate the Upper Great Lakes
thru today. Disturbances rotating around this low will generate sct
-shra at times, most nmrs during the daylight hrs today. Upslope
westerly winds at KIWD/KCMX will result in lower cigs at those
terminals. Initial VFR conditions at KIWD should fall back to MVFR
overnight and then remain MVFR into this evening. MVFR cigs will
prevail at KCMX thru the fcst period. At KSAW, downslope winds
should allow VFR conditions to prevail before MVFR cigs develop by
late morning. Expect some periods of VFR this aftn/evening at all
terminals. While vis will likely remain VFR thru the fcst period at
all terminals, any heavier shra that occur could lead to brief MVFR

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 301 AM EDT TUE MAY 30 2017

As high pressure builds across the Plains and the broad low slowly
shifts to the east, the pressure gradient will tighten across Lake
Superior through Wednesday. This will allow winds to gust to 15 to
25 knots at times through this time period. Toward the end of the
work week, as the surface pressure gradient relaxes behind the
exiting low pressure system and as the high pressure system slides
overhead, winds will decrease to around 10 to 15 knots.

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


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