Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300000

Area Forecast Discussion
National Weather Service Marquette MI
800 PM EDT Mon May 29 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 355 PM EDT MON MAY 29 2017

Persistent scattered rain showers will continue through the short-
term with the best chances during daytime heating.

Tonight and Tuesday: Vertically stacked low pressure will continue
to remain nearly stationary over Ontario through the short-term
portion of the forecast. This will keep generally cloudy skies and
scattered rain showers in the forecast as several shortwaves rotate
through the Upper Great Lakes. There will be a decrease in rain
showers and cloud cover through much of the night as diurnal rain
showers diminish with loss of daytime heating. This will be fairly
short-lived as the next shortwave over southern Manitoba works into
the area late tonight into the day Tuesday. Again, the scattered
rain showers will begin to increase late tonight, but the better
chances will move into the area during the late morning and
afternoon hours Tuesday as daytime heating increases. While a
lightning strike or two cannot be completely ruled out, the chances
are very slim as the instability remains shallow. This will keep the
precipitation more in the form of instability showers with the
colder air aloft associated with the upper-level low.

.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 00Z TAFS through 00Z Tuesday evening)
Issued at 759 PM EDT MON MAY 29 2017

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

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EDT MON MAY 29 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 the first half of the work week. 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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