Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 301027

Area Forecast Discussion
National Weather Service Marquette MI
627 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...(Wednesday through Monday)
Issued at 315 AM EDT TUE MAY 30 2017

The main forecast highlights for the middle to the end of the work
week will be a warming trend through the end of the work week, with
a few chances for rain showers. At this point, we`re not looking at
widespread rain showers, rather more isolated. This weekend there is
still quite a bit of uncertainty in how precipitation chances will
play out, especially towards the end of the weekend and early parts
of next week. However, temperatures are expected to drop a bit this
weekend, but are expected to remain seasonal.

Wednesday, as the main trough axis associated with cutoff energy
aloft beings to finally push east of the region precipitation
chances will diminish from west to east. We could see a few
lingering rain showers across the central and east, but those
showers will continue to exit the area through the afternoon hours.
As upper-level subsidence increase and drier air begins to filter
southeast across the region, cloud cover will also decrease from
west to east. The combination of increasing insolation and cold air
advection modifying across the region will allow temperatures to
warm into the 60s across the west and much of the central. With
cloud cover and precipitation lingering across the east, expect
temperatures to climb into the mid to upper 50s. Clearing skies will
also allow for ample, deep mixing through the day and gusty winds.
BUFKIT momentum transport winds have been consistent with showing 25-
30mph wind gusts possible, especially across the west. Therefore,
have continued this trend within the current forecast package. Given
the drier airmass moving into the region Wednesday/Wednesday night
and ample radiational cooling expected across the interior central,
especially across the higher terrain, did lower overnight
temperatures quite a bit. A few locations may see some patchy frost
in the interior central, so that will be something to monitor.

By Thursday, 850mb warm air advection is progged to increase across
the region ahead of shortwave energy digging south across western
Ontario. With 850mb temperatures progged to reach around 9-14C,
forecast soundings show a nice warm nose that will have no problem
mixing down and promoting seasonal temperatures, upper 60s to
mid 70s. Forecast soundings are also showing hints of steeper low-
level lapse rates due to turbulent mixing on Wednesday. Therefore,
both the NAM and GFS are showing turbulent mixing during the day on
Thursday growing fairly deep. This will allow for another breezy day
across much of the area, albeit weaker than Wednesday. Late Thursday
afternoon into Friday morning, as a shortwave digs across the Upper
Great Lakes, precipitation chances will return to the central and
east. While a few of the medium range models are showing the
potential for some instability ahead of the shortwave, most of this
instability looks like it will be very shallow, as mid-level lapse
rates remain around 5-6C/km. Therefore, opted to leave mentions of
thunder out as the convective layer would be rather shallow,
especially given the deep mixing. Any lingering rain showers will
vacate the areas on Friday, as surface high pressure begins to
build south into the Upper Great Lakes. Friday still looks to be a
seasonal day, but lingering clouds and precipitation may cool
temperatures down by a few degrees.

This up and coming weekend looks like it will start off dry with
high pressure draped across the Upper Great Lakes, but as a
shortwave digs across the the northern Rockies and eventually across
the Great Lakes region, chances for precipitation may increase
towards the latter half. There is still quite a bit of uncertainty
among the medium range models as they are struggling to nail down
the strength and speed of this wave. The GFS is the slowest with
this wave, while the Canadian is the fastest and furthest south.
The ECMWF falls right in the middle and has the wettest projections
for the area. Therefore, confidence remains fairly low, especially
for Saturday night/Sunday as to whether or not locations will see
additional rounds of precipitation. We could see some lingering
showers early next week, but as the shortwave continues to dig south
of the area it does look like we should start to dry out.

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 627 AM EDT TUE MAY 30 2017

Low pressure 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.
Upslope westerly winds at KIWD/KCMX will result in lower cigs at
those terminals. KIWD will 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

.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...


LONG TERM...Ritzman
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