Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221908

Area Forecast Discussion
National Weather Service Marquette MI
308 PM EDT Mon May 22 2017

.SHORT TERM...(Today and tonight)
Issued at 513 AM EDT MON MAY 22 2017

Latest WV imagery and RAP analysis indicated a closed low over
Ontario north of Lake Superior early this morning. Q-vector
convergence out ahead of a shortwave rotating around the southern
periphery of the low was supporting sct showers over central Upper
Mi early this morning, especially over the east half of the U.P.

Today, with continued q-vector convergence ahead of the shortwave
moving through the Upper Lakes, expect numerous shower coverage over
the east half of the cwa this morning. Even with some expected
drying in the wake of the departing shortwave this afternoon,
diurnal heating/weak instability with the mid level trough still in
place over the area may still be enough to support some inland
sct/isold -shra development. Expect highs in the mainly in the 50s,
except for lower 60s far south central.

Tonight, any lingering instability showers should end early evening
with loss of diurnal heating. As closed low lifts from Ontario east
into Quebec, weak mid-level ridging setting up over the area should
ensure mostly dry conditions tonight as noted by models. Min temps
will range from the upper 30s inland to the lower to mid 40s near
the Great Lakes shorelines.

.LONG TERM...(Tuesday night through Monday)
Issued at 307 PM EDT MON MAY 22 2017

The main forecast highlights through the middle to end of the week
will be a drying and warming trend, a few locations across the
interior may see temperatures climb into the lower 70s by Friday!
Rain chances look to return on Friday across the west, and pushing
eastward into Saturday as a cold front pushes east across the area.
There is some uncertainty as to whether or not instability will
return this far north, so confidence in any thunderstorm activity is
low right now. Towards the end of the weekend and beginning of next
week, another system is progged to impact the region, bringing back
better chances for precipitation. Patchy frost looks possible across
the interior west early Thursday morning as a drier air mass moves
in and skies clear giving way to ample diurnal cooling.

Tuesday night, with lingering upper-level energy overhead, as the
main trough axis slowly continues to push east across the area,
expect light rains to linger across the central and eastern portions
of the area. Wednesday, expect clouds to linger across the area
before diminishing through the afternoon as high pressure begins to
build southwest across much of the area. However, the exiting upper-
level low is progged to linger just north of the Ohio River Valley
and may overspread mid and upper-level clouds across the eastern
half of the area. Wednesday night into Thursday, as the upper-level
low begins to lift slightly, a few medium range models bring back
precipitation chances across the far east as weak warm air advection
tries to nudge back to the northwest. The Canadian is by far the
most aggressive with this precipitation, which is likely in response
to lingering shortwave activity being a bit more robust. During the
day on Thursday, the upper-level low will continue to slowly lift
east, but a few lingering wrap around showers may impacted far
eastern portions of the area; therefore, have held onto the slight
chance wording for rain showers through the day. However, across the
rest of the area as weak upper-level ridging builds into the region,
expect skies to be mostly sunny with ample insolation. This will
allow for temperatures to modify back to near normal for this time
of year.

Friday through Friday night a weak cold front is progged to move
east across the area, bringing back chances for rain showers. The
upper-air pattern is rather complex during this time period, with
longwave troughing extending south across the Northern Plains and
transitioning to more zonal flow across the central and southern
Plains. Given this split flow, confidence is not high that enough
moisture will get this far north to support instability for
thunderstorms. This is further supported by medium range models
continuing to trend further south with the northern extent of

Depending on the speed of the front, precipitation may linger into
Saturday. The Canadian is the slowest, with the front moving across
Upper Michigan almost 12-18 hours after the GFS/ECMWF. Saturday may
be a bit cooler in some locations depending on the speed of the cold
front. Sunday into Monday, there is considerable uncertainty in how
things will evolve. The longwave trough across the western CONUS is
much stronger in the GFS and weaker within the Canadian, with the
ECMWF falling in the middle; therefore, model solutions are a bit
all over the place precipitation wise. However, given the lingering
upper-level energy rotating about the region and the possibility for
another shortwave digging south out of central Canada, expect
temperatures to be on a slight downward trend through early next
week with cloudy skies.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 146 PM EDT MON MAY 22 2017

Enough low level moisture remains across the region to support MVFR
cigs that will only gradually imrpove to VFR with increasing mixing
during the afternoon. However, expect cigs to drop again to MVFR
with cooling overnight and additional moisture advection. Winds will
also be light enough to allow fog formation that may drop vsby to
VLIFR for a short period Tuesday morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 513 AM EDT MON MAY 22 2017

A low pres trough lingering over the area will maintain fairly light
winds across the lake into tonight. Winds under 20 kts should then
be the rule Tue into Fri as a relatively flat pres gradient
dominates the Upper Lakes.

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


LONG TERM...Ritzman
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