Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212009

Area Forecast Discussion
National Weather Service Marquette MI
409 PM EDT Sun May 21 2017

.SHORT TERM...(This evening through Monday)
Issued at 407 PM EDT SUN MAY 21 2017

WV imagery and RAP analysis indicated a mid/upper level trough over
the cntrl CONUS with a low center over nrn MN. At the surface, low
pressure was located over far nw WI with an occluded front draped
eastward through srn Upper Michigan. Although most of the pcpn had
ended early this afternoon in the wake of the stronger shortwave
lifting through Lake Superior another weaker shrtwv was bringing
another area of light rain or drizzle through the wrn cwa.

Tonight, models suggest that sct -shra will increase gradually from
west to east as a shortwave over wrn MN slides toward the area and
additional wrap-around moisture filters into the area. However, any
rainfall amounts will be light with QPF of only a few hundredths of
an inch.

Tuesday, expect the greatest pcpn coverage over the east half in the
morning as the shrtwv moves through the area. Even with some drying
in the afternoon, diurnal heating, max readings into the mid to
upper 50s, with the mid level trough over the area may still be
enough to support some inland sct/isold -shra development.

.LONG TERM...(Monday night through Sunday)
Issued at 314 PM EDT SUN MAY 21 2017

The main forecast highlights through the first half of the week will
be cloudy with temperatures running around 5-10 degrees below
normal, with chances for rain showers. Towards the middle of the
work week, cloud cover will begin to diminish and rainfall chances
will vacation the area with temperatures returning to near normal.
The medium range models are not in great agreement with how things
will unfold towards the end of the week and this weekend; however,
with upper-level ridging beginning to exit the region and shortwave
troughing beginning to encroach on the area, wouldn`t be surprised
if we see the return of some precipitation, perhaps with some
isolated thunder.

Monday night a weak cold front will push east across the area as a
weak surface low lifts east of the area over Ontario. As this front
pushes through, there doesn`t look like too much precipitation will
develop along the front as convergence and moisture are lacking,
along with the better upper-level lift well east of the area.
However, into Tuesday morning and through the overnight hours,
chances for precipitation will increase as a shortwave digs south
across the Upper Mississippi River Valley. Models are in good
agreement that height falls associated with this shortwave moving
across the tail of the cold front, which should be sufficient enough
for a weak low pressure system to develop across the Lower Great
Lakes region. The models are not in good agreement with the track of
this low, with the NAM being the furthest north and the ECMWF being
the furthest south. Therefore, confidence in coverage and
precipitation amounts is low at this time and have only opted to
mention chance PoPs for now.

Wednesday onshore/upslope flow may allow some light precipitation to
linger across the central and eastern portions of the area; but
precipitation should wane from west to east through the afternoon
and evening hours as upper-level subsidence increases. Cloud cover
will begin to decrease in coverage as well; however, with lingering
cooler air aloft and still a bit of wrap around moisture over the
area, don`t think skies will completely clear. On Thursday, as a 100-
120kt jet continues to lift meridional on the eastern side of the
upper-level trough to our south, it will begin to lift out of the
Ohio River Valley. This will allow the associated surface low to
lift across eastern Great Lakes with precipitation staying mainly
east of the area. As 850mb temperature begin to modify and
insolation increases on Thursday, expect temperatures to climb back
up into the 60s. A few locations across the south should see
temperatures climb back to near normal, especially where good
downslope winds develop.

Thursday night through Friday, high pressure will begin to build
across portions of the area as weak upper-level ridging begins to
develops across the Upper Great Lakes. 850mb temperatures will
continue to modify a bit by Friday and will likely allow
temperatures to warm a bit further. A few locations may climb into
the upper 60s and possibly even lower 70s. Locations along the
Wisconsin border and locations across south central portions of
Upper Michigan will likely see the best chance at seeing
temperatures climb into the 70s given downsloping effects and
vegetation characteristics. There are some hints of rain showers,
and perhaps a thunderstorm or two, developing across the west as a
subtle shortwave lifts across the area on Friday.

Next weekend, as warm air advection increases, it does look like the
warm temperatures will be around to stay through at least the first
half of the weekend. The GFS seems to be the outlier in regards to
how the next system will evolve with troughing ejecting out of the
northern Plains. Therefore tend to favor the Canadian and ECMWF
solutions keeping the track of low pressure north of the area,
pushing a weak surface trough through the area. This will bring back
chances for rain showers, and perhaps some thunderstorm activity as
MUCAPE values increase to around 500 J/kg. However, the best chance
for precipitation next week looks to be on Sunday as the main upper-
level waves moves overhead.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 333 PM EDT SUN MAY 21 2017

Scattered rain showers will continue across the area with lingering
low pressure. Upslope erly flow into CMX will maintain VLIFR
conditions aob landing mins this afternoon. However, as winds veer
to the ssw, expect some improvement late this afternoon. Additional
veering later tonight to wrly will again result in upslope flow that
help drop or maintain LIFT conditions. Drier air moving in Monday
morning will help bring conditions back to MVFR. Moisture wrapping
around the low will result in mainly IFR conditions at IWD with
improvement by later Monday morning to MVFR. IFR cigs should also
linger at SAW this afternoon. However, winds veering to sw at SAW,
there should be enough of a downslope component to favor MVFR cigs
tonight into Monday morning.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EDT SUN MAY 21 2017

Low pres moving across Lake Superior this evening will result in
diminishing winds and shift in wind direction from e-ne to w-sw late
tonight. Winds under 20 kts should then be the rule Mon into Wed as
a relatively flat pres gradient dominates the Upper Lakes.

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


LONG TERM...Ritzman
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