Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211914

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

.SHORT TERM...(Today and tonight)
Issued at 442 AM EDT SUN MAY 21 2017

08Z WV imagery and RAP analysis indicated a well-defined negative-
tilt shortwave lifting ne through ern IA. At the surface, low
pressure was located over southern MN with an occluded front through
central WI. Despite weak to moderate q-vector convergence ahead of
shortwave lifting ne through the Midwest, mid-level dry slot over
the area has limited pcpn so far this morning to dz or isolated

Today, as stronger qvector convergence ahead of approaching
shortwave and steeper mid level lapse rates greater than 7c/km move
across the area, models indicate another round of shra will move
across Upper Mi from approximately 10-16z with the potential for
isold tsra. The pcpn should then diminish later in the morning into
the afternoon as mid-level drying moves over the area. However, some
additional wrap-around shra may move into the west late. Expect
temps generally in the mid to upper 50s.

Tonight, the presence of the mid-upper low over the area and
continued cyclonic flow could sustain isold to sct showers across
the area tonight despite lingering mid-level dry air over the area
so wl maintain low chc pops for showers. Expect min temps in the low
to mid 40s under cloudy skies.

.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 12Z TAFS through 12Z Monday morning)
Issued at 744 AM EDT SUN MAY 21 2017

Scattered rain showers will continue across the area with
lingering low pressure. Conditions will stay IFR through much of
the forecast period but perhaps fall to LIFR at CMX this morning.
MVFR will develop at KSAW this evening as winds shift to sw
downslope flow.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 442 AM EDT SUN MAY 21 2017

As the low pres area moving across Lake Superior this afternoon and
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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