Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261737

Area Forecast Discussion
National Weather Service Marquette MI
137 PM EDT Fri May 26 2017

.SHORT TERM...(Today and tonight)
Issued at 416 AM EDT FRI MAY 26 2017

Water vapor imagery this morning shows a number of impulses lifting
and digging across the central CONUS this morning. One impulse
lifting north into southern Manitoba this morning sparked a fairly
narrow band of rain showers last night. These showers have been very
slow to move this morning and continue to weaken as moisture
transport has weakened across the area and weak upper-level ridging
aids in suppressing the convection. Some patchy fog has
intermittently developed across the east, otherwise it has remained a
bit more persistent along the shores of Lake Michigan.

With a narrow gap in cloud cover along the main surface ridge axis
closing in, with mid and high clouds encroaching on the area this
morning, do not think widespread dense fog will be an issue. A few
areas could see some patchy fog so did maintain mentions of fog
across portions of the central and east, but increasing cloud cover
should gradually put the breaks on strong radiational cooling early
this morning. Also, the light rain showers off to the west and south
of Upper Michigan this morning should continue to weaken. Cannot
rule out a stray shower or two making it into the west this morning,
so opted to leave at least slight chance wording. Any precipitation
that does fall through the morning hours is expected to remain light.

Later today, a weak surface trough/front is progged to push into the
region, as shortwave activity currently pushing across the
intermountain west lifts northeast across the northern Plains and up
into the Upper Great Lakes Region. Comparing the 1.5 PV anomalies
with water vapor imagery this morning, it appears that the 00Z GFS
is much faster with this shortwave activity, with precipitation
starting to develop along the trough in western portions of the area
early/mid afternoon. Thinking this is a bit too early, and then to
favor the slower high-res and remaining medium range model guidance.
Right now, it looks like showers, possibly even a few rumbles of
thunder, will develop and push into western portions of the area
mid/late this afternoon. A few of the high-res models show pockets
of rain showers developing across the central portions of Upper
Michigan this afternoon ahead of the main surface trough. This
doesn`t seem too terribly unrealistic as warm air advection increase
and moisture begins to lift back northward.

Tonight, as the surface trough slowly lifts northeast across the
area and the mid-level shortwave lifts across Lake Superior, showers
and perhaps a few rumbles of thunder will push east across the area.
High-res and medium range models are fairly consistent with the line
of convection breaking and weakening through the overnight hours as
moisture transport weakens and the better lift pushes north of the

.LONG TERM...(Saturday through Thursday)
Issued at 248 AM EDT FRI MAY 26 2017

Nam shows a closed 500 mb low north of Lake Winnipeg with a trough
extending down into the northern plains into the central Rockies 12z
Sat. This trough moves slowly east and affects the upper Great Lakes
Sat night through Sun night. Nam has some q-vector convergence Sat
night into Sun that moves through the area. With troughing in the
area, pops pretty much anytime cannot be ruled out. Overall, have
some low chance pops in for much of the forecast period and did not
make too many changes to the going forecast.

In the extended, GFS and ECMWF show a 500 mb trough over the central
U.S. 12z Mon with a ridge in the western U.S. which remains
stationary into Tue. The ridge moves into the Rockies 12z Wed, but
the upper Great Lakes still remains in the upper trough into Thu.
Temperatures still look to remain below normal this forecast period.
No real dry periods, but not a total washout either.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 137 PM EDT FRI MAY 26 2017

VFR conditions will continue into late this afternoon and early
evening before a few light showers move through by mid evening west
and overnight central and east. This may lead to occasional MVFR
conditions at each of the sites. While the rain will be light, the
rain that does occur may allow for enough low level moisture to
cause fog to develop late tonight mainly for the KSAW and KCMX TAF
sites. A lot of that hinges on added rainfall along with possibly
clearing skies late tonight; therefore, have left fog out of the TAF
for this issuance. Saturday, a bit drier air will slide through
allowing VFR conditions through the end of the TAF period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 416 AM EDT FRI MAY 26 2017

Through the weekend, winds of 10 to 20 knots are expected across
Lake Superior. Early next week, winds will increase to around 20
knots as an area of low pressure is progged to dig across portions
of the Upper Great Lakes.

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


SHORT TERM...Ritzman
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