Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241729

Area Forecast Discussion
National Weather Service Marquette MI
129 PM EDT Sat Jun 24 2017

.SHORT TERM...(Today and tonight)
Issued at 359 AM EDT SAT JUN 24 2017

Water vapor imagery shows a weak shortwave pushing east across the
area early this morning, with another more potent upper-level wave
rapidly digging across the northern Plains through North Dakota and
into Minnesota. A few scattered showers associated with the first
weak shortwave have developed across the west.

The initial shortwave moving across the area will prime the mid
levels and allow for lingering mid-level moisture to remain in place
ahead of the stronger trailing upper-level wave. As this wave dig
south of the area across Wisconsin, a narrow area of ample upper-
level divergence should allow for showers to become more widespread
this afternoon, especially across the central portions of Upper
Michigan. As previously mentioned, freezing levels will begin to
lower to near 6000-7000ft AGL, but with weak shear across the area
and skinny CAPE profiles showing rather limited amounts of
instability, think that any stronger updrafts will struggle. Tonight
as the main upper-level wave lifts out of northeast Wisconsin and
across lower Michigan, lingering showers and thunderstorms will
continue, especially across the central and east.

.LONG TERM...(Sunday through Friday)
Issued at 300 AM EDT SAT JUN 24 2017

Beginning Sun, The approach of another shortwave combined with
daytime heating will yield numerous afternoon showers inland from
Lake Superior. Coverage should be least over the eastern part of the
fcst area due to greater stabilization from flow off Lake Superior
in that area. With mlcape into the 500-900j/kg range, expect at
least isold-sct t-storms as well. Low wetbulb zero heights in the
5.5-6.5kft range under weak shear environment suggest there could be
a lot of cells producing small hail Sun afternoon. Showers will
again diminish Sun night with loss of daytime heating. Highs on Sun
will be in the 60s, coolest near Lake Superior.

On Mon, heights will begin to rise as the mid-level trough begins to
shift e. However, lingering cold pool aloft and some build up of
instability, should yield isold to sct -shra inland from Lake
Superior, especially over the s central where the more limited
mlcape of 200-300 j/kg will be centered. Temps could be a few
degrees higher than Sun, but will still be mainly in the 60s.

Tue should be a pleasant day as the sfc high pres ridge passes over
the area. Under mostly sunny skies, temps will rise into the 70s
across the area, locally cooler along the Great Lakes.

Wed thru Fri looks to be an active period as a mid-upper level
trough developing into the northern Rockies slowly shifts e. WSW
flow and at least a couple of shortwaves ejecting from the trough
into the Western Great Lakes will generate showers/t-storms with
probably some risk of severe storms given strong deep layer shear
and periods of increased instability. There is reasonable model
agreement for a better potential of showers/t-storms Wed/Wed night
and possibly severe storms. Model agreement diminishes drastically
thereafter on timing of shortwaves, but it appears there will be
another round of showers/t-storms at some point Fri/Sat.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 129 PM EDT SAT JUN 24 2017

Showers and possibly a thunderstorm or two are possible over mainly
over the KSAW TAF site this afternoon into this evening. Ceiling
will be in the MVFR to IFR range at each of the TAF sites this
afternoon as a system shifts by to the south. There may be some
minor improvement tonight before the next system approaches toward
Sunday afternoon. Visbiltiy may be restricted at times under heavier
rain showers; however visibility should generally be in the VFR
range. Winds will be fairly light under a weak pressure gradient
across the Upper Peninsula.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 359 AM EDT SAT JUN 24 2017

Winds of 10 to 15 knots are expected to continue through the first
half of next week as the pressure gradient decreases and high
pressure builds in for the first part of the work week. Towards the
middle of the week, winds will start to increase to around 20 to 25
knots as a system lifts across the Upper Great Lakes. Winds will
then decrease to around or less than 15 knots towards the end of the
week and next weekend.

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


SHORT TERM...Ritzman
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