Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241950

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

.SHORT TERM...(This evening through Sunday)
Issued at 349 PM EDT SAT JUN 24 2017

Tonight: The shortwave/upper low that has been producing showers and
isolated thunderstorms this afternoon will continue to shift to the
southeast of the area through this evening. At the same time, a weak
surface trough will linger across the area. The combination of the
forcing/moisture associated with the departing low and the trough
will keep isolated to scattered showers across the area through
tonight. The better chance of scattered rain showers will be over
the east half as that area will be closer to the system forcing
associated with the shortwave/upper low as it departs. The west half
will likely see a bit of a break in the precipitation or at best
isolated rain showers as minimal daytime heating decreases. At this
point, the east half looks to gain about a tenth of an inch or less
of QPF tonight with the west half looking at a trace to 5 hundreths
of an inch of additional QPF tonight. Any instability will diminish
quickly after sunset, so the small thunder potential tonight will be
limited to mainly the evening hours south-central and east.

Sunday: The aforementioned surface trough will linger nearby
throughout much of the day, helping to focus showers and
thunderstorms across the Upper Peninsula. At the same time, yet
another shortwave will rotate through the broad troughing across the
Upper Great Lakes. This shortwave is expected to slide directly
overhead during the late afternoon into the evening hours. The
combination of the cooler air aloft associated with the shortwave
along with surface heating during the afternoon, will give steadily
increasing chances for showers and thunderstorms. MUCAPE values
around 800 - 1000 J/kg along with freezing hgts and wet bulb zero
hgts at or around 5kft to 6kft agl will give increased chances for
stronger storms to produce small hail. Similar to Saturday, very
little shear in the 10 to 15 knot range will support only
pulse/unorganized thunderstorm activity. No widespread severe
weather is expected with this, just mainly small hail. Some of the
storms that pulse may cause some heavy downpours, again, the best
timing for this would be the afternoon into the early evening hours
and mainly inland from the Great Lakes.

.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 PM Lake Superior forecast issuance)
Issued at 349 PM 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 as the pressure gradient relaxes again.

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


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