Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 171037

Area Forecast Discussion
National Weather Service Marquette MI
637 AM EDT Sat Jun 17 2017

.SHORT TERM...(Today and tonight)
Issued at 327 AM EDT SAT JUN 17 2017

Upper air pattern consists of a 500 mb ridge across the desert sw
and troughing in the ern U.S. and westerlies along the northern U.S.
in zonal flow. There are numerous shortwaves in the westerlies with
one over northern WI this morning. This moves through quickly.
Another shortwave along the Alberta/MT border heads east and digs
into the northern plains this afternoon and evening. GFS, ECMWF and
NAM show 850-500 mb q-vector convergence moving through the area
tonight along with deeper moisture. Overall, did not make too many
changes to the going forecast overall for temperatures or weather.
Highest pops will be tonight with the shortwave moving across the
area. Pops increase this afternoon with lake breeze boundaries and
nearing of shortwave along with diurnal heating all coming together.

.LONG TERM...(Sunday through Friday)
Issued at 345 AM EDT SAT JUN 17 2017

Temporary switch to cooler weather pattern in store late this
weekend into early the upcoming week. Instigator for the change is
shortwave sliding across northern Rockies this morning. By Sun
morning this shortwave trough digs across the Upper Great Lakes into
the base of mean troughing that has persisted over Manitoba and
northern Ontario recently. As this shortwave slides through, sfc low
vcnty of nothern WI into northern Lk Michigan is expected to deepen
as it lifts across southeast to eastern Upper Michigan into early
Sun afternoon. There also may be additional sfc trough or
reinforcing cold front dropping WNW to ESE across Upper Michigan in
the aftn.

Evolution of how convection will work out on Sun is muddled. Based
on shortwave and sfc low position, model qpf and model
reflectivities, seems there is at least a loose signal of convective
complex over scntrl forecast area in the morning sliding into the
eastern forecast area by midday then other showers and possible
thunderstorms developing with some heating during the day along
and ahead of the cold front. If those aftn storms form over the
east then there could be enough shear (25-35 kts) to support
possible marginally severe storms. Otherwise the shear over the
west looks too weak to support severe threat there. Based on
widespread rain falling across still cool waters of Lk Superior,
kept a mention of fog over Lk Superior and adjacent shoreline
areas. If fog forms could linger even as late as Mon aftn
especially across Lk Superior.

Initial shortwave lifts into Quebec by Mon morning. Another
shortwave and upper jet energy digging into central Conus will
continue to deepen the mean trough further allowing cooler than
normal conditions into early this week. Could be some showers and
possible thunderstorms Mon and Tue, mainly during the peak heating
of the aftn. Shear is weak with upper trough axis overhead but
freezing levels will be lower. Suppose either day with enough
heating there could be potential for marginal severe hail. Would
expect smaller hail in any vigorous convection either day. Wed
still looks mainly dry with upper ridge moving in and sfc ridge
drifting across. Temps inland will return toward normal values
well into the 70s but lake breezes will cool down lakeshore
locations by aftn.

Thu into Fri, upper troughing moves from western Canada to
Manitoba and northern Ontario. Sfc low will arc a warm front
across Upper Great Lakes on Thu with cold front crossing region by
Fri as the sfc low crosses northern Ontario. Depending on extent
of clouds and rain on Thu could get very warm with readings into
the 80s in some areas as temps at h85 reach 13-15C. Decent signal
that as forcing from upper trough and sfc low/cold front interact
with edge of elevated mixed layer just to sw of Upper Michigan
there could be strong to severe storms somewhere in our region
late Thu into Thu night. Most of the precip should be east of the
area on Fri as the cold front sweeps instability/tsra out of the
area with drier air returning. Temps on Fri could still reach
above 80 over the scntrl.

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 637 AM EDT SAT JUN 17 2017

More showers are expected as another disturbance moves through the
area this forecast period. Best chances for rain would be tonight.
Expect VFR conditions through most of the period with fog and low
clouds forming tonight at all sites. Lowest conditions will be at
SAW tonight. Will be some lingering IFR/MVFR conditions this morning
at SAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 327 AM EDT SAT JUN 17 2017

There could be some pockets of locally dense fog, especially across
the east through tonight with the widespread rain. Winds look to
stay below 20 knots for this entire forecast period.

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


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