Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 150831

Area Forecast Discussion
National Weather Service Marquette MI
431 AM EDT Tue Aug 15 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 226 PM EDT MON AUG 14 2017

Upper air pattern consists of a 500 mb trough over the upper Great
Lakes today with a shortwave ridge moving in for Tue. Nam shows some
850-500 mb q-vector convergence along with some moisture moving
through the area this afternoon before both move out tonight.
Looking at KMQT radar, a cyclonic spin with a MVC is moving across
the western cwa this afternoon into this evening. This will continue
to produce showers as it slowly moves across and have pops in the
likely to chance category as this moves through. There could also be
some lake breeze convergence showers in the east as well. For
tonight, the showers move south of the area and with light winds,
decent radiational cooling possibilities will set up and went below
guidance for low temperatures. Tue looks quiet and dry. Did not make
too many changes to the going forecast overall.

.LONG TERM...(Wednesday through Monday)
Issued at 430 AM EDT TUE AUG 15 2017

Potential for hazardous weather in the long term is centered on Wed
night into Fri as low pressure system crosses Upper Great Lakes.
Heavy rain possible and there is a small potential for stronger
storms Thu aftn over the south central. Small craft conditions on
parts of Lk Superior and Bay of Green Bay/Lk Michigan looking likely
late Wed Night into Friday.

Higher heights still over Upper Michigan on Wed as lead shortwave
trough moves from central Plains to the Upper Mississippi River
Valley. Mid level moisture advection ahead of shortwave could lead
to some showers over western Upper Michigan through the day but
soundings are dry blo h7 so any rain would be light. Temps on Wed
mainly in 70s with upper 70s interior east with less cloud cover
there through the day. Best chance of rain with this system comes in
later Wed night as primary shortwave trough and associated deep
layer q-vector convergence spreads acrosss Upper Michigan from west
to east. PWATs nearing 2.0 inches into the system could lead to
heavy rain with greatest chance of that on cyclonic nw side of sfc-
h85 lows whch now looks to impact mainly western fringe of Upper
Michigan late Wed night into Thu morning. Could see rain totals over
1.5 inches during this time in those areas while elsewhere totals
could still reach 1 inch. Mid level dry slot working in on Thu will
diminish steady rain, but since sfc low tracks more over north
central U.P. by early aftn and warm sector will affect at least
parts of forecast area could see shra/tsra develop during peak
heating of aftn over scntrl Upper Michigan. If tsra can develop
effective shear 25 to 35 kts could support stronger storms. Still
seems best chance for severe storms will remain south of Upper
Michigan but will need to continue monitoring this potential.

Low pressure will move east of Upper Michigan by Friday morning.
Still will be a lot of low-level moisture lingering in cyclonic NW
flow in wake of the low. Continued to linger clouds/small pops
longer on Friday over the north and east forecast area. Went with
cooler CONSraw temps for highs on Fri which seemed more reasonable
with low to mid 60s near Lk Superior and maybe mid 70s far scntrl.

Dry weekend not as clear cut as it looked yesterday. ECMWF stronger
with secondary shortwave working through on Sat but the other models
are weaker/farther south with the wave that is producing the shra.
Overall all the guidance shows dry weather Sun and increasing
chances of shra/tsra on Monday as cold front approaches. Only main
change was to increase max temps Sun and Mon ahead of the front.
Should see temps each day be able to reach upper 70s or lower 80s.
Could even be warmer with h85 temps 16-18c, but the adjustment
over consensus is a start for now.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 136 AM EDT TUE AUG 15 2017

Radiational fog, dense at times blo mins, will continue to develop
and thicken at KIWD overnight but should be relatively shallow and
variable. Some fog will also develop at KSAW and KCMX but is not
expected to be as thick with only occasional IFR conditions. Expect
the fog to dissipate by mid morning with VFR conditions through
the rest of the day.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 226 PM EDT MON AUG 14 2017

Winds less than 20 kts into Wed with high pressure overhead, then SE-
E winds increase to 15-30 kts late Wed into Thu as a low pressure
system crosses the Upper Great Lakes. Strongest winds, with gusts to
30 kts, will be over western Lk Superior Wed aftn into Wed evening
then shifting to eastern Lk Superior late Wed night into Thu
morning. NW winds behind the low could then reach 20 kts late Thu
into Fri, strongest over east half of Lk Superior. Winds diminish to
20 kts or less next weekend as high pressure builds back overhead.

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


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