Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181919

Area Forecast Discussion
National Weather Service Marquette MI
319 PM EDT Sun Aug 18 2019

.SHORT TERM...(This evening through Monday)
Issued at 314 PM EDT SUN AUG 18 2019

Scattered showers, with thunder generally having subsided within the
forecast area, will push off toward the north and east this
afternoon, with much drier air already knocking on Ironwood`s door.
All precip should be clear of the U.P. by around midnight tonight,
with some uncertainty about whether or not fog will develop on the
backside. Although have included fog mention in some interior
locations (generally close to the WI border), confidence is low
given this dry airmass working its way in. Dewpoint depressions may
very well be low enough to support shallow fog in prone locations,
particularly where better measurable rain fell today. Look for lows
in the 40s in the interior tonight, lingering in the 50s to around
60 along the lakeshores.

Benign weather will dominate tomorrow as surface high pressure
marches into the Great Lakes region. However, tight pressure
gradient will remain overhead with the center of the high well to
the south, yielding gusty winds again tomorrow, particularly for
locations along the lakeshore lines and Isle Royale. With the
aforementioned dry airmass moving in, RHs may easily drop down into
the 30 percent range for inland spots, potentially posing a concern
for fire weather interests. See the latest fire weather discussion
for more details. As for temperatures, widespread 70s and 80s can be
expected for highs, ensuring a beautiful Upper Michigan summer day
is in store.

.LONG TERM...(Monday night through Sunday)
Issued at 318 PM EDT SUN AUG 18 2019

Zonal flow is expected to be in place across the northern CONUS and
southern Canada Monday evening, with an exiting sfc high to the
southeast of Upper Michigan. An upper ridge is expected to amplify
over the PacNW and Big Sky Country through the day Tuesday, with a
closed upper low spinning through northern Manitoba to northern
Ontario and eventually to Maine/New Brunswick by Saturday morning.
Following a quick shortwave passage Tuesday afternoon and evening,
the upper ridge translates slowly east towards the Upper Great Lakes
that will keep conditions mostly dry Wed-Fri. A southern stream
trough will develop late this week over the Plains, potentially
leading to split flow over Upper Michigan next weekend and an
uncertain precipitation forecast for that time period.

On Tuesday, a shortwave and cold front will be crossing MN, reaching
western Upper Michigan by mid afternoon. Some shower and storm
development is possible ahead of the front, but is still quite
questionable as most guidance indicates q-vector convergence will
gradually weaken as the disturbance reaches and crosses our area.
Frontal strength and associated convergence is also a bit fuzzy at
this time, and soundings indicate the cap may not mix out ahead of
the front. If storms are able to develop, a stronger storm or two
cannot be ruled out with ensemble mean MUCAPE ~1250 J/kg near the WI
border west of IMT and 35-40 kts deep layer shear, but at this
juncture the chances of development over Upper Michigan are low
enough to cap POPs at 40 west and lower still over the east.

Ahead of the front, it will be a little breezy with gusts to 20 mph
possible over the east half. It will be warm and dry as well and
early this morning the HDW indices were progged to perhaps reach the
95th percentile. But with RH values not expected to drop much below
40%, I`m not convinced that fire weather concerns will be realized.

Behind the front, an early preview of a fall-like airmass will mean
highs in the mid 60s to mid 70s, coolest Thursday. Conditions will
again be a tad breezy across the region Wednesday. It does appear
mostly dry during this period as the eastern periphery of high
pressure attempts to move in. Another relatively dry trough axis
aloft may move through Wednesday night into Thursday. Although
confidence is too low to warrant introducing POPs at this time, some
isolated drizzle/shower activity will be possible Thursday,
especially near Lake Superior. Cloud cover was increased from the
blend population during the day, however, as we frequently see more
clouds in these CAA regimes late in summer.

Return flow should begin to gradually pick up on Friday, bringing
temperatures back to more seasonal values. Slight chances for
precipitation re-enter the forecast next weekend, primarily over the
west half, but there is relatively low confidence during that time
frame. Better precipitation chances may hold off until early next

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 146 PM EDT SUN AUG 18 2019

MVFR ceilings are currently dominating at all three terminals,
with improvements expected later this afternoon at KIWD/KCMX, and
this evening at KSAW. In the meantime, showers with perhaps some
lightning will persist. Westerly winds, already breezy at KIWD
and KSAW, will pick up at KCMX as the low responsible for today`s
active weather moves off to the northeast, with a tight pressure
gradient on the [leading edge as well as the] backside. Surface
high pressure will be trekking into the Great Lakes region tonight
through tomorrow, leaving Upper Michigan on its windy side
through the remainder of this TAF period, but ushering in dry air
aloft to clear out clouds relatively quickly. Expect VFR
conditions to prevail late tonight into tomorrow.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 257 PM EDT SUN AUG 18 2019

Winds becoming westerly later today into tonight will remain gusty,
with up to localized 30 knot gusts not out of the question. While
there may very well be a lull in gusts after midnight through
tomorrow morning (topping out around 20 knots), gusts pick back up
by the midday hours on Monday, with the highest gusts (25 to 30
knots) expected in the western portions of the lake. Winds will then
taper off to less than 20 knots overnight Monday through Tuesday
night. Wednesday could see some elevated winds again, approaching 25
knot gusts, but is anticipated to be fairly short-lived, simmering
back down to generally less than 15 knots into next weekend.

Any lingering thunderstorms this afternoon will diminish by tonight,
with thunderstorm chances returning on Tuesday. Benign weather
conditions then prevail until around the end of the week when the
next potential storm chances return.

Upper Michigan...
  Beach Hazards Statement until 11 PM EDT this evening for MIZ014.

Lake Superior...
Lake Michigan...


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