Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240745

Area Forecast Discussion
National Weather Service Marquette MI
345 AM EDT Mon Jul 24 2017

.SHORT TERM...(This evening through Monday)
Issued at 244 PM EDT SUN JUL 23 2017

No major weather impacts expected through the short-term portion of
the forecast; however, larger waves and onshore winds will keep a
moderate to high swim risk in place into this evening.

Low pressure over the Lower Great Lakes will steadily shift off to
the east of the U.P. tonight through Monday afternoon. At the same
time, dry high pressure will build into the western half of the U.P.
tonight and then across all of the Upper Peninsula for Monday. There
may be continued cloud cover and a few rain showers in the evening
over the eastern U.P.; however, the trend will be for this to
diminish through the overnight hours. Otherwise, temperatures will
be cool tonight over the west half as skies clear, with temperatures
dropping well into the 40s. The east half may stay generally in the
50s with the clouds lingering through the early overnight hours.
Sunday, temperatures will warm into the 70s under mostly sunny skies
with fairly light winds.

.LONG TERM...(Tuesday through Sunday)
Issued at 344 AM EDT MON JUL 24 2017

The main concern through the extended will be the arrival of a cold
front late Tuesday through Wednesday, with the possibility of a few
strong to severe storms. Otherwise, the latter half of the week and
the first half of the weekend should remain dry as high pressure
takes over behind the exiting cold front. Towards the end of the
weekend, another trailing cold front is progged to move across Upper

Ahead of the cold front there is some uncertainty in how warm 850mb
temperatures will get, for the most part models are ranging between
15 and 20C. This warm air advection coupled with increasing gradient
flow from the south-southwest will allow downsloping to aid in the
warming. Therefore, have continued the trend of bumping temperatures
up a bit, especially across the west and central portions of Upper
Michigan. Winds should increase throughout the day as the pressure
gradient builds ahead of the approaching cold front, so confidence
in any lake breezes developing along Lake Superior are rather low at
this time. Therefore, currently thinking that any storms that do
develop Tuesday afternoon/evening should be confined mostly to the
western portions of the area once the 900-800mb moisture transport
starts to ramp up. A few storms in the evening may be strong to
severe, but it looks like the better instability will not arrive
until the overnight hours as the deeper moisture lifts across the
area. Therefore, Tuesday night with the medium range models
suggesting upwards of 1000-200 J/kg of MUCAPE with moisture
transport streaming across the area wouldn`t be surprised if a few
storms remain strong to marginally severe. As we progress into the
early morning hours on Wednesday, the 1-7km shear really starts to
drop off, from around 30-40 knots to maybe 15-20 knots; therefore,
while showers and storms will continue to push east across Upper
Michigan, the intensity of the convection should begin to wane. On
Wednesday, things get a bit more complicated as ongoing showers and
storms and their resulting cloud cover may inhibit the amount of
diurnal instability that develops during the afternoon hours. It
isn`t out of the question that convection strengthens in the
afternoon as it tries to become more surface based, but it seems
more plausible that storms may just pulse up and down. If storms can
become surface based in the afternoon, with 0-6km shear increasing
to around 40-50 knots, we would be looking at a high shear, low CAPE
day where some rotating updrafts may be able to sustain themselves.

The front is expected to push southeast of the area Wednesday night
into Thursday as a post-frontal dry and stable air mass drops south
from Canada and high pressure begins to take over through the first
half of the weekend. Cold air advection doesn`t look terribly strong
behind the exiting cold front, so afternoon insolation should be
more than enough to modify temperatures nicely during the afternoon
hours each day. The latter half of the weekend a weak cold front
will push south across the area. Confidence at this time is not high
as to whether or not we will see any precipitation out of the front.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1222 AM EDT MON JUL 24 2017

Low level moisture and light winds has resulted in dense fog and
VLIFR conditions already setting up at IWD. Expect litle improvement
through the night but should see quick improvement after sunrise
this morning. Skies have cleared out at CMX and SAW this evening.
Could be some fog at both sites as radiational cooling will be
substantial enough to allow fog to form as high pressure builds over
the area. LIFR vsby of a 1/2sm to 1sm are possible at both sites.
Any low clouds and fog at CMX and SAW should diminish quickly after
sunrise this morning.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 244 PM EDT SUN JUL 23 2017

North to northeast winds gusting 20 knots will gradually diminish
tonight into Monday as high pressure moves across the area and the
pressure gradient weakens. The next chance for stronger winds from
the south to southwest over 20 kts will be Tuesday afternoon into
Wednesday morning over eastern sections as a low pressure trough
crosses the region. Otherwise, winds this week will be 20 kts or

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


LONG TERM...Ritzman
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