Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251743

Area Forecast Discussion
National Weather Service Marquette MI
143 PM EDT Tue Jul 25 2017

.SHORT TERM...(Today and tonight)
Issued at 450 AM EDT TUE JUL 25 2017

Quiet to start the day, but changes begin later today. WV loop and
00z RAOBs show strong upper low over Saskatchewan with h5-h3 jet
ahead of the feature and associated sfc trough aiding in widespread
shra/tsra development over Manitoba to northern Ontario. Other
clusters of tsra are roaming over southern MN along gradient of
MUCAPE over the northern Plains. Area of mid clouds and showers have
expanded across Twin Cities and is pushing into wcntrl WI. Expect
remnants of this convection in form of bkn mid clouds and some light
showers/sprinkles to make it to the western forecast area later this
morning or early aftn. Not sure how far east these remnants make it
by late this aftn but did increase clouds some to account for it.
High temps without this would be able to reach low to mid 80s over
the west but tempered that somewhat with potential for thicker cloud
cover. Still most areas in U.P. should reach upper 70s/around 80 by
late today.

Expect shra/tsra chances to ramp up this eveing over the west as
edge of stronger h5-h3 jets arrive and lead shortwave ahead of the
main upper low moves in. As this occurs, 925mb-850mb moisture
transport will be increasing into northern WI with 1-6km MUCAPE of
1000-1500 j/kg expanding into northern Wi and western Upper
Michigan. Could be strong to severe storms over at least the far
west late evening into the early overnight given the instability and
effective shear to 35 kts. Heavy rain also possible with h85 Td
pushing over 15C/K index over 30 as theta-e advection increases from
the Upper Mississippi River Valley. Shear comes down later after
midnight but elevated CAPE over 500j/kg and stronger system moving
in along with main sfc front pushing over western Upper Michigan
should still support at least some risk of stronger storms making it
across the rest of the forecast area. Shear does increase again late
tonight though after 09z especially over Keweenaw and Lk Superior as
main upper wave is crossing northern Ontario.

Overall there is a risk of strong to severe storms tonight just
about anywhere, especially if stronger shear is more persistent than
models are showing attm. SPC has slight risk over far west and
marginal risk for rest of forecast area. Main hazards would be hail
and gusty winds (since it will be a warm and mixed out night already
with lows staying in the mid to upper 60s and sw winds 10-20 mph
with higher gusts). Heavy rain will be a hazard as well.

.LONG TERM...(Wednesday through Monday)
Issued at 356 AM EDT TUE JUL 25 2017

Overall, busy start to the middle of the work week, but then things
quiet down through the end of the week. A round or two of showers
and storms is possible on Wednesday as a cold front moves across the
area, a few storms could be strong. Also, ahead of this cold front,
strong and gusty southwest winds will create a moderate swim risk on
Wednesday for the northern shores of Lake Michigan. After the cold
front pushes across the area Wednesday night, there will be a slight
chance for showers as a shortwave digs south across the area on
Thursday, then things quiet down through the fist half of the

Wednesday, lingering warm air advection showers and thunderstorms
across the central and east will continue to push eastward
throughout the morning hours. During the afternoon as the cold front
continues to push east across Upper Michigan, another round of
showers and storms will be possible in the afternoon, especially
across the east and south central. While cloud cover from convection
earlier in the day will likely hinder the amount of diurnal
destabilization, it isn`t out of the question that a few storms
could be strong to marginally severe, especially with the main
shortwave trough progged to dig southeast across Lake Superior and
over eastern portions of the area. The SPC has kept us within the
marginal risk for severe storms, which in this case given the
uncertainty in how the atmosphere will recover after early morning
convection seems appropriate. Right now it looks like heavy rain and
perhaps some gusty winds will be the main threat with stronger
convection in the afternoon/evening. However, if the atmosphere can
recover, with freezing levels falling right along the cold front
hail would also be a concern with stronger storms.

Wednesday night into Thursday, the cold front will finally push south
of the area and the weather will quiet down. During the day on
Thursday, a stout, fast moving shortwave is progged to dig south
across the Western Great Lakes region. With this wave progged to
come through during peaking heating, it isn`t out of the question
that we see a few scattered rain showers develop across the west and
central; however, better chances look to be right along the
Wisconsin/Michigan border. With little moisture ahead of this wave,
do not expect precipitation to amount to much. Behind this
shortwave, high pressure will begin to settle into the region
Thursday night through much of the weekend. With ample insolation
each day, expect seasonable highs in the 70s and lower 80s. Low
temperatures should remain very comfortable as clear skies give way
to ample radiational cooling each night. Towards the end of the
weekend/beginning of next week another cold front is progged to push
through the region. Confidence in how precipitation chances will
play out along this front is low right now as models diverge in the
strength and timing of the main shortwave aloft.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 141 PM EDT TUE JUL 25 2017

Attention is on a front and associated convection expected to move
through tonight into Wed. Timing, coverage, and intensity of
precipitation and CIG/VIS is uncertain. In addition, there could be
LLWS tonight, but it looks to be just below wind different
thresholds to include in the TAF.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 450 AM EDT TUE JUL 25 2017

Expect stronger wind gusts from the south to southwest of 20-25 kts
this afternoon into Wednesday morning over eastern sections as a low
pressure trough crosses the region. Strongest winds look to occur
late tonight into Wed morning over far east. Winds rest of this week
will be 15 kts or less with exception of Thu aftn into Thu evening
over east when wind gusts from the NNW could reach over 20 kts for a

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


LONG TERM...Ritzman
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