Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240929

Area Forecast Discussion
National Weather Service Marquette MI
529 AM EDT SUN JUL 24 2016

.SHORT TERM...(Today and tonight)
Issued at 529 AM EDT SUN JUL 24 2016

Water vapor imagery and RAP analysis show a vigorous shortwave along
the Manitoba/Ontario border. Convection that spread from MN
yesterday se into northern IL/IN during the night has hindered more
substantial development farther n into the Upper Great Lakes. An
area of showers did consolidate into central Upper MI. Those shra
are now moving into the eastern fcst area. Latest RAP shows nose of
40kt low-level jet aimed into eastern WI, and that is where
shra/tsra have developed over the last few hrs. Meanwhile, line of
shra/tsra that developed ahead of occluded front in MN last evening
now extends from nw WI n into northern Ontario.

SPC meso analysis overnight has shown mucape increasing just ahead
of the shra/tsra approaching western Upper MI, so this convection
may hold together at least into the w half of Upper MI as it moves e
this morning. Not expecting this activity to pose a svr risk, but
gusty winds may occur along with brief hvy rain. Of much more
interest will be the potential of new convection to develop along
occluded front as it pushes across the area today. Compared to
yesterday, majority of model guidance has shifted new development
farther w into central Upper MI as opposed to eastern Upper MI as
vigorous mid level dry slotting and potential capping does not get
out ahead of the front. With front slicing thru central Upper MI
early to mid aftn, convective temps in the lower 80s being reached,
and mlcapes increasing to 1000-2000j/kg, expect isold/sct tsra
development to occur. Some high res model guidance veer winds more
sharply into n central Upper MI with lake breeze development as
gradient winds diminish near frontal boundary. So, Marquette county
may be the main initiation point for new convection this aftn with
development e and se from there. With deep layer shear of 40-50kt,
if storms develop, they will become well organized with some likely
to become svr. As was the case yesterday, models show impressive sfc-
mid level delta theta-e values of 30c or more, enhancing the risk of
damaging winds. While wet bulb zero heights are on the high end of
the range for favoring large hail, the likelihood of well-organized
storms due to healthy deep layer shear will support a large hail
risk. Expect a very uncomfortable, humid day today as dwpts push aoa
70F. Dwpts will begin to fall over the w this aftn.

Any lingering shra/tsra over the far eastern fcst area will end this
evening. Otherwise, expect mostly clear skies across the area

.LONG TERM...(Monday through Saturday)
Issued at 503 AM EDT SUN JUL 24 2016

Monday and Monday night: The upper level 500mb trough and surface
trough will continue eastward through this time period as high
pressure slides into the area. Aloft zonal flow will slide across
the Upper Great Lakes by Monday afternoon.  Dry air, shown in the
1000-500mb layer, will keep skies mostly clear through this time
period with much more comfortable humidity levels along with
coolerhigh temperatures. The pressure gradient ahead of the surface
ridgewill favor a west-northwest flow across Lake Superior with
gusts upto 25 mph. This will create a moderate to high swim risk for
beachesalong the Alger County shoreline.

Tuesday through Wednesday night: A cold front is progged to sag
southward from Canada into the Upper Great Lakes Region as the
surface high slides to the east. Southerly flow on the back side of
the high will help to increase moisture into the area. This, along
with forcing along the front will provide chances of showers and
thunderstorms for most of the CWA through this time period as the
weak cold front stalls across or just south of the area by Wednesday
night. MUCAPE values are not overly impressive, generally progged to
be around 500-750 J/KG Tuesday afternoon/evening and again Wednesday
afternoon/evening. Severe weather potential is looking very low at
this point, through the entire time period, as the system will lack
any major dynamical support. Shear values are progged to remain
around or below 20 knots through this forecast period. Details will
be ironed out as we move closer; however, at this point, it is not
looking too favorable for severe weather.

Thursday through the extended: Model solutions begin to diverge, as
is typical this far out, but the general trend will be for more of a
troughing pattern across most of the eastern CONUS with upper level
ridging building across the western CONUS. This would keep the Upper
Great Lakes cooler with embedded shortwaves sliding thorough the
area during this time period. Overall confidence in any one specific
model remains fairly low with timing/strength of the aforementioned
waves; therefore, will stick closely to model consensus which keeps
small chances of showers intermittently through Thursday through

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 107 AM EDT SUN JUL 24 2016

Showers continue over portions of Upper Michigan early this morning
with more shower and thunderstorm activity approaching the region
from the west. This second batch of precipitation is associated with
a cold front that will push into the KIWD area around 12Z...and KSAW
before 20Z. Showers and thunderstorms will be possible overnight but
expect most will be confined fairly close to the front. MVFR
conditions are possible with the storms. Once the front passes
through, the precipitation will end as drier air filters in. Daytime
mixing will produce gusty winds over the western sections of the
U.P. with KCMX experiencing the strongest gusts...up to 27 knots...
during the afternoon. Winds will slacken a bit as the evening
approaches at KSAW and KIWD but will remain gusty at KCMX thorough
the evening.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 529 AM EDT SUN JUL 24 2016

In the wake of a cold front pushing across Lake Superior today,
expect w winds to increase up to 20kt with gusts to 25kt from w to e
this aftn/evening after it passes. These stronger winds will persist
into Mon morning before gradually diminishing. Winds for the
remainder of the fcst period will mostly be at or blo 15kt.

Humid air mass over the area ahead of the passing cold front may
allow patchy fog to develop today.

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


SHORT TERM...Rolfson
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