Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240903
AFDMQT

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

.SHORT TERM...(This evening through Sunday)
Issued at 402 PM EDT SAT JUL 23 2016

12Z raobs/latest wv imagery and RAP analysis show an upr rdg over
the Upr MS River Valley extending into NW Ontario, supporting sfc hi
pres over NW Ontario into the Upr Lks. This hi pres and dry airmass
shown on the 12Z GRB raob are bringing a mosunny conditions to Upr
MI today. With h85 temps up to 18-20C near the WI border, sfc temps
away fm lk moderation have risen into the 80s and are even aprchg 90
at a few spots even though hi clds are rolling into the area.
There is a potent shrtwv over srn Saskatchewan moving to the E,
supporting a lo pres moving into Manitoba under 00Z-12Z h5 hgt falls
up to 100m. A complex of showers/TS in the nrn plains ahead of
occluded fnt stretching to triple pt lo pres moving toward wrn MN.
Another band of showers and storms are aligned fm central MN into SW
WI along the warm fnt to the E of this lo and SPC mesoanalysis axis
of hier muCape. Sfc dewpts just to the S of the warm fnt are as hi
as the mid/upr 70s close to area of pwat aprchg 2 inches shown on
the 12Z Omaha/Des Moines raobs.

Main fcst concerns in the short term focus on shower/TS chances as
shrtwv to the W continues along just to the N of the Cndn border and
the potential for some severe TS.

Tonight...Scattered showers/a few TS may dvlp as early as 22-23Z
near Ironwood with aprch of MCV generated by upstream convection in
MN and as the sly flow increases btwn the departing sfc hi pres rdg
and aprchg shrtwv/axis of lo pres and advects some moister air back
into that area even though thickening hi clds wl limit the sfc-based
destabilization. Then more widespread elevated showers/TS wl arrive
over the W by late evng as the strenghtening SW llj, with h85 winds
up to 45-50kts, results in vigorous h85 theta-e advctn/h85-5 qvector
cnvgc. Strong W winds aloft up to 40-45 kts suggest the elevated TS
may tend to bow out. Although bowing storms would favor damaging
winds, hier near sfc stability ahead of warm fnt and rapid
moistening aloft that would reduce negative buoyancy might tend to
offset that threat. Fcst marginal lapse rates/hi frzg lvl arnd
13kft/moist mid lvls wl reduce the threat of large hail. Best chc of
strong winds would be over the W in the evng when residual effects
of daytime warming would support more unstable llvl lapse rates. As
the showers/TS move E, model fcsts of weakening deep lyr shear and
weaker lapse rates/SSI sug the severe threat wl diminish. Some
drying late under the jet surge region of the shrtwv tracking to the
N wl tend to diminish the showers late over the W. With the influx
of deep mstr/clds and steady S winds, lo temps wl hold above 65 at
most places and drop not much blo 70 at a few spots.

Sun...Vigorous dry slotting under the jet surge region of the shrtwv
passing thru Ontario wl diminish pops W-E on Sun perhaps even ahead
of the occluded/cold fropa, but more sfc based showers/TS may dvlp
on Sun if there is sufficient clrg of lingering lo clds and the mid
lvl drying/capping are not overwhelming ahead of the fropa. Models
show some fairly sgnft differences on this impact, but very
aggressive mid lvl drying favors the 12Z WRF-ARW/Regional Cndn model
scenario. These models show dry wx over most of the cwa but
convection redeveloping arnd 18Z over the far ern cwa arnd Newberry,
where the daytime heating cycle/some lk breeze cnvgc under weaker
pres gradient close to slow moving fnt wl have an impact before the
arrival of the more sgnft capping. If storms do dvlp, they could
become severe under axis of strong mid lvl winds/drying with sfc-12k
ft agl delta theta-e exceeding 30C/sfc-6km shear up to 45kts/h7-5
lapse rates up to 7C/km. With more aggressive dry slotting and
faster return of sunshine especially over the W half, temps should
rebound into the 80s at most places.

.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
Saturday.
&&

.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 PM Lake Superior forecast issuance)
Issued at 404 PM EDT SAT JUL 23 2016

Winds will stay less than 20 kts tonight into Sun but west winds
increase to around 20 kts with gusts to 25 kts Sun aftn into Sun
night and on into Mon morning as winds shift northwest behind a cold
front that moves through late Sun night. Another front moves through
Tue night into Wed, but winds beyond Mon will remain 20 kts or less
as pressure gradient stays weak. Patchy fog is possible tonight and
Sun as a humid airmass briefly returns to the Upper Great Lakes.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...KC
LONG TERM...KEC
AVIATION...RJT
MARINE...JLA



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