Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212326
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
726 PM EDT THU JUL 21 2016

.SHORT TERM...(This evening through Friday)
Issued at 354 PM EDT THU JUL 21 2016

MCS/Squall line that produced widespread wind damage over especially
northwest Upper Michigan earlier this morning is now a broken line
of storms from Georgian Bay southeast Lower Michiagn and to northern
Indiana. WV loop shows strong subsidence/drying across Upper
Michigan in the wake of the MCS. Still warm and humid with temps to
near 90 degrees and dwpnts as high as around 70 degrees. Heat index
values have reached mid-upper 90s. Despite the soupy airmass there
is hardly any cu due to drying aloft and capping seen on 12z INL
sounding with convective temp of 99 degrees. Additional area of sct-
bkn mid clouds is sliding eastward across central MN to central WI
and stronger shra/tsra have formed in last couple hours over west
central WI. All this activity is lined up along better PWAT gradient
and attm based on radar extrapolation and veered h85 flow expect it
to stay mostly south of Upper Michigan. Various high res models have
been persistent in showing this as well.

Later this evening stronger shortwave currently crossing northern
Ontario helps propel sfc trough across Lk Superior and Upr Michigan.
The trough will allow winds to shift to the northwest allowing drier
air to advect over the area with dwpnts falling back into the 50s
late tonight into Friday. Even with the convergence on the wind
shift the overall larger scale subsidence/q-vector divergence in
wake of the northern Ontario shortwave should prohibit additional
shra/tsra tonight. Models have been latched on to that scenario for
a while now and it still seems reasonable. Lows tonight will remain
mild in the 60s but will be more in the lower 60s over western Upr
Michigan. On Friday high pressure rolls across and the dry weather
should continue. Temps aloft still quite warm though with h85 temps
up to 22c, warmest over the south central. Increased highs into the
mid 90s south central and kept them in the upper 80s to around 90
elsewhere away fm the Lk Superior shore over western Upr Michigan.
Lower dwpnts though, perhaps as low as 50 over interior west, will
take the edge off of the third consecutive day with very warm
temperatures.

.LONG TERM...(Friday night through Thursday)
Issued at 325 PM EDT THU JUL 21 2016

A mean upr rdg wl bring above normal temps to the area thru this
weekend. Expec a sfc Hudson Bay hi pres rdg to cause dry wx for Upr
MI Fri ngt thru Sat. But then a strong upr disturbance pushing ewd
thru Ontario is then likely to bring more showers/TS Sat ngt into
Sun, and some of the storms could be severe. Drier and somewhat
cooler air wl follow this disturbance early next week before
disturbances moving E thru a WNW flow aloft bring a chc for some
showers/TS mid next week along with near normal temps.

Fri ngt/Sat...Sfc Hudson Bay hi pres rdg ahead of upr rdg axis in MN
is fcst to dominate this fcst period and bring generally dry wx.
Although models hint some hi clds may return over the W on Fri ngt,
some interior locations could see temps fall into the upr 50s with
lgt winds. A strong shrtwv is fcst to push into the nrn plains on
Sat, supporting deepening lo pres in the nrn plains/SCentral Canada.
In general, models have tended to slow down the ewd progression of
this disturbance, so most of the guidance shows Upr MI remaining dry
the entire day even though some hi/mid clds wl drift into the area
ahead of the accompanying lo pres/warm fnt in the Upper MS River
Valley. Although these clds wl tend to cap max temps a bit, h85 temps
rising toward 18-20C over the W in the aftn wl still support max
temps well into the 80s. Locations near the Great Lks wl be cooler
with relatively weak pres gradient allowing lk breeze formation.

Sat ngt/Sun...This period looks like the best chc for some showers/
TS as potent shrtwv moves to the E along the Cndn border,
accompanied by sfc lo pres in Ontario/attendant occluded fnt/warm
conveyor belt with axis of pwat 1.5-2.0 inches. Most of the models
generate some moderate qpf during this period. The 12Z GFS is a bit
of an outlier among the guidance by showing less qpf because this
model fcsts more of the convection wl remain to the S on Sat ngt/Sun
and thus distrupt mstr inflow into Upr MI. While this scenario is
plausible, wl trend the fcst toward hier likely pops until more of
the models move in this direction. Numerous showers and elevated TS
wl arrive over the W half on Sat ngt and then overspread the E
half on Sun mrng. Considering the strength of the disturbance and
ribbon of strong mid lvl winds/h5 winds fcst up to 40-50kts/as well
as plentiful mstr and some instability with SSI fcst up to -3C to
-5C, some of the stronger storms could be severe with large hail
especially over the srn counties even if they are elevated to the N
of warm fnt/triple pt lo that may remain to the S of Upr MI. Vigorous
dry slotting under the jet surge region of the shrtwv wl diminish
pops W-E on Sun following the occluded/cold fropa, but more sfc based
showers/TS may dvlp in the aftn especially over the W and central if
there is sufficient clrg of lingering lo clds and the mid lvl drying/
capping are not overwhelming. If sfc based storms do dvlp, these
could be severe under axis of strong mid lvl winds/drying. Temps wl
fall no lower than the 60s on Sat ngt. Depending on the degree of
clrg on Sun aftn, some places especially over the W half could see
temps rebound well into the 80s.

Sun ngt thru Tue...Arrival of dnva/deep lyr qvector dvgc with more
dry advection in the wake of exiting shrtwv as well as nocturnal
cooling on Sun ngt should diminish any lingering showers/TS over
mainly the E half. A cooler and drier airmass with h85 temps 12-14C
in NW flow ahead of trailing sfc hi pres wl then dominate on Mon.
Tue should be mosunny and a bit warmer under lingering sfc hi pres/
h85 temps rebounding close to 16-17C.

Wed/Thu...As is typical in the summer, explicit model output shows
quite a bit of variability on timing of shrtwvs fcst to impact the
Upper Great Lks under WNW flow aloft mid next week. Wl carry some
chc pops on Wed/Thu to account for this variability.  Temps wl
probably be close to normal as h85 temps are fcst not far fm 15C.
&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 724 PM EDT THU JUL 21 2016

Expect VFR conditions to prevail through Friday as drier air moves
into the region. Only issue will be gusty westerly winds early this
evening and again on Friday especially at the more exposed CMX
location where gusts could exceed 25 knots.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 354 PM EDT THU JUL 21 2016

Expect winds to hold below 20 kts through the forecast period under
a relatively weak pressure gradient and high overwater stability.
Patchy fog through tonight then more fog is possible late in the
weekend as another humid airmass moves over the Upper Lakes.
&&

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

$$

SHORT TERM...JLA
LONG TERM...KC
AVIATION...Voss
MARINE...JLA



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