Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212003

Area Forecast Discussion
National Weather Service Marquette MI
403 PM EDT SUN AUG 21 2016

.SHORT TERM...(This evening through Monday)
Issued at 403 PM EDT SUN AUG 21 2016

12Z raobs/latest wv imagery and RAP analysis show an upr trof axis
extending fm Hudson Bay into the Great Lks downwind of upr rdging
over the Rockies. A diminishing llvl NW flow btwn departing sfc lo
pres in Quebec and an aprchg hi pres rdg stretching fm the Scentral
Plains into MN is beginning to advect drier llvl air shown on the
12Z INL raob into the Upr Lks. Sfc dewpts have fallen as lo as 39 at
Houghton at 19Z. However, the interaction btwn a weak shrtwv aprchg
fm the NW and lingering llvl mstr shown on the 12Z GRB raob under
h85 thermal troffing is still resulting in a good deal of
instability cu/sc and some showers ahead of the line of sharper
drying. Looking farther upstream, there is an area of mid clds over
Manitoba spreading toward NW MN in the SW flow/WAA on the backside
of the sfc hi pres rdg.

Main fcst concerns in the short term focus on cld trends and temps.

Late Today/Tngt...The combination of arriving drier llvl air/incrsg
acyc flow/loss of daytime heating wl cause lingering clds/showers to
give way to clrg skies W-E by sunset. Although skies wl then be
moclr with the passage of sfc rdg axis until some mid clds arrive
over the NW late associated with isentropic ascent depicted on the
305K isentropic sfc, a light NW backing WSW wind under the pres
gradient on the nrn flank of sfc hi pres center passing well to the
S in the OH River valley wl limit the diurnal temp fall a bit and
prevent temps fm reaching current dewpts. Expect the lowest min
temps arnd 45 over the interior Scentral where the gradient wl be a
bit slacker and away fm lk moderation.

Mon...Band of WAA mid clds in the return SW flow behind the
departing sfc hi pres rdg and associated with sharper isentropic
ascent/moistening on the 305K sfc are fcst to impact mainly the N
half of the cwa. Most of the numerical models also generate some
pcpn, but these showers are fcst to remain mainly over Lk Sup and
away fm drier near sfc air over the land cwa and farther S closer to
the sfc hi center in the OH Valley. With incrsg pres gradient, SW
h925 winds are fcst to reach aoa 25 kts during the aftn over the W.
In the presence of daytime heating/ mixing, expect some gusty winds,
especially over the W. H85 temps are fcst to reach near 16C over the
NW half in the aftn, supporting hi temps in the lo 80s in that area.
Expect mid 70s downwind of Lk MI.

.LONG TERM...(Monday through Saturday)
Issued at 503 AM EDT SUN AUG 21 2016

Models suggest that a progressive pattern will prevail with a
mid/upper level low/trough over srn BC/Alberta Monday will move to
nrn Ontario by Friday. This will bring a warmup early in the week
with waa ahead of the sfc low and increasing shra/tsra chances
Wednesday as the sfc trough/front moves into the region. Cooler and
drier weather will then move in toward the weekend as high pressure
builds from the nrn plains into the Great Lakes.

Monday into Monday night, shra/tsra associated with the initial waa
surge and 300k-305k isentropic lift along the 850 mb warm front will
remain from nrn Lake Superior northward. With 850 mb temps climbing
into the 11C-14C range, highs will rebound into the mid 70s east to
around 80 west. 850-700 mb theta-e advection and an increasing low
level jet may support shra/tsra development but coverage/strength
will be limited given the dry antecedent airmass.

Tuesday, continued waa and increasing mid level capping will will
reduce any pcpn chances and allow temps to climb into the mid 80s
with dewpoints into the lower 60s.

Wednesday and Thursday, as the sfc trough moves into the area expect
shra/tsra chances to increase by late wed into wed night as moisture
advection bring PWAT values above 1.5 inches. However, only chance
pops were included with uncertainty remaining with
the timing/position/strength of any shortwaves emerging from the
plains that will help support the pcpn. Instability/shear will be
marginal for any stronger storms. The pcpn chances will shift to
mainly the ern cwa by Thursday morning.

Friday into Saturday, Surface high pressure and upper ridging will
then bring dry and mostly clear conditions Friday into early
Saturday. A transition to a more zonal pattern during the weekend
will allow pcpn chances to increase as models suggest potential for
a shrtwv to bring another round of shra/tsra toward the area.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 136 PM EDT SUN AUG 21 2016

Although there will be some lingering sc clds this aftn and some mid
clds wl move into the area late tngt/Mon, the arrival of drier near
sfc air shown on the 12Z INL raob wl result in VFR conditions at all
3 TAF sites this fcst period. Gusty NW winds this aftn, especially
at the more exposed CMX location, wl diminish this evng with loss of
daytime heating/arrival of hi pres rdg. Expect some gusty SW winds
to dvlp late in the TAF period as the pres gradient sharpens again
on the NW flank of the departing rdg.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 403 PM EDT SUN AUG 21 2016

As a hi pres ridge axis passes Lake Superior tonight, expect NW
winds up to 20-25 kts this evening to diminish and back to the SW by
Mon morning. The pres gradient is fcst to sharpen on Mon thru Tue
between the departing hi pres and an approaching cold front, so
expect the SSW winds to pick up to 20-25 kts again as soon as Mon
night and continue at times into Wed. Winds will shift to the W-NW
up to 25 kts following a cold frontal passage late on Wed and
continue thru Thu. After the trailing hi pres shifts to the E on
Fri, winds will shift back to the SW.

Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for MIZ005-

Lake Superior...
Lake Michigan...


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