Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281905

Area Forecast Discussion
National Weather Service Marquette MI
305 PM EDT Tue Mar 28 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 304 PM EDT TUE MAR 28 2017

12Z raobs/latest wv imagery and RAP analysis show a shrtwv rdg in
the nrn branch flow over scentral Canada that is supporting a sfc hi
pres over nrn Manitoba expanding into Ontario. There is a weak
shrtwv crossing the Upr Lks, but dryness of the mid lvls shown on
local 12Z raobs is allowing for only some patchy mid/hi clds over
mainly the nrn cwa. Area of fog and lo cld that was over the ern cwa
this mrng with llvl mstr trapped under lo subsidence invrn base as
depicted on the 12Z APX raob has dsptd as the incrsgly acyc llvl nne
flow associated with the expanding sfc hi pres rdg is advecting some
drier air into the area in the presence of daytime heating, which
has aided in mixing out this mstr. The lo cld has been most
persistent near Lk MI and over far ern Lk Sup, where the cooling
influence of the waters have slowed daytime heating/mixing out of
the lo cld. Away fm this area, temps have climbed into the 50s away
fm the cooling influence of Lk Sup. There is quite a bit of lo cld
farther n over Ontario under area of colder near sfc temps.

Main fcst concerns in the short term are lo cld trends/temps. Large
scale subsidence under shrtwv rdging/expanding Hudson Bay hi pres wl
tend to suppress the mid/hi cld and bring dry wx.

Tngt...The Hudson Bay hi pres center is fcst to build slowly to the
se and be centered over far nw Ontario just to the w of James Bay by
12Z Wed. Upr MI wl be under the influence of the acyc, slowly
veering llvl flow toward the ene. Even though the diffluent/acyc
nature of this wind would tend to break up lo clds, concern is lo
clds lingering over ern Lk Sup and spreading s thru Ontario wl
redevelop over mainly the ncentral cwa as the expected ene winds
upslope into that area in the presence of nocturnal cooling. Expect
the lowest min temps over the interior w, where the llvl flow wl
downslope and allow for moclr skies. Not out of the question temps
in this area could fall as lo as the upper teens.

Wed...Upr MI wl remain under the influence of Hudson Bay hi pres
moving slowly to the e to over James Bay by 00Z Thu and slowly
veering llvl flow to the e. Expect any lo clds in the mrng over
mainly the ncentral to mix out with daytime heating. Since h85 temps
wl be 2-3C cooler than tday and hi clds wl be on the incrs, expect
Wed max temps to be lower than today, reaching to near 50 over the
interior w with some downsloping away fm lk moderation.

.LONG TERM...(Wednesday through Monday)
Issued at 411 AM EDT TUE MAR 28 2017

Confluent upper level flow in northern branch of split flow pattern
results in sfc high from Hudson Bay to upper Great Lakes on Wed.
Ridge then slides to Quebec and the lower Great Lakes on Thu. East
to northeast sfc flow into the upper Great Lakes keeps conditions
dry. Onshore flow results in temps staying in the mid to upper 30s
along Lk Superior for Wed while rest of the cwa sees readings rise
through the 40s. A 50 degree reading is possible over far west and
along the WI border.

Attn Wed night into Thu turns to upper low in the southern branch of
the split flow pattern and the associated sfc low. This low pressure
system which looked like it could bring wintry precip to parts of
Upper Michigan late this week now looks to remain south of Upper
Michigan as the confluent upper flow in northern stream and
associated sfc Hudson Bay high pressure continue to dominate. Now,
even the ECMWF and GEM which were showing the system farther north
all along only would bring wintry precip as far north as WI and
northern lower MI. 00z ECMWF did bump back some lighter precip into
the southeast U.P. for Thu, but looking at low-level moisture off
the ECMWF any precip would be hard pressed to make it much farther
north than immediate Lk Michigan shoreline. Southward trend on the
ECMWF and GEM began to emerge on Mon and dayshift already cut pops
based on those trends with more influence from the Hudson Bay high.
Consensus from latest models continues to show even lower pops, now
only grazing scntrl to far se cwa with mainly slight chance pops for
rain/snow mix Thu into Thu night. Even though low levels are dry and
minimal precip is expected should see bkn-ovc mid-high level clouds
later Wed aftn through Wed night and Thu as swath of h7-h5 moisture
(10-20kft agl) streams well to north of the southern stream system.

Clouds clear out west to east late Thu night into Fri resulting in
mostly sunny skies. Most areas will see temps in the 40s on Fri and
possibly near 50 along the WI border. Even with the increasing
sunshine compared to Wed and Thu, temps will stay on cool side in
upper 30s near Lk Superior with ENE winds on northern edge of sfc
low crossing the Ohio Valley and lower Great Lakes.

Split flow pattern does not back off for the weekend and on into
next week. Could be a smaller shortwave/weak sfc trough coming
through on Sat with a few rain showers. Next chance of precip would
be early next week. ECMWF has shown stronger system 3 out of last 5
with even a potential for snow, but GEM and GFS are not as insistent
on that. Split flow pattern will make it tough to pin down specifics
right now.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 138 PM EDT TUE MAR 28 2017

Expect VFR conditions and light winds to prevail at all the TAF
sites this fcst period. However, shallow llvl moisture over Lake
Superior could lead to stratus/LIFR conditions tonight at KSAW under
light upslope ne winds. Right now, potential appears very low, but
did include a mention of sct clouds at 500ft to reflect this
possibility. Any fog and lo clds will burn off by late morning.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 304 PM EDT TUE MAR 28 2017
With no significant weather systems affecting the Upper Great Lakes
for the rest of this week, winds will mostly be under 20kt this
forecast period. The stronger winds (gusting to around 20kt) will
occur tonight thru Wed night under slightly tighter pres gradient
btwn Hudson Bay hi pres and lo pres tracking from the southern
Plains toward the Ohio River Valley.

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


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