Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191509

Area Forecast Discussion
National Weather Service Marquette MI
Issued by National Weather Service Gaylord MI
1109 AM EDT Wed Oct 19 2016

Issued at 1109 AM EDT WED OCT 19 2016

12z composite analysis shows a surface cold front crossing western
Lake Superior/western Upper Michigan...trailing southwest back
into southern Wisconsin. Decent low level cold advection behind
this front pulling low clouds into far western Upper and the
Keweenaw Peninsula...12z INL sounding shows a moist layer trapped
between 900-825mb with gravity waves evident in the cloud deck
beneath a sharp inversion. Upper Peninsula lies north of a 130kt
jet axis lifting northeast out of Iowa/southern Wisconsin/northern
Lower Michigan...with general large scale subsidence across the
upper Great Lakes.

Front will continue to traverse the U.P. this afternoon with
winds shifting to the west/northwest in its wake. Biggest issue is
the upstream cloud cover...leading edge of this cloud deck should
continue to advance east this afternoon. Guidance suggests that a
back edge should develop over western Lake Superior and spreading
into western Upper Michigan later this afternoon. Not totally
enamored with this idea given current satellite trends...though
eventually should start to get into some more lake induced
cloudiness by this evening. But should be a decent afternoon
across much of southern/eastern Upper with temperatures well into
the 50s.


.SHORT TERM...(Today and tonight)
Issued at 357 AM EDT WED OCT 19 2016

00Z raobs/latest wv imagery and RAP analysis show some lo amplitude
upr troffing centered over Manitoba extending into the Upr Great
Lks. A shrtwv embedded in this flow/sfc cold fnt is moving toward Lk
Sup, and the accompanying weak dynamic support and mstr shown on the
00Z INL raob has resulted in a good deal of cld cover over nrn MN
moving into the nw cwa. But the relatively weak dynamic forcing/
fairly dry llvls has limited the accompanying pcpn to some isold
showers. Behind the cold fnt, 00Z h85 temps are as lo as -7C at The
Pas Ontario. There is a good deal of lo cld within the thermal trof
trailing the cold fnt.

Today...As the aprchg shrtwv/cold fnt cross Upr MI today, some of
the hi res models generate some lgt pcpn over the Keweenaw this
mrng with upslope w wind enhancing the llvl moistening. So wl add a
mention of some isold light showers in that area. Only some clds wl
accompany the fnt elsewhere. Following the fropa, h85 temps area fcst
to fall to arnd -2C over the w by 00Z Thu, not sufficiently cold for
lk effect pcpn with the wrn Lk Sup buoy reporting a water temp of 9C.
Although the sfc wnw flow wl turn more acyc, upstream sfc obs sug
some lo clds should dvlp/persist over at least the w with the upslope
flow behind the fropa even if the models seem to downplay the lo clds.
Downsloping of the wind should break up these clds over the central.
Max temps wl range fm the upr 40s over the w to the lo 60s over the

Tngt...As the upr trof deepens a bit into the Upr Lks, h85 temps are
progged to fall to -4C to -6C over the nrn tier of the cwa by 12Z
Thu in the nw llvl flow ahead of sfc hi pres moving toward MN. These
temps are sufficiently cold for some lk effect pcpn. Some negatives
for this pcpn are the larger scale acyc flow under fcst deep lyr
qvector dvgc/subsidence and inverted-v nature of the fcst llvl T/Td
profiles shown on the fcst sdngs blo moist lyr at subsidence invrn
base near h85. Since many of the hi res models show some isold
showers over mainly the e half with longer fetch acrs Lk Sup and
downwind of additional moistening off Lk Nipigon, opted to add some
lo chc pops for some showers in the favored nw wind locations e of
Munising. Sfc temps should be sufficiently warm for only rain in
this area given the warm lk temps, as hi as 13C at the Grand Marais

.LONG TERM...(Thursday through Tuesday)
Issued at 323 AM EDT WED OCT 19 2016

Nam shows a 500 mb trough over the upper Great lakes 12z Thu that
digs into the ern U.S. Fri night. GFS and ECMWF show about the same
thing as well. 850 mb temperatures off the GFS and NAM over Lake
Superior drop to around -4C at 12z Thu and then fall to -4C to -6C
over Lake Superior Thu night and Fri. With lake temperatures from 9C
to 12C, this is still enough for lake effect pcpn and had to put in
some slight chance to low chance pops in to cover this into Fri
night. Overall, did not make too many changes to the going forecast
for temperatures or weather except to bump up pops a bit for lake
effect pcpn.

In the extended, GFS and ECMWF show a 500 mb ridge over the southern
plains 12z Sat with a deep 500 mb trough in the ern U.S. 850 mb
temperatures 12z Sat over Lake Superior are from -4C to -6C with
lake temperatures from 9C to 12C. This is still enough for lake
effect pcpn. A shortwave moves into the upper Great Lakes 12z Sun.
the 500 mb ridge builds into the northern plains 12z Mon and this
ridge builds into the upper Great Lakes on Tue. Temperatures will
remain near normal for this forecast period.

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 723 AM EDT WED OCT 19 2016

An extensive area of lo clds/MVFR cigs upstream in MN wl impact IWD
and CMX for at least at time this mrng into the aftn with an
upslope wnw wind before some daytime heating/mixing causes these clds
to sct out. Daytime heating/mixing wl also allow for some gusty
winds today, mainly at the more exposed CMX site. With nocturnal
cooling tngt, expect more clds/MVFR cigs again under subsidence
invrn. Downslope nature of the wnw shifting nw flow at SAW should
result in predominant VFR conditions there.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 357 AM EDT WED OCT 19 2016

Expect winds to remain 20-25 kts or less through the rest of the
week and thru the weekend as a relatively weak pressure gradient

Upper Michigan...None.
Lake Superior... None.
Lake Michigan... None.



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