Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182114
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
414 PM EST Thu Jan 18 2018

.SHORT TERM...(This evening through Friday)
Issued at 152 PM EST THU JAN 18 2018

Upper air pattern consists of a 500 mb shortwave moving through the
upper Great Lakes today and is replaced by shortwave ridging tonight
into Fri. Moisture is limited for this forecast period and will be
mostly sprinkles or flurries at best if they occur. Best chance for
this would be in the Keweenaw and there could be some freezing
drizzle mixed in with it. Overall, no real big changes to the going
forecast.

.LONG TERM...(Friday night through Thursday)
Issued at 414 PM EST THU JAN 18 2018

...Winter storm possible Sunday night through Monday night but ptype
is still uncertain...

Quiet weather Friday night through Saturday night. High temps well
into the 30s on Saturday with low to mid 40s possible, especially if
clouds hold off til Saturday night. Attn then turns to messy winter
storm Sunday night through Monday night.

Saturday evening the southern stream shortwave trough that currently
is still offshore of the Pacific Northwest will be vcnty of four
corners. Lee sfc cyclone 995-1000 mb will be developing over eastern
Colorado. Weaker lead shortwave, fgen and upper jet may result in
stripe of light snow over parts of Upper Michigan late Saturday
night through Sunday afternoon. With more clouds and some snow
around on Sunday, temps will trend cooler than Saturday with upper
20s north to low to mid 30s scntrl.

Shortwave trough moves toward Upper Mississippi River valley Sunday
night. Sfc low now down to 990-995mb should be btwn Des Moines and
Twin Cities at 12z Monday. Widespread warm air advection precip will
be expanding across Minnesota/Wisconsin and Upper Michigan later
Sunday night into Monday morning. ECMWF continues to not be as heavy
with qpf Sun night over Upper Michigan compared to GFS. GEM somewhat
in between those two ideas. Eventually widespread moderate to heavy
precip spreads across most of Upper Michigan on Monday and it should
stay around through at least Monday evening. It is at this point
where big differences emerge in the guidance for ptype. In general
the latest GFS and GEM show sfc low tracking as far north as central
Upper Michigan on Monday aftn. Both those models are warmer compared
to ECMWF which tracks the low more from southern Wisconsin to
northern lower Michigan. GFS soundings show warm layer up to H9/2kft
AGL. GFS and GEM indicate H925 zero line, which would represent
rain/snow line, as far west as Baraga and Iron counties. Meanwhile
the ECMWF is much colder, pretty much keeping all of Upper Michigan
with H925 temps blo 0C. As a comparison showing the degree of spread
between the models with ptype, the H925 temps Dickinson to Marquette
counties at 18z on Monday range from as warm as +2C off the GFS and
around -10C off the ECMWF. Usually don`t like to go against ECMWF
completely and it did verify better with our more recent widespread
system, but since just a couple days ago it was the warmer model of
the suite, increased temps over consensus of models for Monday over
east half of Upper Michigan to get more of a wintry rain/snow mix.
Dry easterly low-level flow could also lead to a freezing rain
threat over interior east if there is a warm layer aloft. Seems that
best chance for ptype staying all snow will be over western Upper
Michigan from Ironwood to Houghton and the snow could be quite
heavy, at least for a time, due to h85-h7 deformation west of sfc-
h85 lows. This rain/snow line could slide back south and east and
that will be one of the main items that determines areas that will
see the heaviest snow out of this system.

Overall the late Sunday through Monday night system will produce
high impact winter weather, but the question is where as there
remains considerable uncertainty in ptype as highlighted above.
Warning criteria snowfall probably will occur somewhere over Upper
Michigan in the Sunday night through Monday night timeframe, but
location and extent will be dictated by how much mixed precipitation
occurs. Will continue to mention this system in Hazardous Weather
Outlook and we have started to message on social media. Our inital
focus will be on mix potential and continued uncertainty. If
colder/snowier ECMWF idea starts to gain support, messaging will
turn toward more snow and less of a mix. Still time to get a handle
on that as main upper level system is just moving onshore the west
coast tonight where it will get better sampled by sfc and ROAB
observation networks from here on out.

No changes to rest of extended. Another potential for widespread
wintry mix and/or snow late in the week.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1205 PM EST THU JAN 18 2018

A shortwave will bring wintry precip at KCMX through this evening
along with MVFR to IFR conditions. Could see freezing drizzle at
KCMX, but not expecting significant accumulations. At KIWD and KSAW,
precipitation is not expected.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 152 PM EST THU JAN 18 2018

Gales look likely late Sun night across western Lake Superior with
northeast gales expected. North to northeast gales across Lake
Superior Mon through Tue are expected as well.
&&

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

$$

SHORT TERM...07
LONG TERM...JLA
AVIATION...07
MARINE...07



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