Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 160011

Area Forecast Discussion
National Weather Service Marquette MI
811 PM EDT Sun Apr 15 2018

.SHORT TERM...(This evening through Monday)
Issued at 428 PM EDT SUN APR 15 2018

...Widespread winter storm continues and may linger through Mon in
some areas...

with secondary surge of moderate snow and blowing snow on Monday we
have extended the warnings for central and eastern forecast area
through Monday. Snow will not be as heavy on Monday compared to what
is occurring at this time, but due to moderate snow and blowing snow
the warning was extended.

Upper low spinning well to the southwest over IA and northern Ill.
sfc low of 1002 mb is well to the south over northern IN. Surge of
deep moisture streaming north into Upper Michigan has supported
prolonged period of S+ all day long over much of Upper Michigan.
Snow totals thus far are 6-9 inches with totals over 10 inches in
Menominee county as they had an earlier start. Due to sharp warm
nose aloft seen on 12z APX sounding this morning, some mixed precip
has been observed with a bit of rain mixed in earlier at ISQ and
sleet into far eastern Upper Michigan. Per radar and HRRR trends,
expect last surge of S+ (1-2"/hr snow rates) to affect most of Upper
Michigan through 00z this evening. Expect some locations to end up
with over a foot of snow just since daybreak this morning.

Shortly after 00z/8 pm ET, snow intensity should diminish sharply to
around 1/2" per hour or even less. Most of snow after 00z this
evening through daybreak Monday will occur over higher terrain of
western and north central Upper Michigan with upslope flow (may see
additional snow accums of 2-4 inches). Dry slot moving up into cntrl
Lk Michigan (see back edge of wideapread radar echoes) will result
in loss of ice aloft by mid evening and we probably, given enough
low-level saturation, are going to see snow transition to freezing
rain or freezing drizzle mainly east of MQT to IMT. Could be light
glaze of ice occur. Will keep ending time of warnings for Iron
through Menominee county at 06z as most precip will be done by that

Focus late tonight into Mon morning turns northern lower Michigan
and eastern Upper Michigan as all the models are starting to come on
board with idea of secondary upper low developing which allows sfc
low to persist and try to back more into eastern Upper Michigan. Net
result of this stronger forcing is support for an area of moderate
snow to re-develop near Lk Superior and east (as enough deeper
moisture moves back in to eliminate any freezing precip from
tonight). NAM/GEM/GFS and latest EC all show the secondary upper
low developing and associated deformation across much of north and
east Upper Michigan. This forcing and moisture will be
supplemented by sfc-H8 N winds with H85 temps -13c. So, good
enough for upslope lift and also lake enhancement. Overall
widespread additional snow on Monday will be 2 to 5 inches, with
higher amounts over ncntrl Upper Michigan. Since the sfc low will
be farther west, pressure gradient remains tight and winds/blowing
snow will be more of a factor. Long story short, due to these
trends, extended warnings for north central and eastern forecast
area. Also did extension for Delta and Schoolcraft though those
may be more marginal. Not confident enough that far west will get
back into the better forcing/moisture for significant lake
enhancement so left those warnings to expire at 12z Mon. Evening
or mid shift can investigate further and make additional headline
decisions over the western forecast area. It appears this late
season storm just doesn`t want to let go!

.LONG TERM...(Monday night through Sunday)
Issued at 254 PM EDT SUN APR 15 2018

NAM shows a closed 500 mb low over the lower Great Lakes 00z Tue
with a trough in the western U.S. The closed low moves into New
England while the trough in the western U.S. moves into the central
plains 12z Wed and into the corn belt by 00z Thu. Nam slowly
diminishes the deep moisture and moves out the 850-500 mb q-vector
convergence Mon night with the moisture moving out on Tue afternoon.
GFS and ECMWF show about the same thing as well. System slowly
departs with some lake effect pcpn continuing behind it. System on
Wed looks to stay mainly to the south of the area.

In the extended, GFS and ECMWF show a 500 mb trough over the eastern
U.S. and another over the western U.S. 12z Thu with a ridge over the
plains. The western U.S. trough moves into the southern Rockies 12z
Fri with the eastern trough in New England. The southern Rockies
trough moves into the central plains 12z Sat. Differences show up on
Sun between the GFS and ECMWF with the GFS moving the trough into
the lower Mississippi River valley and the ECMWF shows a trough in
the southern plains 12z Sun which is slower than the GFS is.
Temperatures look to stay below normal for this forecast period.

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 809 PM EDT SUN APR 15 2018

Improvement in conditions is expected this evening as the area of
heaviest snow departs and winds gradually diminish. Still, IFR
conditions are likely to prevail at all terminals through most of
Monday. With snowfall increasing again Monday morning, ocnl LIFR
vsby may be possible.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 254 PM EDT SUN APR 15 2018

Tight pressure gradient between strong high pressure to the ne and
low pressure in the lower Great Lakes will continue the east to
northeast gales of 35-45kt tonight across Lake Superior along with
freezing spray. Winds will diminish below gale force Mon afternoon.
Winds for the rest of the week will be under 25kt.

Upper Michigan...
  Winter Storm Warning until 8 AM EDT /7 AM CDT/ Monday for

  Winter Storm Warning until 8 PM EDT Monday for MIZ004>007-013-

  Lakeshore Flood Advisory until midnight EDT /11 PM CDT/ tonight
     for MIZ001>006-009.

  Winter Storm Warning until 1 AM CDT Monday for MIZ010>012.

Lake Superior...
  Gale Warning until 6 PM EDT Monday for LSZ243>251-264>267.

  Gale Warning until 1 PM EDT /noon CDT/ Monday for LSZ162-240>242-

Lake Michigan...
  Gale Warning until 2 AM EDT Monday for LMZ221-248-250.



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