Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 201946

Area Forecast Discussion
National Weather Service Marquette MI
246 PM EST Sat Jan 20 2018

.SHORT TERM...(This evening through Sunday)
Issued at 244 PM EST SAT JAN 20 2018

Quiet weather for most though there are some minor forecast issues.
Plenty of mid-high clouds around in Pacifc airmass. Arctic sfc front
with temps in the single digits above zero is over northern Lk
Superior while temps over Upper Michigan have risen to 30s and low
40s. Generally quiet tonight. Front over Lk Superior will not move
much. Light winds over Upper Michigan and dwpnts are into the 30s,
so could be some stratus/fog develop tonight if mid-high clouds thin
out. Will just have patchy fog in forecast, but any fog that forms
could be dense. Also, kept a slight chance for light snow far scntrl
as streak of mid-level moisture/fgen interacts with lift from upper
level jet. Models have trended drier with potential mainly due to
dry layer blo 10kft AGL.

On Sunday, main focus will be on cold front settling toward northern
Upper Michigan in the aftn and evening. Expect developing east to
northeast winds in wake of the front which will result in upslope
lifting from Keweenaw to north central higher terrain. A lot of low
clouds already behind the front today over northern Ontario so
expect situation here on Sunday with additional moisture off Lk
Superior. Could even be enough low-level moisture and lift for
drizzle or freezing drizzle. Only have slight chances for now as it
could end up just being a stratus deck with no precip. Both the low
clouds and increasing high clouds ahead of developing winter storm
will result in cooler temps than last couple days. Readings will be
freezing or maybe below over north U.P. higher terrain while
elsewhere expect temps mainly mid 30s.

As for the incoming winter storm, slower trend continues. Should
just start to see snow develop through the day over Nebraska and
South Dakota as the main sfc low moves from the Texas/Oklahoma
panhandle toward south central Kansas.

.LONG TERM...(Sunday through Friday)
Issued at 529 AM EST SAT JAN 20 2018

...Impacts from potential winter storm likely Monday into Tuesday...

Sunday into Sunday night: Several models suggest a fgen band forming
across south central Upper Mi on Sun in response to upper divergence
in the right entrance region of a 150+ kt 250 mb jet max across
eastern Ontario/western Quebec. Models however indicating fairly
light pcpn with this band (only the NAM printed out a few hundreds
QPF) mainly in form of wet snow which would amount to half an inch
of snow accumulation or less. Max temps on Sunday will remain above
normal with highs in the lower to mid 30s. Models now trending
slower with arrival of pcpn Sun night in advance of approaching
system from the Plains. If any areas see snow Sun night it looks
like it would be late along the Wi border counties.

Attention turns to the approaching winter storm from the Central
Plains expected to impact the Upper Great Lakes Monday into Tuesday.
00Z GFS/NAM and GEM runs in fairly good agreement taking the
developing storm system from the Central Plains late Sunday across
central/northern Lower Mi late Monday night/early Tuesday. The 00z
ECMWF is farther north with sfc low track than GFS/NAM/GEM consensus
but is fairly consistent with these models showing the swath of
heavier system snow across central and eastern Upper Mi Monday
afternoon into Monday evening with dry slotting moving into south
central and eastern Upper Mi overnight Mon night which could result
in some frdz or fzra mixing in with lighter snow over these areas of
the cwa. Given continued model uncertainty, trends toward a slower
arrival of system pcpn on Monday and the threat of a mid-level dry
slot potentially cutting into total snow amounts across portions of
the fcst area later Mon night, have decided to hold off on issuing
winter storm watches for this system.  Instead, will update the SPS
and continue to highlight uncertainty with the storm track and where
the heavier system snowfall will occur. This will also allow the day
shift to look at a model run where hopefully the main shortwave
associated with this system can be better sampled by RAOB and sfc
observing networks as it moves onshore this morning off the southern
CA coast.

As the storm system departs east late Tue and sfc ridging moves
behind it Tue night into Wed, lake effect snow should taper off
and/or become confined to the Keweenaw and far eastern shoreline
areas of cwa. After a period of quieter and milder trending weather
Thu into Fri under a mid-level ridge, models indicate that a trough
will move in from the Plains and impact the western Great Lakes
region with another low pressure system for next weekend.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1247 PM EST SAT JAN 20 2018

VFR conditions expected through the TAF period at all of the
terminals. Expect considerable high and mid clouds to preclude
development of widespread fog/low stratus tonight into Sunday
morning. If there is more prolonged clearing tonight there would
be more radiational cooling and fog and low stratus could develop.
This will have to be monitored. As a cold front currently on
north end of Lk Superior settles across Lk Superior and northern
Upper Michigan by Sunday aftn, expect developing east to northeast
winds to result in upslope low stratus at CMX and SAW by late
Sunday aftn into Sunday evening. May be some freezing drizzle as
well, especially at CMX.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 244 PM EST SAT JAN 20 2018

Strongest winds on Lake Superior during this fcst period will occur
Monday into Tuesday as low pressure tracks from the Southern Plains
to northern Lower MI and to southern Quebec. NE to N gales are
expected over most of Lk Suprior during that time and a gale watch
has been posted. Heavy freezing spray will also develop late Monday
night through Tuesday.

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


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