Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182350

Area Forecast Discussion
National Weather Service Marquette MI
650 PM EST Sun Feb 18 2018

.SHORT TERM...(This evening through Monday)
Issued at 341 PM EST SUN FEB 18 2018

Considerable dry air was in place this morning across much of the
U.P. although with the approaching system to the west profiles began
to moisten aloft and lower ceilings by midday. Several locations are
still being stubborn to saturate which is having an impact on the
ongoing snowfall across the western U.P. and Kewennaw Peninsula.
Radar returns indicate another slug of steadier snow lifting
northeast this afternoon across the Keweenaw Peninsula, with
guidance indicating good lift within the dendritic growth zone. This
should help increase the snowfall totals closer to the current
advisory conditions through this evening to around 3-5 inches and
locally higher totals. Otherwise the focus then turns towards the
overnight into Monday periods.

Tonight the omega field decreases substantially acrosss the U.P.
which raises concerns with p-type. Model soundings indicate some dry
air lingering throughout the DGZ, with considerable moisture
becoming shallow or within the 0-1km layer. Winds will generally be
from the northeast/north, but with a lack of lift to grow moist
parcels to dendrites, expect freezing drizzle to develop across the
central/east U.P. The abundance of liquid doesn`t get too high until
later in the day Mon. Surface temps are progged to linger in the
mid/upr teens across the western U.P. with slightly warmer temps
further east where better warm air advection will occur.

Mon aftn/eve, there appears to be a brief lull between freezing
rain/drizzle events as drier air does try to work into the lower
levels based on latest forecast guidance. Winds will continue to be
northerly, then deeper moisture will begin to arrive aloft late Mon

.LONG TERM...(Monday night through Sunday)
Issued at 355 PM EST SUN FEB 18 2018

...Mess of winter weather early this week...

Summary on weather/headlines: Have opted to issue a long duration
winter weather advisory Mon through Tue evening to cover push of
snow and freezing drizzle on Monday then more light freezing rain or
freezing drizzle Tue into Tue night with some snow as well over far
western U.P. As models and ensembles have trended to recently, seems
risk of seeing warning criteria snowfall from this event is low and
the better chance of seeing warning critiera ice looks like it sets
up south and east of our area closer to stronger moisture advection
along sfc low pressure wave/trough. Still time for later shifts to
upgrade to warnings if needed. At this point though there was just
not enough confidence in seeing higher qpf amounts to go warning.

This period of wintry weather that is ongoing Mon night will
continue through Tue across Upper Michigan. Intitial surge of snow
and freezing drizzle will be exiting east half of Upper Michigan Mon
evening as lead shortwave/H85 low and fgen and right entrance jet
forcing shift east. Soundings indicate wintry mix of sleet and snow
possible far scntrl around Menominee but otherwise it now looks like
most areas with the initial surge of precip should stay snow. After
the initial snow moves out, there is little forcing remaining until
late Mon night over the west. Even without much forcing, forecast
soundings through Mon night indicate moisture depth up to H8-H7/5-
10kft AGL with only weak lift since Upper Michigan stays within area
of occasional H85-H7 fgen in right entrance region of persistent
upper jet over Ontario and Quebec. Temps in the moist layer are cold
enough for snow over west and maybe north central Upper Michigan,
while any precip would likely be freezing drizzle elsewhere with no
ice nucleation within the moist layer. Northeast sfc winds btwn high
pressure ridge over northern Ontario and elongated sfc trough from
central Plains to the central Great Lakes will provide upslope boost
to precip over west and north central Upper Michigan. Overall
though, most areas will see less than 0.10 inch of qpf on Mon night.

Into Tue the large scale trough aloft over the western Conus shifts
to the east with broad southwest flow aloft into the Upper Great
Lakes. Stronger shortwave within this flow aloft will support sfc to
H85 waves lifting into the western Great Lakes. Though sfc waves
remains over WI into lower MI, the H85 low and an additional round
of H85-H7 moisture advection does affect much of Upper Michigan.
Could also be enhanced lift from mid-level fgen and right entrance
region lift with upper jet. Even with the better forcing compared to
Mon night, per a blend of model qpf and ensemble probs seems that
heavier qpf of more than 0.25" will remain over WI and lower MI
closer to sfc trough/low pressure wave and H7 mixing ratios up over
5g/kg. Ptype will be issue Tue into Tue evening before colder air
works in aloft to lead to only snow later Tue night. Until then
though expect mainly freezing rain or frezing drizzle with best
chance of seeing just snow only over the far west U.P. Possible
could see ice accumulations Tue into Tue evening over 0.10 inch,
especially south central and eastern areas. And even though WPC
probabilities point to good chance of seeing that much ice, they
still keep higher probabilitiies for significant 0.25"+ ice amounts
more over southern WI to northern lower Michigan.

Once precip moves out with the early week system on Tue night, there
may be some light lake effect on Wed for northwest U.P. Otherwise,
high pressure brings dry conditions in through Thu night before
another persistent southwest flow aloft and a couple more systems
result in chances of snow or rain/snow returning to the region by
next weekend.

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 640 PM EST SUN FEB 18 2018

VFR conditions at KCMX and KIWD will lower to MVFR/IFR in lake
effect snow as winds turn northerly behind the frontal passage.
System snow Mon afternoon will likely maintain the MVFR to
occasional IFR conditions for KIWD and KCMX.

At KSAW, a moist southerly flow could result in periodic MVFR
stratus into the overnight hours. With the passage of the frontal
later tonight and the likelyhood of more system snow Mon
afternoon, expect conditions to steadily lower from MVFR to IFR by
Mon afternoon.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 341 PM EST SUN FEB 18 2018

South gales to 35 knots are expected over northern Lake Michigan
late through this evening. Otherwise, winds are expected to stay
below gales through the rest of the forecast period.

Upper Michigan...
  Winter Weather Advisory from 11 AM EST /10 AM CST/ Monday to
     midnight EST /11 PM CST/ Tuesday night for MIZ006-007-

  Winter Weather Advisory from 4 AM EST /3 AM CST/ Monday to 7 PM
     EST /6 PM CST/ Tuesday for MIZ004-005-010-011.

  Winter Weather Advisory until 1 AM EST Monday for MIZ001-003.

Lake Superior...
Lake Michigan...
  Gale Warning until 1 AM EST Monday for LMZ248-250.



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