Area Forecast Discussion
Issued by NWS Marquette, MI

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571
FXUS63 KMQT 251009
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
509 AM EST Sat Feb 25 2017

.SHORT TERM...(Today and tonight)
Issued at 506 AM EST SAT FEB 25 2017

Upper low became somewhat closed off and negatively tilted as it
lifted across Upper Great Lakes late last night into early this
morning. Sfc low around 993mb is currently sliding across Lk Huron
toward Georgian Bay. Despite the stronger upper level system, deep
layer of dry air aloft h7-h5 seen on 00z MPX and GRB soundings put
crimp on the deformation band of snow that tried to re form from WI
into western half of Upper Michigan in both coverage and intensity.
Based on reports received and overall look of radar loop, heaviest
snow amounts late evening into early this morning were over higher
terrain of far west and in the higher terrain of ncntrl, mainly
staying north of Michigamme to Negaunee though recently heavier snow
is spreading west to east across much of Marquette county due to mid
level fgen on northwest side of upper level low and also due to lake
enhancement off Lk Superior. Should see this area of moderate to
heavy lake enhanced snow head over eastern cwa this morning boosting
snowfall intensity there. Also seeing expansion of light to perhaps
moderate snow over scntrl as individual pv anamoly/shortwave lifts
ene over northeast WI and central Lk Michigan.

Winds to this point have been not that impressive, but due to cold
air advection and tighter pressure gradient today, expect NNW winds
to increase to 20-25 mph with gusts to 35 mph. Strongest winds will
be near Lk Superior over ncntrl Upr MI into eastern cwa where 925mb
winds of 30-35 kts are forecast and where forecast soundings show
increasingly well mixed profile. The strong winds will result in
areas of blowing snow. After the heavier lake enhanced snow this
morning, rest of day will be characterized by mainly light lake
effect with inversions up to 4kft and h85 temps -14c. Wide open lake
and ideal fetch with NW flow will help out accums, but still looking
at most of the snow (up to 3") into this morning with only minor
accums of an inch or two this aftn into this evening. Current advy
goes until 00z tonight which looks good based on the persistent lake
effect and with increased hazard from blowing/drifting as winds pick
up this morning.

Elsewhere, due to the increasing negative dynamics over west half,
already seeing synoptic snow coming to an end. NNW-NW flow and temps
at 3-5kft inversion top of -16c along with wide open waters could
result in lake effect bringing minor additional accums to far west.
Dry air upstream over MN as seen on 00z INL sounding will restrict
this potential though. Since there is still light snow ongoing along
with patchy blowing snow near the shore kept warnings and advisories
over west going until original expiration time of 12z. Same story
for WI border zones since there is still a bit of snow to go through
early this morning.

Into tonight another system currently showing up as batch of enhanced
cloud along US/Canada border MT to Manitoba and propelling a weak
sfc front along the MT/Alberta/Saskatchewan border (with a little
light snow or flurries noted) is poised to swing over western cwa
after midnight. System is lacking much moisture and warm air
advection and overall punch to lead to much snow on its own.
However, since blyr winds ahead of the system will be from the
west and it will be sufficiently cold enough for lake effect (h85
temps -12c across Lk Superior) and SLRs will be on the higher side
toward 20:1, went with a more bullish solution (in line with NCEP
WRF and NMM) for at least a couple inches of snow across
Keweenaw. Possible that if there is a direct hit from the system
even another inch or two of snow could occur though area seeing
those snow amounts should remain isolated.

.LONG TERM...(Saturday night through Friday)
Issued at 326 PM EST FRI FEB 24 2017

Upper air pattern consists of a 500 mb trough over the northern
plains 00z Sun which heads into the upper Great Lakes on Sun. Nam
shows some 850-500 mb q-vector convergence with deeper moisture
moving through the area Sat night into Sun afternoon. GFS and ECMWF
show about the same thing as well and went with blend of the models
for this forecast. Will have some light snow move into the area late
Sat night into Sun afternoon and have some chance to likely pops in
there for this. Overall, did not make too many major changes to the
going forecast.

In the extended, GFS and ECMWF show a 500 mb trough over the Rockies
12z Tue. This upper trough moves into the upper Great Lakes 12z Wed.
An alberta clipper type system moves into the area Thu with the cold
air moving in for Fri. Temperatures cool from above normal at the
beginning of this period to near normal for most of this period.
Decent chance for mixed pcpn occurs Tue into Tue night and some
freezing rain cannot be ruled out with the snow and rain mixed in
with this system. Will continue to have to watch this system and see
if the mixed pcpn threat continues and will have plenty of
opportunity to watch this next system evolve.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1245 AM EST SAT FEB 25 2017

As a potent upr disturbance moves ne into the Upr Great Lks, mdt to
perhaps heavy sn wl impact the TAF sites early this mrng. Along with
the sn, blsn whipped up by some gusty nne winds wl result in
IFR/LIFR vsbys much of the time until at least 09Z. The aprch of a
high pres rdg/drier llvl air to the w shown on the 00Z INL raob wl
result in improving conditions at CMX and IWD as early as next TAF
issuance. Conditions wl continue to improve w-e on Sat and be
enhanced by a downslope wnw wind at SAW ahead of the incoming rdg
axis. With a more persistent upslope nw backing w wind, MVFR cigs wl
be most persistent at CMX and probably linger thru the end of the
TAF period. The gusty winds wl slowly diminish by later today with
the aprch of the rdg/weaker pres gradient.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 506 AM EST SAT FEB 25 2017

NW gales to 35-40 knots are expected for much of central and eastern
Lake Superior into this evening. Some heavy freezing spray is
possible as well, but coverage will be limited to mainly the
shoreline areas along north central Upper Mi so no headline
anticipated. Beyond today, winds will stay 25 kts or less through
Tue but will then become NE to 30 kts on Wed behind another low
pressure system crossing Great Lakes. Winds diminish to 25 kts or
less into Thu as the low moves toward New England and a high
pressure ridge builds from western Canada to the central Conus.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Warning until 7 AM EST /6 AM CST/ this morning for
     MIZ002-004-005-009.

  Winter Weather Advisory until 7 AM EST /6 AM CST/ this morning
     for MIZ001-003-010>013-084.

  Winter Weather Advisory until 7 PM EST this evening for MIZ006-
     007-014-085.

Lake Superior...
  Gale Warning until 10 PM EST this evening for LSZ264>267.

Lake Michigan...
None.
&&

$$

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



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