Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241218
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
718 AM EST Tue Jan 24 2017

.SHORT TERM...(Today and tonight)
Issued at 522 AM EST TUE JAN 24 2017

WV imagery and RAP analysis indicated a complex pattern with
mid/upper level troughing from Saskatchewan and Manitoba into the
wrn CONUS. A shortwave trough was lifting northeast from nw WI
while another was departing from ern Upper Michigan. At the
surface, an inverted trough extended from Lake Huron to ern Lake
Superior. Although most of the pcpn had departed the ern cwa, some
light ra/sn was moving into n cntrl Upper Michigan with the nrly
convergent flow on the back side of the sfc trough. Otherwise, low
clouds along with patchy fog prevailed across the rest of the
cwa.

Today, after pcpn early this morning dissipates, expect dry
conditions for the rest of the day. Highs will remain in the
relatively narrow range of the last few days with max readings in
the mid to upper 30s.

Tonight, the shortwave trough and mid level low moving out of the
plains will support an expanding area of snow from nrn IA and srn MN
into cntrl WI. However, model trends have slowed the progress of the
pcpn toward Upper Michigan. So, pops, mainly for the srn half, were
reduced to the chance category. In addition, model soundings also
suggest that a dry layer will prevail (moisture remains below
-10C) that will reduce potential for any ice nuclei. So any pcpn
that moves in would be mostly fzdz. Some minor ice accumulation
may be possible near the WI border as the pcpn arrives toward 12z.
However, given models variability and slowing trend, confidence in
pcpn timing and icing potential is low.

.LONG TERM...(Wednesday through Monday)
Issued at 341 AM EST TUE JAN 24 2017

Pretty complicated in the short term as models have significantly
shifted farther south and slower with a shortwave moving through Wed
into Wed night. This not only will change QPF amounts and precip
timing, but will dramatically change ptype expectations over all but
the far southern CWA. Now the expectation is more towards primarily
seeing drizzle/freezing drizzle/snow into Wed night over all but far
southern and southeastern Upper MI, but especially near Lake
Superior due to upslope flow. Could see up to 0.05 inches of ice
accumulation over the higher terrain near Lake Superior Wed morning,
the another 0.03 inches or so Wed night depending on moisture depth.
Far south central and southeast, precip is more likely to be
predominantly snow, with rain possibly mixing in during the
afternoon as SFC temps increase to around 37F. Only have 1-2 inches
of snow over that area Wed and Wed night. Still have uncertainty,
but with models all converging on a drier and more southern
solution, have weighted toward that trend.

Cooler air of -12C to -15C moves across the lake between 00Z Fri and
00Z Sun when NW wind LES will occur. A surge of even colder air of
-15C to -18C moves over Sat night into Sun when N-NW wind LES will
occur...possibly heavy in spots as the shortwave associated with the
colder air moves over. Winds turn southerly ahead of a potential low
pressure system that may move through early next week, bringing
potential for widespread snow with it. Consensus initialization
performed well during this time period, so made very few changes.
&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 715 AM EST TUE JAN 24 2017

With lingering low level moisture over the slowly melting snow pack
and light winds expect low cigs with IFR cigs and ocnl IFR/LIFR fog
possible through the morning. There will be a slow improvement
through the afternoon with some daytime heating, but cigs are likely
to remain in the IFR or low MVFR range. Conditions wwill likely
deteriorate again in the evening, especially at SAW where a low leve
ne wind ahead of a low pres approahcing from the sw will present an
upslope component.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 522 AM EST TUE JAN 24 2017

A relatively weak pressure gradient over the Upper Great Lakes in
the absence of any strong weather systems will continue to result in
winds under 20 kts over Lake Superior today. As a low pressure
system moves from the central Plains to eastern Canada mid to late
week expect NE winds to 25 kts Tue night then N-NW winds to 25 kts
Wed into Fri.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
  Dense Fog Advisory until 10 AM EST this morning for LMZ248-250.

&&

$$

SHORT TERM...JLB
LONG TERM...Titus
AVIATION...JLB
MARINE...JLB



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