Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 232320

Area Forecast Discussion
National Weather Service Marquette MI
720 PM EDT Sun Oct 23 2016

.SHORT TERM...(This evening through Monday)
Issued at 231 PM EDT SUN OCT 23 2016

Water vapor imagery is showing two waves impacting or expected to
impact the area over the next 24 hours. The first, sliding through
late this afternoon is centered directly over the U.P. as of 18Z
with the next wave upstream over central Manitoba. Visible satellite
imagery is showing most of the Upper Great Lakes region socked-in
under cloudy skies. Radar imagery is showing an east-west oriented
line of rain showers sliding to the south and east through the U.P.
along with some noted bright banding.

Tonight and Monday: The shortwave that slid through the area this
afternoon is progged to slide southeastward into the lower Great
Lakes. Colder air will filter in over the east half of the U.P.
tonight into Monday as another shortwave dives through the eastern
half of the area. This will allow 850mb temperatures to drop into
the -5C to -6C range. This cooler air aloft, along with lake surface
temperatures around 10-11C, will allow for delta-T values in the 15
to 17C range. This combination will provide continued lake effect
cloud cover and lake effect rain showers over mainly the east half
of the U.P. as winds will be out of the northwest and that area is
under the shortwave as it slides through. Even though deeper layer
moisture will slide east, the increased fetch on the northwest flow
will keep enough lake modified air in place to keep the rain showers
around for tonight into Monday. The western U.P. may continue to see
increased cloud cover, but the cooler 850mb temperatures for lake
effect rain showers will remain over the east. Another feature
inhibiting shower potential over the west will be subsidence
associated with a surface/upper level ridge sliding into the area
through the day Monday. Lows tonight will be in the low 30s with
highs Monday expected to be mainly in the 40s.

.LONG TERM...(Monday night through Sunday)
Issued at 117 PM EDT SUN OCT 23 2016

Do not have good confidence in any hazardous weather events in the
long term. There is some potential for minor snow accumulations Wed
night, but that is very uncertain.

Should see some lake effect precip mainly over the E Mon night into
Tue. PoPs may need to be extended slightly west due to more
northerly winds over the central lake, but a SFC ridge and dry air
moving in from the west should inhibit that. Could see some mixed
precip over interior E with those showers, but not expecting any
significant amounts due to low temps AOA 32F.

Next system to move through the region is on Wed/Wed night. Not
surprisingly, models have changed from yesterday due to uncertainty
with the phasing of two shortwaves. Expect that uncertainty continue
and be no better over the next couple of days, lending very limited
confidence in the details of the forecast. The biggest questions
related to type over mainly the higher terrain of the central and
west. Depending of the strength/track/timing, could see precip mix
with or change to snow in these areas Wed night. However, unless the
system ends up on the stronger side, no significant accumulations
are expected due to SFC and near-SFC temps.

The previous run of models agreed well for Thu-Fri in showing temps
cold enough for lake effect, but not models disagree substantially
from Thu through Sun with all forecast elements. Will not adjust
blended initialization after Wed night given the uncertainty.

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 720 PM EDT SUN OCT 23 2016

Clouds will linger through Monday morning bringing MVFR to VFR
celings across the area. Visibility does not look to be a major
issue at this point.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 231 PM EDT SUN OCT 23 2016

Winds will remain below gales through the period. A tightening
gradient between a deep low pressure system moving through Quebec
and a high pressure ridge building into the Plains will lead to a
period of NW winds gusting to 30 knots over eastern Lake Superior
tonight into Monday. High pressure will then build across the area
Monday afternoon through Wednesday, keeping winds generally light
across Lake Superior. There will be a trough passage on Thursday but
winds should still remain fairly light.

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


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