Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 170901
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
501 AM EDT Mon Apr 17 2017

.SHORT TERM...(Today and tonight)
Issued at 500 AM EDT MON APR 17 2017

The latest water vapor imagery and RAP analysis shows a shortwave
trough upstream over the Northern Plains poised to move into the
Upper Great Lakes later this morning. Weak to moderate deep layer q-
vector convergence is supporting mainly scattered rain and snow
showers out ahead of the shortwave over eastern MN and nw WI as
noted on regional radar imagery and sfc obs.  Shortwave forcing may
even be aiding shsn into north central Upper Mi which are also being
enhanced by upslope northerly flow. Snow accumlations of half an
inch to an inch on grass and parked vehicles have been observed
early this morning from Marquette through Negaunee to Gwinn in MQT
county.

Models do indicate the shortwave weakening as it moves east into the
Upper Great Lakes later this morning, but associated forcing should
continued to support isolated to scattered rain and snow showers
into the morning hours for the western two thirds of Upper Mi.
Forecast soundings and upstream sfc obs also argue that dz/fzdz
could mix in with rain and snow, but again any accumulation of snow
(less than an inch) or fzdz should be minimal and not seriously
impact travel this morning. Pcpn will be tapering off or ending by
early afternoon as sfc high pressure builds in fm Ontario. Northerly
flow will keep temps cool near Lk Superior (generally in the mid
30s) while temps much farther inland should reach into the lower to
mid 40s.

Tonight...Clearing skies this evening and light winds along with
layer pwats dropping to around .25 inch should result in ideal
radiational cooling conditions at least into the early overnight.
Sided on the cooler side of model guidance as inland mid temps
dip into the lower 20s central and east. Increasing waa clouds
from west and earlier onset of downslope se winds ahead of
approaching system over the Northern Plains will result in warmer
temps over the western counties, generally in the upper 20s to
lower 30s. 00Z models in fairly good agreement that any pcpn
should hold off until 12z or after for most of the western
counties of the cwa.

.LONG TERM...(Tuesday through Sunday)
Issued at 416 AM EDT MON APR 17 2017

Rain showers will move through on Tue into Tue night, but no
significant impacts are expected. Only potential for impactful
conditions will come Wed night into Thu, although at this time
impactful conditions are not in the forecast. Models had been
generally showing area-wide precip, some of which may have been snow
with some potentially significant amounts, all latest runs have
shifted south. The CMC and NAM keep nearly the entire CWA dry, while
the ECMWF is farthest N and brings precip to all but the Keweenaw.
The GFS splits the difference. Thermal fields are borderline for
rain snow determination over NW Upper MI Wed night, if precip falls,
but Thu should be all or mostly rain. If models shift back north and
thermal fields line up right, significant snowfall amounts are
possible. However, at this time, it looks like mostly rain with
limited impacts. Thu high temps are the only place where conditions
were changed from initialization when NE SFC winds will keep many
areas cooler than guidance suggests.

Fri through Mon looks nicer with mostly clear skies and minimal
precip chances, at best, Sat night and Sun
&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1144 PM EDT SUN APR 16 2017

A few breaks in the cloud cover late this evening; however, expect
clouds to thicken back up overnight. Winds turning north/northeast
or onshore from Lake Superior, this has allowed the marine fog
layer to move inland towards KSAW. This has brought VSBYs back to
around 1/4sm with patchy dense fog. Guidance indicates that for
KSAW fog will linger through much of the overnight, and likely
keep VSBYs down at or less than 1sm through daybreak Mon.
Confidence has increased with this scenario, and have adjusted
TAFs accordingly to reflect the lower VSBYs. In addition shallow
cigs will also accompany the fog, with LIFR/VLIFR conds expected
for KSAW. KCMX and KIWD will end up seeing reduced VSBYs and CIGs
later tonight, although confidence is not has high that LIFR/VLIFR
conds will develop. Have held the lowest conds at IFR for both
sites, and the duration should not be as long. Winds are progged
to remain light from the northeast to east, then turn northwest
after daybreak Mon. With some drier air slowly filtering in mid-
morning Mon, expect CIGs and VSBYs to finally push back to MVFR
conds.

Tonight there will be a weak system sliding east acorss the region,
and could help to touch off a few rain or perhaps snow showers.
Although the vertical component could be challenged, and may result
in simply patchy or areas of -DZ rather than light rain or snow
showers.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 500 AM EDT MON APR 17 2017

In general winds are expected to be below 25 kts through the
forecast period. However, there may be stronger southeast winds of
25 to 30 kts Tue afternoon on the east half as low pressure tracks
over the Great Lakes. More strong winds to 30 kts are possible late
Wed night into Thu as another low pressure system affects the Upper
Great Lakes. At this time, no gales are expected through the
upcoming week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...Titus
AVIATION...Beachler
MARINE...Voss



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