Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 171904

Area Forecast Discussion
National Weather Service Marquette MI
304 PM EDT Tue Apr 17 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 304 PM EDT TUE APR 17 2018

Numerous shortwaves were observed rotating about the main upper-
level low that has slowly been moving east of the region. The light
to moderate lake effect snow showers that impacted the north wind
snow belts earlier today has gradually begun to diminish, with only
remnant flurries hanging around in some areas. Upstream of the
region, Ontario was split between a much drier air mass across the
west and a much more humid airmass across the east half, north of
Lake Superior.

Tonight through Wednesday morning, the main forecast concern is the
potential for patchy freezing drizzle as flow backs towards the
northeast late tonight into Wednesday and upslope flow increases.
Right now confidence is not high that this freezing drizzle will
develop as forecast soundings are not showing a great depth to
development of this low-level moisture; but, there may be enough
shear near the top of the inversion to favor better chances for
cloud drops to grow large enough to reach the surface. Temperatures
will be tricky tonight and will depend highly on how cloud cover
evolves. Clouds have begun to erode slightly across the far
southwest and interior near the Wisconsin border, so thinking that
as we lose insolation through the evening cloud cover will begin to
break up slightly. Therefore, have the coldest temperatures across
the interior west, where we could see temperature drop into the
teens. Elsewhere, clouds will keep temperatures in the 20s. If more
clearing does develop temperatures could bottom out even more so
given the fresh snowpack.

During the rest of the day on Wednesday temperatures will gradually
warm, with most locations climbing close to or just above freezing
across the north half and mid to upper 30s elsewhere. As a potent
quick moving system tracks south of the Great Lakes the main large-
scale forcing will stay well south of the area. This far north, what
is left of the lingering low-level moisture and upslope flow will
allow for at least a slight chance mentions for drizzle through the
late afternoon/evening across the higher terrain.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 255 PM EDT TUE APR 17 2018

After a very active period, we return to quiet weather with average
to above average temperatures and little to no precipitation. The
main concern (believe it or not) is actually on above-average
temperatures and the potential for increased snowmelt across the
region next week. For more discussion on the potential for snow
melt, see the hydrology discussion at the end of this product.

A general warming trend is expected into the weekend with highs in
the 40s on Thursday and Friday to lower 50s by Saturday. On
Sunday, low to mid-level winds will veer southwesterly to
westerly, respectively, in accordance with an upper-level low
passing through northern Ontario. As 850 mb temperatures warm to
5 C or greater on Sunday and Monday, surface temperatures very
well may "spring" to the upper 50s to lower 60s across at least
southern portions of the forecast area. Of course it is hard to
put much stock into forecast warm temperatures with so much snow
on the ground (especially upstream of our area in Wisconsin).
However, a healthy snowpack doesn`t always equate to colder
temperatures across Upper Michigan owing to our abundance of jack-
knife coniferous trees. Overall, Sunday and Monday look quite
warm for our area.

A cold front will sweep through the Great Lakes in the
Tuesday/Wednesday time frame with a light rain, perhaps mixing
with snow. A peek into the longer range depicts warm temperatures
persisting across the area toward the end of next week. Such a
scenario would jive with the 8-14 day temperature outlook produced
by the Climate Prediction Center.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 148 PM EDT TUE APR 17 2018

MVFR ceilings have lingered through the morning and will continue
to do so through the rest of the afternoon and into the evening
hours at all terminals, except KIWD/KCMX should see a brief break
this evening as they`re right along the leading edge of the drier
air. Light wintry precipitation continues to impact KCMX/KIWD, but
sharply reduced visibilities haven`t been reported. Tonight
through mid-day on Wednesday north to northeast flow will provide
additional lift and support for lowering ceilings through the
latter half of this TAF period. Models are fairly consistent with
ceilings dropping down into the IFR category, especially at KSAW.
However, confidence was not high enough that cloud depths will be
deep enough to support the development of freezing drizzle after
these lower ceilings fill in, so opted to only include mentions of
vicinity showers for now to hint towards the potential for some
light precipitation.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 304 PM EDT TUE APR 17 2018

Winds will remain between 20 to 30 knots through Thursday morning,
with the strongest winds expected Wednesday evening through Thursday
morning as a surface low tracks south of the Great Lakes region.
Thursday night winds will gradually diminish from west to east
across the Lake to under 15 knots as high pressure builds into the
region. Winds will remain under 15 knots through the weekend.

Issued at 255 PM EDT TUE APR 17 2018

As confidence increases in above average temperatures next week,
so does the concern for increased snowmelt across at least the
west and southern portions of Upper Michigan. After some
discussion within the office, we`ve discovered that mid-April 2013
was eerily similar in snow depth and snow water equivalent (SWE)
to where we are now. In fact, there is *more* snow/SWE on the
ground now than in 2013, especially across the south and east. As
many may remember, the end of April 2013 was marked by much above
average temperatures (mid to upper 60s) dropping the snowpack from
30+ inches to below 5 in just a few days. Such a drop led to
considerable river flooding across southern Upper Michigan. With
above average high (and potentially low) temperatures with little
to no precipitation expected across the upper Great Lakes over the
next 7-10 days, residents across the west and south are
encouraged to stay up to date on the forecast, especially in
regions that are prone to river flooding.

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


SHORT TERM...Ritzman
LONG TERM...Borchardt
HYDROLOGY...Borchardt is the U.S. government's official web portal to all federal, state and local government web resources and services.