Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 180932

Area Forecast Discussion
National Weather Service Marquette MI
532 AM EDT Wed Apr 18 2018

.SHORT TERM...(Today and tonight)
Issued at 532 AM EDT WED APR 18 2018

With the NE low level flow, we saw some isolated upslope snow
showers over the higher terrain earlier, occassionally with a spit
of freezing drizzle, but that has since dissipated. Could see some
more of that over the next few hours early this morning, but nothing
significant. Otherwise, we will see winds gust to 20-30mph today
between a shortwave well to our S and an approaching ridge to the
NW. Skies will be clearing over the N this afternoon with highs in
the 30s across the area.

Mostly clear skies tonight with breezy winds will lead to lows in
the 20s.

.LONG TERM...(Thursday through Tuesday)
Issued at 444 AM EDT WED APR 18 2018

An extended period of quiet weather is shaping up for the Upper
Lakes with temperatures returning to more typical mid/late Apr
values. The quiet weather will be ideal as we don`t need to add any
rain to the snowpack which will begin the spring meltdown under
warmer conditions and high spring sun angle. Several days ago, it
appeared that an active weather pattern would continue for Upper MI
as a series of vigorous shortwaves move off the N Pacific and across
the CONUS. That won`t be the case. Building positive height anomaly
across s central Canada and Hudson Bay will force the next shortwave
s of the area today/tonight, keeping an accumulating snowfall s of
Upper MI. Second shortwave will pass way to the s across the Lower
Mississippi Valley/SE States late weekend/early next week. A
progressive stream will then develop across southern Canada next
week. Right now, looks like just a small chc of some
-shra early next week with the first shortwave trof. A warming trend
will be underway thru the upcoming weekend as development of
positive height anomalies across s central Canada ensure no buildup
of late season cold air to the n. Looks like a steady warmup with
snowcover not really inhibiting warming given the high sun angle
working on the forested Upper MI landscape on mostly sunny days.

There are no major weather concerns for this fcst cycle. Mean
mid/upper level ridging over s central Canada to Hudson Bay will
support sfc high pres over the Upper Mississippi Valley on Thu and
then over the Great Lakes region Fri thru Sun, resulting in dry
weather. The GFS spits out some pcpn Fri aftn and Sat aftn in the
lake breeze convergence zone central, a result of too much low-level
moisture from melting snow. This has been a bias seen in the model
in recent weeks. Outside of some high clouds at times, generally
sunny days and clear nights are expected, a fairly typical spring
time scenario for Upper MI. Winds will be on the light side Fri thru
Sun with high pres over the Great Lakes region and meso highs
setting up each afternoon over the waters, particularly Fri/Sat,
leading to the usual chill near the lakes each aftn (temps in the
30s). Gradient w to nw wind on Thu ahead of the approaching sfc high
will spread cooling from Lake Superior well inland. Away from lake
cooling, high temps will be in the mid/upper 40s Thu and the 50s Fri
thru Sun. Wouldn`t be surprised at all to see some locations top 60F
Sat/Sun. Best chc of seeing more widespread max temps at or above
60F will be on Mon ahead of approaching cold front. With good
radiational cooling nights coming up, favored the bias corrected
global CMC for mins as it is typically a superior performer on such
nights. Dry air mass and little cloud cover will support large
diurnal temps swings, especially while snow cover is still
consistent across the landscape. Interior mins should fall to the
teens Thu night, around 20F Fri night and low/mid 20s Sat night.
Utilized some of the lower dwpt guidance to adjust dwpts down into
the upcoming weekend.

Cold front should pass Mon night or Tue. Nothing more than schc/chc
pops are warranted as southern stream system moving from the Lower
Mississippi Valley to the SE States will prevent Gulf moisture
return. Might see some -shra/-shsn on Wed under mid-level trof

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 134 AM EDT WED APR 18 2018

Overnight through mid-day Wednesday north to northeast flow will
provide enough lift to support low cigs. Models are fairly
consistent with ceilings dropping down into the IFR category at KSAW
and KIWD with lower end MVFR at KCMX. With additional low level
moisture moving toward the area where upslope flow will prevail some
fzdz is possible. However, confidence is not high enough to include
mention in the TAF. Enoug dry air will move in on Wednesday for
conditions to improve to VFR ty mid to late afternoon west and early
evenin at KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 532 AM EDT WED APR 18 2018

Winds will remain between 20 to 30 knots through Thursday morning,
with the strongest winds expected this 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 444 AM EDT WED APR 18 2018

Snowpack will begin to melt in the coming days as a warming trend
gets underway with temps rising to around normal under mostly sunny
days. With nighttime temps falling blo freezing and dwpts likely
low, ripening of snowpack will be slow, leading to a gradual
melting/runoff. Early next week, min temps may not fall blo freezing
for a night or two, increasing runoff potential, though dwpts will
likely remain low, keeping melting of snow slower than would
otherwise occur. The addition of notable rainfall would be the
biggest concern to increase flooding potential. Fortunately, there
will be no pcpn thru the weekend and only a small chc of light pcpn
early next week when a cold front passes. The following temporary
cool down will then slow down the snow melt. Overall, these
conditions don`t suggest any significant concerns with the snow melt
over the next 7 days. While melting will likely be relatively
controlled given the forecast, rivers will begin to respond this
weekend and minor flooding is quite possible at some point down the
road on the usual rivers that experience spring flooding.

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


LONG TERM...Rolfson
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