Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 280852

Area Forecast Discussion
National Weather Service Marquette MI
452 AM EDT Thu May 28 2020

.SHORT TERM...(Today and tonight)
Issued at 349 AM EDT THU MAY 28 2020

The pattern shifts today and tonight from moist southerly flow to
cool northwest flow bringing temperatures back down near seasonal
averages or below for the weekend.

An upper level ridge of high pressure over eastern U.S continues to
flatten with more progressive pattern taking hold. The cut off low
pressure over southern plains will get absorbed into the trough as
it swings east today. This will bring an end to the SW low and mid
level flow that has been pumping moisture into the area for the last
several days. Dewpoints will drop over the west today and eventually
the east tonight as a surface trough moves east. Cooler and drier
air will arrive with a cold front tonight. Pressure rises behind the
cold front are only on the order of 2 to 3 mb in 3 hours so not
expecting strong winds with the front, however, the cool breeze will
be quite noticeable after the warm and humid weather we have been
experiencing the last several days.

Precipitation will continue to develop over the central and east
this morning as a surface low tracks northeast from MO to the
eastern UP by this evening. Frontogenesis and upper level support
will increase with the strongest axis of fgen over the eastern
counties. Expecting widespread rainfall of an inch or more from
Menominee county to Alger county and east with the lift and positive
precipitable water anomalies resulting in heavy downpours. While the
flooding threat is not high enough to warrant headlines there could
be localized issues where stronger showers and thunderstorms train
over the same areas. WPC continues to highlight the east with a
marginal risk of excessive rainfall. The rain will shut off from
west to east this afternoon and evening.

Temperatures by Friday morning will be in the 40s with clearing
skies except for the west where clouds will develop as the cool air
passes over Lake Superior.

.LONG TERM...(Friday through Wednesday)
Issued at 452 AM EDT THU MAY 28 2020

The expected significant change in the pattern to occur over N
America over the next several days is still on track. A ridge is now
in the process of amplifying over the western CONUS into western
Canada, and it will link up with a positive height anomaly over
northern AK and the adjacent Arctic Ocean. This will force a
deepening trof from Hudson Bay to the Great Lakes later today thru
Sat. This amplification of the pattern will be progressive so that
by Mon the ridge will be shifting toward central N America and the
trof toward New England. Beyond the weekend, there has been a fairly
notable trend in the ensemble means over the last 24hrs. Strong
ridging/positive height anomaly is fcst to build toward southern
Greenland early next week, slowing the pattern progression and
resulting in the troffing holding up over the ne U.S. thru at least
midweek. The upstream ridge will also deamplify/broaden over central
N America. Little over a week from now, next weekend, there is good
ensemble agreement for troffing to amplify along the W Coast, which
will force the upstream ridge to build toward/over the Great Lakes
region. As a result of these changes in the large scale pattern,
there will be a dramatic change from the recent anomalous warmth and
humid conditions to sharply cooler conditions/blo normal temps
Fri/Sat. Warming will then quickly get underway early next week with
temps rising to around or a little above normal. Should become
warmer next weekend. As for pcpn, other than some isold
-shra Fri, dry weather will return thru the weekend under cool/dry
air mass associated with amplifying trof. As the mid-level ridge to
the w shifts e and a shortwave rounds it, strong waa pattern will
likely lead to some convection in the later Mon/Tue time frame. With
the trof getting held up over the ne U.S., cold front associated
with the shortwave will likely push well to the s. While this should
lead to dry weather for the midweek period, the flatter ridge may
allow for additional shortwaves to affect the area.

Beginning Fri, it will be a cooler day under caa which drops 850mb
temps to 2 to 5C by evening. Expect high temps in the upper 50s/lwr
60s w and n to the mid 60s s central. At lakeside locations where w
to nw winds are off Lake Superior, temps will probably be in the 40s
for most, it not all, of the day. A weak shortwave will pass across
the area on Fri, and 00z models are now in good agreement showing
some -shra associated with this feature. Fcst will reflect shc/chc
pops spreading from western Upper MI in the morning to s central
Upper MI in the aftn.

As another weak shortwave approaches late Fri night, there should be
enough sct cloudiness along with some wind to prevent a frost
concern. Low temps will range from the upper 30s to the middle 40s.

Not out of the question that the shortwave could produce a few
sprinkles or isold -shra Sat morning as it passes. Otherwise, Sat
will be the coolest day as midday 850mb temps only range from +1 to
-3C. Expect highs in the mid/upper 50s n and e to the lower 60s s
central. Along Lake Superior, most lakeside locations will not get
out of the 40s. Will be especially chilly e of Marquette due to long
fetch of nw winds across the cold lake waters.

Sfc high pres will settle over the western Great Lakes Sat night,
setting up a cold late May night. However, models are trending a
little sharper with another shortwave dropping se across northern
Ontario Sat night, which results in the high pres settling a little
farther s than previously expected. This will allow for a little
more wind, especially across the n. Still, expect some areas of
frost, but it may end up confined to the s half of the fcst area.
Expect low temps in the mid 30s in the interior to the lower 40s
closer to Lake Superior where winds will be stirring more. A few of
the traditional cold spots may slip blo freezing.

Temps will begin to rebound on Sun. Expect highs into the mid/upper
60s in the interior and 50s near Lake Superior.

Mid-level ridge will shift e into the central U.S. early next week
while deamplifying as a shortwave moves around it. Responding strong
waa pattern should yield some convection later Mon/Tue. Cold front
associated with the shortwave will likely settle well s of the area
as the wave drops into the trof over the ne U.S. This should support
dry weather into the midweek period, but there are some indications
that additional shortwaves may affect the area, perhaps leading to
some shra.

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 122 AM EDT THU MAY 28 2020

Scattered showers are affecting many of the terminals late this
evening. No immediate concerns for thunderstorms at the terminals,
although KSAW might see an isolated t-storm in the vicinity from 06-
09Z into the overnight. Did not include vicinity mention as coverage
of t-storms should be pretty isolated. Conditions at KIWD have
improved to VFR and should remain that way through period as showers
should stay east. Lingering low-level moisture and lighter upslope
winds may bring fog to CMX tonight, resulting in mainly MVFR to IFR
conditions, then expect improving conditions to VFR by midday Thu.
KSAW will lower to MVFR to IFR overnight as showers fill in ahead of
a trough, and as mentioned, thunder not out of question. As showers
shift east of KSAW late Thursday morning with movement of
trough/frontal boundary, conditions will gradually improve to VFR by
mid to late afternoon as drier air works in from the west.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 349 AM EDT THU MAY 28 2020

Winds generally stay light today but will increase from
the WNW tonight as a cold front pushes though the area. Winds
over the western third of the lake could reach 20 knots with
higher gusts behind the front tonight. Winds will then increase
over the central and east Friday morning as the cold front
continues to push east. Wind diminish for the weekend except over
the far east where they could reach 20 knots at times.

Upper Michigan...
Lake Superior...
Lake Michigan...
  Dense Fog Advisory until 11 AM EDT this morning for LMZ248-250.



LONG TERM...Rolfson
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