Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141847

Area Forecast Discussion
National Weather Service Marquette MI
247 PM EDT Wed Mar 14 2018

.SHORT TERM...(Today and tonight)
Issued at 456 AM EDT WED MAR 14 2018

Today and tonight: A weak ridge of high pressure, stretching across
the U.P. this morning, will quickly shift to the south and east of
the area late in the morning. Behind the surface ridge, a surface
trough/cold front and associated shortwave will slide through the
area this afternoon, with another shortwave progged to slide through
the area tonight. After the trough moves through and the shortwaves
slide across the area, temperatures will steadily cool at the
surface and aloft. The main impact this will have is the development
of lake effect/enhanced snow for north to northwest wind favored
snow belts, especially over the central and eastern U.P. 850mb temps
will drop from -7C this morning and early afternoon to -16C this
evening and overnight as the shortwaves slide through. Again, this
temperature difference would be very favorable for lake effect

Moisture will be deep enough to reach into the DGZ; however, this
layer looks to be fairly shallow initially and winds through that
layer look to be gusty. This would likely keep flake size fairly
small, keeping accumulations in check. Visibility may be reduced
in the snow showers due to the combination of small flakes and
blowing and drifting snow. Current thinking is that north to
northwest wind favored snow belts would see snow totals in the 1
to 4 inch range tonight through Thursday morning; however,
anywhere that a band focuses a bit more could see isolated higher
amounts. No need for any headlines at this point. Impacts would
likely be limited as most of the snow would occur at night, during
less travel periods.

.LONG TERM...(Thursday through Tuesday)
Issued at 443 AM EDT WED MAR 14 2018

A mostly quiet stretch of late winter/early spring weather is on the
way thru the middle of next week. A deep trof is currently located
over the eastern CONUS downstream of an amplified ridge over western
Canada and upstream of a positive height anomaly centered just e of
Labrador. Over the next several days, the western Canada ridge will
shift e slightly, then fade away before reaching the Upper Lakes.
Before it weakens, it will force one more shortwave to dive into the
Great Lakes region later today/tonight, bringing a reinforcing surge
of colder air and another round of LES off Lake Superior. As the
ridge fades away, split flow will develop across N America late this
week thru the middle of next week. With the northern stream
featuring a trof over eastern Canada, any shortwaves and associated
pcpn tracking across the CONUS in the southern stream will likely be
forced s of the area by the eastern Canada trof. As a result, any
pcpn that occurs over the next 7 days will be exclusively LES, the
theme of this cold season which has lacked significant synoptic
snows. One period of LES will occur tonight into Thu, following
aformentioned shortwave and its reinforcing surge of cold air. There
may be some LES off Lake Superior again late weekend/early next week
as a shortwave dropping into the eastern Canada trof pushes colder
air into the Upper Lakes. Otherwise, that`s all there is for pcpn
over the next 7 days. As for temps, readings will fluctuate roughly
5-10 degrees either side of normal thru the middle of next week. The
colder days with blo normal temps are expected Thu and Mon, and
maybe Tue. Warmest day will be Sat.

Beginning Thu, 850mb thermal trof of -15 to -18C will be arriving
during the morning. Lack of deep moisture with low inversions of 4-
5kft will limit this round of LES compared to the event Mon
night/Tue morning. However, the dgz will occupy most of the
convective layer over the e half of Lake Superior where coldest part
of the thermal trof passes. So, may be able to fluff up locally 2-3
inches of snow into the n central and eastern fcst area under nnw
winds. LES will be lighter over the w. LES will diminish during the
aftn as inversion falls slightly and effects of mid Mar daytime
heating disrupt lake effect processes. Skies will probably begin to
clear over the w. Expect high temps in the 20s to around 30F.

Any lingering LES over the e will end Thu night under weak waa. High
pres ridge nosing se into Upper MI should support a cold night over
the w under good radiational cooling conditions. Little concerned
that there could be some lake stratocu over the w with diminishing
low-level flow still maintaining a wind component off the lake.
Positive aspect for clear skies would be that low-level winds become
increasingly anticylonic thru the night. For now, favored the lower
side of guidance, represented by the bias-corrected global CMC which
is typically a superior performer on radiational cooling nights.
Tradiational cold spots should see temps bottom out toward -5F.
Sct-bkn clouds will probably hold on over the e for much, if not
all, of the night, keeping temps higher.

With sfc high pres dominating, should see a sunny day on Fri though
some clouds may linger over the e at least thru the morning. The sfc
high will remain over the area into Sat, allowing for another sunny
day. A cold front will be approaching from the n on Sat in
association with a shortwave tracking se thru northern Ontario, but
that front will not pass until Sat night. Highs on Fri should
approach 40F over the interior w. On Sat, highs will be warmer,
rising into the 40s over the interior w half.

Colder air will begin to ease into the Upper Lakes on Sun in the
wake of cold fropa. However, 00Z medium range models have all
trended weaker with the caa, casting doubt on redevelopment of LES
early next week as 850mb temps don`t fall enough. Fcst reflects a
drier scenario for now.

Shortwave tracking across the CONUS in the southern stream early
next week should pass well s of the area due to the se Canada
troffing in the northern stream. However, there are quite a few CMC
ensembles and a few GFS ensembles that are far enough n to bring
pcpn into the area. While fcst will carry dry weather into mid week,
confidence in a dry fcst is diminished.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 247 PM EDT WED MAR 14 2018

Lake effect clouds and snow will move in this evening and continue
into Thursday. Models continue to handle lake effect quite poorly,
so there is uncertainty with visibilities. Don`t think visibilities
will drop too far given light snowfall expected, but that will need
fine tuning as conditions develop.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 456 AM EDT WED MAR 14 2018

Relatively calm winds will prevail until tonight into Thursday as
winds increase to 20 to 30 knots, strongest over the east half of
the lake. There could be a few gale force gusts tonight into
Thursday morning, but should not be widespread. Otherwise, the
rest of the week into the weekend, winds should remain at or below
20kts on Lake Superior.

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


LONG TERM...Rolfson
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