Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211754

Area Forecast Discussion
National Weather Service Marquette MI
154 PM EDT Tue Mar 21 2017

.SHORT TERM...(Today and tonight)
Issued at 427 AM EDT TUE MAR 21 2017

The shortwave is currently just N of Lake Superior with a 1010mb SFC
low just ENE of Lake Superior. A cold front has moved through the
Keweenaw, prompting gusts of 40-45 mph just behind the front. This is
very similar to conditions that occurred for a very short period of
time upstream. 850mb should currently be AOA -10C, but will fall to
around -18C by 15Z today. GOES-16 does not show any low level LES
development over the big lake yet, but that will come over the next
2-4 hours. NW-NNW wind LES will then persist through much of
tonight. However, LES will really struggle due to very dry upstream
air. Not looking at significant snowfall at all, have 24 hour
snowfall amounts of 1-2" with potential for local amounts up to 3".

.LONG TERM...(Wednesday through Monday)
Issued at 409 AM EDT TUE MAR 21 2017

Nam shows a 500 mb trough on the west coast, a ridge over the plains
and a deep trough on the east coast 12z Wed. This ridge slowly moves
across the plains and into the upper Great Lakes Thu into Fri
morning while a closed 500 mb low moves into the southern Rockies.
Nam brings in some 850-500 mb q-vector convergence and deeper
moisture Thu night into the area late. Still looks like there could
be a wintry mix of pcpn for Thu night into Fri morning of snow,
sleet, rain and freezing rain switching over to all rain on Fri.
Temperatures warm aloft while the lower levels remain cold and this
is enough to keep the mix in. Overall, did not make too many changes
to the going forecast.

In the extended, GFS and ECMWF show a 500 mb closed low over western
KS 12z Fri with a ridge in the sern U.S. This closed 500 mb low and
trough moves eastward 12z Sat with upper ridging over the upper
Great Lakes. The upper low and trough move into northern IL 12z Sun
and to the lower Great Lakes 12z Mon. Another trough moves into the
central plains 12z Mon and gets ejected into the upper Great Lakes
on Tue. Temperatures look to be near normal for this forecast period
with rain/snow mix especially during the late night and morning

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 152 PM EDT TUE MAR 21 2017

At IWD and CMX, conditions have already improved as very dry air
upstream moves over Lk Superior and Upper Michigan. Both of those
sites will see cigs around 030 or higher this aftn along with
minimal vsby reductions as light snow comes to an end. Only a few
clouds will linger late this aftn into tonight as air remains dry
closer to approaching high pressure ridge.

At SAW, expect more persistent snow showers through late this aftn
before dry air eventually takes toll on ongoing lake effect.
Conditions will mostly be MVFR through the aftn, though brief IFR
vsby is possible during heavier snow showers. Clouds should scatter
out by early evening as the dry air moves in. Then later tonight
into Wed morning expect MVFR to lower VFR clouds and flurries to
return as winds turn out of the N off Lk Superior. Skies will
graudally clear out on Wed aftn though it may take some time as
onshore winds persist off Lk Superior.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EDT TUE MAR 21 2017

Gales will gradually diminish into tonight, with no other gales
expected otherwise. Some isolated heavy freezing spray is expected
over far eastern Lake Superior today into tonight, but not enough to
warrant a warning.

Upper Michigan...
Lake Superior...
  Gale Warning until 2 AM EDT Wednesday for LSZ249>251-266-267.

  Gale Warning until 4 PM EDT this afternoon for LSZ243>248-264-

Lake Michigan...


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