Area Forecast Discussion
Issued by NWS Marquette, MI

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835
FXUS63 KMQT 251942
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
342 PM EDT Tue Apr 25 2017

.SHORT TERM...(Today and tonight)
Issued at 314 AM EDT TUE APR 25 2017

Upper air pattern consists of a 500 mb trough over the Rockies and a
shortwave over the northern plains this morning. This shortwave
moves to the east into the upper Great Lakes this afternoon. The
trough over the Rockies moves into the northern plains late tonight.
Nam shows deeper moisture and 850-500 mb q-vector convergence
arriving this evening and remaining overnight. GFS and ECMWF show
this too. However, NAM looks to be too cold with sfc temperatures
tonight and did not use them for this forecast. Went with the warmer
temperatures of the GFS and ECMWF which keep the pcpn as all rain.
One other major change to the going forecast was to keep the dry air
in longer today and pushed the timing of pops back a bit with slight
chance only in the far west late today and then categorical pops
overspreading the area tonight. These were the only major changes
done to the going forecast.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 342 PM EDT TUE APR 25 2017

Main concerns in the long term will be light wintry mix Wednesday
night into Thursday along with increased river levels through
Thursday night.

Wednesday night through Thursday night: Low pressure sliding through
the Upper Great Lakes region is expected to slide directly across
the central U.P. Wednesday night to near James Bay Thursday night.
At the same time, a close 500mb low is progged to slide across the
Northern Plains into the western part of the CWA. The better chances
for precipitation will occur Wednesday night and again during the
day Thursday into Thursday night as 1000-500mb RH is in place and
deep layer forcing is maximized through that layer. There will be a
gradual diminishing trend from the southwest Thursday evening into
the overnight hours. Overall, the precipiation should remain in the
form of rain across most of the U.P.; however, as the upper level
low drops into the far western CWA, colder air will allow the
precipitation to transition to a mix of rain, freezing rain, sleet
and snow especially Wednesday night. Ice and snow accumulations are
expected to be limited and generally confined to elevated surfaces
and grassy surfaces. The accumulation will largely be limited due to
the warmer surfaces, as temperatures have generally been above
normal over the past few days. Otherwise, rainfall totals are
expected to be between a half an inch and three-quraters of an inch
through this time period, with the heaviest totals expected over the
east. This additional rainfall along with the expected rainfall
through Wednesday will keep river levels elevated through this time
period, as previous shift mentioned at least minor flooding is not
out of the question through Thursday night.

Friday through Saturday: A surface ridge and drier air is expected
to build into the area during this time period allowing skies to
become partly cloudy with only minor chances for rain and snow
showers. Temperatures are expected to be slightly below normal
through this time period.

Saturday night through the extended: Low pressure is expected to
develop over the Southern Plains late Saturday night and slide
through the Upper Great Lakes Sunday into early next week. Models
are in generall agreement; however, there are some timing and
placement differences in the solutions. The GFS/Canadian have
similar tracks and timing; however, the GFS is deeper with the
surface low and upper level low. These models each have the low
moving out of the area Tuesday afternoon. The previous run of the EC
was much faster with the low having the system out of the area by
Monday afternoon; however, the 12Z run has the timeing similar to
the GFS/Canadian. The EC is continues to trend farther west with the
system. If the GFS/Canadian are correct there could be accumulating
snowfall across the west half of the U.P.; however, if the EC
solution is correct, then most areas may end up seeing mainly  rain.
this will definitely need to be watched in later forecast packages,
at this point will stick with a consensus of the models bringing
widespread precipiation to the area.
&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 145 PM EDT TUE APR 25 2017

Under mid and high clouds, a dry low-level air mass will dominate
the area through this afternoon with conditions at all sites. A sfc
trof drifting se into Upper MI this evening will result in
deteriorating conditions as shallow cold air undercuts warmer air
and -ra develops. Expect IFR conditions at IWD by late evening and
at CMX/SAW overnight. Cigs are also expeced to drop to LIFR which
will persist through Wednesday morning.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 314 AM EDT TUE APR 25 2017

Northeast gales look to start up across west and central lake
Superior late today and continue through Wed evening. By late
Wednesday night into Thursday morning winds will begin to subside to
20 to 30 knots as winds become northerly. Late Thursday through
Friday, winds will further decrease to 10 to 20 knots as winds
become westerly. Winds of 10 to 20 knots are expected through the
weekend and into early next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 8 PM EDT /7 PM CDT/ this evening to 11 PM EDT
     /10 PM CDT/ Wednesday for LSZ162.

  Gale Warning from 8 PM this evening to 3 AM EDT Thursday for
     LSZ264.

  Gale Warning from 7 PM this evening to 2 AM EDT Thursday for
     LSZ263.

Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...KEC
AVIATION...JLB
MARINE...07



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