Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300744

Area Forecast Discussion
National Weather Service Marquette MI
344 AM EDT Sun Apr 30 2017

.SHORT TERM...(This evening through Sunday)
Issued at 342 PM EDT SAT APR 29 2017

The main weather concerns during this time period will be an
approaching low pressure system from the southwest, introducing a
chance of rain very late tonight through Sunday.

Tonight: Low pressure over the Southern Plains is expected to slowly
lift northward toward the Upper Great Lakes region through this time
period. As this happens, the surface low and upper level 500mb low
are both expected to intensify. The main impact that this will have
on the U.P. tonight, will be a steady increase in moisture flow into
the area. Initially, high clouds will be on the increase this
evening and then steadily increase in depth through the overnight
hours. Isentropic upglide will slowly increase across far south
central portions of the U.P. overnight, which may give a few rain
showers. The precipitation will likely have trouble lifting too far
to the north as dry high pressure remains in place over southern
Hudson Bay, helping to continue pumping low to mid level dry air
into the area. In fact, models continue to trend a bit slower with
the onset of the precipitation.

Sunday: This system will continue northward, reaching southwest Iowa
by 00Z Monday. Again, the main concern will be the continued/steady
increase in moisture across the area as the high over southern
Hudson Bay continues to shift to the east and the low slowly
approaches. A majority of the system forcing will remain to the
south of the U.P. through late Sunday afternoon; however, the
isentropic upglide will continue to steadily increase throughout the
day. This will lead to at least scattered rain showers building
across mainly the south half of the area, with cloud cover
increasing across the north half. Precipitation totals through
Sunday afternoon will be between a tenth to a quarter of an inch
south half with a tenth or less north half.

.LONG TERM...(Monday through Saturday)
Issued at 342 AM EDT SUN APR 30 2017

Expect an active beginning to the work week as low pressure lifts
northeast across the Upper Great Lakes. The best chance for
precipitation will coincide with this system, on Monday and Tuesday.
There will be another chance for precipitation later in the week as
a cold front pushes south across the area. Otherwise, for the most
part the weather looks like it will quiet down a bit later this week
and through the weekend. Temperatures will start off below normal,
before climbing back up into the 50s, which near normal for this
time of year.

On Monday as the above mentioned low pressure system lifts across
the Wisconsin and up into central/eastern portion of the area,
expect the rain to continue. With strong upper-level diffluence
overspreading the region ahead of the main cutoff energy lifting
northeast, the combination of strong synoptic-scale lift and PWATs
running upwards of 150-200% of normal, the heaviest rain is expected
to linger through the mid/late morning hours, especially across the
norther on Monday. The medium range models are consistent with
elevated instability lifting northeast with the main branch of mid-
level moisture transport. Therefore, would not be surprised if we
hear a few rumbles of thunder through the morning hours. By the
afternoon hours on Monday, the strong warm, moisture advection will
lift northeast of the area as the surface trough lifts into central
portions of the area, allowing for the left exit region of the upper-
level jet and main upper-level vort-maxes to move across the area.
This additional synoptic-scale lift will allow rain to linger
through the day on Monday.

Monday night through Tuesday, as the main surface and and upper-
level low lift across eastern portions of the area, expect
precipitation to linger and change over to snow in some locations as
cold air advection wraps around the exiting system. Based on current
forecast soundings, looks like precipitation across the west and
north central should remain mostly snow, especially across the
higher terrain. Depending on how deep the moisture is behind the
system, a few locations could pick up a couple of inches of wet,
heavy snow, especially across the west and the higher terrain in the
north central portions of the area. Further east and across south
central portions of the area, any lingering precipitation should
remain mostly liquid.

Wednesday things will begin to dry out as heights rise across the
area and high pressure briefly traverses the region. Precipitation
chances will return Thursday as an upper-level wave and weak cold
front push across the area. As the upper-level wave digs across the
region, we will remain under northwest flow into the weekend. With
embedded shortwave activity Thursday night and Friday, we may see
lingering rain showers; however, any precipitation should remain
fairly light.

This weekend, there are discrepancies among the GFS/ECMWF/Canadian,
all being a bit different in the placement and progressiveness of
upper-level energy. Depending on where the upper-level trough sets
up and how cutoff energy that is progged to lift out of the
southeast interacts with the upper-level flow, we could could have a
cooler weekend in store with a chances for precipitation late in the

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 137 AM EDT SUN APR 30 2017

VFR conditions will prevail into late afternoon; however, there may
be lower clouds into the MVFR range that try to build into the KSAW
TAF site late afternoon as rain moves northward into the area. With
more persistent rain during the evening, expect cigs to lower to
MVFR at IWD and to IFR at SAW by the end of the period. The dry air
should perist longer to the north with cigs remaining above MVFR at
CMX. However, confidence is lower this evening.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EDT SAT APR 29 2017

High pressure will remain in place across Lake Superior through
tonight, keeping winds light northeast in the evening, turning
easterly overnight. Winds will remain at or less than 15 to 20
knots. Sunday, low pressure will approach the Upper Great Lakes from
the southwest allowing the pressure gradient to tighten once again.
This will allow winds to increast to 20 to 30 knots over much of
Lake Superior, with the strongest gusts expected over the west half
of the lake due to terrain enhancements on a favored norhteast wind.
As the pres gradient tightens over the Upper Lakes on Sun night
ahead of deep lo pres approaching from the sw, ne winds will
increase to gale force over at least portions of the w and central
lake. Expect the strongest gales up to 40 kts over the w, where the
terrain will funnel the ne flow and further enhance the wind speeds.
Issued gale warnings for the areas to be impacted. As the pres
gradient begins to weaken on Mon night into Tue behind the departing
lo pres, winds will diminish and back toward the n ahead of
approaching hi pres that will build over the Upper Lakes on Wed and
further reduce wind speeds under 20 kts thru Thu.

Upper Michigan...
Lake Superior...
  Gale Warning from 2 AM to 2 PM EDT Monday for LSZ265-266.

  Gale Warning from 8 PM EDT /7 PM CDT/ this evening to 5 PM EDT
     /4 PM CDT/ Monday for LSZ162.

  Gale Warning from 2 AM to 8 PM EDT Monday for LSZ263-264.

  Gale Warning from 5 AM to 2 PM EDT Monday for LSZ243>246.

Lake Michigan...
  Gale Warning from 2 PM this afternoon to 8 AM EDT Monday for



LONG TERM...Ritzman
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