Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181953

Area Forecast Discussion
National Weather Service Marquette MI
353 PM EDT Tue Apr 18 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM EDT TUE APR 18 2017

Low pressure continues to track towards western portions of the area
this afternoon as a robust shortwave, evident on the water vapor
imagery, continues to lift northeast. With warm, moist air advecting
in ahead of this system, fairly widespread rain developed across
Minnesota and Wisconsin and streamed northeast into western portions
of the area throughout the late morning and early afternoon hours.

Through the rest of the afternoon and into the overnight hours,
expect the ongoing rain to lift northeast across the west and
central portions of Upper Michigan as warm, moist accent continues
ahead of the upper level vort-max. Across the west, rain is expected
to remain light, but training precipitation will allow precipitation
amounts to possibly exceed a quarter of an inch through the rest of
the afternoon and overnight hours. Further east across central and
eastern portions of the area, rainfall amounts are expected to be
much lower as the main forcing lift northeast across central Lake
Superior. During the overnight hours, as the trailing cold front
pushes east across the area, expect the widespread rain to come to
an end from west to east. However, with increasing cold air
advection behind the system, forecast soundings are consistent with
stratus settling into the area. Therefore, we could see some spotty
drizzle develop and linger into early Wednesday morning across the
west and central, especially across the higher terrain.

On Wednesday things will dry out, but models are fairly persistent
in maintaining stratus through a good portion of the day. Could see
a few pockets of clearing, especially across the south where
downsloping winds will be persistent, but upper-level clouds will
begin to stream northward ahead of another approaching system.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 353 PM EDT TUE APR 18 2017

A split upr flow wl dominate the wx pattern acrs NAmerica during the
medium/extended range. The recent models have trended to track the
next srn branch shrtwv/sfc lo pres to impact Upr MI farther n and
across the central Great Lks on Wed night/Thu, bringing the
potential for some mdt to heavy wet snow to mainly the hier terrain
of the ncentral cwa. Hudson Bay hi pres expanding into the area in
the wake of this disturbance wl then bring a period of dry wx for at
least Fri and Sat. Although a cold fnt associated with a nrn branch
shrtwv may pass Upr MI Sat ngt or early Sun, accompanying pcpn
should be on the light side. The next disturbance to impact the area
may arrive as early as next Sun ngt/Mon, but wl likely hold off
until Tue. Expect temps to run aob normal during the medium/extended

Wed ngt thru Thu ngt...A disturbance and accompanying sfc lo pres
moving e thru the srn branch flow dominating the n half of the CONUS
are progged to move thru the Great Lks area during this time. The
great majority of the shorter range guidance has trended farther to
the n with the track of this shrtwv/sfc lo pres and now show sgnft
qpf over much of Upr MI under the large scale dpva under the
diffluent upr flow ahead of the shrtwv that wl cause 12hr h5 hgt
falls up to 100m on the cyc side of the associated h85 lo track.
An upslope, strengthening cyc ne flow wl enhance pcpn rates over the
hier terrain of the ncentral. Pcpn ahead of this system is fcst to
overspread the cwa on Wed ngt under incrsg isentropic ascent and upr
dvgc in the rrq of 120kt h3 jet max near James Bay. The fcst thermal
profiles suggest the pcpn wl begin as ra but then mix with or change
to sn over at least the hier terrain of the nw half by sometime on
Thu mrng as the vigorous uvv results in sufficient dynamic cooling
thru a deep enuf lyr. Expect the pcpn to diminish w-e on Thu ngt as
the shrtwv/dynamic support exit to the e. But clds and some lighter
sn wl persist thru the ngt especially over the nrn tier with
lingering cyc upslope nne flow. The 12Z GFS paints the most storm
total qpf as hi as about an inch over the hier terrain of the nw
half, where the upslope enhancement wl be most sgnft. As much as 4
to 6 to perhaps 8 inches of wet and heavy sn may fall over the Huron
Mtns/hier terrain of the ncentral where the upslope cooling/
enhancement wl be maximized in this scenario. Although some of the
other models show less pcpn--in fact the 12Z local WRF-arw shows the
shrtwv/sfc lo tracking farther to the s so that the bulk of the pcpn
misses the cwa--and there are still concerns about the thermal
fields/ptype, wl issue an SPS for the ncentral to highlight the
potential for some heavy sn that could cause dangerous travel and
power outages due to sn buildup on tree limbs/power lines and some
gusty winds.

Fri thru Sat...Hudson Bay hi pres bldg into the Upr Lks in the wake
of the departing lo pres will bring a drying trend to Upr MI on Fri,
with some clrg as the llvl flow becomes more acyc. Although a weak
shrtwv is fcst to move thru the area on Fri, the large scale drying
and incrsgly acyc llvl flow behind the exiting lo pres wl restict
pcpn chcs. Lingering clds and llvl n winds off Lk Sup wl hold down
the rise in max temps, especially near the Lk. The combination of
light winds/clrg skies and pwat falling under 0.25 inch in the
subsidence behind the shrtwv wl allow temps on Fri ngt to fall into
the chilly 20s over the interior. A good deal of sunshine and h85
temps rebounding to near 4C on Sat will allow the mercury to rebound
as hi as the lo 60s away fm the cooling influence of the lk.

Late Weekend...The medium range guidance indicates a shrtwv in the
nrn branch flow wl push thru Ontario and drag a cold front across
the Upr Lks on Sat ngt/Sun mrng. Although there are timing
differences, all the models show an absence of mstr inflow that wl
diminish the potential for any sgnft pcpn, especially since the
sharper forcing ahead of the shrtwv wl remain to the n. Even if
there is a return of at least some sunshine with trailing hi pres on
Sun, a n wind off Lk Sup and h85 temps falling as lo as -8C wl
result in blo normal temps.

Early next week...Uncertainty increases early next week as the
longer range guidance varies on the timing of the next shrtwv/lo
pres that is fcst to aprch fm the w and on the persistence of Hudson
Bay hi pres over the Upr Lks. Some of the longer range models show
pcpn returning as soon as early as Sun ngt/Mon.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 149 PM EDT TUE APR 18 2017

Low pressure lifting northeast across western portions of Upper
Michigan this afternoon and evening will spread rain across all
terminals, with KIWD/KCMX being impacted already this afternoon and
KSAW later this afternoon and evening. The increasing pressure
gradient across the area will work in concert with falling
precipitation to mix down gusty winds through the rest of the
afternoon. Visibilities will also be impacted from the rain as they
may drop down into the MVFR category within the heavier pockets of
rain. The rain will come to an end at KIWD/KCMX later this evening,
and may linger into the overnight hours at KSAW. Behind this system,
expect low stratus to fill in with ceilings possibly dropping down
into the LIFR category at times. Depending on how deep the stratus
can grow, we could see some lingering drizzle in locations that see
remnant deeper moisture. As a 45 to 55 knot low-level jet tracks
northeast across central and eastern portions of the area tonight,
have included mentions of low-level wind shear at KSAW as the
surface winds are expected to relax a bit. With gusty northwest
winds expected to also filter southward across the area tonight into
Wednesday morning, the boundary layer looks like it will be a bit
too mixy for the development of any visbility restrictions at this


Southeast gales to 35 knots over the e half of Lake Superior this
afternoon under the tight pres gradient ahead of a lo pres tracking
thru MN toward the Upper Lakes will diminish this evening following
the passage of the lo pres. In its wake, expect winds to shift to
the nnw up to 25-30 knots tonight before further diminishing and
veering to the ne on Wed as trailing high pres crosses Ontario/Lake
Superior. Depending on the track of another lo pres approaching the
Lower Great Lakes on Thu, ene winds up to 25-30 kts are likely then.
If the lo pres is deep enough, there could be some gales. As hi pres
builds back into the Upper Lakes late in the week following this lo
pres, winds will diminish under 25 kts on Fri and Sat. N winds could
increase up to 25 kts Sat night and Sun following a cold frontal

Upper Michigan...
Lake Superior...
  Gale Warning until 11 PM EDT this evening for LSZ266-267.

  Gale Warning until 8 PM EDT this evening for LSZ244-245-264-265.

Lake Michigan...


SHORT TERM...Ritzman
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