Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181142

Area Forecast Discussion
National Weather Service Marquette MI
742 AM EDT Thu May 18 2017

.SHORT TERM...(Today)
Issued at 413 AM EDT THU MAY 18 2017

Attention into this evening is on precip placement and amounts and
gusty N winds.

The upper level low is just SW of the CWA, with the SFC low lagging
a bit more to the SSW over far W WI. Rain showers on the NW side of
the low track will be the main focus precip wise through today, with
up to an inch of QPF over NW Upper MI possible. These amounts will
not cause any flash flood issues, so the watch was cancelled. Do
expect elevated river levels, but nothing looks noteworthy at this
time. Upslope moist flow on the back side of the system will lead to
upslope precip in the NW wind favored areas this afternoon, but that
should diminish quickly from W to E this evening and SFC ridging and
much drier air works in.

N-NW gales over Lake Superior will turn N as the system moves
through today, with gusting winds up to 35 mph expected near Lake
Superior. As a result, Lake Superior waves will increase to 8-12
feet today, which may cause minor beach erosion.

.LONG TERM...(Tonight through Wednesday)
Issued at 318 AM EDT THU MAY 18 2017

A dry hi pres moving fm Manitoba e across Ontario just n of Lk Sup
will bring uneventful but cool wx tngt thru Fri before a
disturbance/lo pres aprchg fm the sw brings a return of showers
over the weekend. Much of next week looks to be on the cool side
as an upr trof deepens over the wrn Great Lks.

Tngt...Expect lingering clds and gusty winds over the ern cwa to
exit to the e ahead of dry hi pres that is fcst to build into wrn Lk
Sup. With diminishing winds and the arrival of pwat as lo as 0.15
inch, tended toward the lo end of guidance for min temps over the
interior w. A steadier ne flow under a bit tighter pres gradient
over the rest of the cwa wl limit the diurnal temp drop there
despite the arrival of drier air.

Fri/Fri ngt...As an upr rdg axis drifts ovhd, the sfc hi pres wl bld
over the Upr Lks. The very dry airmass wl bring plenty of sunshine,
but some hi clds may drift into the area during the aftn as some hi
lvl mstr in advance of a negatively tilted shrtwv lifting newd in
the Plains spills over the upr rdg axis. Since h85 temps wl rise no
hier than about 4C, expect blo normal temps, especially near Lk Sup
with an ene flow off the chilly water. One change to the
consensus fcst was to lower dewpts in the aftn with daytime mixing
of the very dry air above the sfc. Although the diurnal temp fall
on Fri ngt wl be limited by incrsg/thickening clds ahead of the
aprchg disturbance/sfc lo pres to the sw and an incrsg gradient se
flow under the tightening pres gradient btwn the departing sfc hi
pres and the lo moving toward Iowa, min temps wl still dip into
the 30s at many places with the lingering llvl dry air. Some of
the guidance indicates some pcpn could reach the WI border by
daybreak on Sat, but dryness of the antecedent airmass suggests
only lo chc pops are in order.

Weekend...Shrtwv and sfc lo pres to the sw are fcst to lift nnewd
and thru the Upr Lks on Sun. Most of the medium range guidance shows
a lo tracking n acrs wrn Lk Sup on Sat ngt into wrn Ontario on
Sun and dragging an occluded fnt acrs the cwa on Sat ngt/early
Sun. Showers ahead of the lo/occluded fnt and under the waa/
diffluent flow alf/some dpva wl arrive fm the sw on Sat before
diminishing under some dry slotting late Sat ngt into Sun. Some of
the models show a cyc w flow lingering on Sun, but large scale
subsidence in the wake of the shrtwv passing to the n wl limit
lingering shower chcs to the lo chc category, mainly over the wrn
cwa where the llvl wly flow wl present an upslope wind component.

Mon thru Wed...Depending on how quickly the cyc flow arnd the slowly
exiting lo pres in Ontario weakens/shifts to the n on Mon, some
showers may linger into Mon. Many of the longer range models show
another shrtwv digging sewd toward the Upr MS River Valley sliding
far enuf to the s on Mon ngt within a deepening upr trof so that
accompanying pcpn should pass to the s of the cwa and thru WI. As
the upr trof continues to deepen over the Upr Lks on Wed, upr
disturbances digging thru the area and a llvl cyc flow may result in
some showers on Tue/Wed. But some of the longer range models
indicate a hi pres rdg may be present then. Although there is much
uncertainty on the details of the fcst wx for this time, looks
like temps wl be blo normal under the upr trof with h85 temps no
more than a couple degrees above 0C within the upr troffing.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 741 AM EDT THU MAY 18 2017

Overall should see CIG and VIS improve through the TAF period,
especially this afternoon and early evening as much drier air moves
in. Windy will be gusty out of the NNW today, but will diminish this
evening into tonight.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 318 AM EDT THU MAY 18 2017

Ongoing nne gales over the west and central lake will overspread the
east early this morning as the tight pres gradient on the nw flank
of lo pres shifting to the e follows into that area. The gales will
then diminish w to e during the afternoon as a flatter gradient
ahead of hi pres building toward the area arrives. Winds under 20
knots are then expected into Sat, when the sharpening pres gradient
between hi pres departing toward Quebec and another lo pres
approaching from the sw results in e winds increasing up to 25 to
perhaps 30 kts. Expect the strongest winds over the w, where the
topography will funnel/enhance this flow. After the lo pres drifts
to the n on Sun/Mon, winds will shift to the w. Depending on how
tight the pres gradient is on the southern flank of the departing lo
pres, these w winds could be up to 25 kts.

Lingering fog over the e half of the lake will dissipate this
morning as the nne gales draw drier air into the area.

Upper Michigan...
Lake Superior...
  Gale Warning until 8 PM EDT this evening for LSZ267.

  Gale Warning until 5 PM EDT this afternoon for LSZ244-245-265-

  Gale Warning until 11 AM EDT /10 AM CDT/ this morning for LSZ162-

  Gale Warning until 2 PM EDT this afternoon for LSZ242-243-246-

  Gale Warning from noon today to 5 PM EDT this afternoon for

  Gale Warning from 2 PM this afternoon to 8 PM EDT this evening
     for LSZ251.

  Gale Warning until 5 PM EDT this afternoon for LSZ248.

Lake Michigan...
  Gale Warning from 11 AM this morning to 11 PM EDT this evening
     for LMZ221-248-250.



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