Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 190656

Area Forecast Discussion
National Weather Service Marquette MI
256 AM EDT TUE JUL 19 2016

.SHORT TERM...(Today and tonight)
Issued at 225 AM EDT TUE JUL 19 2016

Nam shows a deep 500 mb trough on the west coast and a broad trough
over ern North America with a broad 500 mb ridge over the southern
U.S. pushing up into the plains and Canadian prairies. A shortwave
over western Nebraska and another over northern MT this morning try
to move through the ridge and affect the upper Great Lakes late
tonight. Nam does bring in some weak 850-500 mb q-vector convergence
and some limited moisture into the western cwa late tonight. Nam,
Gfs, Canadian and Ecmwf do show some moisture around 800-750mb along
with some weak lift on I310K surface moving into the west late
tonight as well. Even with the ridge in place, hard to argue that
there will not be some type of elevated convection late tonight and
could see an accas field and all models are putting out some qpf, so
went with low chance pops late tonight across the west half of upper
Michigan. Otherwise, did not make too many changes to the going
forecast overall.

.LONG TERM...(Wednesday through Monday)
Issued at 256 AM EDT TUE JUL 19 2016

Not much has changed in the last couple of days. Upper ridge
building overhead will promote hot and humid conditions and a few
shortwaves moving through or near the CWA Wed into Fri with a more
significant shortwave possible late in the work week or early
weekend. Sun and Mon is a toss-up on the pattern with the ECMWF
showing a deepening upper trough while the GFS has zonal flow or
slight ridging aloft. With a significant amount of uncertainty due
to convectively induced/altered shortwaves through Fri and vast
model disagreement/discontinuity later in the forecast period, stuck
with or close to the consensus guidance. Forecast confidence with
such shortwaves typically only increases within 12 hours of
occurrence. With ample instability, if convection can break the cap
it very easily could become strong to severe Wed through Fri.

Some details, where available/useful, are as follows.

A decaying convective cluster may move through on Wed, as shown by
the GFS, NAM, and to a similar degree the ECMWF. Will keep POPs
below likely given limited confidence. Of course, confidence in
temps is limited since the timing/extent of convection is uncertain.

Thu may see a convective complex dive through, as noted in the GFS
and NAM. If that does occur, temperatures would likely need to be
cut significantly.

After that the predictability is just too low to meaningfully
comment on.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 120 AM EDT TUE JUL 19 2016

With high pres dominating, vfr conditions and light winds will be
the rule thru this fcst period at KIWD/KCMX/KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 225 AM EDT TUE JUL 19 2016

Winds will stay below 20 knots through the forecast period under
relatively a weak pressure gradient and high overwater stability.
Warm and humid air will flow across Lake Superior Wednesday through
Friday, which will allow fog to form, locally dense at times.

Upper Michigan...
Lake Superior...
Lake Michigan...


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