Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 230902

Area Forecast Discussion
National Weather Service Marquette MI
502 AM EDT TUE AUG 23 2016

.SHORT TERM...(Today and tonight)
Issued at 400 AM EDT TUE AUG 23 2016

Upper air pattern consists of a closed 500 mb low over southern
Alberta with a trough in New England and a 500 mb ridge across the
sern U.S. There is also a shortwave in the western high plains that
will head northeast into the lower Missouri river valley tonight and
into the upper Great Lakes late tonight.

Lift associated with the LLJ which kicked off some showers and
thunderstorms overnight will continue to weaken this morning and the
convection will end. Next wave moves in late tonight with some weak
850-500 mb q-vector convergence and deeper moisture and have some
low chance pops late across the west half of the cwa. Otherwise,
fairly quiet for today into tonight. Made very few changes to going
forecast for temperatures.

.LONG TERM...(Wednesday through Monday)
Issued at 459 AM EDT TUE AUG 23 2016

Models suggest that a progressive pattern will prevail with a
mid/upper level low/trough over srn Sask/Manitoba Wednesday that will
move to nrn Ontario Thursday. This will bring increasing shra/tsra
chances Wednesday as the sfc trough/front moves toward the region.
Cooler and drier weather will then build into the nrn Great Lakes from
Thursday into Friday as high pressure builds from the nrn plains into
the Great Lakes. Unsettled weather returns by the weekend as the low
amplitude pattern will allow another mid level trough to move into
the region.

Wednesday and Wednesday night, as the sfc trough moves closer to the
area expect shra/tsra chances to increase as moisture advection
bring PWAT values above 1.5 inches. There is still considerable
uncertainty with the timing/position/strength of any convectively
modified shortwaves emerging from the plains that will help support
the pcpn. However, models have trended toward the idea that the
shra/tsra with a shrtwv will move in to mainly the srn cwa in the
morning and over the east in the afternoon. With the thicker clouds
and pcpn moving in during the morning instability (MLCAPE values into
the 500-1000 J/Kg range) and shear(0-6km 25 to 30 knots) will be
marginal for any stronger storms. The pcpn chances will shift to
mainly the ern cwa by late afternoon and evening. There still could
be some lingering isold/sct shrat/tsra over the west as the sfc
trough approaches if instability recovers during the afternoon.

Thursday into Thursday night, a trailing secondary cold front and
shrtwv could bring some isold -shra into wrn cwa Thursday night.
Otherwise, cooler air and drier air will prevail with highs from the
upper 60s west to mid 70s south and east and dewpoints falling into
the mid 50s.

Friday-Monday, surface high pressure and upper ridging will then
bring dry and mostly clear conditions Friday into early Saturday.
With a continued progressive pattern, pcpn chances will increase as
models suggest potential for a shrtwv to bring another round of
shra/tsra toward the area from later Saturday into early Sunday with
clearing/drying Sunday into Monday. However, confidence in any
details is low given models differences and lack of consistency.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 117 AM EDT TUE AUG 23 2016

Shra/tsra that have been affecting KSAW during the evening have
shifted e of the terminal with no new development expected
overnight. As a result, VFR conditions are expected thru this fcst
period at KIWD/KCMX/KSAW. Low-level jet over the area will result in
LLWS at all terminals for the remainder of the night. Winds will
become gusty today, especially at KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 400 AM EDT TUE AUG 23 2016

South to southwest winds of 15 to 25 knots are expected through much
of Wednesday as a low pressure trough over the Plains tracks toward
the Upper Great Lakes while high pressure exits to the east.
The trough will cross Lake Superior Wednesday afternoon and evening,
then usher in west winds of 15 to 25 knots Wednesday night and
Thursday. High pressure will then bring NW to SW winds less than 20
knots through Saturday. No gales seen anytime soon.

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


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