Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261851

Area Forecast Discussion
National Weather Service Marquette MI
251 PM EDT TUE JUL 26 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 250 PM EDT TUE JUL 26 2016

Upper air pattern consists of a shortwave across MN and the ern
Dakotas this morning that will move across the area this afternoon
into early evening. Nam shows some 850-500 mb q-vector convergence
over the area through 00z Thu with another shortwave affecting
mainly the southern cwa on Wed.

Couple things going against the convection for this afternoon. KMPX
and KGRB 12z soundings show dry mid levels and also the possibility
with sfc heating this afternoon mixing out the dew points in the
lower levels in the afternoon with sfc dew points falling in the
afternoon. This appears to be the case as sfc dew points have been
slowly falling and mixing out this afternoon which will tend to cut
down the instability this afternoon and because of this, have cut
the pops down a bit and delayed them a bit as well. Models also show
the strongest shear to the northeast with less instability and more
instability with less shear to the southwest of area. We cannot seem
to get everything to come together, so this argues for cutting pops
a bit. Still have chance pops in though for late this afternoon into
this evening in case some convection gets going on the lake breeze
boundaries which would be a possibility with lake breeze
convergence. Still kept in some chance pops in for Wed across the
south as well as a shortwave goes by to the south of the area and
have it dry to the north. Overall, did not make too many changes to
the going forecast for temperatures or weather.

.LONG TERM...(Wednesday through Monday)
Issued at 357 AM EDT TUE JUL 26 2016

Wednesday and Wednesday night: A cold front is progged to continue
sagging southward through the area Wednesday before stalling to the
south of the U.P. Wednesday night. A shortwave is progged to slide
through the Upper Great Lakes region Wednesday afternoon and evening
before sliding south and east of the area Wednesday night.
Steeper lapse rates associated with the shortwave along with
increased forcing across the southern U.P. will help to increase
chances for showers and thunderstorms. Again, the southern areas of
the U.P., in closer proximity to the slowing cold front, will have
the better chances due to increased forcing. MUCAPE values are
progged to be between 1000-2000 J/kg Wednesday afternoon/evening
south of the front. The severe weather potential looks low at this
point, through this time period as shear values are only expected to
be around or below 25-35 knots, oriented along the forcing
mechanism. Some of the storms during the afternoon/evening may pulse
up and become strong to severe, on a very isolated basis, but
organized/widespread severe weather is not expected. Storm motion
would most likely be from the west at or around 30 to 35 mph. The
main threat from any of the stronger storms would be small hail and
gusty winds.

Thursday through Friday night: High pressure and dry air is still
progged to slide into the area from Canada by Thursday morning and
then linger through this time period. Aloft, the Upper Great Lakes
region will be under a slight troughing pattern to near zonal flow.
This flow along with fairly dry air in place will keep the bulk of
the precipitation to the south of the U.P., while also helping to
keep temperatures closer to or slightly below normal for this time
of year. For reference, normal highs are right around 77 while
normal lows are around 55. The coolest night is expected to be
Thursday night as the surface ridge is centered overhead. This will
allow skies to clear and wind to become light and variable. The
combination of light winds, clear skies and precipitable water
values around 50 percent of normal will provide ideal radiational
cooling conditions. Inland locations may drop down into the low to
mid 40s for Thursday night.

Saturday and Saturday night: The aforementioned high pressure system
will slide to the east of the area through this time period.
As this happens, warmer and more moist, southerly flow will return
to the Upper Great Lakes region. Aloft, it looks as if there may be
a shortwave that slides across the area late Saturday, bringing
small chances for showers and thunderstorms.  Details will be fine-
tuned as the weekend approaches as the exact timing will be key for
increased chances of showers and thunderstorms.

Sunday through Tuesday: An upper-level 500mb ridge is expected to
build across the Upper Great Lakes region allowing temperatures to
warm above normal once again and reducing the chances for showers
and thunderstorms through Monday night. Models then hint at an
approaching cold front for Tuesday, but there are differences in
timing of the front for Tuesday; therefore, have gone with a
consensus of the models.  This will keep a chance of showers and
thunderstorms in the forecast for Tuesday.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 118 PM EDT TUE JUL 26 2016

VFR conditions should prevail at KIWD/KCMX/KSAW thru this fcst
period. Building instability this aftn along with approaching cold
front and lake breeze development will trigger sct shra/tsra. These
shra/tsra are most likely to occur around KSAW, and possibly around
KIWD as well. Only included a VCTS mention with uncertainty in
coverage of pcpn and uncertainty in whether either terminal will
actually be impacted. If pcpn does occur, mvfr conditions will be
possible with brief ifr not out of the question.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 250 PM EDT TUE JUL 26 2016

Winds across Lake Superior for the remainder of the week should be
mostly 15kt or less as the pressure gradient remains on the weak
side across the Upper Great Lakes.

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


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