Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200901

Area Forecast Discussion
National Weather Service Marquette MI
501 AM EDT Sun Aug 20 2017

.SHORT TERM...(Today and tonight)
Issued at 500 AM EDT SUN AUG 20 2017

WV imagery and RAP analysis indicated zonal mid/upper level flow
across the nrn CONUS with the main upstream shortwave trough over
wrn Manitoba. At the surface, sw flow was increasing over nrn MN and
Lake Superior between a ridge from PA into lower MI and nrn WI and a
cold front into the nw corner of MN.

Today, Expect that with plenty of sunshine and sw flow WAA pushing
850 mb temps to around 17C, highs will climb into the mid 80s, with
the higher readings in downslope locations near Lake Superior and
lower temps in the mid and upper 70s downwind of Lake Michigan. The
warming combined with dewpoints in the lower to mid 60s will result
in MLCAPE values in the 1k-2k J/Kg range. As the front moves into
the area along with lake breeze boundaries, sct shra/tsra should
develop by mid to late afternoon over the nw half and spread into
cntrl Upper Michigan early this evening. There is still some
uncertainty with the coverage/POPs with the amount of capping as the
stronger qvector conv and height falls remain well to the north.
With 0-6km shear values in the 30-35 knot range, some organized
stronger convection may develop with the potential for small hail
along with gusty winds. Relatively high freezing levels around 14k
ft will limit the potential for larger hail.

Tonight, the sct shra/tsra should move through the rest of the cntrl
and ern cwa between 00z-06z with drier air moving into the west
overnight behind the front.

.LONG TERM...(Monday through Saturday)
Issued at 258 AM EDT SUN AUG 20 2017

Overall, the weather looks to remain active, especially across the
south central and eastern portions of Upper Michigan through early
parts of the week. Then as high pressure drops down across the Upper
Great Lakes region, cooler and drier air will advect south across
the area for the middle and end of the work week.

Monday, the cold front that is progged to drop southeast across the
area Sunday into Sunday night will stall out just to our south.
Therefore, the best precipitation chances look to remain south of
the area across Wisconsin and lower Michigan. As drier air begins to
filter in behind the front, things are looking a bit better cloud
cover wise for the viewing of the partial solar eclipse on Monday
afternoon, especially across the north central. Late Monday into
Tuesday, as longwave troughing digs across the Upper Great Lakes,
the stalled out front will lift back northward. This will allow
chances to increase for showers and thunderstorms Monday night.
There is some uncertainty in how far north this front and the better
instability will get; however, chances still look best across the
south central and eastern portions of Upper Michigan. Tuesday
morning, lingering showers and thunderstorms will push east-
southeast across the area eventually vacating Upper Michigan as a
stable post-frontal air mass works its way into the region.

Wednesday through the end of the work week the weather looks to
remain quiet as surface ridging takes hold on the Upper Great Lakes
region as longwave troughing anchors across the northeast. Wednesday
looks to be the coolest day of the week, with temperatures in the
60s, as cold air advection will continue to spread southward.
Overnight lows will be rather chilly as well, with a few interior
locations across the west and central possibly seeing temperatures
drop down into the upper 30s early Thursday morning. Thursday
through Friday, temperatures will rebound a bit each day as the
better cold air advection shifts east of the region, and warm air
advection gradually returns. Temperatures will return to near normal
through the weekend as warm air advection increases through ahead of
the next system dropping down across the north central CONUS. The
best precipitation chances this weekend look to be on Sunday.

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 138 AM EDT SUN AUG 20 2017

VFR conditions expected through end of TAF period. S winds may gust
over 20 kts on Sun afternoon at SAW and there could be scattered
showers or thunderstorms at all the TAF sites late Sun aftn into
early Sun evening as a cold front crosses the region.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 500 AM EDT SUN AUG 20 2017

Winds will remain at or below 20 knots through the first half of the
work week as the pressure gradient remains fairly weak across Lake
Superior. Southwest winds may gust close to 25 knots this afternoon
ahead of a cold front moving through, but it should be for a short
duration. The next chance for gusty winds will be Wednesday as low
pressure slides to the northeast of Lake Superior. Northwest winds
may gust as high as 25 knots during that time period.

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


LONG TERM...Ritzman
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