Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141826

Area Forecast Discussion
National Weather Service Marquette MI
226 PM EDT Mon Aug 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 226 PM EDT MON AUG 14 2017

Upper air pattern consists of a 500 mb trough over the upper Great
Lakes today with a shortwave ridge moving in for Tue. Nam shows some
850-500 mb q-vector convergence along with some moisture moving
through the area this afternoon before both move out tonight.
Looking at KMQT radar, a cyclonic spin with a MVC is moving across
the western cwa this afternoon into this evening. This will continue
to produce showers as it slowly moves across and have pops in the
likely to chance category as this moves through. There could also be
some lake breeze convergence showers in the east as well. For
tonight, the showers move south of the area and with light winds,
decent radiational cooling possibilities will set up and went below
guidance for low temperatures. Tue looks quiet and dry. Did not make
too many changes to the going forecast overall.

.LONG TERM...(Tuesday through Sunday)
Issued at 404 AM EDT MON AUG 14 2017

Main issue this week is showers and thunderstorms moving through Wed
Night into Thu as a low pressure system crosses the Upper Great
Lakes. Could also be strong/gusty winds and potential small craft
conditions on both Lk Superior and Lk Michigan as the low pressure
system moves through. High pressure building back over the region
late this week into next weekend should result in generally quiet
weather with a warming trend.

Shortwave trough that brings potential for shra/tsra today will be
sliding east of area on Tue. High pressure builds in and will bring
dry weather into Tue night if not Wed morning. 00z models continue
to trend slower with arrival of shortwave trough and sfc low over
the middle Conus. Kept what blends gave for pops/sky on Wed, but if
slower trends continue, could see much of forecast area except far
west staying dry all day. SE winds may increase in the aftn but look
to become stronger during Wed evening as the sfc low moves to
western WI and sfc high slides toward New England.

Eventually the trough and sfc low should track across portions the
Upper Lakes late Wed night through Thu. Main slug of moisture
advection over forecast area occurs after midnight Wed night into
Thu morning and think that is when greatest chances of showers
should occur. Elevated instability seems sufficient enough to have
at least slight chances of thunder. As has been case a lot in recent
weeks though even with sufficient instability of possibly over 500
j/kg of MUCAPE, the overall shear remains weak so not expecting any
severe storms at this time. Temps kind of tricky as h85 temps remain
warm even after sfc low passes by to the east on Thu aftn. If there
is enough clearing after initial push of showers and storms move
though could see parts of forecast area seeing temps above 80
degrees. Stronger cold air advection does not occur until Thu night
and Fri. Breezy NW winds off Lk Superior behind the low along with
lingering 1000-850mb moisture spells low clouds and possible drizzle
and fog especially for northern forecast area closer to Lk Superior.
Not sure if we are looking at as dismal weather as occurred this
last Friday but there is at least some potential of that. For a
start, increased cloud cover and lowered temps near Lk Superior into
the low to mid 60s. Might be too optimistic, but for now kept temps
farther inland and near Lk Michigan in the low to mid 70s, close to
extended model blend.

Most areas will stay dry next weekend but cannot rule out small
chances of aftn/evening shra/tsra especially inland where highest
instability will build up each day. Temps in the low to mid 70s on
Sat should reach upper 70s to lower 80s on Sun as warmer air
begins to spill across the Upper Great Lakes with increasingly
zonal flow aloft.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 107 PM EDT MON AUG 14 2017

Showers will be moving across portions of Upper MI, especially
around KIWD. Certainly possible that conditions could fall to MVFR
at times during periods of shra at KIWD this afternoon. As shra
depart tonight and clouds begin to clear out, radiational fog should
develop. KIWD is most likely to see denser fog with potential of
VLIFR conditions late. While KSAW is likely to fall to MVFR late.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 226 PM EDT MON AUG 14 2017

Winds less than 20 kts into Wed with high pressure overhead, then SE-
E winds increase to 15-30 kts late Wed into Thu as a low pressure
system crosses the Upper Great Lakes. Strongest winds, with gusts to
30 kts, will be over western Lk Superior Wed aftn into Wed evening
then shifting to eastern Lk Superior late Wed night into Thu
morning. NW winds behind the low could then reach 20 kts late Thu
into Fri, strongest over east half of Lk Superior. Winds diminish to
20 kts or less next weekend as high pressure builds back overhead.

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


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