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Area Forecast Discussion (AFD)

Issued by Marquette, MI (MQT)

FXUS63 KMQT 211854

Area Forecast Discussion
National Weather Service Marquette MI
254 PM EDT Wed Aug 21 2019

.SHORT TERM...(Today and tonight)
Issued at 417 AM EDT WED AUG 21 2019

A few isolated showers brought a quick-burst of rainfall to a few 
locations as the cold front continued to push eastward overnight. 
Otherwise, conditions remained dry, with lingering cloud cover in 
the vicinity of the front and some pockets of fog out west. 
Shortwave energy progged to pivot across the region throughout the 
day today is currently digging south towards the Arrowhead of 
Minnesota. Today the main weather hazards will come from the gusty 
northwest winds, as unfavorable conditions develop for small crafts 
along parts of the eastern Lake Superior shoreline and a moderate 
swim risk develops east of Marquette later this afternoon. 

As the above mentioned shortwave traverses the Upper Great Lakes 
region today, increasing cold air advection and subsidence behind 
the shortwave will allow for gusty northwest winds to develop, 
primarily west to east across the Upper Peninsula throughout the 
day. As the colder air moves in, this will favor mixing upwards of 7-
8kft and tapping into 25 to 30 knot winds aloft. While much of Upper 
Michigan will see gusty winds develop, the northwest half and east 
halves of Upper Michigan look to see the strongest winds gusts, 
upwards of 25 to 30 mph. A few BUFKIT soundings show momentum 
transport values exceeding 30 mph, so it's not out of the question 
that winds could gust slightly higher in spots. Otherwise, the rest 
of Upper Michigan stands to see 20 to 25 mph wind gusts today. The 
increasing cold air advection throughout the day will keep day-time 
highs down in the mid to upper 60s for much of the area. Localized 
warming, due to northwesterly downsloping winds, is expected across 
the south central and east, near Lake Michigan, where temperatures 
will climb into the low to mid 70s. While a very dry air mass will 
be moving into the region today, cooler temperatures will help keep 
RHs in the 40 to 45% range inland from Lake Superior, reducing fire 
weather concerns.  

As the sunsets tonight, diurnally-driven gusty winds will relax as 
mixing diminishes and the boundary layer decouples nicely. Given the 
dry airmass that will be in place tonight, overnight lows are 
expected to get rather chilly inland from Lake Superior. Overnight 
lows look to bottom out in the low 40s across much of the interior, 
with perhaps a few locations seeing upper 30s. Closer to Lake 
Superior, northerly flow will keep temperatures locally warmer, into 
the 50s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 254 PM EDT WED AUG 21 2019

Upper air pattern will consists of a trough in the western U.S., a 
ridge over the plains and a trough in the lower Great Lakes region 
and New England 00z Fri. The ridge gets moves into the upper Great 
Lakes Fri night into Sat as the trough moves eastward to the 
northern plains. Looks quiet and dry for this forecast with cooler 
than normal temperatures. Could even be some patchy frost Thu night 
in interior sections.

In the extended, the GFS and ECMWF show a 500 mb ridge across the 
southern half of the U.S. extending up into the upper Great Lakes 
12z Sun with troughing across the northern Rockies and northern 
plains. The troughing moves closer to the upper Great Lakes 12z Mon 
and into the area 12z Tue with a sfc cold front moving through the 
U.P. then. More troughing then comes into the area on Wed. 
Temperatures go above normal for this forecast period. Best chance 
for pcpn appears Mon.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 115 PM EDT WED AUG 21 2019

VFR conditions will prevail across the region today into tonight. 
Northwest winds will be a little breezy through the afternoon. Some 
diurnal cumulus will dissipate later today leaving only a few 
passing high clouds through tonight. Can't completely rule out fog 
development at KIWD tonight, but it seems unlikely at this time. As 
winds shift to northerly tomorrow morning, a period of MVFR ceilings 
is expected to develop at KCMX and KSAW. It's also possible that 
KIWD would see these lower ceilings, but confidence is lower there.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 417 AM EDT WED AUG 21 2019

As cold air advection increases over the lake today, unstable 
conditions will develop and allow northwest winds to reach 15 to 25 
knots mainly across the east half. With winds aloft expected to be a 
bit stronger, it is not out of the higher platforms could gust to 30 
knots at times this afternoon. Tonight through Thursday, winds will 
become northerly and slacken in speed somewhat, between 10 and 20 
knots. The strongest winds are expected to be across the south half 
of the lake near the shorelines, especially funneling into the 
Duluth Harbor and Whitefish Bay. High pressure then takes over for 
the end of the week into the first half of the weekend, reducing 
winds to speeds below 15 knots. Towards the end of the weekend, high 
pressure moves east of the region, and southerly flow will start to 
ramp up across the lake, with wind 15 to 20 knots.

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


SHORT TERM...Ritzman