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Area Forecast Discussion (AFD)

Issued by Marquette, MI (MQT)

                            
000
FXUS63 KMQT 220817
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
417 AM EDT Thu Aug 22 2019

.SHORT TERM...(Today and tonight)
Issued at 417 AM EDT THU AUG 22 2019

...A BRIEF TASTE OF FALL HAS ARRIVED...

Chilly predawn temperatures were observed inland from Lake Superior, 
as lows dropped into the 40s for many locations. Closer to the big 
lake, northerly flow coming onshore kept lows in the 50s and 
lower 60s for most locations. Satellite trends this morning show mid-
level clouds spreading to the southeast as another shortwave digs 
south towards the region. However, much of the Upper Peninsula 
remained cloud-free this morning, outside of the west. 

Today will be cooler compared to yesterday, with predominately 
northerly wind across the area. Clouds currently off to our north 
and west will gradually work into the area, and increase in 
coverage as diurnal heat and cold air aloft favor the development of 
stratocu later today. Cloud cover looks more widespread across the 
west half of Upper Michigan, where diurnal heating will allow for 
local destabilization within the boundary layer. The destabilization 
across the west and central this afternoon does look to favor the 
development of diurnally driven rain showers. Confidence isn't high 
in regards to how widespread these rain showers will get, but given 
the cold air aloft and a narrow pocket of unstable air towards the 
top of the boundary layer, certainly looks like a day for convective 
rain showers. Out east, northerly flow off of Lake Superior 
funneling down into Lake Michigan should keep conditions 
more stable, with less clouds. These stable conditions will inhibit 
the development of afternoon showers. However, out east, winds off 
of Lake Superior, and remnant stronger winds aloft will make for 
gustier winds at times late this morning and afternoon. The 
lingering dry conditions across the area, but cooler temperature are 
expected to keep RHs in the 40-55% range, locally driest across the 
southern parts of Upper Michigan across the south central and east, 
where downsloping northerly winds help dry things out further.

Tonight, high pressure starts to drop south into the western parts 
of Upper Michigan. This increased subsidence and locally veering of 
the winds across the interior parts of Upper Michigan does look like 
it will favor clearing skies. Given the already dry air mass 
expected to be in place, with ample radiational cooling and 
decoupling of the nocturnal boundary layer, overnight lows look to 
tank into the low 30s to around 40 inland from the Great Lakes. The 
areas across the interior west certainly look to be the cold spots 
Friday morning, meaning we could see some early-season frost 
develop. Using the Model Certainty Tool this morning, it appears 
that the current forecast lows fall right around the 25th 
percentile, so towards the lower end of the distribution among the 
model guidance. That being said, will let the day shift re-evaluate 
later today as to whether or not a frost advisory will be needed.

.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 06Z TAFS through 06Z Thursday night)
Issued at 121 AM EDT THU AUG 22 2019

VFR conditions should generally prevail across the TAF sites through 
much of the forecast period. Lake clouds will become more prevalent 
overnight as colder air works across Lake Superior in a nw flow, 
especially impacting KIWD and KCMX. As winds shift northerly Thu 
morning, a period of MVFR ceilings is possible at all the terminals 
but generally expect prevailing VFR conditions. Expect more diurnal 
cu and lake clouds on Thu than on Wed.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 417 AM EDT THU AUG 22 2019

Northerly winds between 10 and 20 knots are expected today. The 
strongest winds are expected to be across the south half of the lake 
near the shorelines during the day, especially with some funneling 
into the Duluth Harbor and Whitefish Bay in the afternoon. 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 winds 15 to 20 knots Saturday night through Monday. Late in the 
day Monday through Monday night, south winds over the east half of 
the lake could gust upwards of 30 knots ahead of an approaching 
front from the west.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...07
AVIATION...Ritzman
MARINE...Ritzman