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Area Forecast Discussion (AFD)

Issued by Marquette, MI (MQT)

FXUS63 KMQT 240537

Area Forecast Discussion
National Weather Service Marquette MI
137 AM EDT Sat Aug 24 2019

.SHORT TERM...(This evening through Saturday)
Issued at 255 PM EDT FRI AUG 23 2019

Upper air pattern consists of a 500 mb trough in the Rockies and 
another over the lower Great Lakes and New England with a ridge 
across the central and northern plains. The ridge moves into the 
upper Great Lakes tonight into Sat. Quiet weather will continue for 
this forecast period. There will be some patchy fog tonight along 
with patchy frost again in a few places. Will handle the frost with 
a special weather statement since the area will be small again like 
last night.

.LONG TERM...(Saturday night through Friday)
Issued at 350 PM EDT FRI AUG 23 2019

An area of high pressure will exit the Great Lakes region this 
period. As the ridge moves out, an upper-level trough will move into 
the Northern Plains and Northwest Ontario early this week bringing a 
good shot at precipitation across Upper Michigan. This trough will 
remain across the Upper Great Lakes region through most of the work 
week with models hinting at another trough and chance for 
precipitation near the end of the week.

On Sunday, a ridge of high pressure will will exit to the east 
through the day as an upper-level trough approaches from the west. 
Clouds will begin to increase across the west late in the day on 
Sunday but precipitation looks to hold off through the day. 
Precipitation chances slowly move into western UP by Monday morning 
as the first initial shortwave and area of PVA and q-vector conv 
move over Upper Michigan. Some models hint at light precipitation 
out in front of the wave as it ejects into the Great Lakes 
region(see NAM/GFS), but have went with a slightly slower and toned 
out approach, given uncertainty and trends over last few runs. 
Overall, there is a good chance at QPFs to end up over 1 inch across 
much of western and central UP, with some uncertainty more towards 
the east. PWATs across the models still remain above 1.5 inches for 
most of the cwa, so the potential is there for some much needed 
precipitation through Tuesday morning for some. A slight chance of 
thunderstorms was included, but for the most part, with rain moving 
in overnight, the instability is lacking. Temperatures through this 
period will remain a bit cool with lows into the upper 40s in the 
interior and highs into the 70s.

After Tuesday, temperatures cool off slightly again with lows on 
Tuesday night falling into the mid 40s inland with 60s near the 
lake. Highs on Wednesday will fall into the mid 60s in the west and 
70s in the east. Models differ on intensity, but agree that the low 
will lift to the north into Canada, deepening at the same time. The 
06Z GFS had bombogenesis pressure falls during an 18-hour time 
frame, but has backed off that idea with the 12Z run. Overall, windy 
conditions are expected, and will likely persist through the week as 
the trough maintains hold across the Upper Great Lakes region. As 
the trough meanders slowly out of the area, some models anticipate a 
few weak embedded shortwaves to lift across the area bringing weak 
chances at precipitation through the week. GFS model 850-
temperatures fall to near 4C, with ECMWF to near 6C on Wednesday and 
will also bring the chance at light lake-effect rain showers. The 
ECMWF has shown a trough swinging through again on Friday morning 
the last few runs(latest GFS hints at this idea) bringing another 
chance of precipitation to end the week.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 132 AM EDT SAT AUG 24 2019

There is the potential for fog development overnight, especially at 
KSAW and KCMX so included reduced visibilities to hint towards this 
potential. Otherwise, VFR conditions and light winds are expected.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 255 PM EDT FRI AUG 23 2019

The wind will remain at or below 20 knots through Sunday and then 
increase to 15 to 25 knots Sun night into Monday. The wind increases 
to 30 knots with a few gale force gusts to 35 knots across the 
extreme eastern part of Lake Superior Mon night out of the south.
Winds then are 20 to 30 knots across all of Lake Superior on Tue 
through Wed with a cold front moving through the area. Tue through 
Wed would be the strongest wind for the forecast period out of the 
west at that time.

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