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Area Forecast Discussion (AFD)

Issued by Marquette, MI (MQT)

FXUS63 KMQT 191904

Area Forecast Discussion
National Weather Service Marquette MI
304 PM EDT Thu Sep 19 2019

.SHORT TERM...(Today and tonight)
Issued at 437 AM EDT THU SEP 19 2019

Active morning with periods of very heavy, efficient rain moving 
across the south central and east. Radar estimates show widespread 
0.5-1.0 inch rainfall estimates across the south central with 
embedded swaths of 2+ inches in spots that saw a few rounds of 
stronger storms and heavy rainfall. This convection was anchored to 
stout 925-850mb moisture transport, associated with a 30+ low-level 
jet lifting across the area. Elsewhere, stratus began to lift 
northeast as southwest flow continued to advection low-level moist 
air into the region. 

Today's forecast will be tricky, as the weakening, washed-out front 
stalls across the south central and east half of Upper Michigan, 
maintaining persistent, albeit gradually weakening, moisture 
transport. This lingering deeper moisture, and a weak shortwave 
progged to move in from the west later today/tonight looks to keep 
chances for showers and storms throughout the day and tonight, 
especially across the south central and east. However, given how 
washed out the front is confidence is not high in regards to 
coverage, and just how far west convection may develop later on 
today. Given that the deeper moisture has stalled with the weakening 
front, PWATs look to remain around 1.5 inches, so any stronger 
storms will be more then capable of producing efficient, heavy 
rainfall. If storms do consistently train, there could be some minor 
hydro concerns - mostly in the form of ponding of water on roadways, 
especially in poor drainage areas. Due to the uncertainty in 
precipitation coverage over southern Schoolcraft County later today, 
did opt to issue the beach hazard statement to highlight the high 
swim risk for today. 

Temperatures should climb into the 70s today, with mild temperatures 
expected again tonight. As winds relax overnight, the above 
mentioned washed-out, stalled front will allow for moisture to 
linger and thus the development of fog tonight.

.LONG TERM...(Friday night through Thursday)
Issued at 302 PM EDT THU SEP 19 2019

Friday evening, a broad eastern CONUS ridge and western CONUS trough 
will be in place, with a somewhat disorganized area of weak to 
lift generated by WAA and spotty PVA lifting northeastward 
out of the central Plains towards the Upper Great Lakes. Relatively 
unidirectional SWerly flow through the column will increase 
through the day and pump deep moisture into Upper MI with sfc 
dewpoints Saturday well into the 60s and PWats upwards of 1.5-1.75". 
Afternoon wind gusts of 20-30 mph and locally higher are expected.

At this time, models are in relatively good agreement that there 
will be little to no large scale forcing for ascent reaching the UP 
through the day Saturday. Thus, only a couple of spotty showers and 
perhaps a thunderstorm are expected at least through the early 
afternoon. Instability should build to about 1000 J/kg, with 
isolated pockets possibly approaching 1500 J/kg if some sunshine is 
able to break through. Effective shear will also build through the 
afternoon to 25-30 kts. But with a lack of forcing to speak of, 
widespread thunderstorm development appears unlikely until later 
in the afternoon over the west. 

While precip chances will increase through the evening and 
continue overnight as the forcing arrives, the cold front will 
likely traverse the UP too late in the diurnal cycle for much 
concern of severe weather. That said, in addition to the main threat 
of heavy rainfall, isolated gusty winds or large hail will be 
possible Saturday night. Precip will continue over the east Sunday 
morning but by the afternoon, the system should be moving out, 
leaving a cooler, drier airmass over the UP that is much more 
seasonal for late September. 

The large scale pattern will become more progressive early next 
week. Mid-level ridging will briefly build in Monday afternoon 
through Tuesday morning and allow for a quick return to warmer 
temps but a deep trough will begin to dig down southeastward out of 
Canada late Tuesday through Wednesday that will likely bring 
additional precip chances midweek and a shot of cooler air for late 
next week.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 212 PM EDT THU SEP 19 2019

IFR conditions are lingering at SAW this afternoon, but should 
lifting into VFR late this afternoon. VFR conditions at CMX/IWD will 
fall into IFR tonight. Fog is possible tonight at all sites, but 
will be more prevalent at IWD and SAW. LIFR conditions at SAW and 
IWD are possible tonight but have not included that in the TAFs for 

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 437 AM EDT THU SEP 19 2019

A weakening front sags south of the lake and winds diminish below 20 
knots throughout today. This front remains fairly washed out and 
high pressure takes hold through Friday night, keeping winds below 
15 knots. Saturday through Sunday, southerly winds veers westerly as 
a cold front pushes east across the lake. Ahead of and behind the 
front, winds of 20-30 knots are expected. It is possible there could 
be a window of gales in there as well.

Occasional fog will remain possible through the end of the week, 
likely until we can get drier air to move in with a stronger cold 
front arriving over the weekend. The most likely locations for fog 
over the west half today, especially near the Arrowhead of Minnesota 
and Isle Royale. Heavy rain associated with thunderstorms that move 
over the east half of the lake may also make for some foggy 
conditions this morning.

Upper Michigan...
  Beach Hazards Statement until 6 PM EDT this evening for MIZ014.

Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman