Area Forecast Discussion

FXUS63 KMQT 291952

Area Forecast Discussion
National Weather Service Marquette MI
352 PM EDT Fri Sep 29 2023

.SHORT TERM...(Through tonight) 
Issued at 224 PM EDT FRI SEP 29 2023

Early afternoon water vapor imagery shows broad troughing over 
western North America with downstream ridging from the Upper 
Midwest into eastern Canada. Area of showers and embedded 
thunderstorms developed earlier this morning along the nocturnal 
low-level jet over central MN is now over NW WI and approaching 
the far western UP. No electrical activity noted with this complex
near the UP, and it is on a weakening trend overall, but some 
rain may fall over the northwest Superior shoreline counties this 
afternoon. Elsewhere, skies are partly to mostly sunny over 
roughly the eastern half of the UP, though there are still 
fragments of lower clouds streaming northward off Lake Michigan. 
Over the west half, skies are mostly cloudy due to a combination 
of low stratocu that has been slow to burn off, and high cirrus 
canopy associated with the aforementioned area of rain. Raised 
temps a bit over the east half and lowered over the west half this
afternoon to reflect these cloud trends.

Tonight, the ridge will shift a bit east, opening the door for weak 
height falls from the west. Another round of LLJ-fueled convection 
is expected to develop across central MN, focused especially along 
and on the cool side of a SW/NE oriented low-level trough. Model 
consensus indicates this activity moving into the far western UP 
after 06Z (1 am CDT). HREF mean MUCAPE of 500-1000 J/kg along with 
30-40 kt of deep-layer shear supports a small hail threat with any 
convection that moves into the western UP. This activity should tend 
to weaken with northeastward extent through the night as it works 
away from the better forcing, although some leftover showers and 
isolated storms could make it as far east as western Alger to 
Dickinson Counties by 12Z (8 am EDT). It should be a rather mild 
night due to the increasing clouds, southerly flow, and seasonably 
high moisture content, with lows mainly in the mid-50s to near 60. 
Lows were bumped up from NBM guidance due to pattern recognition.

.LONG TERM...(Saturday through Friday) 
Issued at 351 PM EDT FRI SEP 29 2023

Key Messages:
-Precip chances return over mainly the west and north tonight into 
Saturday; mostly dry weather returns by Sunday afternoon.
-Well above-normal temperatures are expected over the weekend, 
continuing through the middle of next week.
-Weather turns fall-like by the end of next week with increasingly 
cooler and unsettled/rainy conditions expected.

Ridging centered over the Mid Mississippi River Valley builds 
northward through the weekend becoming amplified over the Midwest 
and Great Lakes region in response to a mid-level trough digging 
south over the West Coast and carving out a closed low Saturday 
night over Nevada. This amplified pattern along with increasing WAA 
into the Upper Great Lakes will yield summer-like/possibly record 
temps this weekend into next week. West and north central Upper 
Michigan have best chances for rain and thunderstorms later tonight 
into Saturday as a cold front sags southeast toward the area. A more 
unsettled and much cooler weather pattern is expected for the U.P. 
later next week as the amplified pattern shifts east and the 
departing ridge is replaced by the western CONUS trough which will 
amplify over the Upper Great Lakes by late next week.

A shortwave riding northeast along the ridge just north of Lake 
Superior will push a frontal boundary toward the western and 
northern side of the U.P. tonight through Saturday before lifting 
north on Sunday. With convergence along the boundary, HREF ensemble 
mean MUCAPE up to a few hundred J/Kg (staying below 500 J/Kg), and 
PWATs approaching 1.3 to 1.7 inches, scattered showers and 
thunderstorms are expected. Best chances are expected for the west 
with closer proximity to the boundary, higher available moisture, 
and convergence; the far south and east may possibly stay dry 
through Saturday. Despite bulk shear building up to around 30 knots 
over the north and west Friday night into Saturday, no severe storms 
are expected. Some heavy downpours late tonight over the far west 
could bring up to 0.5-0.75 inches of rain.

Southerly WAA flow behind the ridge axis brings 850 mb temps up to 
15-18C Saturday and 17-19C Monday into Tuesday. The ECMWF EFI has 
0.6 to 0.9 over the U.P. for max and min temps starting Saturday 
with SoT > 0 starting Sunday, both begin to drop off late next week; 
this signal is also supportive of the expected warming pattern. 
Daily high and low temps could challenge record high and warm 
minimum temps with highs this weekend/early next week reaching well 
into the 70s with possible low to mid 80s over the west half Sunday-
Tuesday. Lows are expected in the 50s (except probably lower to mid 
60s for downsloping areas near Lake Superior) through the middle of 
next week.

As the amplified pattern begins to shift eastward next week, model 
guidance comes to a general agreement with a shortwave trough and 
accompanying cold front moving through the Upper Midwest/Upper Great 
Lakes later Wednesday into Wednesday night. Look for scattered 
showers and a few isolated thunderstorms. Despite bulk shear values 
of 40-50 kts no severe storms are expected as MUCAPE values 
generally are less than 500 j/kg. CAA behind the front is expected 
to continue into the weekend as 850 mb temps fall below 0C and 
perhaps as low as -5C by late next weekend. This CAA along with mid 
lake water temps of 15C under a persistent cyclonic northwest flow 
will lead to increasingly blustery conditions along with increased 
coverage of lake effect/lake enhanced rain showers for the northwest 
flow favored lake precipitation belts.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 141 PM EDT FRI SEP 29 2023

Stubborn low stratus has finally eroded at SAW/IWD, but continues at 
CMX at the start of the 18z TAF cycle. Low confidence on erosion 
timing but best guess is that CMX will follow IWD and scatter out by 
19Z. This leaves VFR for the remainder of the day until at least the 
first half of tonight. An area of rain is approaching IWD and may 
brush past CMX but is unlikely to impact vsby/cigs this afternoon.

Late tonight, another stratus deck is likely to develop at SAW due 
to moist upslope flow. Cigs likely fall to MVFR after 06Z, with IFR 
also possible toward 12Z. Elsewhere, a complex of showers and 
embedded thunderstorms is likely to move into IWD after 06Z. 
Strengthening low-level winds may also bring LLWS conditions to IWD 
00-06Z as well. Forecast has VFR prevailing, but a PROB30 was 
included for TS to impact cigs/vsby 09-13Z. Remnants of this complex 
or sct shower development may reach SAW late tonight/early Saturday, 
but confidence is too low for more than a VCSH mention. At both 
IWD/CMX, an MVFR deck is expected to develop again in the 12-18Z 

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 351 PM EDT FRI SEP 29 2023

Expect south-southeast winds across the lake today into tonight to 
stay below 20 knots. The exception to this would be a brief period 
this evening over the north-central portion of the lake where some 
gusts up to 25 knots are expected. A cold front moving into the area 
late tonight through Saturday will shift winds through the day on 
Saturday to out of the northeast over western and north central 
portions of the lake. Winds will gradually veer south by Sunday 
night, staying below 20 knots. South winds are generally expected to 
stay below 20 knots through the early part of the week but will 
probably ramp up to near 30 knots on Wednesday ahead of the next 
incoming cold front, especially east half. The cold front moving 
through tonight through Saturday will bring scattered showers and 
thunderstorms across the lake. Some isolated showers are possible 
through Sunday morning, otherwise expect mostly dry weather through 

Issued at 351 PM EDT FRI SEP 29 2023

Record high temperatures at the NWS Office in Negaunee: 
Sep 30: 80 (2000) 
Oct. 1: 83 (1976) 
Oct. 2: 87 (1992)
Oct. 3: 78 (2005) 
Oct. 4: 76 (2007/2011) 

Record warm low temperatures at the NWS Office in Negaunee: 
Sep 30: 58 (2002) 
Oct. 1: 57 (2000) 
Oct. 2: 60 (2005)
Oct. 3: 65 (2005)
Oct. 4: 60 (2005)

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


SHORT TERM...Thompson