950 FXUS63 KARX 070728 AFDARXArea Forecast Discussion National Weather Service La Crosse WI 228 AM CDT Sun Sep 7 2025
.KEY MESSAGES...
- Unseasonably cool temperatures today with highs in the upper 50s to middle to 60s. Then temperatures warm into the 70s by middle of this week.
- Showers and a few storms expected Monday afternoon into Tuesday. Then mainly dry weather for the rest of the week.
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.DISCUSSION... Issued at 226 AM CDT Sun Sep 7 2025
Today through tonight
Latest surface analysis shows ridge of high pressure extending from northern Missouri into northern Minnesota. The surface ridge will be the dominant weather feature across the forecast area today. Subsidence under surface will allow for mostly sunny skies...light winds (less than 10 miles per hour) and dry weather across the forecast area. Temperatures will remain unseasonably cool as latest NAEFS suggest standard anomalies of minus 2 to minus 4 degree celsius over the region. High temperatures are expected to be in the upper 50s to middle 60s.
Monday into Tuesday night
Ridge axis builds east of the area and southerly flow aloft develops over the Northern Plains/Upper Great Lakes Monday. Shortwave trough moves into Northern Plains Monday afternoon/night. The latest 07.00z GFS/ECMWF/NAM show decent moisture convergence with the shortwave trough. The axis of moisture convergence is over west central Wisconsin/eastern part of Minnesota and the far northwest portions of the forecast area will be on the fringe of this axis Monday evening. As shortwave trough slowly pushes east this moisture axis will track over the forecast area and spread convection into the area Monday night. Forcing/vertical motion...moisture convergence wanes across forecast area Tuesday and convection will diminish during the day. CAPE is limited with the shortwave trough...as suggest 0-6km most unstable CAPE of 100-200 j/kg over the northwest/western parts of the forecast area with the main axis of instability west of the forecast area. Coverage of storms should be isolated to scattered across the forecast area Monday evening into Tuesday morning. Any storms that develop should remain below severe limits...as CAPE is limited below 500 j/kg surface/elevated CAPE and 0-3km shear is less than 20 knots.
Wednesday through Saturday
The latest deterministic models are in decent agreement Wednesday through Friday on building upper level ridge over the central United States/Northern Plains States. Then...the models/ensembles are in disagreement on when upper level ridge breaks down and placement of upper level troughs/lows. Subsidence underneath upper level ridge will provide mainly dry weather across the forecast area Wednesday through Friday. Temperatures will be warmer...as warmer air aloft advects into the region. 07.00z ECMWF/GFS indicate 925mb temperatures warming to plus 15 to plus 18 degrees celsius by 12z Friday. High temperatures are expected to climb into the 70s and possibly in the low 80s at few locations late in the week. With upper level ridge breaking down Friday night into Saturday there is the possibility of some showers or storms moving into the area. However...confidence is low on precipitation chances...based on how fast the ridge breaks down and placement of upper level troughs/lows over the northern tier United States.
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.AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1230 AM CDT Sun Sep 7 2025
Monitoring fog and/or low stratus potential early this morning as T/Td depressions currently range from 0-2 degrees with largely calm winds. Stronger 15-20 kt winds just off the surface are the main limiting factor to fog development, but already seeing some pockets of fog reported in parts of MN/IA. Thinking RST and LSE should remain VFR, but cannot rule out patches of fog or scattered low stratus through daybreak.
Otherwise VFR conditions during the day with light northwesterly winds becoming southerly this evening. Some fair weather cumulus this afternoon.
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.ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None.
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DISCUSSION...DTJ AVIATION...Kurz
NWS ARX Office Area Forecast Discussion