187 FXUS63 KARX 182314 AFDARXArea Forecast Discussion National Weather Service La Crosse WI 614 PM CDT Thu Sep 18 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms through the weekend with increasing coverage Friday afternoon/evening and again on Saturday and Sunday during the afternoons.
- Warmer temperatures continue today with highs mainly in the 80s, then drop into the 70s through early next week.
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.DISCUSSION... Issued at 203 PM CDT Thu Sep 18 2025
Shower and Storm Chances Through the Weekend:
As an upper level low continues to sit over the northern Plains through Friday, a ridge is off to our east. Then the low moves off to the northeast towards the Upper Midwest as the ridge shifts off to the east. The low lingers over the Upper Midwest through Sunday. Between today and Sunday, several shortwaves will move through the area and bring increased shower and thunderstorm chances. While these waves will bring the highest chances of rain, with PWATs mainly between 1.25 and 1.5" and enough lift present outside of these individual waves, convection could form anywhere in the CWA through the weekend (mostly 15 to 30% at any given time). The main potential hazard with these storms would be localized heavy rainfall as the HREF LPMM has pockets of 1.5 to 2" of rain over the next 48 hours. While a strong to severe thunderstorm cannot be ruled out, it is unlikely that they would form. It would depend on how much clearing takes place during the daytime hours (which is not expected given the amount of cloud cover) and if destabilization occurs. There is also limited instability as MLCAPE values of up to 1500 J/kg will be possible.
Rain Potential Early Next Week:
Heading into early next week, a low moves down from Canada into the central Plains. There is a shortwave that comes into the area ahead of the low on Monday that brings low end PoPs (20 to 30%) to portions of the CWA. Ensemble guidance shows the trough over the central CONUS early next week however there are differences in location and intensity, as well as how long this trough sticks around for. If a scenario where the low is closer to our CWA, rain chances would increase, however if the low is further south, which ensembles at this moment in time favor, then a drier solution would be more likely.
Temperatures Through Midweek:
Today will be the warmest day with highs in the upper 70s to mid 80s. Over the next few days as the low passes by, slightly cooler air moves in and as a result, high temperatures will stay in the low to mid 70s. With the trough moving over the central US next week, temperatures are expected to stay in the low to mid 70s.
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.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 609 PM CDT Thu Sep 18 2025
VFR conditions currently present across the area with scattered showers and storms mainly impacting SW Wisconsin and SE Minnesota. These will continue to track north/northeast through the evening hours. Chances for rain will increase again overnight, especially for areas along and west of the Mississippi, primarily impacting the RST terminal. Visibilities and CIGs with this activity should remain VFR but some isolated instances of MVFR/IFR are possible in stronger convection. Rain chances will decrease towards daybreak but HREF and NBH guidance both continue to hint at MVFR/LIFR CIGs building in after 09Z at the terminals and lingering through the morning. CIGs should return to VFR across the area between 18-22Z. Rain chances will return in earnest after 18Z tomorrow, building in from the west. Winds through the period are expected to stay at or below 10 kts out of the east/southeast.
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.ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None.
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DISCUSSION...Cecava AVIATION...Barendse
NWS ARX Office Area Forecast Discussion