499 FXUS63 KDMX 300854 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 354 AM CDT Mon Aug 30 2021 .DISCUSSION.../Today through Sunday/ Issued at 354 AM CDT Mon Aug 30 2021 Forecast Highlights: -- Seasonable temperatures much of this week -- Storm chances tonight into Tuesday morning -- Additional storm chances late in the week Details: The cold front that pushed through the state settled farther south over central Missouri and have seen recent thunderstorm development northwest of St. Louis, MO this morning. GOES-East Nighttime Microphysics RGB shows an expansive area of stratus clouds over Nebraska lifting northward in the warm air advection over that area. There are also indications of patchy fog in some river valleys, notably over southwestern Iowa/northwestern Missouri and southwestern Wisconsin on the GOES-East Night Fog imagery. Surface observations in central Iowa largely have visibility above 6 miles. GOES-East upper level water vapor imagery shows the fast westerly flow moving over the northern states. For today, have removed any lingering PoPs until late this afternoon leaving much of the daylight hours dry with temperatures and humidity comparable to yesterday. Thunderstorm chances will increase through the evening and overnight hours as a mid-level shortwave trough, which the RAP analyzes approaching the Oregon coast early this morning, moves into the region. This trough interacting with the stalled boundary stretching through Nebraska will be the focus for initial storm development over parts of Nebraska and South Dakota later this afternoon. These storms will likely move southeastward along this boundary and the instability gradient. As these storms move into Iowa tonight, their severity is expected to be waning with forecast soundings at CRL and CSQ showing 25 to 30 knots of deep layer shear and a shallow inversion meaning likely elevated storms. However, 6z HRRR and 0z WRF ARW show a bowing segment moving into Iowa with potential for strong wind gusts. If this bowing segment were to materialize, the 06z HRRR and 00z HREF wind gusts look to be largely below 50 knots as they move into our forecast area. If the bowing segment does not materialize, then the elevated storms would pose a hail risk. Overall, the severe risk is low with the most likely location of a severe report in our west central or southwestern counties if at all. Conditions will turn drier and brighter through the day Tuesday as the storms push out of the state. The mid-level shortwave will dive southeastward as the remnants of Hurricane Ida move over Tennessee. Ridging to the west of Iowa will develop with a warm front moving across the state on Thursday and this may promote scattered storms over northern Iowa into Minnesota. The ridge will be pushed eastward on Friday as a lead shortwave trough rotates around a sprawling closed low over central Canada. This will help to bring a cold front into the state with scattered storms. While deep layer shear would support strong storms, the instability is quite weak and not supportive of stronger storms at this time, but will monitor trends in the coming days. Another shortwave trough rounding the base of the central Canadian closed low will help to finally push the cold front through the state on Saturday and bring an end to the storm chances. && .AVIATION.../For the 06Z TAFS through 06Z Monday night/ Issued at 1149 PM CDT Sun Aug 29 2021 VFR conditions look to continue through the TAF period. Only concern remains some fog potential for MCW and possibly FOD and ALO. However, low confidence with the widespread nature and the duration of the fog and thus left out mention of any MVFR conditions for the northern TAF sites. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...KCM AVIATION...Podrazik