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Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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657 FXUS63 KDMX 130000 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 700 PM CDT Mon Aug 12 2024 ...Updated for the 00z Aviation Discussion... .KEY MESSAGES... - Lingering showers this afternoon will taper off, then patchy fog expected overnight into Tuesday morning. - Showers and thunderstorms return late Tuesday evening into Wednesday and again Wednesday into Thursday. Heavy rain and a few strong storms are possible, but the overall severe threat is low. && .DISCUSSION... Issued at 230 PM CDT Mon Aug 12 2024 Showers have lingered across central Iowa for much of the day, due in part to a trailing vorticity lobe behind the main shortwave that passed over the area overnight and early this morning. CAMs have struggled with this precipitation all day, squashing precipitation with each new run. While models struggle with the evolution, extrapolation of satellite and surface observations shows the weak wave should pass out of the area late this afternoon. In the wake of the system, overnight patchy fog is expected to develop and last into Tuesday morning. Widespread dense fog is not anticipated, however the HREF does indicate pockets of visibility under 1 mile are possible. Tuesday will see a brief break from the activity, but as the upper ridge shifts east it will bring with it a little more upper level smoke from western US wildfires. Meanwhile, a low will deepen across the central plains and lift out of Nebraska late Tuesday night and into Wednesday across the area. Instability is fairly weak overnight with modest shear around 30-40kts as the the nose of the LLJ into SW Iowa helps fuels activity through the overnight. While widespread severe storms are not expected, a few stronger storms are possible as this passes over the area. Quickly on it`s heels is a second more robust shortwave that will move across the area Wednesday into Thursday. Timing and placement inconsistency continue with the GFS a little slower and further north than the EC. Shear and instability are displaced which may limit more robust severe storms, but the slower flow will contribute to a heavy rain set up, along with deep warm cloud layers and PWATs over 2". In most cases rivers can take this much precipitation, but there may be instances of ponding or flash flooding, particularly in urban areas. Despite model differences, at this time it appears both solutions are mainly dry Friday into the weekend. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 658 PM CDT Mon Aug 12 2024 Lingering drizzle through 06z with fog already developing across the southern half of the area. Have left out of KDSM and KOTM for now as vsby restrictions appear more likely after 06z for these sites. IFR fog and stratus to develop after 08z and last through sunrise with MVFR cigs likely lasting through the TAF period for KDSM and KOTM. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hagenhoff AVIATION...Jimenez