Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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136 FXUS63 KDMX 051747 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1247 PM CDT Sun May 5 2024 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... -Strong to severe thunderstorms Monday later afternoon and overnight into early Tuesday. Damaging wind and perhaps few tornadoes are the primary hazards. Pockets of locally heavy rain also possible. -Active pattern continues late week with additional thunderstorm chances. && .DISCUSSION... Issued at 318 AM CDT Sun May 5 2024 Surface high pressure has settled across the area early this morning, resulting in calm winds and clear skies (excepting the high cirrus blowing across southern Iowa from the complex impacting the southern plains overnight). This has allowed for patchy fog to develop early this morning, primarily in low lying areas. More widespread fog development is not anticipated this morning but patchy dense fog will likely continue through sunrise. High pressure will continue to influence the area throughout the day as it slides east, allowing for abundant sunshine and generally quiet conditions. Our attention then turns to a robust upper level trough swinging across the Rockies on Monday. Early impacts come in the form of a tightening pressure gradient across the area which will induce breezy winds out of the southeast ahead of the approaching system. By late afternoon/early evening the leading edge of the trough nudges into western Iowa. Initial environment into SW Iowa includes around 1000-1500 J/kg of MLCAPE with 40-50+ kts of 0-6 km shear. Low level hodographs continue to show nicely swept areas and SRH remains around 200 m2/s2 to start. With lackluster lapse rates, hail is not a big concern. And while CAPE may not support sustained severe storms, damaging winds would be the primary concern with a linear storm mode. The tornado risk is also worth keeping an eye on, hinging mainly on whether storms can remain surface based versus becoming elevated through the overnight. While the low- level jet will help to maintain storms overnight, instability diminishes further east and would expect to see diminishment into Tuesday morning. At the same time, a widespread 1-1.5" of rain is anticipated with embedded locally higher amounts pushing 2+" possible. Given the progressive nature of storms, flash flooding shouldn`t be a problem, however recent heavy rains in the last week could leave localized areas more susceptible to hydro problems. The rest of the week will see additional storm chances as the main trough axis passes across the area. How exactly this plays out is less certain as models diverge in handling of these interacting systems. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1246 PM CDT Sun May 5 2024 Widespread VFR conditions are forecast across Iowa through midday on Monday. Surface winds remains light through tonight but increase fairly quickly from the east to southeast on Monday morning. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && $$ DISCUSSION...Hagenhoff AVIATION...Cogil