095 FXUS63 KDMX 182322 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 622 PM CDT Fri Jun 18 2021 .DISCUSSION.../Tonight through Friday/ Issued at 304 PM CDT Fri Jun 18 2021 Messaging Highlights: 1) Increasing threat for severe thunderstorms this evening and overnight. Primary threat large hail and damaging winds. 2) Relatively quiet weather Saturday with seasonal conditions 3) Additional rounds of thunderstorms, possibly strong to severe on Saturday night and Sunday. 4) Cool down with quiet and pleasant weather early next week This evening and tonight...Confidence: Medium to High As of 3pm today...satellite imagery indicated several waves of mostly mid-level clouds moving from west to east across the region associated a plume of mid-level moisture and weak lift. Occasional light, high based showers with an few lightning strokes have been observed. Big moisture gradient noted today across Iowa, with sfc dewpoints in the upper 60s south, and in the upper 40s north. Highs today should top out in the mid 80s to lower 90s. Later this evening, things should get interesting in a hurry. A weak upper shortwave will move across the upper Midwest initiating a modest 30-40 kt LLJ after 00Z. Moderate WAA and moisture convergence along a west/east frontal boundary across southern Iowa is expected to initiate deep convection between about 02Z and 04Z, mainly south of Interstate 80. A potent CAPE/shear environment is expected in this vicinity, with MUCAPE values greater than 2500 J/kg, very steep mid level lapse rates of 8C+ per KM, and strong deep layer of 40- 50kts. Model sounding "analogs" indicate a fairly robust signal for large to very large hail (golfball or larger). In addition, the various CAMS/HREF output show a strong updraft helicity (UH) signal in this region, further supporting the notion of rotating storms and severe weather. The primary threat appears to be large/very large hail and damaging wind, The limiting factor for tornadoes is higher LCLs /cloud bases/. SPC upgraded to an Enhanced Risk in this region which looks appears justified. Finally, while areas of heavy rainfall are possible, due to the ambient dry soils and drought conditions, that area can take a lot of rainfall so hydro issues are not currently anticipated. Saturday: Confidence: Medium to High Any lingering showers/tstms should be south and east of the CWA by Saturday morning. Weak high pressure building across the region should result in quiet weather the remainder of the day. A northerly wind flow with usher in a drier airmass with dewpoints statewide in the upper 40s to low 60s. Highs will still be warm in the mid 80s to lower 90s. Saturday Night and Sunday: Confidence: Medium The quiet weather will be short lived as another upper level shortwave quickly ejects from the 4-Corners region on Saturday night into the Midwest on Sunday. In response, a moderate ~40 kt LLJ will develop on Saturday night with Iowa in the exit region. Strong moisture advection and isentropic ascent is expected to initiate cluster of showers and thunderstorms late Sat night into Sunday morning. Elevated hailers would be the primary threat with this first round of precipitation. This initial wave should push east, with partial clearing developing by Sunday afternoon ahead of an approaching cold front. Depending on the magnitude of moisture return and instability, another round of severe weather is possible Sunday afternoon along and ahead of the cold front. Additional details on this severe weather threat should become more evident over the next few days. Extended Forecast Monday thru Thursday...Confidence: Medium A respite from the recent heat will arrive next week as much cooler and drier conditions are expected behind the cold front. Expect highs only in the 60s and 70s and Monday with 70s on Tuesday. There will be a few additional chances for precipitation next week, namely Tuesday night and again Thursday thru Friday. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 622 PM CDT Fri Jun 18 2021 Main concern will be convection potential from about 03z through 08z across the south. KOTM will mostly be affected but KDSM may be brushed by a few cells. Large hail potential and wind also possible. Otherwise, remainder of the period will be quiet with VFR conditions and light north winds, which again may mix to 15 to 16 kts aft 14z Sat due to dry conditions and larger boundary layer growth. Will monitor KDMX for higher risk of storms through 06z, for now will continue with VCTS only. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Fowle AVIATION...REV