NZUS93 KSGF 050843 LLLSGF KSZ073-097-101-MOZ055>058-066>071-077>083-088>098-101>106-052043- Public Information Statement National Weather Service Springfield MO 343 AM CDT Mon Aug 5 2024 Winds are light from the southeast, skies are clear, and high pressure is dominating conditions at the surface in Missouri and Kansas. A broad ridge and area of high pressure aloft continues to build and tighten its grip on the southwest and south-central CONUS as an upper-level trough shuffles further to our east. A weak low-level jet is advecting warm air from the Mexican Plateau into the Plains to our west, and a special 06Z sounding with very dry mid-levels confirms that very little moisture is being advected northward. With the ridge firmly in place to our west, it is nearly certain that temperatures will continue their slow climb towards the triple digits through Tuesday. High temperatures on Monday will be in the upper 90s, with the highest temperatures along the Osage River Basin into the Osage Plains and along the Missouri/Arkansas border. Monday will be more of a dry heat, with heat indices only 3-5 degrees higher than high temperatures. Lows will be between 70 and 75 degrees overnight into Tuesday. Tuesday will be slightly warmer, with highs between 95-102 degrees along and south of the I-44 corridor; north of the I-44 corridor will reach highs between 95-100 degrees. Dew points will rise by a few degrees ahead of a cold front on Tuesday, and those couple of degrees will bring heat indices across the region up to 100-105 degrees. Localized areas of heat indices above 105 degrees are not out of the question, but the chances of heat indices reaching 105+ degrees are 0-20% in far southeast Kansas and <15% elsewhere, per the 00Z HREF. Because heat indices of 105-110 degrees are not expected to be widespread, we continue to hold off on a Heat Advisory; day shift may reconsider if morning short-term model guidance increases temperatures by a few degrees. Regardless, these high temperatures are still 5-10 degrees above normal for August 6, and will likely cause impacts to most heat-sensitive individuals and infrastructure across the Ozarks. Tuesday evening will see a cold frontal passage reach our area from the north-northwest, reaching far southern Missouri just after midnight. If the boundary passes through central Missouri a bit earlier than models currently suggest (2-3pm rather than 4-6pm), areas around and north of Hwy 54 may only reach upper 80s rather than low 90s. As the front passes, dew points at 850mb will drop nearly 15 degrees and around 10 degrees at the surface… the dry air will keep the environment far too stable for convection or precipitation. PoPs with the frontal passage remain <10%. From Wednesday through the weekend: Despite a persistent upper-level over the Continental Divide and central Plains, our position on the far west periphery of Hurricane Debby’s influence keeps us in a northeasterly flow pattern that strengthens through the week. As the boundary stalls in far southern Missouri, a steep temperature gradient may develop, with temperatures Wednesday and Thursday in the low 80s in central Missouri, increasing with southwesterly extent to potentially upper 90s towards far southwest Missouri. Temperatures will cool off again into the weekend as the cold air advection increases, though the magnitude of Debby’s influence and the subsequent cold air advection remains poorly resolved, especially southwest of a Nevada-to-Tecumseh line. In this area, NBM 50th percentile temperature spreads are anywhere from 5-10 degrees Thursday-Sunday, so current highs may range anywhere from low 80s to low 90s through the weekend.