Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 13 2024 16:28:04 ACUS01 KWNS 131627 SWODY1 SPC AC 131626 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Tue Aug 13 2024 Valid 131630Z - 141200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST CO INTO SOUTHWEST NE AND FAR NORTHWEST KS... ....SUMMARY... Severe thunderstorms are possible this afternoon and evening from northeast Colorado into southwest Nebraska and far northwest Kansas. Strong to isolated severe thunderstorms are also possible this afternoon and evening across parts of the eastern Great Basin/northern Intermountain region into the northern/central High Plains and central Great Plains, as well as South Carolina. ....Central High Plains into the Central Plains... Low-amplitude shortwave trough currently moving through the Four Corners vicinity is expected to continue northeastward, helping to support afternoon thunderstorms across the central Rockies. Favorable low-level moisture will exist within the airmass downstream across the central High Plains, characterized by late afternoon dewpoints in the low to mid 60s. Ongoing cloud covered may delay heating a bit, but temperatures are still expected to reach the mid 80s by the late afternoon. These low-level thermodynamic conditions will help remove convective inhibition while also supporting moderate buoyancy. The westerly/southwesterly flow aloft should remain relatively modest (i.e. 20 to 30 kt at 500 mb), but the veering wind profiles expected to be in place will still result in moderate vertical shear. Current expectation is for 0-6 km bulk shear to range from 25 to 35 kt, with the highest values located over northeast CO into western NE. A predominantly multicellular mode is anticipated, with isolated large hail and a damaging gusts possible. The stronger shear over northeast CO suggests a more organized mode is possible here, with the development of a forward-propagating convective line anticipated. Strong gusts will be possible within this line. This line may continue eastward into the central Plains overnight, supported by a moderate low-level jet. ....Lower MO Valley into southeast NE... Ongoing convective complex moving through southwest MO is expected to continue southeastward while gradually weakening. Some re-development is possible during the evening, beginning across southwest MO, as warm-air advection occurs along the remnant outflow. Thunderstorm development should then expand northwestward into northeast KS, northwest MO, and southeast NE as the low-level jet continues to strengthen. Some isolated hail is possible within the strongest storms. Additionally, despite their elevated character, downdrafts could become strong enough to penetrate any low-level stability, with some damaging gusts possible. ....Intermountain West into the northern High Plains... Early-day satellite imagery shows upper ridging centered over the southern Plains and upper troughing from Pacific Northwest into central CA. Moderately enhanced southwesterly flow aloft is in place between these two features, from the Great Basin across much of the Intermountain West and into the northern High Plains. A shortwave trough currently moving through the western Great Basin is expected to progress through this southwesterly flow, reaching the northern High Plains by early Wednesday morning. Favorable moisture is in place ahead of this wave, as evidence by PWATs around 1" sampled by the 12Z soundings at SLC and GJT, with near 0.9" at BOI as well. Scattered to numerous thunderstorms are expected across the region, as northeastward-progressing shortwave trough interacts with this favorable moisture. Ongoing cloud cover and filtered daytime heating is expected to keep temperatures in the upper 70s across much of the region, with slightly warmer temperatures possible across eastern ID and northeastern UT. These temperatures combined with the mid-level moisture already in place will support moderate buoyancy, with the enhanced mid-level flow supporting moderate vertical shear as well. As a result, a largely multicellular mode is anticipated, but a few more organized storms are possible, with occasional bowing segments capable of producing strong gusts. The only exception is across the eastern ID/northeast UT vicinity, where slightly better buoyancy and shear could result in a few supercells. Anticipated isolated coverage currently precludes the need for higher severe probabilities. ....South Carolina... A weak surface low is near the southern SC coast this morning. Modest low-level convergence from this low northwestward into western SC/northeast GA is helping support showers and occasional thunderstorms. This convergence will likely persist throughout the day, with the showers and thunderstorms progressing gradually eastward. A very moist airmass is in place, as evidenced by 16.7 g/kg lowest 100-mb mean mixing ratio on the 12Z CHS sounding, and will diurnally destabilize today. Moderate west-northwesterlies (around 30 kt at 500 mb) may aid in some multicellular organization. Isolated gusts 50-60 mph capable of wind damage will be the primary concern with the stronger storms. ...Mosier/Weinman.. 08/13/2024 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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