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Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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231 FXUS63 KTOP 181644 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1144 AM CDT Sun Aug 18 2024 .KEY MESSAGES... - Showers and thunderstorms are possible today (30-50%) and tonight (30-55% chance). A few severe storms are not out of the question. - Below normal temperatures to start the workweek before temperatures gradually warm into next weekend. && .UPDATE... Issued at 942 AM CDT Sun Aug 18 2024 Convective cluster across central NEB continues to make steady progress south in spite of most earlier runs of the CAMs showing it falling apart. There remains quite a bit of inhibition for surface or mixed layer parcels (100+ J/kg on the 13Z RAP forecast soundings) over the forecast area. But the latest RAP shows the warm air advection with good isentropic assent holding together into the afternoon. This makes me think we will see the showers and storms make it into the forecast area but I suspect the storms will become increasingly elevated. Bulk shear remains favorable for organized updrafts so there could be some hail with the storms. But the main concern will be damaging wind gusts with downdraft CAPE on the order of 1000 J/kg. Have increased POPs across the area this afternoon for scattered coverage and will continue to monitor trends. && .DISCUSSION... Issued at 319 AM CDT Sun Aug 18 2024 Upper ridging persists across the Southern Plains and Desert Southwest this morning with a couple of perturbations rounding the ridge. Surface high pressure is in control of the middle of the CONUS, keeping conditions across the forecast area benign overnight. Lift associated with the aforementioned waves along with isentropic ascent have generated showers and storms across South Dakota and Nebraska. As these features continue around the ridge, sufficient lift and saturation in the mid-levels will support the development of showers and storms later this morning into the afternoon. Uncertainty remains in coverage and intensity of storms with CAMs showing a wide variety of solutions. Several CAMs show a complex of storms moving along the instability gradient into northeast Kansas. Others suggest a more scattered natured to convection with recent runs of the HRRR being an outlier solution, showing little to no precipitation across the area through the day. The passing waves are fairly weak and isentropic ascent becomes better focused across eastern Kansas this afternoon and evening. This supports isolated to scattered storms through the afternoon and evening as the most probable solution. Elevated instability of 500-1000 J/kg coupled with 45-50kts of effective shear would support a low-end severe threat and the strongest storms could produce hail up to quarter size and damaging wind gusts. If an organized MCS moves into the area, the potential for severe storms increases with damaging wind gusts being the main hazard. CAMs are in good agreement with additional storms developing this evening and overnight as a slightly stronger wave progresses southeast and isentropic ascent increases. Instability is progged to be weak (<500 J/kg) which should preclude any severe weather potential. A surface high builds south on Monday and Tuesday bringing in drier air and keeping temperatures in the 80s. Another wave rounds the ridge Monday night into Tuesday, bringing a small chance of precipitation across central Kansas. Upper ridging builds overhead Wednesday with gradually warming temperatures and dry conditions into next weekend. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1144 AM CDT Sun Aug 18 2024 CAMs still want to weaken the convection as it moves southeast and have generally be a little to far northeast with the track of the stronger cells. Forecast soundings still show a fair amount of inhibition but think elevated showers and thunderstorms will be able to ride the instability gradient southeast. Have adjusted the track of the CAMs southwest which would put the terminals in line for some TS. They have shown a tendency to weaken over the last hour or so and think the most likely impact at the terminals will be some temporary gusty winds of 20KT to 25KT. Have kept CIGS VFR but visibility will probably drop with the rain for a brief period of time. Once the afternoon convection moves off, additional TS are expected to redevelop overnight with the low level jet. There has been some variability in the location of the narrow axis of TS so confidence in impacts at the terminals are only medium for now. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Wolters DISCUSSION...Flanagan AVIATION...Wolters