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Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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913 FXUS63 KTOP 151950 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 250 PM CDT Thu Aug 15 2024 .KEY MESSAGES... - Another round of thunderstorms are possible (20 to 50 percent chance) Friday afternoon and evening. - Quiet weather and cooler temperatures expected this weekend and into early next week. && .DISCUSSION... Issued at 250 PM CDT Thu Aug 15 2024 20Z water vapor imagery showed a nearly zonal pattern across the central parts of the country with an upper wave moving into northern MN and another upper wave over OR. Surface obs had a low pressure system over northwestern MN with a cold front stretching south along the MO river and into central KS. For the late afternoon and evening time frame, there remains a lot of available energy for thunderstorm development across easter KS. The 19Z SPC mesoanalysis showed MLCAPE values of 2500 to 3000 J/kg with bulk shear between 35KT and 40KT. But models prog the better dynamics to pass just north of the area with forecast soundings holding onto some convective inhibition. Think the chances for convection are small and the latest CAM runs still don`t generate storms over the forecast area. Have left some small POPs in the forecast for the outside chance a storm develops. But think as the boundary layer cools this evening and energy to the north continues east, this risk for convection will progressively decrease to only 5 or 10 percent by 10 o`clock. With weak high pressure building into the area overnight and skies clearing out, the setup for ground fog looks good. Have added a mention of fog in low lying areas for now, but if moisture doesn`t scour out the fog could be a little more widespread. Friday the models have a shortwave diving down the back side of the upper ridge. This energy is progged to affect central KS around mid day with most guidance showing a signal for precip moving southeast through the afternoon. It is not out of the question some of these storms could be severe with reasonable bulk shear and mid level lapse rates around 7.5C/km. The NAM is struggling with instability parameters from convective feedback in the model and the GFS shunts the best instability and moisture just southwest of the forecast area with weak ridging over northeast KS. So will need to reevaluate the severe potential overnight. For the rest of the forecast period, models re-amplify the upper ridge over the central Rockies with high pressure over the Upper Midwest ridging into northeast KS. There is some variability in the strength of the surface ridging, and given the amplitude of the upper ridge and a little skeptical of the ECMWF and it`s cooler surface temps. But overall a quieter period of weather is anticipated. There could be a shortwave or two round the ridge and potentially create some precip chances. Did not see any reason to deviate from the NBM which has some 20 to 30 percent chances early next week. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1206 PM CDT Thu Aug 15 2024 Forecast soundings show some, if weak, inhibition holding on through peak heating this afternoon and the latest runs of the CAMs don`t really develop storms. So will keep a dry VFR forecast going. Gusty winds this morning should subside this afternoon as the pre-frontal trough continues east. Favorable conditions are forecast overnight for ground fog development, especially in the river valleys. So will have some MVFR visibilities for at least TOP and MHK through the early morning hours. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wolters AVIATION...Wolters