Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
Issued by NWS Kansas City/Pleasant Hill, MO
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793 FXUS63 KEAX 042048 AFDEAX Area Forecast Discussion National Weather Service Kansas City/Pleasant Hill MO 348 PM CDT Tue Jun 4 2024 .KEY MESSAGES... - Thunderstorms are expected this evening in much of the area (50 to 85 percent chance). Severe storms cannot be ruled out, with damaging winds and marginally severe hail the main threats. - Dry and near-seasonal temperatures expected through the rest of the work week. - Chances for storms return this weekend. && .DISCUSSION... Issued at 259 PM CDT Tue Jun 4 2024 Main forecast challenge remains the threat of severe weather this evening. A vigorous upper-level trough is moving through the northern Plains this afternoon, with a surface cold front moving east/southeast, extending from western Minnesota to northern Kansas early this afternoon. A few storms have initiated near the boundary in central Kansas, in advance of a weak perturbation moving into the central/southern Plains and along the northern periphery of moderately to strongly unstable air (2000-3000 J/kg MLCAPE) and in the wake of an instability minimum in portions of the CWA (via a departing MCV). CAMs increase coverage of convection gradually through the evening hours, though how quickly and to what extent remains rather variable. Recent HRRR simulations are relatively aggressive, producing scattered convection in northeast Kansas and northwest Missouri through much of the evening before a somewhat more organized broken line of convection moves through the CWA later in the evening. The 12z NAM Nest is similar, though a little more skittish on convection through mid evening. One limiting factor to a more substantial severe threat is the marginal shear in place (e.g., 0-6 km bulk shear < 30 kt). With low-level winds remaining weak, the tornado threat is quite low; however, dry midlevels and modest midlevel flow may permit the development of strong wind gusts with the strongest convective cores. Additionally, substantial instability should permit the development of hail in the strongest cores (given what we are observing to the west), particularly if convection remains somewhat discrete. The greatest severe threat appears to be from 7 to 11 pm this evening, as the front moves into the CWA and more substantial instability remains. The severe threat should gradually diminish with time late in the evening/overnight as nocturnal stabilization increases and convective outflow becomes dominant. The front will sweep through the CWA overnight, with any precipitation exiting to our south and east by daybreak. The remainder of the week will be dominated by northwest flow and a surface high shifting southeastward through the Plains. This should result in a dry/seasonal/pleasant period for the region. Eventually, a midlevel ridge in the western U.S. will progress into the Intermountain West, providing a more favorable track for ejecting perturbations riding the ridge southeastward into the Plains. Meanwhile, the surface high should move well to our southeast by the weekend. This is a setup favorable for MCS development in the warm season. Models are beginning to converge on the first of such events occurring Friday night into Saturday (e.g., the 12z GFS and CMC). The pattern is low- predictability owing to the low amplitude of the overall upper flow and potential convective augmentation of the midlevel vorticity maxima. Nevertheless, with the increasingly favorable overall pattern, think mention of low-chance (below 40 percent) PoPs is warranted Friday night and Saturday. Subsequent perturbations may track farther south (as suggested by deterministic models), so PoPs are lower later in the weekend. However, considerable modification to the forecast may occur given the aforementioned low predictability. Forecast uncertainty increases further next week as models diverge in their handling of a weak upper low within the broader upper ridging to our west. In the evolving pattern, would think precipitation chances gradually increase, though specific timing is quite uncertain at this point. Of higher certainty is the continued near-seasonal temperature forecast given the lack of high-amplitude ridging and the periodic chances of storms this weekend onward. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1224 PM CDT Tue Jun 4 2024 MVFR stratus has been longer to linger and recent trends suggest at least brief ceilings will continue early in this forecast. Continued daytime heating should lead to VFR conditions by 21Z. Have delayed TS timing by an hour or so based on model consensus though confidence in coverage is too low to add any prevailing or TEMPO group despite its relatively near onset time. VFR conditions should return by 07Z. && .EAX WATCHES/WARNINGS/ADVISORIES... MO...None. KS...None. && $$ DISCUSSION...CMS AVIATION...WFO TOP