Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
Issued by NWS Kansas City/Pleasant Hill, MO
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973 FXUS63 KEAX 101758 AFDEAX Area Forecast Discussion National Weather Service Kansas City/Pleasant Hill MO 1258 PM CDT Wed Jul 10 2024 .KEY MESSAGES... - Isolated to scattered thunderstorms are forecast to develop this afternoon into tonight in much of the region. An isolated strong to severe storm is possible, with strong wind gusts the primary threat. - Another round of isolated thunderstorms is possible (<30 percent chance) on Thursday afternoon and night. - Increasing heat and humidity are expected late this week into early next week. Heat indices exceeding 100 degrees are quite probable (>90 percent chance) by Sunday and Monday. && .DISCUSSION... Issued at 237 AM CDT Wed Jul 10 2024 A deep trough in the Midwest is forcing the remnants of Beryl quickly northeast away from the central U.S. early this morning, but a kicker shortwave trough is digging southward through the Dakotas and Minnesota. Associated lift with this system is promoting convection in this area overnight and is a harbinger of what is to come for much of the central Plains this afternoon and evening. Short-range models continue the progression of this perturbation south-southeastward today, roughly in vicinity of eastern Nebraska and southern Iowa by 00z Thursday, as it begins to pivot in a more east-southeast direction. Given its favorable timing near peak heating and fairly strong lift via differential cyclonic vorticity advection, isolated to scattered convection should readily develop during the afternoon to our north, gradually progressing south-southeastward through the evening hours, in an environment characterized by steep low-level lapse rates and inverted-v boundary-layer profiles and cooling midlevels from the increasing ascent aloft. SBCAPEs of 1000-2000 J/kg should be common in advance of the perturbation during the afternoon. Wind profiles will be generally weak through the troposphere, with deep-layer shear of 20-30 kt. These characteristics suggest primarily pulse-type convection, with briefly strong updrafts associated with the most vigorous storms. The strongest convective cores may be capable of producing strong to locally severe wind gusts, though a lack of stronger winds aloft should preclude increased organization/frequency of the overall threat. Convection- allowing models (CAMs) have tended to keep convection going well into the evening, which suggests that the larger-scale forcing may be sufficiently strong to keep probabilities of precipitation mentionable through the overnight hours (similar to what is being observed in the northern Plains early this morning). The main perturbation shifts eastward of the lower Missouri Valley on Thursday, but a larger-scale trough should linger in much of the Midwest. There are subtle hints of a weaker perturbation shifting southeastward during the afternoon in the Upper Midwest. This perturbation and the lingering cooler air aloft may be sufficient to initiate convection in the region again Thursday afternoon/evening. Given the weaker look to the overall forcing, would expect convective coverage to be less than that expected on Wednesday. Nevertheless, did increase PoPs for much of the region Thursday afternoon and evening given model soundings looking sufficiently unstable and uncapped during peak heating. The overall environment is similar, with pulse-type convection favored. By Friday, the amplified ridge in the western U.S. builds/expands eastward, encompassing most areas west of the Mississippi River by Saturday. The ridge becomes quite prominent by late in the weekend into early next week, with our next round of hot/humid weather becoming fully entrenched during this time period. Forecast temperatures remain quite hot (mid to upper 90s by Sunday), with heat indices easily exceeding 100 Sunday and Monday. Forecast temperatures/heat indices on Monday easily exceed advisory criteria, and if current trends continue, headlines look like a good bet in future forecasts. The forecast becomes more uncertain by the end of the seven-day period, however. The northwest flow downstream of the ridge begins to dig a little more noticeably into the Great Lakes and eastern U.S. by this time. Several perturbations will traverse this faster flow from the southern Canadian prairies southeastward. By next Tuesday, these perturbations may begin to influence the larger-scale trough sufficiently to force the ridging farther west. This could even bring a front and attendant threat for convection close to or even through the area by midweek. Model variability is pretty high by this point, but there are tell-tale signs that this next round of heat may not last too long into next week. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1254 PM CDT Wed Jul 10 2024 VFR conditions are expected to last through the day. There is a potential for thunderstorms later tonight into overnight Thursday. These storms are expected to move to the east of the terminals by early Thursday morning. Winds will remain fairly weak and variable throughout the TAF period. && .EAX WATCHES/WARNINGS/ADVISORIES... MO...None. KS...None. && $$ DISCUSSION...CMS AVIATION...Collier