Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
Issued by NWS Kansas City/Pleasant Hill, MO
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492 FXUS63 KEAX 211738 AFDEAX Area Forecast Discussion National Weather Service Kansas City/Pleasant Hill MO 1238 PM CDT Sat Sep 21 2024 ...Updated 18z Aviation... .KEY MESSAGES... * Active weather through the weekend * Welcome widespread rainfall, especially later tonight through Sun * Low severe storm and flood threats * Cooler late weekend into next week - Highs 60s to 70s && .DISCUSSION... Issued at 352 AM CDT Sat Sep 21 2024 The beginnings of an active weekend were seen early in the overnight hours as a cluster of storms worked through Kansas and into west- central and southwest Missouri. A few storms were on the strong to severe side, primarily winds, in Kansas, before weakening as they worked into the area and a less supportive storm environment. Activity does continue early this morning as the parent shortwave continues to move through southern Missouri, and should remain largely general thunderstorms to showers. That will be just the first of multiple rounds of showers and storms through the remainder of the weekend, including more widespread opportunities to help relieve recent drought/dryness across much of the area. Quickly looking big picture, features that will be most responsible for our activity remain the SW CONUS trough sliding eastward across the southern Rockies and a northern stream trough working eastward across the southern Canadian Plains and US-Canadian border area. For today, shortwave energy coming off the SW CONUS trough will continue to develop broad surface low over the High Plains and aide in boosting southerly flow enough to lift the cool front over the area back northward as a warm front. As this occurs, ongoing moisture return/theta-e advection will provide broad and persistent lift and the opportunity for scattered shower and storm activity. This activity will be markedly further north than last night/this morning as a result. While there will be some elevated instability to work with, HREF depictions of 500-1500 J/kg, the effective shear environment will be such that organization is not expected. Some of the stronger storms may produce some small hail and gusty winds, but severe threat is not expected and also reflected within the SPC Day 1 Convective Outlook with Marginal Risk over northwest CWA to General Thunder elsewhere. Probably of more interest will be the rain and heavy rain potential. Ongoing and persistent moisture advection will keep and push PWat values to around 2 inches and remain through the weekend. With the more scattered nature and lack of feature to focus/cause training storms, the hydrologic threat will be low. Rather, the rain is likely to be welcome given the recent very dry/drought conditions. NBM QPF 24 hour (ending Sunday 1am) probabilities of 1" or greater as high as 50 to 60 percent over large portions of northern Missouri and 0.5" probabilities largely 70 to 80 percent over the same area. Of note, there are pockets of 40 to near 50 percent probabilities for 2.0". More on that in a minute. By late tonight and into/through Sunday, SW CONUS trough will begin to move out into the Plains, enhancing surface low development and continued moisture advection and isentropic lift into the area. Concurrently, cold front sliding southward from the parent Canadian surface low, enhanced by developing northern High Plains surface high, will approach and move into/through the CWA. These, plus better upper level support/lift will work to continue and enhance shower/storm development and coverage. Bulk of activity Sunday within the CAW appears to be overriding the cold front, limiting strong/severe storm development. CAMs suggest frontal boundary will push far enough south that best strong to severe risk may reside in the SGF CWA Sunday afternoon. With mean winds roughly parallel to the front, training showers/storms will provide another opportunity for areas of moderate to heavy rainfall. NBM 24 hour probabilities (ending Monday 1am) of 2.0" or greater again peak over northern Missouri, in the neighborhood of 50 to near 70 percent. This could provide an opportunity for a flood threat should similar areas see amounts in excess of 2" to 3" each day this weekend. Even so, threat remains lower-end given current hydrologic capacity and duration over which these rains will occur. Lighter precipitation activity may continue into/through Monday, especially over eastern areas of the CWA, as the original SW CONUS trough weakens and passes over the state. Aside from today, temperatures will be markedly cooler Sunday and through the work week with highs in the 60s Monday then rebounding a bit into the 70s rest of the week. Uncertain precipitation opportunities during the week as well with various depictions of a closed low developing and parking itself over some portion of the region. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1235 PM CDT Sat Sep 21 2024 Showers will continue through the remainder of the afternoon and evening. Cold front moves back through late tonight, and will result in thunderstorm activity between 04-08z. Timing could be slightly earlier of the front moves through faster, and then some uncertainty with how long it will linger. As front moves through, also expecting a brief period of IFR conditions, with longer low-end MVFR conditions. Gusty winds expected with the approach of the thunderstorms. && .EAX WATCHES/WARNINGS/ADVISORIES... MO...None. KS...None. && $$ DISCUSSION...Curtis AVIATION...Krull