Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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685 FXUS63 KLSX 191858 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 158 PM CDT Wed Jun 19 2024 .KEY MESSAGES... - Temperatures today will be warmer than yesterday. There is a chance for isolated showers and thunderstorms this morning through this afternoon mainly from central Missouri through west-central Illinois (20-30%). - Above normal temperatures are expected to continue Thursday through next week with Friday and especially Saturday being the hottest. The next chance of showers and thunderstorms will be late Saturday into Sunday (20-60%). && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 411 AM CDT Wed Jun 19 2024 A positively tilted mid-level ridge/high over the Mid-Atlantic region is visible in current water vapor imagery. As a result, much of the eastern CONUS is dominated by deep high pressure and the associated anticyclonic flow about the high is transporting a large fetch of moisture from the Gulf of Mexico into the region. Apart from this mid-level ridge/high is a mid-level long wave trough over the northwest CONUS with a series of vorticity maxima within the southwest flow over the east-central Plains. Attendant with the long wave trough over the western CONUS is a cold front that extends from the Upper Midwest through northwest Missouri into the Oklahoma Panhandle. Showers and thunderstorms associated with the cold front are seen on radar. It is expected that this cold front will slowly continue east- northeast over the next couple hours and stall across north-central and northeast Missouri by mid-morning. This will be the focus for isolated to scattered convection through the day today. Upper-level support associated with this cold front is minimal and weak mid- level lapse rates and around 20kts of 0-6km shear over our area. Support in the lower-levels is greater but still rather limited and SBCAPE values between 500-1500 J/kg will support isolated to scattered showers and thunderstorms across central and northeast Missouri through west-central Illinois. Northeast Missouri and west- central Illinois have greatest chance (20-30%) for seeing a shower or thunderstorm. Throughout today, the mid-level ridge/high will begin its westward movement. This will favor warmer temperatures with highs in the upper 80s to mid 90s. A suppressor of highs is a large area of cloud cover embedded in the southerly flow about the mid-level high. As the mid-level ridge/high begins to shift westward, areas across southeast Missouri and southern Illinois could see some increased cloud cover, thus keeping temperatures on the "cooler" side of the high temperature range. With deep high pressure continuing to shift west tomorrow, rain chances will be confined to northeast Missouri and west-central Illinois and temperatures are expected to continue to warm up with the associated height rises. Temperatures will have no trouble reaching the low to mid 90s area wide. MMG/Glass && .LONG TERM... (Thursday Night through Tuesday) Issued at 411 AM CDT Wed Jun 19 2024 Dry weather and increasingly hot temperatures will continue Friday through late Saturday afternoon as the mid-level high makes its anticipated westward expansion. Rising heights and southwest low level flow will favor temperatures warming up well into the 90s and nearing 100 in the St. Louis Metro area by Saturday. This is further supported by the NBM interquartile range of high temperatures having a 4-7 degree spread both days. However, it is important to note that NBM temperatures have had a few degree warm bias over the past few days which provides uncertainty to how hot temperatures will get. The next chance for shower and thunderstorm activity will be late Saturday into Sunday as a mid-level shortwave and vorticity maxima traverses across the region. This will trek a cold front across the region Sunday with expected shower and thunderstorm activity along and ahead of the cold front. Over 70% of ensemble guidance members indicate precipitation during this time fame, further increasing confidence in its occurrence. By next week there is consensus that mid-level ridging will build in across the central CONUS and favor a continuation of these above normal hot temperatures. MMG/Glass && .AVIATION... (For the 18z TAFs through 18z Thursday Afternoon) Issued at 153 PM CDT Wed Jun 19 2024 VFR conditions will prevail at all local terminals through the majority of the 18Z TAF cycle. A few weak showers and thunderstorms will be possible at a few terminals this afternoon and evening, with showers most likely to impact UIN by a slim margin. Even here, the probability of a direct impact to the terminal is low (around 30%), but just high enough to support a VCTS mention in the TAF. Briefly strong wind gusts will be possible with showers if they do manage to directly impact a terminal. Showers will diminish this evening, along with breezy southerly winds. Otherwise, while some shallow patchy fog will be possible overnight at primarily SUS, this is not expected to be widespread and VFR conditions will persist through the remainder of the period. BRC && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX