Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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171 FXUS63 KLSX 300342 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1042 PM CDT Sat Jun 29 2024 .KEY MESSAGES... - Isolated strong to severe storms possible late this afternoon through this evening, mainly along and south of I-70. The primary threat is damaging winds. Though brief bursts of heavier rain and occasional large hail are possible as well. - Despite slightly cooler temperatures this afternoon, the humidity remains high with heat index values between 100-105 degrees over sections of southeast Missouri. So heat advisory will remain in effect until 7PM today. - Next chance of showers and thunderstorms will be Wednesday through Thursday. && .SHORT TERM... (Through Late Sunday Night) Issued at 312 PM CDT Sat Jun 29 2024 The atmosphere is beginning to recover across the area this afternoon since the cloud cover continues to diminish from the earlier activity. Also, the latest HREF ensemble indicates that CIN will continue to weaken and mean surface based CAPE is expected to increase to between 2500-3500 J/kg by 21z along and ahead of the cold front. The cold front has been a bit slower in it`s movement to the south today and as of 19z it extends from northeastern IL southwestward into northeast MO (just north of Quincy) to just south of Kansas City. The front as well as outflow boundaries across southern Missouri will be the focusing mechanisms for storms to develop late this afternoon through this evening. So could see one area of activity just north of the St. Louis metro and another area south of the St. Louis metro area initially. Latest CAMs indicate that the best chances of strong to severe storms will be south of I- 70. The main threat will be damaging winds, though brief bursts of heavier rain and occasional large hail are possible as well. Another issue to deal with late this afternoon is the heat advisory for portions of southeast Missouri. Even though temperatures have been slow to recover, should still see them warm up into the low 90s with heat index values between 100 and 105, so heat advisory will remain in effect until 7PM this evening. The cold front will continue to sink south through the region, exiting the forecast area early on Sunday. So precipitation will taper off by daybreak. Then strong surface high pressure ridge will build over the area beginning on Sunday. Much cooler and drier air will filter in Sunday into Monday with below normal temperatures. Byrd && .LONG TERM... (Monday through Next Saturday) Issued at 312 PM CDT Sat Jun 29 2024 While enjoying the cooler than normal weather through Monday, upper level ridge will begin to build in from the Plains. By Tuesday, surface flow will become southerly once again with highs back in the 90s. However, low level moisture return will be a bit slower, with the main axis of higher dewpoints just to our west, though dewpoints will be near 70 degrees in portions of central Missouri, so could see heat index values around 100 Tuesday afternoon. By Wednesday, dewpoints will be in the 70s across the entire area with heat index values between 100 and 105 along and south of I-70. In the meantime, the next system will be approaching the central CONUS. The pattern will be similar to what we are currently experiencing with a system sliding east along the US/Canadian border and cold front approaching the region by Wednesday. There is better agreement among the deterministic as well as ensembles on timing, location and strength of the system, so have likely POPs Wednesday night into Thursday. Still some uncertainty on coverage of the activity, so don`t want to say that the Fourth of July holiday will be a washout at this time, but will need to keep an eye out on model trends over the next several days. With the chances of precipitation for the last half of the work week, temperatures will be a tad cooler, in the 80s. Byrd && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1036 PM CDT Sat Jun 29 2024 Convection is now south of the TAF sites ahead of a weak surface boundary dropping through the region at this hour. Dry air is scouring any low clouds amidst weak but persistent northerly winds. While weak showers may threaten the I-70 corridor through 09Z, the terminals will likely remain dry. VFR conditions will then persist through the valid TAF period with surface high pressure dominating our sensible weather. MRB && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX