Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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004 FXUS63 KLSX 100326 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1026 PM CDT Sun Jun 9 2024 .KEY MESSAGES... -Monday will be the coolest day of the week. -Temperatures will start to warm Tuesday and jump above normal by Thursday, lingering into the weekend. && .SHORT TERM... (Through Late Monday Night) Issued at 115 PM CDT Sun Jun 9 2024 Precipitation will continue to weaken and push southeastward this afternoon in tandem with the mid-level disturbance across southern Missouri. A surface high is pushing into the mid-Mississippi Valley from the northwest, which is also helping to shunt precipitation and associated cloud cover out of the forecast area. Aloft a mid- level trough is digging into the eastern CONUS while a mid-level ridge strengthens across the inner Mountain West. The resulting deep northwesterly flow will bring cool air into the region starting today, and a clearing sky and light winds will promote additional cooling tonight. Temperatures overnight will cool into the 50s. Patchy fog formation is possible tonight within the river valleys and hollows where winds will be able to go calm, specifically across southeast Missouri where rain lingered longer today and where the overnight lows will come close to the crossover temperature from this afternoon. Deep northwesterly flow will continue Monday while the axis of the surface high scoots into the mid-Mississippi Valley. Despite the clear sky, cool 850 mb temperatures in the upper single digits and northwesterly surface flow will keep temperatures roughly 5-10 degrees below normal for early June. The axis of the surface high will slide across the forecast area overnight, allowing surface winds to go calm. Efficient cooling combined with calm surface winds will make Monday night the coolest of the week. MRM && .LONG TERM... (Tuesday through Next Sunday) Issued at 115 PM CDT Sun Jun 9 2024 Surface and low-level flow will become more southerly Tuesday as the axis of the surface high moves east of the region, and warm air advection will increase across the area. Thus begins the warming trend that will last through the week as low-level winds remain southwesterly, bringing warm, moist air into the mid-Mississippi Valley. While there are areas of uncertainty with regard to the high temperature through the remainder of the work week and into the weekend (cloud cover, surface wind direction, precipitation chances), the interquartile spread for high temperatures is around 5 degrees. Even the 25th percentile is above normal from Thursday onward, both of these increase confidence that summer-like temperatures will take hold of the region through the end of the extended period. By mid-week the mid-level trough over the eastern CONUS will exit into the Atlantic and a broad but progressive ridge will build into the Desert southwest. The mid-level ridge will slide eastward across the southern US through the second half of the work week, while the forecast area remains on the northern edge of the ridge. This leaves the region open to ridge-running disturbances that could bring precipitation chances to the region, though there is little signal for these disturbances at this point. Rather, long term guidance has been hinting at at least one frontal passage moving through the mid- Mississippi Valley associated with a low over the Great Lakes region during the mid to late week period. Confidence in this occurrence is low at this point, given the run to run changes in the strength and timing of these features, but it is something to watch as it could bring our next chance of showers and thunderstorms to the region. MRM && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1025 PM CDT Sun Jun 9 2024 Dry, VFR flight conditions will persist through the end of the TAF period with diurnal cumulus developing during the day on Monday. Surface high pressure will continue to move into the region, favoring light north-northwesterly winds overnight. By Monday morning, winds will become northerly. MMG/Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX