Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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182 FXUS63 KLSX 270738 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 238 AM CDT Mon May 27 2024 .KEY MESSAGES... -Memorial Day will be largely dry, though a stray shower or thunderstorm cannot be ruled out across far NE Missouri and west- central Illinois late this afternoon. -Dry weather with near normal temperatures will persist through the work week. && .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 224 AM CDT Mon May 27 2024 With the abundance of surface moisture and a mostly clear sky there is a risk for patchy fog this morning, particularly in the river valleys and hollows where winds will be sheltered. Any fog that develops will mix out shortly after sunrise. In the wake of Sunday`s severe weather a cold front is stretched across the mid- Mississippi Valley. The front will continue to sink southward through the morning as the mid-level trough lifts eastward out of the forecast area and the surface low follows in lockstep. Behind this system, northwesterly mid-level flow will establish as a mid- level trough becomes rooted over the eastern CONUS, and a mid- level ridge sets up over the Mountain West. A shortwave disturbance will propagate down the northwesterly flow this afternoon/evening, while a 850 mb jet noses into the northern forecast area. While moisture will be limited across the area, I cannot rule out a quick shower or thunderstorm popping up across far northeast Missouri and west-central Illinois during the late afternoon and early evening. Limited moisture and instability (around 300 J/kg of MUCAPE) keep the chance for strong thunderstorms very low. Otherwise, rising heights will keep the remainder of the forecast area dry today and Tuesday. Temperatures will return to seasonal levels, with highs peaking in the upper 70s across northeast Missouri and west-central Illinois and just around 80 along and south of the I-70 corridor Monday and Tuesday. MRM && .LONG TERM... (Tuesday Night through Sunday) Issued at 224 AM CDT Mon May 27 2024 The mid-Mississippi Valley will remain in northwest flow aloft as the mid-level trough and ridge stay locked in across the eastern CONUS and Mountain West, respectively. This will keep the work week largely dry with seasonal temperatures. The interquartile spread for high temperatures through the work week is very small, around 3 degrees. This increases confidence that temperatures will indeed be near normal for late May. As the weekend approaches so does the mid-level ridge, which will throw the region back into southwesterly flow over the weekend. This will open the region back up to shortwave disturbances as well as warm, moist advection. While specifics vary on the location and timing of shortwaves, confidence is increasing that chances for precipitation will return to the region over the weekend. MRM && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1218 AM CDT Mon May 27 2024 By and large convection has ended across the region, and the remainder of the TAF period is expected to be dry. A largely sky and recent rainfall increases the potential for patchy fog tonight, particularly in the valleys and river bottoms where winds will be more sheltered. However, given the lingering cloud cover still around, I don`t yet have enough confidence to include a mention of visibility reduction at any of the TAF sites just yet. If fog does develop it will clear by 12-13Z with sunrise. Winds will remain from the northwest through the period, becoming strong (sustained winds above 10 kts) and gusty (near 20 kts) during the afternoon hours tomorrow. MRM && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX