928 FXUS63 KLSX 141109 AFDLSXArea Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 609 AM CDT Sun Sep 14 2025
.KEY MESSAGES...
- Hot weather will continue through the middle of this week.
- There is a slight chance (15 - 25%) of showers and thunderstorms each afternoon from today through Tuesday. Precipitation chances increase to 30 - 50% mid to late this week.
&&
.SHORT TERM... (Through Late Monday Afternoon) Issued at 328 AM CDT Sun Sep 14 2025
Mid-level ridging will continue to be the primary influence on our sensible weather today through Tuesday. Expect highs in the 90s each day. Monday and Tuesday will be a few degrees less hot than today as a weak backdoor cold front ushers slightly cooler air into the region and as we get increased mid-level cloud cover from a mid- level trough to the west.
The mid-level trough over the central and northern Plains will provide lift for isolated to widely scattered showers and thunderstorms this afternoon into this evening. Deep layer shear values will be lower than those of yesterday, only peaking at 10 - 15 kts. So although SBCAPE values will be on the order of 1500 - 2000 J/kg, a lack of appreciable shear will favor non-severe pulse convection. Showers and thunderstorms are expected again Monday and Tuesday afternoons. With the trough kicking out of the region and the ridge expanding over the area, coverage will likely be more isolated than today. Otherwise, fairly similar CAPE and shear values warrant more pulse convection each day.Jaja
&&
.LONG TERM... (Monday Night through Saturday) Issued at 328 AM CDT Sun Sep 14 2025
The ridge finally erodes in the middle of this week as a trough dips into the central CONUS. This feature will be responsible for a much anticipated cooldown, but its slow-moving nature will drag the transition out. Because of this, its only impact on Wednesday will be increased chances of showers and non-severe thunderstorms in Missouri that afternoon. More tangible and widespread rain chances arrive on Thursday, though this should be characterized more as a higher chance of light rain than a chance at drought relief. LREF probabilities of receiving 0.25" of rain in 24 hours ending at 00z Friday are still under 50%.
Thursday is also when cooler air will begin to filter into the region. Confidence is increasing that a significant portion of the northern and western CWA will see highs below 90 degrees beginning Thursday with the rest of our counties following on Friday. Despite the sub-90 highs, it likely won`t be until next weekend that we return to near seasonal average highs region-wide.
Jaja
&&
.AVIATION... (For the 12z TAFs through 12z Monday Morning) Issued at 605 AM CDT Sun Sep 14 2025
VFR conditions with light, variable winds will prevail through the TAF period.
There is a slight chance of isolated showers and thunderstorms this afternoon areawide and overnight mainly west of the Mississippi River. Confidence in direct impacts to terminals is still too low to mention in the TAFs. If a thunderstorm does hit a terminal, expect brief downpours and gusty winds.
Jaja
&&
.CLIMATE... Issued at 218 PM CDT Wed Sep 10 2025
Record daily highs Friday 9/12 through Monday 9/15:
9/12 | 9/13 | 9/14 | 9/15 STL 98 100 101 101 COU 100 99 104 101 UIN 99 100 99 100
Delia
&&
.LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. &&
$$
WFO LSX
NWS LSX Office Area Forecast Discussion