![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
879 FXUS63 KLSX 191915 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 215 PM CDT Fri Jul 19 2024 .KEY MESSAGES... - Mild mid-summer temperatures continue through Sunday with seasonally low humidity. - Humidity increases Monday and Tuesday along with chances for showers and thunderstorms. && .SHORT TERM... (Through Late Saturday Night) Issued at 215 PM CDT Fri Jul 19 2024 Surface high pressure remains centered near our area with mild mid-summer temperatures and low humidity. Afternoon cumulus will dissipate this evening leading to another night with efficient radiational cooling. Some thunderstorms upstream in South Dakota and Nebraska may send some high level cloudiness toward our area overnight which could limit the cooling a little bit. But in areas where it remains clear, another pleasant summer night in the 50s is expected, with urban areas warmer. Patchy fog is likely mainly in the Ozark river valleys. Saturday will be pretty similar today with light winds and mild temperatures. Humidity gradually creeps up, though, so temperatures Saturday night won`t be quite as cool. Kimble && .LONG TERM... (Sunday through Next Friday) Issued at 215 PM CDT Fri Jul 19 2024 Upper ridging remains parked over the western US, even backing up toward the West Coast a bit next week. Broad troughing will persist downstream across the central and eastern US, though where the subtle shortwave impulses within this trough exist will be a key in determining rain chances next week. Moisture returns from the Gulf of Mexico bringing dewpoints back up to near 70 or higher for Monday and Tuesday. While temperatures remain somewhat mild, the humidity will be noticeable compared to this weekend. With that added moisture we`ll see the return of instability and the chance for showers and thunderstorms. It`s likely that there will be one or more shortwave troughs embedded in the flow that will serve as a focus for showers and thunderstorms Monday and Tuesday, though where they will be is still highly uncertain. Our rain chances are highest on these days as it is more likely that the trough axis will be nearby. Thunderstorm chances are greatest in the afternoon and evening when instability should maximize. The severe weather threat with these storms should be low considering a remarkable lack of shear. While we are climatologically toward the time of year when flash flooding is a greater concern, total moisture content does not look high enough to warrant this concern especially in the absence of a forcing mechanism to trigger storm training. PWAT is expected to peak around 1.5 inches, much lower than what was seen last week. As the shortwave trough moves east, a weak cold front moves south in its wake. Another deeper trough drops into the western Great Lakes behind it with another cold front associated with it. While we do maintain low PoPs Wednesday through the end of the week, the forcing for more widespread showers and storms looks pretty weak at this point leading to the lower confidence in those precipitation chances. Kimble && .AVIATION... (For the 18z TAFs through 18z Saturday Afternoon) Issued at 1220 PM CDT Fri Jul 19 2024 Primary aviation impact for most locations is diurnal cumulus otherwise winds are very light and often variable. It is possible that fog develops in the river valleys tonight, with this threat greatest at SUS. If this occurs it will be for just a few hour window near 12Z. Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX