SHORT TERM
(Through Late Saturday Night)
Issued at 241 PM CDT Fri Jul 26 2024

The surface front is located just to our south this afternoon across far southern Missouri although it has become increasingly less defined. Slightly cooler air behind the front has led to more pleasant temperatures today, although the drier air has been lagging behind. Regional satellite imagery today has shown high level clouds streaming southwest to northeast from Texas to Indiana while just to our north the high level blow off from earlier thunderstorms in southern Iowa was tracking northeast to southwest. This is indicative of the overall upper level flow regime which implies a weak trough axis over our area. More effectively, though, it's a weakness between two ridges, one to the southeast near the Florida Panhandle and the other nudging into Minnesota. The result is little to no mid and upper level forcing across our area today. Showers and thunderstorms have already begun to develop in the unstable air mass near the frontal zone. With little to no flow these will take the form of pulse thunderstorms with concentric outflows potentially driving new development into the evening when the activity should cease. The severe weather risk is very low, with lightning and local downpours the primary threats.

The ridge advancing eastward across the northern US fully cuts off the upper trough in Texas tonight. As the ridge moves east on Saturday it will allow the trough to escape northward behind it.
This is going to bring our best rain chances this weekend. This trough has been hanging out in coastal Texas for several days, so it will bring some tropical moisture with it. PWATs in parts of the area rise to near or over 2 inches, a sign that when it rains it will pour. Much of the rain will be generated by the synoptic forcing from the upper low, but convective elements will take full advantage of the depth of moisture. Although storm training doesn't look like a strong factor, just these heavy rainfall rates alone could lead to some minor flooding issues especially if they fall in vulnerable locations. For Saturday, the best synoptic forcing moves through eastern Missouri, but due to extensive cloud cover overall instability is limited. Further west some breaks in the clouds are more likely over central Missouri where afternoon pop up thunderstorms are a bit more likely. Overall moisture content (PWAT)
is lower to the west, though, so the best moisture and best convective potential are not aligned well enough for us to consider a Flash Flood Watch at this point. If flash flooding occurs it is likely to be much more localized than what occurred last week.

Kimble

LONG TERM
(Sunday through Next Friday)
Issued at 241 PM CDT Fri Jul 26 2024

The upper low moves out of the area on Sunday, with the rain exiting to the east as well. While POPs for any one period of the forecast are still somewhat modest due to timing uncertainties, when integrated over the entire weekend it is clear that just about everyone will see rain at some point. Ensemble probability of measurable rainfall over the combined Saturday to Sunday period is above 90 percent giving us the strong confidence that everyone will get wet at some point. The heavy rain threat will remain much more localized.

As the trough moves east, ridging over the western US expands east behind it opening us up to some hot weather. One more trough tracking east around the top of the ridge brings another chance of thunderstorms on Monday, but this should be more progressive as we head towards a hotter weather pattern. Daytime highs in the mid 90s are expected most days this week, with some daily variation.
Humidity remains moderate to high, leading to heat index values routinely rising to 100 or higher. The greatest uncertainty is with rain chances as being on the eastern side of the ridge we'll be in the line of fire for frequent "ridge runners," or convective complexes that generally form and track around the periphery of a ridge. While these would carry the potential for damaging winds when they occur, they also would bring heat relief especially if extensive clouds impact daytime heating. Confidence on which day this might occur is low, but it seems likely we'll be affected at some point. On days where storms stay away we could be even hotter, with heat index values exceeding 105.

The trend later in the week is for the ridge to retrograde to the west pulling the core of the heat westward with it. So there does seem to be an end point to this heat wave centered around the end of the coming week.

Kimble

AVIATION
(For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1221 PM CDT Fri Jul 26 2024

Afternoon cumulus develops beneath an increasing high level cloud cover today. Thunderstorms are expected to be limited to the south today and unlikely to affect any of the terminals. More expansive cloud cover moves in tomorrow, including some MVFR ceilings.
However it's unclear if those ceilings make it all the way to the terminals before daytime heating mixes the low levels and raises the cloud bases. Thunderstorms are expected to develop again on Saturday with the favored area being central Missouri in the afternoon. Elsewhere some scattered showers are the more likely impact.

Kimble

LSX WATCHES/WARNINGS/ADVISORIES
MO...None.
IL...None.