11/1/2024 7:00 PM
Friday Night: Mostly Clear | Low: 42°F
Saturday: Increasing Clouds (Mostly Sunny to Partly Cloudy) | Chance of rain – 20% | High: 68°F
Saturday Night: Rain, perhaps heavy at times, with some rumbles of thunder | Chance of rain – 80% | Low: 59°F
Sunday: More rain, perhaps heavy, and more thunder | Chance of rain – 90% | High: 71°F
Sunday Night: Heavy rain and thunderstorms likely, low chance of flash flooding | Chance of rain – 100% | Low: 64°F
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General Discussion : Dry time will remain tonight, and through most of tomorrow. Rain will begin to move in Saturday night, and will continue through the remainder of the forecast period. Rain is expected to be particularly heavy Sunday night, with rumbles of thunder also expected. Ponding on roads is expected, and localized flooding is possible. The Weather Prediction Center has a Slight Risk (2/5) for flash flooding Sunday and Monday. If in a flood prone area, ensure you go over your safety plans. The good news is this rainfall will bring relief to drought.
–Schwent, Slutter, Yost
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Key Messages :
- Significant rainfall is expected this weekend, (2.0-2.5 inches within the period, more beyond)
- There is a low chance (10%) of localized flash flooding Sunday night
- This rain is expected to bring substantial drought relief
Technical Discussion :
The Central Missouri area is poised to enter an active weather period starting this weekend. Currently, we are under a zonal flow pattern influenced by a neutrally tilted trough situated to our west. A high-pressure system is moving eastward, exiting our region as of Friday night. Southerly surface flow is promoting warm air advection, with a warm, moist air mass lingering in the Gulf of Mexico states due to thunderstorms that occurred Wednesday night into Thursday, “shoving” the airmass south. Satellite observations this afternoon show a cirrus band just south of our region, which will migrate northward overnight, leading to mostly clear skies and signaling the first signs of this airmass’ resurgence into the central US.
Friday night will be pivotal for the upcoming weekend weather. While weak (5-10 kt) low-level flow will promote some minor warm air advection, stronger forcing will be lacking. As the upper-level trough shifts, we expect the upper winds to transition to a southwesterly flow. This change will correspond with the development of robust thunderstorms in the southern plains on Saturday, which may enhance low-level moisture advection into our area, though rain chances remain low at approximately 20% due to the distance from the driving surface low and trough.
Overnight Saturday, the exit region of the upper trough will move into our area, increasing its influence. Numerous shortwaves combined with a moist layer extending through much of the atmosphere will generate sufficient forcing for showers and thunderstorms. These storms are not predicted to be severe, due to anomalous warm air advection at all levels, inhibiting significant instability. Notably, a pre-trough subtropical jet streak will augment θe advection by tapping into Pacific moisture, culminating in high precipitable water values (1.3″, <99% climatology). Rainfall amounts overnight Saturday are anticipated to be between 0.25″ to 0.50″, with intermittent showers and thunderstorms as shortwaves traverse the region.
Conditions will largely persist into Sunday, with continued warm air advection promoting enhanced rainfall rates (0.5″ to 1.00″). Southwesterly flow from the upper trough is expected to exceed 50 kts, and divergence aloft courtesy of the trough will create some destabilization. The sheared, moist atmosphere will support thunderstorm activity, although severe storms are not anticipated.
The most active period is projected for Sunday night, as both the subtropical and polar jet streams converge over our area with 50-80 kt upper-level winds. This dynamic setup will likely result in near-constant rainfall, with PWATs remaining notably high (1.4″). A new series of shortwaves at lower levels will enhance forcing for ascent, while the low-level jet ramps up to at least 60 kts. The NAM model suggests an aggressive jet streak approaching 70 kts in our region. Overnight Sunday, we expect over an inch of rain, with localized totals potentially reaching up to 4 inches in areas around Columbia, given the spatial variability indicated by model guidance. This could lead to localized flash flooding.
Future forecast shifts need to monitor Monday, as it is most likely to be the highest-impact day of this sequence. Additional heavy rainfall is likely, and the Storm Prediction Center has highlighted the possibility of Severe Thunderstorms for our area, which the large-scale pattern underpinning us supports. The silver lining in all of this is that when it’s all said and done, the drought will be significantly improved.
-Schwent