Saturday Night: Overcast. Showers and thunderstorms likely with decreasing potential past midnight. Low: 66
Current thunderstorms will continue into Thursday night with a low of 65. Chances for rain will clear into Friday morning, with chances increasing again in the afternoon. Temperatures will reach a high of 75. Clouds and rain will continue into the night on Friday. As a cold front approaches Saturday, chances for rain will increase and continue throughout the day. If you're planning on going to the Mizzou Football game, umbrellas and ponchos are recommended. Saturday night will be overcast with decreasing chances for thunderstorms towards daybreak. Total rainfall expected for through the rest of the week is around 1"-1.5".
Forecasters: Heienickle, Meyer, Orr
Date Issued: 09/30/21 5:30 PM CST
This forecast was created using the 12Z run of both the NAM and GFS. Both models were performing extremely poorly, both with inaccurate initial conditions and a poor handling of the current rain showers in Columbia. SREF and GEFS plumes were also used to aid in forecasting temperatures, and overlaid soundings of the GFS and NAM were used to help forecast rainfall and thunderstorm potential.
At 250-mb, plots of heights, winds, and divergence depict meridional flow over the United States. A large ridge over Missouri moves east around 00Z Saturday, and a large trough soon makes its way over Missouri. Higher amounts of divergence associated with this trough pass over the forecast area Friday night near 06Z and Saturday night around 21Z, with a short break in between. The trough becomes negatively tilted by 03Z Sunday as it continues to pass over the state.
500-mb plots of heights and vorticity support PVA as the trough makes its way toward Missouri. By 03Z Saturday, small circulations begin to make their way into Mid-Missouri. Higher amounts of vorticity associated with the base of the trough move in Sunday at 00Z, providing another chance for thunderstorm development.
700-mb plots of heights and relative humidity show varying amounts of humidity over Missouri for the entirety of the forecast period. Friday morning sees a brief break in the higher amount of RH, but Missouri will return to saturated conditions soon after. The highest amounts of RH enter the region Saturday at 06Z and remain until around 06Z Sunday. Favorable amounts of moisture are present throughout the entirety of the forecast period, especially during the times when conditions at upper levels are also favorable.
Heights, winds, and temperatures at 850-mb reveal the source of the abundant moisture for the next few days. Winds are disorganized, but southerly until around Friday at 06Z, when winds shift to a stronger, more organized southerly direction. This is the formation of the LLJ, which will provide the moisture for on and off rainfall seen for the entirety of the forecast period. These southerly winds also keep temperatures slightly warmer than average for this time of year. A cold front will make its way into northwest Missouri by 09Z Sunday. Future forecasters should watch for its impact of the central Missouri region.
At the surface, MSLP, thickness, and winds continue to support what was seen at upper levels. Winds remain in a southerly direction for the next few days, providing more support for the warmer temperatures. Sunday's cold front is visible in MSLP as well.
GFS and NAM soundings were overlaid on each other to help establish timing of rainfall and the potential for storms. The two were used in conjunction due to the poor model performance and overall lack of consensus. On-again off-again rainfall is what dominates this forecast. When the soundings weren't saturated enough for rainfall, there will still be enough saturation for decent cloud cover. Varying amounts of CAPE and UVM are present Friday and Friday night, creating the potential for scattered thunderstorms. The highest potential for thunderstorms occurs on Saturday afternoon and evening, with very negative Omega values and an MUCAPE range of 1100-1500 J/kg between the two models. Total PW values for the forecast period range from 1" to 1.6" inches.