Those planning to attend homecoming festivities should expect fair weather this weekend; however, it will be somewhat breezy. Temperatures will be on the rise on Saturday, but dry air and winds will keep things relatively pleasant. There will be some clouds throughout the forecast period, but high pressure will keep skies mostly clear. Sunday will be more of the same until overnight when an approaching low pressure system brings increasing cloud cover and showers or thunderstorms become possible.
- Ethridge, Millsap
Forecasters: Ethridge, Millsap, Travis
Date Issued: 10/8/21 5:00 PM CST
Yet another shot of summer-like weather is in store for mid-Missouri this weekend. Strong WAA out ahead of an approaching low-pressure system is the main concern for this forecast period. Also of concern, is the potential for convection at the very end of this period ahead of the approaching system. There was good consensus between the NAM and GFS in diagnosing the large-scale upper-level pattern. However, the NAM had a better handling on temperatures while the GFS was noticeably too warm. Ensemble plumes were used to assess model performance. Huge spread in the GEFS members and little spread in the SREF members, as well as nice continuity, pushed towards predominately NAM guidance.
NAM 250-hPa plots of height and wind depict meridional, large-scale flow. The cut-off low that sat to the south over the Lower Mississippi Valley has since begun to move off to the NE. Ridging over the central CONUS has moved in to take its place. Amplified flow will ensure that ridging will not stick around for long as another longwave trough digs into the region from the Pacific Northwest.
NAM 500-hPa height and absolute vorticity show a similar pattern as 250. As the upper-level low pushes off to the NE, the building ridge remains void of large-scale circulation. This will keep things nice and calm. By the end of the period, Sunday night, the approaching trough digs into the region and brings with it disturbed flow. The effects of this system will largely occur outside of the forecast period, but vorticity maxima ahead of the system may bring trouble.
A look at NAM relative humidity and vertical motion at 700 hPa shows very little saturated air existing within the ridge. Fast forwarding to Sunday night, increased moisture and lift out ahead of the LPS suggests cloud cover will be on the increase overnight. A look at NAM soundings reveals a clearer picture of the potential for isolated convection. Instability is present as the model soundings show ~1000 to 1500 J/kg of CAPE in the overnight hours. That being said, a lack of deep moisture would suggest that any showers or thunderstorms that do develop, will likely be isolated in nature.
At 850 hPa, temperature and wind show strong WAA occurring early Saturday, bringing in temperatures >20C from the SW CONUS. Winds at this level will exceed 40 to 50 knots suggesting pretty breezy conditions at the surface. Persistent winds in excess of 40 knots at 850 will keep breezy conditions around into Sunday.
Plots of MSLP and 1000-500-hPa thickness show a very similar idea. Tight WAA solenoids set up overnight Friday into Saturday supporting te idea for strong WAA. A frontal boundary pushes into NW Missouri, but stalls and struggles to make it to Columbia before the low passes directly over mid-Missouri Monday. This is something that Monday's forecasters need to pay close attention to.