Current Conditions at Sanborn Field
Thursday: Rain throughout the day. High: 79
Thursday Night: Mostly cloudy with scattered showers. Low: 65
Discussion:
Starting tonight, winds from the Gulf of Mexico will bring moisture into the area. Developing clouds pair with extra moisture from an approaching low pressure system transition into rain tonight. Significant cloud cover and rain will lower our temperatures slightly over the next few days. Late Friday afternoon, there is a chance of thunderstorms for Columbia. Rainfall totals through Friday night are expected to be about 0.75 inches.
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Forecasters: McMullen, Noblitt, Cochran
Date Issued: 09/29/21 5:00 PM CST
Technical discussion:
The 12Z GFS model run was used in the forecast today because it handled the movement of the LPS over South Dakota and it's associated front with more accuracy than the NAM. GEFS and SREF plumes were referenced for temperatures and hourly and total QPF values. Lastly, GFS soundings were used to evaluate CAPE and LI values as well as timing for precipitation.
The 250-mb plots of heights, winds, and divergence show a long-wave ridge dominating the central United States at the start of the forecasting period until Saturday around 15Z. This keeps the area in meridional flow with southerly winds until an approaching LPS shifts our winds to the SW Saturday afternoon.
Vorticity plotted against heights at 500 mb shows Missouri under the influence of an area of PVA from the exit of the upper-level ridge. This circulation continues to build as we move later into the week, supporting cloud development for the region. More vorticity approaches with a LPS over Kansas as we move into the beginning of the weekend.
A collection of moisture takes place over Columbia seen on the 500-mb plots of heights, vertical velocity, and relative humidity. The start of the building moisture comes from the Gulf region and meets up with moisture coming from the western LPS. Our area is saturated at this level from Thursday at 12Z until the conclusion of the forecast period.
The 850 mb plots of heights, winds, and temperatures show that the low level jet is prominent for the time period, aiding in moisture advection. However, the 1000mb-500mb thickness and MSLP plot show little to no temperature advection, so no drastic changes in temperatures are expected.
The GFS soundings show the atmosphere becoming more and more saturated throughout the rest of the week. They also show the maximum value of CAPE reaching almost 1300 kJ on Friday at 21Z. The LI at this time is -4, suggesting a stormy afternoon. GEFS and SREF plumes suggest the total-QPF for the forecast to fall around 0.75 inches.
Future forecasters should pay attention to the approaching LPS and it's associated moisture and vorticity.
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