Current Conditions at Sanborn Field
Wednesday Night: Rain overnight. Low: 62
Thursday: Cloudy with afternoon showers. High: 70
Thursday Night: Cloudy. Low: 61
Friday: Overcast with a slight chance of afternoon showers. High: 62
Friday Night: Clearing through the night. Low: 42
Discussion:
Mid-Missouri has a rainy and cloudy week to look forward to as fall weather sets in. As moisture is brought in by southwesterly winds, Wednesday's rain will continue through the night leaving Thursday overcast with afternoon showers. Thursday night will see the beginning of our falling temperatures with a wind shift to the northwest. Friday brings a slight chance of afternoon showers as an approaching low pressure system brings additional moisture into the area. Temperatures continue to drop through Friday night reaching into the low 40s. Total rainfall for the rest of this week is expected to be approximately 1.25".
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Forecasters: McMullen, Noblitt, Cochran
Date Issued: 10/13/21 5:00 PM CST
Technical discussion:
For this forecast, the 12Z run of the GFS20 was chosen. The pressure contours of the NAM and the GFS surface maps looked similar to the 15Z surface map produced by the NWS. However, the GFS performed better than the NAM when modeled surface temperatures were compared to the current temperatures. GFS soundings were used for sky conditions and GEFS plumes were used for temperatures and QPF values.
At 250 mb, heights, winds, and divergence show upper-level divergence over our area brought in by the trough over the Four Corners region at 4Z Thursday. This positively-tilted trough will continue to move through Mid-Missouri during the rest of our forecast period. The jet stream continues to strengthen over the Central US through the rest of the week.
At 500 mb, heights and vorticity show increasing vorticity from Wednesday night into late Thursday morning. We can see circulation building again from 9Z Friday over Mid-Missouri reaching a vort max at 8Z Saturday. A small area of increasing vorticity moves through our area about 12Z Saturday. These bands are brought in with the trough moving through the Central US. These areas of vorticity will aide in cloud development throughout the forecasting period.
At 700 mb, heights, vertical velocity, and relative humidity show a steady line of moisture moving into our area from the SW. This line of moisture will gradually move NE, eventually joining with saturation associated with the previously discussed upper-level trough. This moisture will leave our area at the end of our forecasting period.
At 850 mb, heights, winds, and temperature show continuous southwesterly flow through 21Z Friday. At this time, we will see a sharp shift in the winds to the NW. This coincides with strong CAA and a cold front as seen in the MSLP and 1000-500 mb thickness plots. This all leads to a decrease in temperatures throughout Friday and into Saturday.
GFS soundings show no indications of severe weather with no significant CAPE or LI values. Columns of saturation which will lead to cloud cover and periodic showers for the rest of the week. Rainfalls totals are expected to be about 1.25" for the forecasting period based on the GEFS QPF plumes.
Future forecasters should pay attention to the exiting trough.
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