Tuesday, November 16, 2021

Tuesday Night:
Increasing clouds. Light showers possible.
Low: 56

Wednesday: Cloudy. Rain. High:61

Wednesday Night:
Clear. Low: 32

Partly cloudy. High: 44

Thursday Night:
Mostly cloudy. Light showers. Low: 34


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It would be wise to wear a windbreaker or bring an umbrella this week as we are going to be getting some strong north and south westerly winds with showers. Warmer temperatures are going to persist throughout the morning, but will be affected by a cold front Wednesday afternoon with temperatures cooling back to seasonal values. Rain will fall Wednesday morning with cloudy conditions persisting through the remaining of the forecast period.

- Watts


Forecasters: Watts, VanUnnik, Bongard

Date Issued: 11/16/21 5:00PM CST

Technical discussion:

The 12 Z run of GFS20 was chosen for this forecast, along with the use of GFS soundings as well as plumes. While the NAM40 showed a slightly closer prediction to the observed temperature at Sanborn Field, it also had a much wider spread in temperatures over the next few days, while GFS20 reached a much better consensus on temperatures, having a smaller spread. Both GFS20 and NAM40 placed the Low Pressure System in the Northwest CONUS well, along with having very similar height contours. The main focus of this forecast is the cold front that will make its way into mid-Missouri on Wednesday.
Tuesday Night begins with a westerly flow at 250-mb, that transitions into a southwesterly flow on Wednesday. With a jet stream reaching the area on Wednesday night. Missouri will experience slight divergence aloft, though it is short-lived. A trough axis generated by the Low pressure system to the North will advect into the area on Thursday, with a slightly positive tilt to it, followed by a wind shift to northwesterly in the afternoon.
An area of circulation is shown on the 500-mb map on Wednesday night, right before the aforementioned trough axis reaches Missouri, bringing with it a stronger circulation pattern, and again, a wind shift to northwesterly.
Moisture is abundant on Wednesday, which is evident on both the 700-mb and the 850-mb maps. The moisture hangs around longer aloft than at the surface, as a cold front dries out the surface sooner than the upper atmosphere.
The 850-mb analysis gives much more detail on the FROPA, which is going to be the reason for most of the weather we will be experiencing these next few days. Tuesday night begins with a southwesterly flow, bringing warm temperatures along with it. Due to the southerly nature, the high temperature on Wednesday will occur overnight. By afternoon, temperatures will be falling as the cold front impacts the region. At 06 Z Wednesday, a LLJ advects over mid-Missouri, and at 18 Z, the NW wind shift occurs. Winds remain northerly until the cold front has left the area on Friday, and future forecasters should see calmer weather.
WAA Solenoids transition into CAA Solenoids from Tuesday night to Wednesday night, as the cold front passes over the area. The 540 line enters the region on Wednesday night. Northerly winds take hold of Columbia from Wednesday morning until Thursday night, when the front has passed and slightly warmer temperatures return.
GFS Soundings, along with moisture profile, helped with cloud and precipitation forecasting. Clouds are on the increase Tuesday night, with rain ahead of the cold front Wednesday morning. About .05-.1" is expected. The 12 Z sounding for Wednesday showed a frontal inversion at 12 Z, and the wind profile helped to forecast timing of the FROPA, 18 Z. The sky remains cloudy throughout Thursday, and begins to clear Thursday night into Friday, again, when weather clears up after the front is no longer influencing weather over Missouri.

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