Current Conditions at Sanborn Field
Wednesday: Overcast. Rain beginning early afternoon building into the evening. High: 71
Wednesday Night: Chance of isolated thunderstorms before midnight. Low: 63
Thursday: Mostly cloudy with morning fog. High: 73
Thursday Night: Mostly cloudy. Low: 65
Friday: Sky clearing mid-morning. High: 79
Discussion:
Better keep that umbrella handy--today brings our best chance of rain, with accumulations being just under a 1/4". Going into tonight, don't be surprised if you hear a rumble of thunder or two, as we are expecting some isolated thunderstorms this evening. These should clear out by midnight. For the remainder of the forecast period, we will remain dry and cloudy before the sky begins to clear Friday morning. Friday will also bring us some warmer temperatures as we head into homecoming weekend.
- Kobielusz, Macko
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Forecasters: Kobielusz, Macko, Bongard
Date Issued: 10/6/21 10:00 AM CST
Technical discussion:
The 06Z run of the NAM40 was used to create this forecast. Both the GFS and the NAM accurately depicted current conditions, but the NAM has been repeatedly selected as the model to help forecast the activity of this system. Soundings for Columbia were also utilized in rain, thunderstorm, and fog potential.
The 250-mb plot is dominated by an upper-level low pressure system near the Missouri-Arkansas border. Throughout the day on Wednesday, this LPS is expected to continue to push north into mid-Missouri. Upper-level divergence was detected for the early evening hours, adding to the possibility of thunderstorm development. By midnight, Columbia will be under the center of the low before moving northeast on Thursday. The jetstream off to our west will cross the Missouri-Kansas border overnight on Thursday before making it to Columbia during daylight hours Friday.
The NAM40 500-mb plot indicates increasing vorticity throughout the day today. Maximum vorticity is anticipated just before midnight tonight, further encouraging thunderstorm activity. Vorticity begins to weaken during the night on Wednesday before dissipating on Thursday.
There is significant moisture at the 700-mb level throughout Wednesday with relative humidity values exceeding 95% due to southerly winds, leading us to believe that it will not only be cloudy but also that precipitation is likely today. The relative humidity values will decrease slightly throughout the night. The change in humidity overnight into Friday is much more significant as the atmosphere turns even drier, reducing the amount of cloud cover we will see on Friday.
Less moisture is evident at 850-mb today, although the layer is still moist (RH ~ 75-85%). The layer will gradually dry out through Friday. The winds at this level are also rather calm, reaching a maximum speed of about 20 knots today. As it concerns advection, the NAM40 showed that there would be a mix of both WAA and CAA over Columbia throughout the day today. However, neither seemed to be of great significance.
At the surface, we consulted soundings to assess our chances for thunderstorms and potential fog development. The CAPE values found in these soundings were less than those seen using the NAM40 yesterday. Due to the decreased convective potential, it is unlikely that any of the thunderstorms we will see this evening will be strong or severe. However, K-values have remained relatively consistent in the lower 30s, suggesting that isolated downpours may be associated with the showers and thunderstorms today. Upon analysis of a sounding for 12Z tomorrow, temperatures and dewpoint temperatures overlap along with calm winds leads us to believe that there is a potential for fog.
- Kobielusz, Macko
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