Current Conditions at Sanborn Field
Tuesday: Clearing sky. High: 73
Tuesday Night: Mostly clear. Low: 52
Wednesday: Partly cloudy. Isolated showers in the morning. High: 75
Wednesday Night: Mostly clear. Low: 48
Thursday: Mostly cloudy. High: 62
Discussion:
Did someone order sunshine with a side of clouds? Today and tomorrow will bring us a bit of sunshine as well as some clouds. Mid-morning on Wednesday will be our best chance of rain with accumulations of around 0.05". Mild conditions will persist throughout the rest of the forecast period, and cooler temperatures will arrive later in the week.
- Macko
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Forecasters: Macko
Date Issued: 10/19/21 10:00 AM CST
Technical discussion:
This forecast was guided through the use of the 06Z run of the GFS20. Although both the NAM and the GFS both modeled the low-pressure system in eastern Colorado with accuracy, the NAM was several degrees too warm in modeling last night's low temperature. The GFS, on the other hand, predicted the low temperature correctly.
The most prominent feature at 250-mb is the upper-level jet associated with the area of low pressure over NW Colorado. During the day on Tuesday, the jet will continue to round the trough in this region before moving into NW Missouri during the evening hours. Upper-level divergence is also associated with this system through Tuesday evening. By Wednesday night, the jet streak will lie north of the forecast area with the forecast area falling under the influence of a weaker portion of the jet. Upon moving into Missouri, upper-level divergence becomes decreasingly significant. The upper-level jet will maintain its position over Missouri on Thursday.
At 500-mb, the GFS indicated that there may be some vorticity over the forecast area today, but it would be minimal. By daytime on Wednesday, vorticity with greater magnitude is anticipated over northern portions of Missouri. Central Missouri will also see some vorticity at this time, but it will be of less significance. Greater positive vorticity is indicated late Wednesday and early Thursday which will likely increase the chances of cloudiness Wednesday evening and throughout the day on Thursday.
The GFS 700-mb chart suggests that moisture at this level will reach a relative humidity of 60% by late afternoon on Tuesday, causing the building of some additional clouds in Central Missouri. However, the relative humidity drops considerably by early evening, and further clearing is to be expected. The atmosphere will become increasingly moist early Wednesday morning at this level before drying out extensively during the afternoon hours. Vertical velocity was negligible throughout the forecast period.
At 850-mb, the atmosphere will be much drier on Tuesday. However, this level will become increasingly saturated by the early morning hours on Wednesday, and this is expected to persist through early afternoon. This level will dry out by Wednesday evening. Relative humidity values are anticipated to near 95% by late Friday afternoon. A low-level jet is also seen off to the west during the day on Tuesday, reaching mid-Missouri by Wednesday. At this point, it will have weakened before moving to the southeast.
At the surface, the GFS modeled a cooler night on Wednesday. This is likely associated with the passing of a cold front associated with the low pressure system currently located in NW Colorado. Consequently, cooler temperatures are also expected on Thursday. An area of high pressure is located in central Kansas late Thursday and may impact the weather heading into the weekend.
PWAT values peak at about an inch Wednesday morning. Additional precipitation outside of this time frame is not to be counted on due to low PWAT values. The high relative humidity percentages demonstrated at 700-mb and 850-mb will result in clouds rather than precipitation considering the unimpressive PWAT values.
Future forecast shifts should further evaluate tomorrow morning's precipitation chances and accumulations.
- Macko
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