Current Conditions at Sanborn Field
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Discussion: Clouds will be the trend this week along with a few waves of showers. The first wave of rain will move through tonight with the second wave of rain expected during the day on Thursday. Rain totals will be light with the combined rainfall from both waves of rain expected to be less than 0.50". Keep an umbrella on hand along with a coat as high temperatures will remain below average (avg high: 53) for the remainder of the week.
Forecasters: McCormack, Peine, Smith
Date Issued: 03/07/2023 5:00 PM CST
Both the GFS and NAM were referenced for today's forecast with the GFS serving as the primary model used as it more accurately represented the current SFC pressure systems and frontal zones than when compared to the NAM.
This week sees persistence in upper level maps throughout the week as the jet stream is coasting through the center of the US with jet streaks sitting north of Missouri and little to no divergence aloft. An exiting ridge to Missouri’s east and a strong LPS moving through the center of Canada work together to leave Mid-Mo in an area of zonal flow.
The 500 MB vorticity map shows a small band of circulation moving through Mid-MO at approximately 6-12Z on Wednesday. These maps also show the development of a small shortwave trough that moves through the Upper Rockies and then Upper Midwest and transitions into a cutoff low later this weekend which will have little direct impact on our weather at the surface.
Some moisture enters the region as the 700 MB charts show a developing LPS over the Pacific Northwest sliding into mid-Missouri by 21Z Thursday. This is likely loosely tied with the developing cutoff low from above. Additionally, a HPS over the Gulf of Mexico aids moisture advection and these two regions of moisture will come together over Mid-MO, fully saturating the column of air, as seen on soundings, by 3Z Wednesday. Then as the LPS moves over Iowa, these two systems interact again to saturate the mid to lower levels of the atmosphere on 15Z Thursday. 850 MB charts show the region dominated by WAA until the passage of the Pacific NW Low at roughly 0Z Friday.
At the surface, a HPS will sit over Canada for the duration of this forecast with another seen over the gulf. A small trough will work its way between these two systems. Following behind the trough will be the saturation of the air as previously mentioned. This first saturation will lead to light precipitation starting at 6Z on Wednesday. This is the same time as the vort band moves over and soundings show noticeable levels of lift. However, soundings show low CAPE, a low K index and a high Lifted index so thunderstorms are highly unlikely. The NAM shows significantly more lift but slightly less moisture. Regardless of which model verifies the area will not see a whole lot of rain. Expected totals are 0.1-0.25 inches. This precipitation should peter out by 15Z Wednesday. Following behind this system is another more defined LPS originating over New Mexico. This system will track directly over MO, being directly overhead at roughly 0Z Friday. Although the pressure system is more defined, there is not much in the way of storm producing factors. There is ample moisture for rainfall but nothing to support any level of convection. Rain is expected to start falling at 15Z Thursday and continue until 0Z Friday. The NAM shows the rainfall starting earlier and ending later but it has lower intensity precipitation. Both models agree on the amount expected which will be the same as the previous showers, 0.1-0.25 inches. This will bring us to an expected 0.2-0.5 inches of rain for the whole week. Regardless of these rain events, temperatures will remain relatively consistent throughout the week. Highs will be in the mid 40s and lows in the upper 30s. These temperatures are slightly lower than average for this time of year which is 53 degrees. Soundings show that the sky will be full of clouds with very little sunshine making it through for the remainder of the week.
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