Current Conditions at Sanborn Field

Monday Night: Rain. Low:52

 

Tuesday: Cloudy with scattered showers. High: 65

 

Tuesday Night: Rain with chance of thunderstorms early evening. Low: 42

 

Wednesday: Cloudy with rain. High: 46

 

Wednesday Night: Cloudy with intermittent showers. Low: 38

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Discussion: 

Get your umbrellas ready for wet and cool weather for the next few days! A low pressure system from the Southwest United States will be the cause of our gloomy weather this week. A majority of the severe weather associated with this system will remain to our south in Texas and Louisiana; however, there is a chance for thunderstorms Tuesday night! Temperatures will continue to fall with the passage of a cold front early Wednesday morning. Precipitation values are expected to be about 0.5" to 0.75" Wednesday night.

-McMullen

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Forecasters: McMullen, Millsap, Cochran

Date Issued: 3/21/2022 05:00PM CDT

Technical Discussion: 

 

The model chosen for this forecast was the NAM, mainly due to its sufficient handling of an incoming low-pressure system and accuracy in relation to observed surface temperatures. A low-pressure system is moving from the Four Corners region into the Central Plains. Persistent rain will occur ahead of the system as it moves closer to the CWA. Since there is also a small chance of thunderstorms, RAP and HRRR were also utilized.

Wind speed and divergence plots at 250 mb show a significant amount of upper-level divergence near the entrance region of a jet streak as an highly amplified trough slowly moves its way across the western CONUS. This divergence suggests that the atmosphere will become unstable. The CWA sits underneath the jet stream until Wednesday morning, resulting in cooler conditions in store for that day. The 500 mb vorticity map showed a great amount of circulation surrounding the trough around 00Z Wednesday, further indicating meridional flow in the central CONUS.

According the the 700 mb relative humidity map, there will be significant moisture present at the mid-levels which stays to the north and south of the CWA on Tuesday. The model soundings indicate saturation at the surface, however since the remainder of the atmosphere remains dry, precipitation on Tuesday may be light. Moisture will then be reintroduced on Wednesday as the soundings become more consistently saturated in the lower to mid levels. Decreasing omega values indicate significant lift ahead of the trough on Monday night followed by an equally significant downdraft overnight. This could be evidence of the atmosphere becoming increasingly unstable and then later producing precipitation due to the downdraft.

850 mb winds maintain a southerly component until late Wednesday afternoon, adopting a northerly direction as the low-pressure system passes over the CWA. In comparison, winds at the surface are primarily southeasterly on Tuesday with solenoids and modest wind speeds indicating WAA. This should help maintain warm temperatures until Wednesday afternoon as winds will shift to a WNW track, introducing cooler temperatures into the Mid-Mississippi River Valley.

Model soundings indicate significant moisture throughout the atmosphere Monday night and throughout the day on Wednesday. At 03Z Tuesday, omega values significantly lower than -10 are located throughout the mid to upper atmosphere. Despite this, a minuscule MU CAPE value of 29 J/kg would not be enough to encourage significant convection. The possibility of thunderstorms remains slight through the forecast period, although the greatest chance will come on Tuesday evening. The 18Z sounding on Tuesday showed greater CAPE values nearing 1000 J/kg and a veering wind profile, meaning that the possibility for thunderstorms Tuesday evening can not be ruled out.

-Millsap