Current Conditions at Sanborn Field

Flood watch in effect from March 11, 6:00PM CST until March 13, 6:00PM CST

Thursday Night - Cloudy. Low: 40-44

Friday - Mostly Cloudy.

High: 50-54

Friday Night - Overcast, Rain beginning between 4pm and 6pm.    Low: 42-46

Saturday - Cloudy, rain continuing throughout the day. High: 50-54

Sunday - Cloudy, isolated showers becoming widespread into the evening. High: 50-54

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Discussion: 

The majority of this forecast period will be dominated by widespread cloud cover and rain as a result of a low pressure system moving into the area. A large amount of moisture is expected to remain in the area throughout the weekend, providing the basis for the significant amount of rain we will experience starting Friday night. Saturday will see a break in the rain during the day because of slightly rising pressures as well as small decrease in moisture in the atmosphere. As the impending low-pressure system approaches the area on Sunday evening, it will bring much more moisture back into the area causing isolated showers in the area to become more widespread moving into Monday. The constant cloud cover will help keep our temperatures around the low 50s throughout the forecast period.

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Forecaster: Lamb, Nixon, Cochran, Travis

Issued: 6:00 PM CST 11 March 2021

Technical Discussion (The nerdy stuff we are discussing in class):

 

    The 20km GFS was primarily used for this forecast because when compared to the NAM, it presented a better handling of temperatures and the placement of the low pressure system sweeping across the western United States. GFS soundings, GEFS, and SREF plumes were also referenced. This forecast period mainly focuses on the low pressure system bringing precipitation throughout the weekend.

    Seen at the 250-mb level, a jet streak starts to emerge over the area Thursday evening. Increasing divergence aloft as a result of the jet streak helps contribute to UVM closer to the surface. The jet streak continues to flow over Missouri until it pushes northward beginning around Saturday at 12Z. A short-wave ridge follows, creating a dry period in the afternoon on Saturday and paves the way for the low pressure system to reach the area around Monday at 00Z.

    Throughout the day on Friday, we will experience sporadic upper-level circulations and UVM depicted by GFS soundings and the 500-mb plot of heights and vorticity. These values increase throughout Friday evening, but decrease on Saturday as the ridge passes through the area. However, as the low pressure system starts to reach Mid-Missouri on Sunday evening, we start to see a vort max move in as the system approaches.

    The 700-mb plot of height and relative humidity shows the area contains large amounts of moisture throughout the forecast period. Through GFS soundings, deep columns of saturation can be seen at various levels throughout the atmosphere starting Friday evening. This remains until Saturday around 15Z due to the incoming upper-level ridge where a dry layer emerges between the 700-500-mb level. However, the atmosphere quickly re-saturates as the low-pressure system approaches around Sunday at 00Z. The GEFS and SREF plumes for total-QPF are predicting around 1.75 inches of rain accumulating throughout the weekend. The NWS has issued a flood watch for the area from Thursday evening till Saturday evening.

    Plots of height and wind at the 850-mb level show winds shifting from westerly to southerly as the low-pressure system approaches. The solenoids present at the surface MSLP and 500-1000-mb thickness plot indicate weak WAA beginning Saturday at 18Z and strengthening out ahead of the low-pressure system. When looking at GEFS and SREF 2-m temperature plumes, there is a large spread in predicated temperatures indicating uncertainty in whether the WAA will be strong enough to affect temperatures.

    The next forecast period should focus on the development of the low-pressure system and its effect on the area.