Current Conditions at Sanborn Field
Friday Night: Partly cloudy. Low: 47
Saturday: Mostly cloudy with increasing chance of showers. High: 62
Saturday Night: Mostly cloudy with chance of showers. Low: 57
Sunday: Cloudy with showers and thunderstorms. High: 75
Sunday Night: Cloudy with showers and thunderstorms. Low: 50
Discussion:
Fall festivities may need to go on the back burner this weekend as showers and thunderstorms are on the approach. Temperatures should rise steadily as the weekend progresses as should the chance for showers. A low pressure system is headed this way on Sunday night preceded by developing showers and thunderstorms, with showers expected on Saturday as well. Flooding is a potential concern for Sunday lending unsafe conditions to the roads with around 1.25 inches of rain expected over the weekend. These rainy conditions should begin easing up on Monday.
-Ethridge, Millsap
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Forecasters: Ethridge, Millsap, Cochran
Date Issued: 10/22/21 5:00 PM CST
Technical discussion:
The 12Z GFS was the model of choice for this weekend's forecast. When both GFS and NAM 300 mb heights were compared to the CONUS water vapor satellite, GFS had a better handling of incoming storms and the corresponding low pressure system in the northwestern US. This was outlined by a more amplified trough in comparison to the NAM heights. In addition, there was greater consensus in the GEFS 2m-temperature ensemble models than in the SREF plumes.
Friday night will begin relatively calm with one of the only features of interest being a portion of the jet stream making its exit out of the Midwest indicated by the 250 mb map. The other notable feature would be the increase in moisture at 700 mb, indicative of an increase in cloud cover during the overnight hours.
The following day presents continually increasing cloud cover with a possibility of showers in the afternoon. The 700 mb moisture projection indicates the humidity from the previous night will linger, but nothing stood out in terms of any signs of major precipitation. The same can be said for Saturday night precipitation-wise, but the temperatures will be showing a steady incline. This is likely due to the WAA indicated by the solenoids on the surface level thickness map as well as the veering wind profile on the 12Z soundings. Increasing temperatures associated with the WAA should make the atmosphere more unstable as time progresses, lending a greater possibility of developing showers.
Sunday will make way for the low pressure system's arrival, bringing with it an increased chance for showers and thunderstorms. The 250 mb map showed an amplified trough in the jet stream, which is correlated to the large amount of divergence aloft. This should continue into the overnight hours and into Monday. The 500 mb level indicated a minor ridge over the forecast area followed by a major uptick in vorticity overnight on Sunday around 03 Z. The 700 mb level shows some consensus in regards to the timing of the circulation with omega values displaying a negative value, indicative of upward lift. With over an inch of precipitation expected for the weekend, this lift will provide the energy needed for such thunderstorms to develop. Aside from the steady increase in temperature over the weekend, there will be no drastic changes in this regard. However, the winds at 850 mb show a noticeable increase in speed on Sunday. The winds should also experience a shift to the northwest on Sunday night. This could mean that a cold front will succeed once the low pressure system has passed.
-Millsap, Ethridge
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