Current Conditions at Sanborn Field 

Friday Night: Mostly cloudy, rain. Low: 62

Saturday: Mostly cloudy with showers in the morning. High: 74

Saturday Night: Cloudy with a chance of light rain. Low: 50

Sunday: Partly cloudy. High: 68

Sunday Night: Clear. Low: 50

Discussion: 

I would keep an umbrella handy with you this weekend as Missouri is going to have a cloudy/rainy forecast. Because of the low pressure system led by strong winds, Missouri will see precipiation that'll be followed up by some thunderstorms and moderate showers. The same thing is going to occur on Saturday but with lower temperatures dipping to the 50s due to a cold front passing through the Midwest. While most of this forecast will be gloomy and sticky, Sunday will be the day we can all look forward to because it's going to be less cloudy with pleasant temperatures. 

-Watts 

Forecasters: Watts, McDonald, Travis

Date Issued: 04/29/2022 5:00PM CDT

Technical Discussion:

The GFS was used for today’s forecast, as it’s initialization of current features - such as low pressure over Southwest South Dakota - was much more accurate in terms of both placement and intensity. Current temperatures were also more accurate under the GFS, whereas the NAM had current conditions too warm. The main forecasting issue of the weekend will be the movement of a powerful low, of which the position will determine the potential for rain. 

 

Though negatively tilted, deep low pressure is visible at 250 and 300 mb, with the system expected to maintain its intensity through the weekend. Currently positioned over southwestern South Dakota, the low pressure deepens further as it slowly moves northeast, finally dissipating over Canada Sunday night. With both the trough and jet stream tracking so far to the north, Missouri will see little activity in the upper atmosphere.

 

While there is still some vorticity present through Saturday morning, the 500 mb level stays quiet for the remainder of the weekend. Strong, tight circulation is associated with the trough to the north, but it stays north of Missouri in southern Iowa through Sunday. A slight southern deviation in this circulation though, could change impacts at the surface. 

 

Moisture content tells a similar story at 700 mb. There is plenty of moisture and omega through Saturday morning, but the atmosphere quickly dries up Saturday afternoon. An abundance of moisture is present throughout the entire weekend in Iowa, though, making the difference between clear and cloudy skies a sharp one. 

 

While cooler air prevails for tonight, warm air begins to be advected into mid-Missouri Saturday morning, as our winds shift from west to South at 850 mb. The winds will shift back to the west Sunday morning, but with wind speeds strengthening and cold air being contained to our north, temperatures should remain warmer. 

 

Surface analysis depicts WAA starting tonight and continuing through Saturday night, raising surface temperatures by more than 10 degrees for tomorrow’s high. Advection dissipates into Sunday, but the northerly trough will likely not extend far enough to change the clam conditions. 

 

GFS soundings show a solid chance of continued rain over the next 18 hours, but the window for strong thunderstorms has likely been shut. CAPE below 1000 J/kg, a K-Index below 30, and CIN values increasing overnight will certainly not produce the kind of severe weather expected over the Great Plains. Weaker storms and continuous rain showers are the only likely precipitation events to occur with these values. Soundings indicate increasingly dry conditions after Saturday afternoon, with moisture not returning until late Sunday night. 

 

Future forecasters should closely monitor the Central Rockies, as another deep low may begin to form there Monday morning. 

 - McDonald