Current Conditions at Sanborn Field 

 

 

Tuesday Night: Cloudy. Thunderstorms, some may be severe. Low: 63

 

Wednesday: Overcast. Thunderstorms ending around noon, rain continuing. High: 63

 

Wednesday Night: Clouds clearing out. Low: 36

 

Thursday: Partly Cloudy. High: 60

Thursday Night: Scattered clouds. Low: 43

 

 

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Discussion:

Today's warm and windy weather will be fueling storms to our north and eventually in mid-Missouri. Throughout tonight and into tomorrow, the strong southerly wind will continue until a cold front passes through around 7AM CDT, causing thunderstorms to begin about three hours prior. These thunderstorms could become severe with impacts including strong winds, heavy rain, damaging hail and possibly an isolated tornado. Once the cold front passes, temperatures will drop throughout the day causing us to hit our daily high temperature early Wednesday morning. The thunderstorms will subside into showers around noon on Wednesday and continue raining until around 10PM CDT Wednesday night. After the rain stops, the sky will begin clearing giving us a pleasant, although slightly cool, Thursday and Thursday night.

-Alexander

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Forecasters: Alexander, Duff, Orr

Date Issued: 04/12/2022 5:00PM CDT

Technical Discussion: 

The problem of this forecast stems from a deep mid-level trough and low-pressure system with an associated cold front that will move through Missouri late Tuesday night and early Wednesday morning. The biggest problem is diagnosing convection and the chance for strong and severe thunderstorms. The Storm Prediction Centers outlook for day includes a Slight risk for Columbia. The biggest risk for Mid-Missouri is the possibility of heavy rain, hail, and strong wind gusts. An isolated tornado cannot be ruled out.

Due to the difficulty of this forecast a few different models and products were used. The NAM was chosen for its placement of the surface low over the Central Great Plains and for its handling of surface temperatures. Since severe weather is expected the NAM Nest was used for its convective application. Both models’ soundings were useful in diagnosing timing and convective potential. After the event, both the GEFS and SREF have significant spread in forecasting surface temperatures and the NAM has a significant cold bias. So, the NBM was used to forecast surface temperatures for the end of the forecast period.

At the top of the atmosphere, divergence associated with the right entrance region of a jet streak at 250mb aided in the development of showers yesterday. The jet streak moves off to the northeast today and, behind it, another jet streak rounds the base of a shortwave trough over the Western CONUS. The greatest divergence associated with this streak occurs early Wednesday morning.

The shortwave trough and low pressure are evident at 500mb and move towards Missouri over the next 24 hours. Vorticity at this level is minimal for the type of weather expected early on Wednesday. High values of vorticity are apparent as a negatively tilted trough approaches Wednesday afternoon. This is likely the support for any rain and thunderstorms that will occur later Wednesday.

The atmosphere will remain dry at the 700-mb level until early Wednesday morning when moisture associated with the low-pressure system moves in. It is likely that any moisture to support storms later Tuesday and overnight will be at the lower levels. Higher values of Omega are also present around the same time.

More moisture is apparent at the 850mb level and relative humidity values are above 80 percent. This will aid in the development of any storms. A low-level jet has been pumping warm air and moisture into Mid-Missouri over the last 12 hours. 1000-500mb thickness and MSLP plots indicate significant warm air advection into the region on Tuesday. The southerly LLJ helps to create wind shear, which is important for the development of any storms.

A strong southerly wind at the surface has been advecting warm air and moisture into Mid-Missouri throughout the day on Tuesday. The forcing mechanism for this event is a cold front which is expected to move through around 12Z Wednesday. After the passage winds will become more northerly and temperatures are expected to drop throughout the day.

The use of soundings in this forecast was helpful in diagnosing any potential hazards, the extent of the severe weather, as well as the timing. According to NAM soundings thunderstorms are expected to start after 08Z Wednesday and continue throughout the morning. After the passage of the cold front the atmosphere may remain primed for thunderstorms, but the chances dwindle by early afternoon on Wednesday. Tuesday evening soundings forecast an unstable atmosphere with CAPE values greater than 3000 J/kg and significant low level wind shear due a veering wind profile, but a lack of moisture and a significant cap is preventing any development. The greatest threat still appears to be early Wednesday morning ahead of the cold front when the moisture arrives, and the inversion breaks down. NAM Nest soundings for Wednesday morning show signs of sufficient wind shear and CAPE values between 1000-2000 J/kg. The K index is greater than 25 and the Total totals index is greater than 50, both indicating the possibility of severe thunderstorms. Isolated tornados can also not be ruled out at this time.

Overall, the biggest threat is still the potential for heavy rain, hail, and strong winds. Since this event is very dependent on many ingredients future forecasters should watch closely for moisture and how the atmosphere will react after the passage of the cold front.

-Duff