Current Conditions at Sanborn Field

 

Thursday: Overcast Light Rain Possible. High: 63

Thursday Night: Light Rain. Low: 48

 

 

Friday: Partly Sunny. High: 70

 

 

Friday Night: Light Showers. Low:51

 

 

 

Saturday : Clearing to Mostly Sunny. High: 68

 

 

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Discussion:

Prepare for a chance for rain today, tonight, and overnight Friday. Make sure to bring a raincoat or your trusty umbrella!

-Samson

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Forecasters: Hefner, Macko, Samson

Date Issued: 4/27/2023 10:00 AM CDT

Technical Discussion: 

 

The biggest concerns for this forecasting period (Thursday 12Z to Sunday 00Z) are rain chances Thursday and Thursday night and overnight Friday, potentially into Saturday. The GFS and NAM resolved most features similarly; however, preference was given to the GFS because it has been trusted more over recent forecasts than the NAM.

Beginning at the 250mb level, a shortwave trough is situated over the Oklahoma-Texas panhandle. As this shortwave begins to propagate towards the northeast on Thursday, moving into the Ohio River Valley, upper-level divergence will occur ahead of the shortwave. The upper-level divergence indicates lower-level convergence, which is rising air motion. However, none of this upper-level divergence will occur over Columbia. When the shortwave has passed through, and out of the Columbia area (Friday 09Z), a deepening trough will propagate into Missouri on Saturday at 00Z. This trough will bring upper-level divergence, affecting the Columbia area at 09Z. However, this upper-level divergence only lasts for a short time.

 

Continuing with forcing features at the 500mb level, the shortwave trough noted above, as it propagates to the northeast, slight circulation (spinning air parcels) starting at 12Z Thursday will pass over Columbia with the shortwave’s passing. There will always be very minimal amounts of circulation passing over Columbia. Although as the trough talked about above begins to pass over Columbia, circulation will ramp back up starting at 03Z Saturday and continue until 21Z Saturday. After 21Z Saturday, the circulation associated with the trough will have passed through and no longer affect Columbia.

 

While the circulation is more consistently present at the 500mb level, vertical lift is not as prevalent at the 700mb level. Negative Omega values remain on the lower end until 03Z Saturday with the passage of the longwave trough. At 03Z Saturday, negative Omega values will increase with trough propagating and last until 15Z Saturday. This lift and relative humidity could lead to cloud formation and potential for precipitation if saturation is reached (relative humidity >90%). And Columbia will have consistent moisture support at the 700mb level starting at 15Z Thursday and continuing until 15Z Saturday when the atmosphere will dry out. Since there will be significant negative Omega occurring 03Z Saturday with the moisture support, there is potential for rain.

Moving on to moisture support at the 850 mb level, the GFS is resolving notable relative humidity (values >70%) from 12Z Thursday until 15Z Saturday. A brief dry patch will last until 18Z Saturday when moisture will build back in. The present moisture increases our rain chances today, tonight, and overnight Saturday. The low-level jet will not impact Columbia until 00Z Sunday when a low-level jet will bring cold, moist air into the Columbia area from the north.

Speaking of cold air, at the surface level, there will be cold FROPA between 03Z and 06Z Saturday. This cold FROPA will play a role in our rain chances for Saturday morning.

When diagnosing rain chances for this forecast, GFS forecast soundings were used. Soundings for Thursday at 18Z show upper-level saturation over Columbia from 850mb level to around 700mb, with dry air between the 850mb level and the surface. At this point, it appears to be a coin flip over whether or not rain will happen today. Saturation could evaporate and not hit the surface, or any precipitation that reaches the 850mb level could cause the dry layer to saturate, allowing rain to reach the surface. Rain, however, does seem more certain at 09Z Friday, where the air between the surface and the 850mb level will moisten. However, any rain that will occur seems light due to low negative Omega values. Rain seems more likely overnight Friday starting at 06Z Saturday. This rain could potentially last into the daytime Saturday (12Z). Similar to rain on Thursday, any rain that will happen will be on the lighter side due to weak forcing.

For precipitation amounts and temperature for our forecast, the National Blend of Models and SREF plumes were consulted for guidance. For total precipitation, Columbia could get .10” of rain and, at the very least, 0.02” of rain.

-Samson