Friday: Partly Cloudy. High: 80
Friday Night: Partly Cloudy. Low: 60
Saturday: Light rain throughout the day. High: 75
Saturday Night: Heavy rain, Thunderstorm possible. Low: 42
Sunday: Chance rain. High: 50
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Discussion:
Temperatures are cooling as we get some rain this weekend. Light rain will begin midmorning on Saturday and increasing into the night with possible thunderstorms. There are chances of rain on Sunday, however there is some uncertainty on when the rain will stop.
-Allen
Forecasters: Sallot, Allen, McGuire
Date Issued: 4/14/2023 10:00AM CDT
The main concern of this forecast is a cold front bringing thunderstorms on Saturday night into Sunday, with the possibility of these storms being severe.
Upon initialization and for the beginning of the forecast period, there was much agreement between the GFS and the NAM, but differences in timing and intensity of the cold front lead to some uncertainty in the precip type in the overnight hours, but overall, both models were used to construct this forecast.
On Friday, we are still under the influence of the Rex block as it continues to push to the east. A negatively tilted longwave trough moves through the Rocky Mountains around Saturday 00z and moves into the plains, reaching MO by Sun 00z. The jet stream is stronger on the west side of the trough, helping to amplify this trough. The meridional nature of this longwave enhances rising motion and upper level divergence on the east side of the trough. This upper level divergence is prevalent in central and northwestern MO around Saturday 06z to Sunday 09z, supporting the development of precipitation and convection on Saturday night.
At 500mb, a shortwave passes through NE, IA, and northwest MO around Saturday 09Z. The NAM resolves this shortwave further south and east, closer to the forecast area, compared to the GFS. Either way, this shortwave may help advect vorticity and support the development of clouds and precip Saturday night.
There is saturation at 700mb around Saturday 09z to around Sunday 21z in the GFS, but the NAM holds onto the moisture a little longer until about Mon 00z. This plentiful moisture coupled with rising motion on Saturday around 09z to about Sunday 18z will further support precipitation on Saturday night and Sunday.
Analysis of forecast soundings indicate thunderstorm development around Saturday at 18z to 21z. High CAPE with low CIN around this time indicates a possibility for severe thunderstorms.
Additionally, the soundings show a saturated column below freezing until the near surface layer during the precipitation on Saturday night. A shallow warm layer with surface temperatures around 36F to 38F (NAM and GFS respectively), some frozen precip may reach the surface, but with the warm soil temperatures, no accumulation is expected. As such, the precip type will likely be mixed. The precip should be only rain on Sunday, as the temperature rises throughout the day.
- Sallot
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