Thursday Night: Partly Cloudy. Low: 54
Friday: Partly Cloudy. High: 80
Friday Night: Mostly cloudy. Light rain possible later. Low: 60
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Discussion:
Things will remain warm and clear, as the streak of nice weather continues. However, the streak of nice weather will be broken by a chance for rain this Saturday.Forecasters: Chirpich, Cook
Date Issued: 4/12/2023 5:00 PM CDT
The weather recently has been in a warm and clear pattern due to a Rex block pattern set up over the CONUS. This will change over the weekend, as a low moves into the region, bringing with it the chance for precipitation and lower temperatures for Saturday. The GFS, at the time of forecasting, resolved the current conditions better than other models, and was used for the formation of this forecast.
Looking above, the Rex blocking pattern is very apparent at 250mb. There exists a stationary cut off low situated over Louisiana. The GFS models that this low will be forced to move by a deep trough that currently exists over the western CONUS. This trough will move over the inter-mountain west, forcing the low to move off to the northeast gradually throughout the forecast period. As the trough moves farther into the CONUS, it will become negatively tilted. The negative tilt of the trough suggests the possibility for active weather in the Midwest for Friday night into Saturday morning. This is supported by significant divergence signatures at 250mb over eastern Nebraska and western Iowa. These signatures look to stay mainly to the north of our CWA. There are weaker divergence signatures modeled over mid Missouri Saturday morning, suggesting lighter active weather for our CWA Saturday morning. Any activity later Saturday resides outside of our forecast period.
The GFS at 500mb shows widely scattered vorticity signatures over Missouri from Thursday night till Saturday morning. For Thursday night through Friday night, 700mb and 850mb shows no moisture present, disallowing any chance for precipitation. Looking at Late Friday night into Saturday morning, three exists a LLJ at 850mb extending from the Gulf up into Nebraska/Iowa which will serve as a transport for moisture up into the Midwest. This allows a chance for rain Saturday morning as that moisture moves eastward into our CWA. Rain Saturday morning will be light. Any accumulating precipitation that occurs later Saturday resides outside of our forecast period.
The deepened trough is associated with a surface low that is modeled to pass over Iowa, staying to our north. The low will pass to our north during daytime Saturday, and any effects of this surface low, such as major wind shifts and temperature changes will occur later Saturday. Later forecasting shifts should monitor the timing of the passage of the low in order to find the timing and intensity of the effects of the passage of the low.
-Cook
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