Thursday Night: Scattered Thunderstorms. Low: 53 F
Friday: Severe Thunderstorms likely by afternoon. High: 70 F
Friday Night: Scattered Severe Thunderstorms Low: 62 F
Saturday: Cloudy in the morning, partial clearing by afternoon High: 81 F
Saturday Night: Severe Thunderstorms Low: 67 F
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General Discussion:
Hello and happy Thursday! We have some thunderstorms that will be passing through the region today that will not pose any type of severe weather threat. Heading into Friday afternoon and evening, severe thunderstorms look likely across the region. Some partial clearing is possible by Saturday afternoon but by Saturday night, severe thunderstorms look to again move into the region again ahead of a approaching cold front.
– Thomas
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Forecasters: Thomas, Melton, Peine
Date Issued: 04/25/2024 6:00 PM CDT
Technical Discussion:
Key Messages:
- 90% confidence in rainfall greater than 0.5 inches before noon on Friday
- Severe thunderstorms and possible tornadoes are expected from Saturday afternoon until the end of the forecast period
Both the NAM and the GFS were used for this forecast. They have some disagreement that will be noted below.
The forecast period begins with a deep, negatively tilted trough over the Rockies and an LPS moving to the northeast at 250mb. There will also be some significant upper-level divergence early Friday morning. With this, a shortwave trough is expected, seen at both 250 and 500mb. Circulation is expected over the forecast area at the beginning of the forecast period until late Friday morning. Moisture will advect through the region from the beginning of the forecast period until early Friday afternoon at 700mb and until late Friday evening at 850mb. High wind speeds at 850mb (40-60kts) associated with the LLJ are expected from late Thursday night through the end of the forecast period. All of this leads to the expectation of rain throughout Friday morning, with 90% confidence that it will accumulate to greater than 0.5 inches, and 60% confidence that it will reach an inch by noon.
As we progress into Friday evening and Saturday morning, an LPS much larger will move from the Rockies towards the Great Lakes region at 250mb bringing with it some divergence Saturday. At 500mb, the region will experience high levels of circulation into the mid-morning hours of Saturday. There is little moisture throughout the day at 700mb, but there will be much more moisture at 850mb on Saturday afternoon and evening. Additionally, there will be significant WAA throughout Saturday. These predictions lead to the expectation of little to no precipitation on Saturday, however there will be increasing clouds throughout the day.
Saturday evening and Sunday morning are when the effects of this large LPS are expected to be most severe. Late Saturday night the LPS will be directly over CO/KS, and there is significant divergence predicted over the entire Midwest at 250mb. Early Sunday morning will bring some circulation over the forecast area, and another shortwave can be seen at both 250 and 500mb during this time. At both 700 and 850mb, there are high amounts of moisture moving into the region beginning Saturday afternoon/evening and continuing until the end of the forecast period. Forecasted soundings throughout Saturday afternoon, evening, and Sunday morning show CAPE values reaching 3,000+ J/kg, LI reaching -8, TT reaching 55, and KI reaching 31. These along with many other factors and indices point to a very unstable atmosphere during this period. Wind barbs from these soundings also show both speed and directional shear. Due to the predictions above, severe thunderstorms are likely on Saturday evening with the possibility of tornadoes.
Future forecasters should continue to watch the large LPS and note how it will continue to affect the region.