Thursday Night: Mostly Clear. Low: 68
Friday: Mostly Sunny. High: 92
Friday Night: Partly Cloudy. Low: 72
Saturday: Mostly Sunny with Scattered Showers and Thunderstorms. High: 84
Saturday Night: Cloudy with Repeated Rounds of Showers and Thunderstorms Likely. Low: 70
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General Discussion:
Above average temperatures will continue through Sunday Morning. There will be multiple chances of rain throughout the forecast period. Severe weather is not expected, but a stray storm could bring strong wind gusts and small hail.
– Franciscus, Russell, Nightingale
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Forecasters: Franciscus, Nightingale, Russell, Daniel
Date Issued: 09/19/2024 5:00 PM CDT
Technical Discussion:
Key Messages:
-Above average temperatures will continue throughout the forecast period
– Precipitation chances will increase, peaking saturday night when a slim chance of severe weather (1 inch diameter hail or wind gusts up to 60mph) will be possible
As of 21:40 UTC we have southeasterly surface winds, a building ridge to the south and a sunny sky. This has allowed temperatures to warm into the low 90s amidst weak warm air advection. Throughout the evening the main upper level trough to the north will eject across the upper midwest bringing a chance of severe thunderstorms along the cold front. Further south into the lower Missouri river valley, forcing is much more subtle and the cap is stronger. Given mid 60s dewpoints, modest to moderate instability and a puff of upper level flow, A severe storm is possible IF updrafts are able to breach the cap and maintain themselves along the cold front. Some uncertainty comes from the strength of the front as it begins to dissipate as the trough and low move off to the north.
Tomorrow, we should see similar temperatures and mostly sunny conditions with highs in the low 90s. Although unlikely, a brief spot shower is possible if the convective temperature can be breached. Given dry air near the surface and a lack of forcing aloft we will more than likely maintain dry and warm conditions with temperatures well above average for mid september. With dew points in the 60s, the air will definitely have a muggy feel with heat indices peaking in the mid to upper 90s. Overnight lows should settle around 70 with a very small chance of isolated convection. Saturday should start off with similar sunny and warm conditions before our attention turns to the threat of widespread convection during the overnight.
Conditions will be mostly sunny with minimal cloud coverage. The clouds that are present will be mostly mid to upper level. Saturday night, there will be a higher chance of precipitation with accumulation of .5 inches. We will also see a greater chance of thunderstorms with severe weather possible if there is a lifting mechanism. A shortwave that is traversing along the upper level ridging will be our primary focus for storm development. Vort max associated with the shortwave makes active weather possible. We will see repeated rounds of thunderstorms of ranging intensity through early Sunday morning. CAPE values are significant but a weak shear and strong cap keeps things from developing initially. As capping weakens, widespread showers and thunderstorms will develop west and shift into the area. While shear is weak, it is sufficient for an isolated severe thunderstorm if the updrafts can maintain themselves. At minimum, storms could contain very heavy rain with high Pwat values over 2 in. If storms train over the same area, isolated flash flooding is possible.
Future forecasters should monitor the approaching trough and progression of the cold front which current modeling indicates will stall to the northwest at the end of our forecasting period.
-Franciscus, Russell, Nightingale