After a quiet and warm start to the work week, the weather will begin to become more active Tuesday night into Thursday as a couple disturbances move through the region. A low risk of severe weather is in place f
A deep upper-level trough is expected to dig into the Oklahoma and Texas panhandle on Wednesday evening with a strong jet stream from the Southern Plains through the Mid-Mississippi Valley. At the surface, a low pressure center will develop over north central Kansas Wednesday morning, moving eastward through the day. A cold front will drape south of this towards New Mexico with a warm front to the east towards the Ohio Valley. Meanwhile, a secondary center should form over the Texas panhandle during the afternoon hours.
These synoptic features will set the stage for widespread thunderstorm development throughout the region Wednesday afternoon and evening. Temperatures south of Interstate 80 are expected to peak into the 70s with a wide open Gulf advecting plenty of moisture northward, equating to dew points in the 60s and precipitable water values around 1.25″. The GFS is the most aggressive with CAPE (commonly used to visualize instability) values well over 2,000 j/kg over south central Iowa.
Some elevated storms may be ongoing early Wednesday morning ahead of the northward-moving warm front. These should clear by mid-morning. However, as the low and southward-draped cold front approaches the area, elevated scattered showers and thunderstorms should begin to re-develop. A strong cap initially will prevent these from becoming surface-based. Models show the cap being punched closer to late afternoon, with the best window for severe storms being roughly around 5:00 p.m. to 8:00 p.m. south of Interstate 80. Strong updrafts ahead of the front would support primarily a large hail threat, though gusty winds is still possible. The tornado threat will be greatest near the low, though this would be a bigger concern if the warm front decided to stall out closer to the activity as opposed to accelerating northward.
Ultimately the severe threat should wind down past sunset as the environment wanes down. Rain will continue overnight before drying out Thursday morning. The SPC has removed eastern Iowa completely from the threat Thursday; cooler and dryer air will be in place across the state before we rebound closer to the weekend.
Stay tuned to the Iowa Weather Network for the latest information!