The overall weather pattern over the next week or so is expected to remain fairly tranquil with normal temperatures in the low-to-mid 80s. Showers and thunderstorms will be possible tomorrow morning across the northern half of the state. With some modest instability, an isolated strong-to-severe thunderstorm will be possible, however with weak shear, this threat should be fairly minimal. The Storm Prediction Center has a marginal risk of severe weather in place across much of the state for this reason on Tuesday. With some of the stronger storms that develop, wind gusts to 40 MPH and dime sized hail will be possible. High pressure pushes into the area on Wednesday, keeping precipitation chances away through Thursday.
The weather turns more active with a pattern change by the weekend. A cold front will move into the region on Friday morning, extending southwestward from an occluded front and associated 1000mb low pressure center in Hudson Bay – draped roughly from north central Wisconsin to north central Iowa to north central Kansas. This synoptic setup will provide the stage for severe weather development later in the day.
A somewhat ripe environment for severe thunderstorm development will be seen on Friday, however, not without some uncertainty and differences. Moisture will be advecting northward from the Gulf of Mexico with precipitable water values nearing 1.75 to 2 inches in some areas, with associated dew points in the low 70s. This would support a threat of locally heavy rainfall regardless of whether storms are severe or not. Flooding will not be as much of a concern as it has been thanks to the dryer conditions as of late and quicker storm movement.
Temperatures on Friday will reach the mid-80s for most areas Moderate instability should develop by early-to-mid afternoon into the 2500-3500 j/kg range – the capping inversion seen initially should erode as the day goes on. With some sufficient shear expected ahead of the front, showers and thunderstorms should begin developing by the late afternoon hours with large hail and damaging winds possible. The threat should wind itself down after sunset as most the instability tapers off.
There is a little bit of uncertainty with this forecast due to model differences across the American GFS and European ECMWF models. A lot of the details as far as the placement of the frontal boundary and associated shear is going to be the main wild card within the forecast, which will have to be worked out of the next several days. The Storm Prediction Center has placed an 15% area (elevated risk) for a large chunk of the region, which will be ahead of the front. Details should be worked out over the next few days with more clarity and confidence.
Stay tuned to the Iowa Weather Network for the latest information!
