SIOUX CITY, Iowa (KCAU) – Portions of Siouxland could see severe storms Wednesday evening into early Thursday morning.
The Storm Prediction Center (SPC) has already issued a slight risk for severe weather for most of Siouxland.
Scattered severe storms are possible around the Siouxland area Wednesday, with the main area of concern sitting under the slight risk.
Given the current weather patterns Siouxland has experienced over the past few days, severe storm production is possible for Wednesday, especially since Wednesday is looking to be another hot and humid day with plenty of sunshine throughout the morning and afternoon.
The potential for severe weather Wednesday is looking to move into the area late Wednesday night, with storms possibly moving through during the overnight hours into early Thursday morning.
The main threats for Wednesday night’s storms include the possibility of severe wind and hail.
The storms that are projected to move into the area are looking to move in between 10 p.m. Wednesday and 5 a.m. Thursday. The projected storms will most likely be moving in a line that is oriented north, south through the area and should not last all night.
With the potential incoming storms Wednesday night, Siouxland could see periods of heavy rainfall as the storms pass, lots of lightning, hail up to an inch in diameter or larger possible, and winds up to 60 mph or higher. The threat for tornadoes at this time is so minimal it is not likely one will be produced.
Below is additional background information on severe storm classification.
The National Weather Service (NWS) has three specific criteria for storms to be classified as severe:
- Wind gusts up to 60 mph or higher
- Hail one inch in diameter or larger
- A tornado is produced
As soon as one of the three criteria is met, the NWS will issue a severe thunderstorm warning for the storm that is producing high winds, large hail, or a tornado. Only one of the guidelines has to be met for a storm to be labeled as severe. If a tornado is radar indicated or spotted by a trained spotter, the NWS will then issue a tornado watch and possible warning.
Watches vs. warnings:
- A watch is usually issued when conditions are favorable for severe storm or tornado production.
- A warning is issued when one of the three criteria listed above is met for severe weather.
The SPC has six different storm categories from general thunderstorm risks to a high risk, and each category has a general explanation of what an area can expect severe weather wise. The categories and a general definition with some examples are listed below.
- General thunderstorm risk:
- This risk doesn’t have a label and is shown by the lightest green shade (see SPC outlook image above). When a thunderstorm risk is put out, there are typically no severe storms expected in the thunderstorm risk area. Lightning and flooding are still possible threats as they will always be with any risk category.
- Marginal risk:
- This risk is the darker green on an outlook map with the label MRGL. When a marginal risk is put out, isolated severe thunderstorms are possible. Storms typically don’t last long and don’t necessarily cover as large of an area as they are usually isolated storms. Marginal risk storms can be strong to severe with the main threats including large hail up to the size of a quarter and strong winds up to 60 mph possible.
- Slight risk:
- This risk is the yellow color on the outlook map with the label SLGT. When a slight risk is put out, scattered severe storms are possible. This means you could see a cluster of storms that go severe vs. an isolated storm like in the marginal risk. Slight risk storms are also typically short lived. The main threats with severe storms in a slight risk are generally large hail possible and high winds, tornadoes cannot be completely ruled out on a slight risk day.
- Enhanced risk:
- This risk is the orange risk on the outlook map legend with the label ENH. When a slight risk is put out, numerous severe storms are possible. This means clusters of storms could be severe, more persistent. With an enhanced risk, all types of severe weather are possible from large hail, high winds, and tornadoes.
- Moderate risk:
- This risk is the red risk on the outlook map legend and has the label MDT. When a moderate risk is put out, it means widespread severe storms are likely. These storms are more likely to be widespread, intense, and long-lived. Moderate risks are issued when significant severe weather is likely for an area, meaning tornadoes are likely along with large hail and high winds.
- High risk:
- This risk is the pinkish risk on the outlook map legend and has the label HIGH. When a high risk is issued, it means widespread severe storms are expected. These storms are typically long-lived, very widespread, and particularly intense, meaning all forms of severe weather are likely with high winds and large hail expected.