Storms could dump a lot of rain in a short amount of time Thursday
The threat of severe storms Thursday and Friday is pretty low, but thunderstorms that develop across western and southern Minnesota will be quite efficient rain producers.
In other words, there will be clouds in the sky that are extremely good at making rain.
Evidence of how much moisture the atmosphere is working with was seen overnight in western Minnesota, where the National Weather Service observed an efficient rainstorm in the Madison area. This from the forecast discussion from the Twin Cities office of the NWS:
"This storm happened to hit a rain gauge between Madison and Marietta and it picked up 1.5" of rain in an hour and finished with nearly 2" by the time all was said and done."
Not everyone will get a soaking, but where the stronger cells develop there will be a better chance for higher rain totals.
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"Basically, it's a have the umbrella and rain gear ready kind of forecast if you have any outdoor plans this afternoon/evening anywhere in central and southern MN (save for southeast MN)," the NWS Twin Cities says.
Showers and thunderstorms are expected to be "fairly numerous" this afternoon, mainly west of Interstate 35. The HRRR model shows isolated storms in southwest and south-central Minnesota developing during the mid to late afternoon hours, with more robust convection developing in southern Minnesota after 7 p.m.
The HRRR model is currently projecting 1-4 inches (high amounts very isolated) in southwest and south-central Minnesota, with much lower totals in the Twin Cities (under half an inch).
Meteorologist Sven Sundgaard says it "doesn't look like anything really creeps into the metro until after dark," noting that there could be "isolated good downpours of 1”-2” in a few spots.
"Part of the reason is we actually have humidity (unusual with warmth in almost October), dew points in the low 60s & even higher southwest," said Sundgaard in an email. "Precipitable water content is high (water in the atmospheric column to be squeezed out as precipitation)… in fact double the averages!"
We'll have to see how accurate the HRRR is because the other scenario is a complete bust, which is basically what the NAM computer model is showing. Here's the NAM radar simulation, which is much quieter than the HRRR.
Novak Weather should have a better handle on the situation when he releases his weather briefing Thursday afternoon. Check back for that update.