Today's updated U.S. Drought Monitor confirms what I've suspected and posted about this week. Drought is expanding its foot print on northeast Minnesota.
The latest report out today plunges Minnesota's Arrowhead region into the "severe drought" category. Moderate drought now covers most of northeast Minnesota and extends southward into the northern metro.
Rain chances increase:
Our long awaited western weather system is finally here.
Thankfully, rain chances will gradually increase across much of Minnesota through tonight into Friday. The trick with this system will be getting soaking rains in any widespread fashion. Such is often the nature of spring and summertime "convective" precipitation.
Two part system?
There are increasing signs this system will come in two waves. Wave 1 is bringing some showers to primarily north central Minnesota today.
Wave 2 is expected to trigger showers and thunderstorms in northwest Iowa and send them plowing into southern Minnesota this afternoon and evening. This second wave appears to have the best shot at brining a much needed half an inch or more of rainfall to the southern half of Minnesota.
NAM 84 hour rainfall forecast hints at the potential for a "split" rain pattern with heavier bands north and south of the metro.
Slight risk of severe weather:
There is a slight risk that a few of the storms that do develop through tonight could reach severe limits. Remember, a severe thunderstorm is defined by winds of at least 58mph and hail at least 1" in diameter. The NWS smartly upgraded the hail size threshold for severe thunderstorms from 3/4" to 1" last season in the central U.S. region, and took it nationwide this year. Studies have shown that it takes hail about 1" in diameter to begin to cause damage to crops and property.
Many of the best minds in severe weather work at the NOAA's Storm Prediction Center in Norman, Oklahoma. One of the things they do is differentiate between the likelihood of severe weather types, such as large hail, high winds or tornadoes. The best threat for (isolated) damaging thunderstorms appear to be from large hail and high winds through tonight, and not as much from tornadoes. While SPC mentions the remote possibility (2%) of an isolated tornado in the Upper Midwest, the greater likelihood is for large hail and damaging winds (10-15%).
During the 9 years I spent as Chief Meteorologist for the ABC affiliate in Tucson, Arizona I heard this saying more than once. "You're as welcome as rain." That's a compliment in a desert climate. Let's hope you get some meaningful rain in your back yard tonight.