1. 2. 3. Northern Wisconsin Weather: Wisconsin's drought, Superior's ice, and severe hail criteria. 4. 12. 15. 16. 17. 18. 19. 20. 23. 24.

25. 26. Wisconsin's drought, Superior's ice, and severe hail criteria. 27. 28.

I have been watching the US Drought Monitor this winter and have noticed that a portion of Wisconsin has remained under the D2 category - Severe Drought.

After going back in the archives I found that the trend began on the July 1st 2008. I took each map of Wisconsin since July 1st and created an animation up to the most recent map - 24 Feb.
[Thanks for the help, J!]

The US Drought Monitor uses five indicators to classify drought conditions. More information on these five indicators can be found (here).

In areas where there is snow cover, the melting of snow will lessen the drought conditions because the USGS's streamflow data is part of the assessment. However, the drought classification is also based on present soil moisture as well as recent precipitation. This would indicate that snow melt may not produce a dramatic change and that more precipitation is needed throughout the coming months to prevent the drought from expanding and becoming more severe.

At this time, the driest region is the north-central and northeast portions of the state. Already the NWS in Green Bay has issued their first spring flood outlook. The outlook indicates that because of the dry conditions there will be a minimal threat of flooding across the upper Wisconsin River valley, the Wolf River watershed, and the Green Bay watershed. While this is good news, it may be only the first real effects we see from the continuing dry conditions. With spring planting only a short time away, we may see more impacts as time progresses.

Lake Superior's ice coverage has most likely reached the maximum extent.

As I have been watching the expanding ice on Lake Superior, so has the NWS in Marquette. On March 3rd they published an article to highlight that Lake Superior may have reached the maximum ice coverage for this winter. Along with the article they included this satellite image (to the left).

Thick ice is easily seen as solid white along the south shore of Lake Superior with thinner and broken ice farther from shore.

To get a better look at how much ice has actually formed, I grabbed an image from the Canadian Ice Service's website.

This graphic (to the right) shows a detailed analysis of the ice covering the lake, broken down into sections.
Each section is classified by age, extent, and coverage.

The green areas denote the thickest ice, the purples are medium ice, and the light pink indicates the thinnest ice. The only areas of open water are two small pockets in the center of the eastern section of the Lake, with the light blue coloration.

The Ice Service also has several graphs showing recent and historical data. This graph (to the left) shows the weekly percent of ice coverage this winter (blue bars) versus average ice coverage (green line).

The week of March 5th shows that ice coverage almost reached 100%. We'll have to see what this week brings. Warmer weather and stronger winds may help to break up some of the thinner ice in the middle of the Lake, but the graph shows ice on Lake Superior lingers into May.

Severe hail size threshold change.

The Central Region of the National Weather Service will be changing the threshold definition of severe hail. This map (to the right) shows which areas will see the change -- the blue colored CWA areas.

The change will only be implemented in the Central Region as a test. If successful and positive, the change may be extended to other areas of the US later.

The previous criteria for severe hail was 3/4" diameter or greater - this is general equivalent to a penny. The new criteria will be 1" - the equivalent of a quarter - and will be fully functional by July 1st (many will do so before July).

Based on a five-year trial in Kansas, it appears that hail less than 1" does not do sufficient damage to issue warnings. Once hail approaches 1" in diameter it begins to cause physical damage and then deserves a warning. It is believed that this change will reduce the number of marginal hail warnings.
Unchanged will be the wind threshold of a severe thunderstorm warning at 50 knots (50 mph).

An online video discussing this change can be viewed (here).

So far, in Wisconsin, the NWS offices in Green Bay and in Milwaukee have stated they will will implement the new threshold on April 1st. The other offices serving Wisconsin have not issued a statement concerning the change yet.

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