Nice October weekend; NWS changes ‘severe risk’

Frost on the pumpkin

Frost laced the rooftops around the Weather Lab on the Prairie this morning in the southwest metro.

We actually tied the coldest morning so far this year in the Twin Cities as temps bottomed out at 35 degrees at Minneapolis-St. Paul International Airport today. Here are some other low temps today, as many locations saw the coldest temps of the fall season so far.

• 33 degrees St. Paul and Eden Prairie

• 28 degrees at Lakeville

• 19 degrees at Fosston in northwest Minnesota

Yes, Jack Frost will soon routinely grace Minnesota spruce trees. Friday and Saturday mornings have a 50-50 shot at delivering the first 32-degree temp of the season at MSP Airport.

Nice October weekend

All things considered, this will be a pretty decent weekend for mid-October. The high pressure cell I've been tracking all week drops south from Canada into Minnesota tomorrow. By Saturday, we are on the back side of the high. That means a milder southwest air flow, and temps should respond nicely toward 60 degrees on a sunny Saturday afternoon.

Here's the breakdown through the weekend. The sprawling high pressure cell  delivers plenty of crisp October sunshine, and temps will gradually respond as southerly winds return. I still think the National Oceanic and Atmospheric Administration's Global Forecast System output (below) is too pessimistic on temps Saturday afternoon.

My money is on at least 60 degrees for the metro Saturday afternoon.

Hints of Indian summer next week

The most recent model runs continue to support the notion of Indian summer late next week. Check out the GFS upper air chart for Saturday Oct. 18, as a nicely amplified high pressure ridge builds over the Upper Midwest.

It's early to be precise, but the GFS still pushes a few days of upper 60s into the metro, with a shot at the so far elusive in October 70 degree mark.

NOAA: How about some additional severe risk categories?

Without being too snarky, let me just say right up front I'm not a fan of this decision. As somebody who communicates weather risk to a large audience every day, I know how much clear communication is critical in weather. NOAA's decision to add two more 'risk categories' muddies the waters in my opinion.

Starting Oct. 22, NOAA's Storm Prediction Center adds "marginal" and "enhanced" to the current slight, moderate, and high risk categories for severe weather in their convective outlooks.

Here's the logic from NOAA.

The SPC will revise Day 1 through Day 3 categorical severe weather outlooks to better communicate risk and describe the likelihood of severe weather. Format changes will also improve the use of SPC severe weather forecasts for customers who incorporate SPC outlooks into GIS systems.

The SPC is expanding the risk categories from four to five and clarifying the risk previously labeled as "See Text." That descriptor will be replaced by a categorical line and the term "Marginal" to denote areas with a 5 percent probability of severe weather. The upper end of the "Slight Risk" category will be renamed "Enhanced" (short for "Enhanced Slight") to denote a threshold 30 percent probability of severe wind or hail and/or a 10 percent chance of a tornado during the Day 1 period. For Days 2 and 3, the "Enhanced" risk category will denote a 30 percent total severe probability. The Moderate and High risk thresholds will remain essentially unchanged.

Current:

1. See Text

2. Slight (SLGT)

3. Moderate (MDT)

4. High (HIGH)

Proposed:

1. Marginal (MRGL) - replaces the current SEE TEXT and now is described with Categorical line on the SPC Outlook.

2. Slight (SLGT)

3. Enhanced (ENH) - will replace upper-end SLGT risk probabilities, but is not a MDT risk

4. Moderate (MDT)

5. High (HIGH)

My view is that the current risk categories (slight, moderate, high) provide plenty of descriptive benefit for the weather consumer. I also believe NOAA's SPC and the current state of the science of meterology lacks the precision and resolution to accurately refine severe weather risk into additional categories. There are enough days when a moderate risk produces little severe weather, and when slight risk areas produce widespread damage.

At this point, I am not likely to change the terms I use on air to communicate with our weather audience. Will a 'weather stoplight' with more than three colors really produce any benefit to our audience?

I am very curious to know what you, the Updraft reader and severe weather consumer, thinks of the changes, so please, let the comments fly!