Thursday rain gives way to a nice weekend; signs of a mild winter ahead?

Forecast changes Thursday?

Our next weather system sweeps across Minnesota Thursday. The latest model trends favor a more southerly track with the surface low. That could reduce rainfall totals in northern Minnesota, and focus the heaviest rains and severe risk in southern Minnesota counties.

NOAA's GFS model has now become one of the more southerly solutions and portrays more of a showery glancing blow to the Twin Cities and most of central and northern Minnesota vs. the all-day rain scenario it was painting just 24 hours ago.

The European and other models have also reduced rainfall potential Thursday for the Twin Cities and especially northern Minnesota. The heaviest rainfall zone now favors southwest through southern Minnesota. Here's NOAA's latest NAM model run.

If this was a winter storm we'd be losing what hair we have left trying to pinpoint snowfall totals on the edge of the heavy snow band southwest of the Twin Cities. I'm grateful it's July.

Temperatures: Minnesota nice

A few showers may linger Friday. The weekend looks sunnier. Temperatures in the next 10 days or so are still coming up rosy.

Mild winter ahead?

Climate forecasters keep close tabs on ocean temperatures in the tropical Pacific. They can give us clues to seasonal forecast months in advance. The latest trends in the tropical Pacific show warmer waters brewing.

NOAA's latest El Nino Diagnostic Discussion gives a 70% chance of El Nino conditions forming by next winter.

The forecaster consensus favors the onset of El Niño during the Northern Hemisphere fall, which would then continue through winter. These forecasts are supported by the anomalous subsurface warmth across the eastern half of the tropical Pacific Ocean. In summary, ENSO-neutral is favored through Northern Hemisphere

summer 2018, with the chance for El Niño increasing to about 65% during fall, and to about 70% during

winter 2018-19 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month

period).

El Nino phases can suppress Atlantic hurricane activity and tend to favor milder winters in the Upper Midwest.

Saharan dust event

Here's more on the recent Saharan dust plume blowing across the Atlantic this month. You can see why Saharan dust has been found in soils along the U.S. east coast.

Over the final week of June and into early July, haze settled in over the tropical Atlantic. The plume came from small dust particles that were picked up from the Sahara Desert in Africa and transported thousands of miles by the wind. Besides some beautiful sunsets, it has meant poor air quality in the United States and a relatively quiet period during the 2018 Atlantic hurricane season.

Plumes of African dust across the Atlantic are not uncommon. In fact, hundreds of millions of tons of soil is lifted from the Sahara ever year. However, this recent event is on the larger side.

This large amount of dust doesn’t just make for amazing sunsets, though; it has a major impact on ecosystems across the tropical Atlantic. Not only does the dust help fertilize the vast Amazon rainforest and provide mineral nutrients for phytoplankton in the ocean, but it also helped to build beaches across the Caribbean after being deposited for thousands of years.

Atmospherically, the dust sits in what meteorologists call the Saharan air layer, a hot and dry layer of the atmosphere that sits directly above cooler and more humid air above the Atlantic Ocean. This hot, dusty air puts a stop to any thunderstorms that may develop in the moist layer beneath it. In the summer in the tropics, a cap of Saharan dust can temporarily suppress hurricane formation or keep storms that have formed from potentially getting stronger. Hurricane seasons dominated by a large number of Saharan dust events tend to see a lower number of storms develop.