Friday, November 30, 2018

Heavy Snows Return this Weekend for Some

Another winter storm is poised to move towards the Midwest by the weekend. Rain will develop late Friday night across the Plains and begin to changeover to mainly snow through the day on Saturday. Snow will eventually spread north and east into the Upper Midwest late in the day Saturday. Some of the precipitation will begin as a light wintry mix of freezing rain and sleet, but will change over to all snow through a lifting mechanism that will act to cool the layer. The area of heaviest snow will be localized across Nebraska, with lesser amounts outward from there.

The lack of a large swath of heavier snow has to do with the life stage of the low pressure system. In many cases storms emerge from the Rockies and develop from that point forward. With similar systems across this part of the world, the life stage of strongest precipitation usually last 1-3 days. However, the weekend winter storm developed on the west coast and dumped heavy rain and snow across the Southwest Thursday. Being in its mature stage, the area of snow will quickly develop Saturday, then quickly fall apart Saturday into Sunday. It can also be seen in a 500mb chart below, where the closed upper low is a sign of future weakening, as the system become occluded. Nonetheless, a band of snow is expected to sit and pivot over Nebraska, where many will see over a foot of snow by Sunday. Areas further south across the Mid-Lower Mississippi River Valley will see severe weather Friday and Saturday, as the cold front provides a mechanism for lift in an unstable environment. Isolated tornadoes are possible, with an upper jet superimposed over the same locations, providing turning with height for tornadic thunderstorms. As always, be sure to follow on Twitter for more updates and weather content.

Saturday, November 24, 2018

First Round of Heavy Snow for Many Sunday-Monday

A storm system will emerge from the Rockies this afternoon and march towards the north and east through the overnight into Sunday. A very narrow strip of heavy snow will develop to the northwest of the low, as warm air is tossed over a warm front into colder air. The storm is expected to drop several inches of snow over a wide area, but a narrow area of only 15-30 miles will see amounts in excess of 6". Some spots could surprise with almost a foot of snow as bands park over the same area for a long period of time. It is difficult to see exactly where the heaviest snow will set-up, but chances favor somewhere between Milwaukee and Chicago into Michigan. Below is a computer simulation of what the radar may look like heading through Monday morning. As we march more into winter, be sure to keep it to Midwest Weather for updates throughout the winter. More weather content will be posted on our Facebook page and especially on Twitter.

Friday, November 2, 2018

Official Midwest Weather Winter Outlook 2018-2019

It's about that time, when everyone is asking, what will the winter be like? Well, we have some of the answers you are looking for. The winter forecast is not as clear cut as some years in the past, but there are some trends out there that show clues into what the fine winter enthusiasts of this site should expect.

First, let's start with the process into how the outlook was constructed. We will use 4 major teleconnections that are useful to forecast the weather out several months to a year in the future. The most influential and most common lies in the level that ENSO is expected to be in. ENSO is essentially a measure of how warm the ocean temperatures are in the Central Pacific. If the specific region is warmer than normal it is classified as an El Nino, colder is classified as a La Nina, and near normal is in the neutral phase. The phase tends to flip from El Nino to La Nina every 8 month to over a year at times. For our purposes in the winter forecast, we are currently in the neutral phase and expected to trend towards an El Nino moving into winter. Consequently, we will only use years that followed the same trend.

The Pacific Decadal Oscillation (PDO) is a similar measure or oscillation that goes from the warm to cold stage every 5-10+ years, and examines ocean temperatures in the northern Pacific. It is near neutral and is likely to hover around the neutral stage through the winter, we will give it 2x weight. The Atlantic Multidecadal Oscillation (AMO) is similar to the PDO, and should stay in the warm phase through 2019, as its period of change can be well over a decade. Since the AMO is a measure in the North Atlantic, we will use less of a weight, since it is downstream of the weather in the United States. Finally the Quasi-Biennial Oscillation (QBO) is a regular variation in the wind direction near the equator located in the stratosphere and can influence the weather around the world. It is a wind that blows in the same direction for roughly 14 months then completely flips direction. Based on history, the QBO should eventually flip direction, which should occur sometime during the winter, so years with a flip from negative to positive during the winter will be used for the forecast.

Putting it all together, 5 similar years since 1950 were looked at then averaged against the values from the entire period. Essentially, the map above is what we may expect in terms of temperatures during the months of December through February this winter. Notice the colder air from the Plains down through the Southeast. Some warmer temperatures are housed in the Great Lakes, but overall cooler than normal temperatures are expected this winter across the Midwest.

Looking and precipitation now, we see an above normal signal across the Midwest, and a well above normal signal across the West Coast. Colder than normal and above normal precipitation will also favor above normal snowfall overall. However, notice there are some southwest to northeast strips of above/below normal areas east of the Rockies. It may signal the risk for larger storm systems, and more hit/miss events in aggregate through the winter season. At the end of the day, slightly above normal snowfall is favored, but as always it will come down to where each individual storm track goes. There will be an above normal amount of chances for snow this winter, so be sure to keep up to date with Midwest Weather through the winter, as the blog becomes much more active. You are also going to want to 'Like' us on Facebook and follow on Twitter for continued weather updates and conversation.