The anticipated change in the overall weather pattern continues to develop, and is expected to last through much of the last half of January. During much of the first half of January, a strong Pacific jet stream has kept the storm track well south of the northern plains. At the same time, a secondary weaker northern jet has kept the coldest air bottled-up well to the north.
The developing pattern change will cause a large ridge of high pressure to develop in the Pacific, forcing that strong jet stream up toward Alaska. Once there, the jet stream will grab hold of the cold air that has been developing in the arctic region, and then start to push it south. Once this pattern becomes established, it is expected to be in place for about 2 weeks.
Will the region be frigid the entire time? Not quite! While much of our weather is forecast to be coming from the north, the upper level flow will occasionally shift to the west, allowing low pressure systems to briefly bring milder air into the region. During these times, temperatures will moderate, with the threat for snow. The passage of these low pressure systems will drag a cold front across the region, ushering in a reinforcing shot of cold air.
What is often typical during these types of upper level patterns can be dangerous wind chill events. As the low pressure systems develop and pass through the area, southerly flows will increase causing bitter wind chills. Then, once the cold front passes and high pressure builds in, wind chills again become a threat. Depending on the strength of the wind, the intensity of the cold air moving in and available moisture, light snow will often accompany the passage of the low systems. The combination of falling snow and wind may cause reduced visibility, especially in open country.
Please remember this is a general threats outlook for the overall weather pattern through the rest of January. While overall colder than normal weather is expected the next two weeks, day-to-day variability will occur. Please pay attention to the actual forecasts issued by your NOAA’s National Weather Service, as well as any watches, advisories or warnings. Also, please check out the National Hazards Briefing here.
For additional infomation please contact your National Weather Service or visit our web site at www.crh.noaa.gov/fgf