I am going to try something different today. I am going to summarize some of the “trouble spots” around the country today in this weather blog post.
The composite National Weather Service (NWS) map shows quite a bit of activity this morning.
One common feature this morning is the large number of Freeze Warnings and Hard Freeze Warnings in the southwest. Temperatures will reach below freezing over the entire southwest, including the northern Los Angeles suburbs, through southern Arizona and New Mexico and almost into the Big Bend area in Texas. The surface map (from the Storm Prediction Center) shows the low temperatures this morning across the region.
This is in response to the massive cold front that has passed through the area and the continental polar high pressure system that trails behind it. The surface pressure map (from the Storm Prediction Center) shows the high pressure system over Utah and Colorado, with a pressure maxima of 1032 mb.
The high pressure tapers off to the east, leading to Frost Watches across the eastern Texas Panhandle and western Oklahoma.
One interesting side note is how strong the thermal inversion has become in some of these mountainous regions. For example, look at the 12Z sounding from Flagstaff, AZ. The temperature at the surface is 14 F, but if you climb just 50 mb above the surface, the temperature rises to 41 F!
In the Great Lakes region, Michigan, Indiana and Ohio have High Wind Warnings in place. The high winds are due to the sharp pressure gradient associated with the mid-latitude cyclone that is centered over Green Bay, WI. This system has a central low pressure of 986 mb, which is lower than the last few tropical systems I’ve tracked. This strong mid-latitude cyclone has just started its occlusion, and will begin to weaken.
This mid-latitude cyclone has a very long, sharp cold front draping across the nation. On the national radar image, this cold front shows up as a line of precipitation that extends from Houston, TX, to Philadelphia, PA.
The frontal boundary is not very thick, as shown on the visible satellite imagery.
In terms of general synoptics, the strongest thermal advection (as shown by the 850 mb NAM chart) will occur from the Oklahoma/Arkansas border to the Nebraska/Iowa border. Cold Air Advection (CAA) is quite strong through this region, so expect temperatures to drop significantly this afternoon and evening.
In summary, the two dominant forces today are the high pressure system over the western Rocky Mountains, which is bringing cold temperatures to much of the southwest, and the strong mid-latitude cyclone over the Great Lakes which is producing a large cold front and windy conditions.
Thank you for reading my post. Let me know what you think of this format.
The upper air soundings and mesoscale analysis plots are from the Storm Prediction Center website.
The forecasted upper air soundings are from TwisterData.com.
The surface observation and upper level charts are from Unisys Weather.
The satellite data is from NASA – MSFC