Good morning bloggers,
Another winter storm is taking aim on the plains states as a cold air mass has blasted south and is in place. This is setting the stage for a winter storm to begin tonight. There is a chance of some significant icing. How much ice does it take to cause a problem? Let’s take a look.
Freezing rain is liquid water, or just regular old rain that freezes on contact with surfaces that are below freezing at the surface. Frozen rain is sleet, or ice pellets, and very different from freezing rain. The set up for tonight near Kansas City is for some snow, then sleet, then freezing rain to be the precipitation types. There may be a period of snow at the very beginning of the precipitation, but a quick transition to the other precipitation types is likely. How much ice accumulation does it take to begin producing problems? Well, a thin layer 1/100th of an inch thick will cause many problems with slipping, sliding, and falling. For potential power outages, less than 1/4″ of ice accumulation is not enough to cause any power outages. Let’s take a look:
Here is a Powercast from last nights data:
This forecast map shows that most areas may stay just below the criteria that would begin the concern for power outages.
Temperatures will be rising above freezing later in the day Friday, and the icing will immediately come to an end if those temperatures do rise to just above 32°. I have experienced ice storms that stopped producing ice the second the temperatures rose to 32.1°. It is incredible how delicate it is, as the freezing temperature is 32.0°. Once it rises above that number, melting immediately begins.
Here is the new HRRR valid as the precipitation arrives near KC:
As you can see, on this HRRR model, the precipitation begins as snow, and then is about to quickly transition to sleet or freezing rain. If the snow can last for an hour or two, some accumulation would be likely before the change occurs. Northern Missouri has a better chance of snow accumulation before the precipitation type changes.
Forecast for Arrowhead on Sunday:
What I just analyzed on the new NAM:
- On the new NAM model, the precipitation doesn’t start until around 6 AM Friday. If it waits that long, any chance of snow is low. The chance of snow would only arrive if the precipitation starts earlier than this latest model is showing.
- On this new NAM, the precipitation starts as sleet, which would be bad for roads, but good for power outages.
- By mid-morning, the sleet changes to freezing rain and ice would then begin accumulating on power lines and trees
- By late afternoon, the dew points are forecast to jump to 32 degrees which would force the air temperature at the surface to be 32 or warmer and the freezing rain would then change to rain. The amount of freezing rain accumulation into ice is the big question, and right now it appears that it could come close to 1/4″. This would limit any major problems, but any longer duration of icing would begin causing bigger problems.
Thank you for participating and sharing in this weather experience. Have a great Thursday.