Arctic air is pouring into the region tonight as temperatures are falling from the 30s to the 20s. Lows should drop into the teens in many spots tonight, and even a few areas could see single digit lows. A few flurries or a snow shower isn't out of the question tonight, with a dusting possible in spots. With winds around 10-25mph we can expect wind chill values in the neighborhood of -10 to +5 overnight. A Wind Chill Advisory is in effect for a few counties in the viewing area near the Iowa border, including the town of Trenton.
With arctic high pressure nearby on Sunday highs will generally be in the low 20s around the metro area with a north to northeast wind. It will certainly remind us that winter is not over quite yet! The cold air and just how far south it settles in will be key for the Monday storm. Let's discuss a few things in regards to this storm. First off, as of right now the precipitation totals look to be under 0.25" in almost all areas, and many spots with a trace to 0.10". Here is a quick look at some of the important data in regards to precipitation type.
Data is from the 12Z NAM & GFS for KCI.
Total Forecast Precipitation:
NAM 0.08" GFS 0.07"
NAM 850mb Temp(C): Noon Monday: -1.2 6pm Monday: +0.6
GFS 850mb Temp(C): Noon Monday: +1.6 6pm Monday: +0.6
Surface temps for both models are sub-freezing. The NAM was in the lows 20s and the GFS about 24-30 degrees.
So what does this translate too? In order for freezing rain or sleet to occur a warm layer must exist and by looking at this data straight from the model there is a warm layer...especially on the GFS. Both models above would support a freezing rain/sleet/maybe mix scenrio. If the warm layer is shallow then sleet would occur, if the warm layer is deeper, then freezing rain. While at the moment it looks like this won't even be close to a repeat of 2002 or even earlier this season the storm in St. Joe, there could be problems on the roads as surface temps will be sub freezing. Earlier this year there was a trace of freezing rain in parts of Kansas City and it caused numerous accidents.
On Monday some areas may see a mix or mainly snow, at this moment those locations look to be north of Kansas City. This storm is still 36 hours away and will change its look many times. But with the cold air settling in and a slow departure on Monday with moisture moving in I wanted to make people aware that some freezing rain or sleet is possible on Monday. A slight shift one way or another would lead to snow in some areas or maybe more or less precip. in others. Regardless, the latest 00Z NAM still is showing light precip. totals for the area. Below is the total liquid precipitation forecast from the 00Z NAM.
If anyone is wondering how snow, sleet, or freezing rain forms please check out the information below courtesy of the NWS. I found this in an online tutorial. Have a great night and enjoy the cold air on Sunday!
Winter precipitation types and their environments
The vertical distribution of temperature will often determine the type of precipitation (rain vs. snow vs. sleet vs. freezing rain) that occurs at the surface during the wintertime. More often than not, the temperature does not decrease with height but increases, many times by several degrees, before decreasing. This increase, then decrease is called and inversion. In winter, an inversion can be critical in determining the type or types of weather.
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In the image (left) the green dashed line is the temperature in respect to elevation. The surface temperature is 25°F (-4°C) and increases with height before decreasing. However, since the temperature remains below freezing any precipitation that falls will remain as snow. |
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In this image the surface temperature is higher, 27°F (-3°C). Also as elevation increases, the temperature increases to a point where some of the atmosphere is above freezing before the temperature lowers again below freezing.
As snow falls into the layer of air where the temperature is above freezing, the snow flakes partially melt. As the precipitation reenters the air that is below freezing, the precipitation will re-freeze into ice pellets that bounce off the ground, commonly called sleet. The most likely place for freezing rain and sleet is to the north of warm fronts. The cause of the wintertime mess is a layer of air above freezing aloft. |
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Freezing rain will occur if the warm layer in the atmosphere is deep with only a shallow layer of below freezing air at the surface. The precipitation can begin as either rain and/or snow but becomes all rain in the warm layer. The rain falls back into the air that is below freezing but since the depth is shallow, the rain does not have time to freeze into sleet.
Upon hitting the ground or objects such as bridges and vehicles, the rain freezes on contact. Some of the most disastrous winter weather storms are due primarily to freezing rain. |