Today's Weather Discussion: White Christmas?
Thursday, Dec. 23:
Are you dreaming of a white Christmas this year??? Based on historical weather records and climatology, our area averages about a 15% chance of a white Christmas each year. Of course, the last time our region experienced a white Christmas was in 2004, when a record-setting snowfall on Dec. 22 brought over a foot of snow to much of the region. This year, it looks as though a fast-moving storm system may bring at least parts of the region a batch of light accumulating snow Christmas Eve night and early on Christmas Day.
A Winter Weather Advisory has been issued for parts of Southern IL & Southeast MO from Noon Christmas Eve through Noon Christmas Day.
This storm system is still developing, and forecast models are just now starting to come into agreement on the timing and strength of the system, but more adjustments may need to be made to this forecast, so be sure to stay tuned to Local 6 tonight and tomorrow for the very latest.
There have been two areas of interest going into the weekend, with a bit of a "split-flow" pattern to the mid and upper level winds....with a northern system and a southern system. Our region will be affected by the northern system....a fast-moving mid-level disturbance that will dive southeast from southern Canada. The image below shows the mid-level disturbance on the 500 mb chart as of Friday at 6PM.
As this trough swings through the region, it will pull in some moisture and generate some atmospheric lift. The latest trends with forecast models over the past day or two has been to slow down the arrival of this system, to keep temperatures just a bit warmer, and to dry out the system. That means we'll likely see a later onset of precip Friday evening, perhaps a short window of mixed precip at the onset, and that previous forecasts of 1-3" may be a bit too high.
As the system enters the picture tomorrow afternoon, we may start to see some returns showing up on radar, but things may take a while to actually reach the ground. This is a phenomenon called "virga", where precipitation aloft evaporates before reaching the surface. Eventually, the atmosphere will fully moisten from top to bottom, and considering the latest data, I think snow, perhaps briefly mixed with light sleet or rain will begin to affect the region just after dark.
Snow total forecasts over the past few days have been in the 1-3" range, and as I just mentioned, my gut has me leaning toward the lower totals (even though the kid in me wants lots of snow). The latest 18Z (Noon) NAM forecast model run shows a total of only about 1.2" at Paducah, beginning at around 9PM Friday, and tapering off around 9AM Saturday. Snow totals are under 1" using the latest run of the GFS forecast model. In general, I think around 1" or so is a safe-bet for now, with perhaps 2-3" around and north of line from Perrryville to Harrisburg to Madisonville. Here are some of the different forecast graphics I've looked at today:
NAM Bufkit (shows snowfall at Paducah from 9PM Friday-9AM Saturday, with 1.2" accumulation:
NAM snowfall map:
GFS snowfall map:
HPC/NOAA 24-hr probability of at least 1" of snow from 6PM Friday through 6PM Saturday:
HPC/NOAA 24-hr probability of at least 2" of snow from 6PM Friday through 6PM Saturday:
For our region, this looks like a decent compromise for snow-lovers and those looking to travel this weekend....a nice fresh coating of snowfall for Christmas morning, but not really enough to cause major travel headaches. Most of the primary roadways around the region have been pre-treated, as with temperatures expected to stay in the 20's and 30's, most of what falls on treated pavement should melt away.
If your travel plans take you out of our region, snowfall is expected to be a little heavier and make more of an impact if you are going north or east. If you need to get the forecast for a specific point anywhere in the U.S., click here for the latest forecast from the National Weather Service. And be sure to plan ahead as the latest interstate forecast does include some trouble spots across the eastern 1/3rd of the country over the next few days:
That's the latest as of Friday afternoon. Chief Meteorologist Jennifer Rukavina will be in with the latest updates tonight on Local 6 at 5,6,9, & 10, and I'll be back early in the morning tracking this system on Local 6 Today & Midday. Be sure to check back for the latest updates, and keep doing those snow dances!