Good evening ISCN followers. Just going to do a brief update on the potential for a white Christmas. This afternoon the 18z GFS provided a little hope for a white Christmas across northern Iowa, and I believe this does appear to be possible. From the image above, you can see that snowfall totals through Christmas morning would be very light, generally and inch or less. However, this evening, the 00z GFS is coming in with a couple more systems before Christmas, which was a little surprising.
Starting out with the first one, this has been the one that continues to be picked up on each model run. This one will be a rain maker for most the state Sunday as temperatures will be in the 40’s, but as cooler air gets pulled in on the back side, rain will transition over to snow across northern Iowa. The 00z GFS continues to show snowfall accumulations under an inch, which is reasonable.
The next system will arrive on Wednesday morning, and this one will also start out as a rain maker. Rain will continue throughout the day Wednesday before eventually wrapping up by Wednesday evening. After this system, is where the 00z GFS gets interesting.
After Wednesday’s system pulls out, a second low moves into western Iowa early Thursday morning. Temperatures are cold enough Thursday that it is painting in snow from northwest to north central Iowa from sunrise to noon Thursday.
Just as soon as you thought our snow chances were done, ANOTHER one moves in on Christmas morning. This one lingers around through the early morning hours of the 26th. If this model run were to verify, it would seem plausible for a white Christmas north of a line from Omaha, Fort Dodge, to Waterloo. Since this is just one model and model run, you can’t put all of your eggs in one basket yet. As we near Thursday, we will be able to compare it to the NAM and see if the GFS corrects itself in following runs.
After Christmas, the models were all over the place, but they were picking up on a larger storm system around the 27th into the 28th. Nothing to get concerned with yet, but if you have travel plans, make sure to continue checking back for the latest updates.