GFS 6 Hourly Precipitation Christmas Bomb


You may have see #SantaBomb being spread around on social media, but what is it? And why are people talking about it? Well for the past few days we have been telling you about a large winter storm that will be intensifying over the northeast. But why is it being called #SantaBomb? Well lets back up a few days and start with how it will form.

GFS 18z MondayWhile this weekend is going to be cloudy with chances of drizzle, some potentially freezing on surfaces that are below freezing, Monday a more impressive system will be approaching the state. A low pressure system will be tracking across southern Minnesota and northern Iowa during the day on Monday. Since most of the precipitation is south of this low will be in the warm sector, this means the majority of this precipitation will fall as rain initially. It isn’t until the low slides off further to the east that colder air will being to move into the state and will transition rain over to snow on Tuesday 12/23. Eventually as the low pulls further off to the east, so will the precipitation. Things will be clearing up early Wednesday morning 12/24.

gfs_6hr_snow_acc_conus_22The greatest snowfall accumulations will be across western and northern Iowa. This is were a couple of inches will be possible. Any change in track and timing would change these totals, however, things have been pretty consistent over the past few days.


During the day on Christmas Eve, the winds will be increasing as the low will be intensifying. A strong northwest wind of 20-30mph with higher gusts, will lead to blowing snow across northern Iowa. Winds will continue to increase during the day Wednesday, so blowing snow will still be likely during the evening hours on Christmas Eve. This may have an impact on visibilities, so if you will be traveling on Christmas eve to the north, you will want to check the very latest road conditions.  The top 15 analogs exceeding 1 or more hours of near blizzard conditions in 24 hours using the GFS has a strong analog signal for blizzard conditions across Minnesota, Iowa, North Dakota, and South Dakota on Christmas eve as this storm intensifies.

BoMBSo why is this storm called #SantaBomb? Well as it continues off to the east, this low will begin to interact with the jet stream. As this low begins to interact with the jet streaks, or areas with the greatest wind speeds in the jet stream, this will help strengthen the low. A “bomb” or also called bombogenesis, is when rapid strengthening of an extratropical cyclone takes place by at least 24 millibars over the course of 24 hours. This system may come close to this classification, but may not fully make it. Whether it does or not, it is still going to have major impacts on the Great Lakes and the northeast. The only effect this is going to have here back at home is the increase in wind speed.

GFS 18z Friday

High pressure will build into the state before our next system moves into the region by Friday 12/26. Right now the track and timing continue to be an issue. The latest GFS trends have pushed this low further to the north than previous model runs which would impact snowfall totals across the state. If the more northerly track would to verify, than the heaviest snowfall totals would be across South Dakota, southern Minnesota, and northern Iowa, into southern Wisconsin. Earlier this track was more to the south which tracked the greatest accumulations across Iowa. This track will continued to be watched, but it looks to be our next best chance at accumulating snowfall. We will continue to keep a tab on everything as many of you are traveling this week, and will bring all the very latest updates on our Facebook and Twitter pages, and right here at iowachase.com.

Zach Sharpe

My name is Zach Sharpe. I am the president and forecaster for the Iowa Storm Chasing Network. You can find me on Twitter @Stormchaserzach and on Facebook at: https://www.facebook.com/stormchaserzach/

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