A significant blizzard is current on track to affect the state early next week, beginning late Monday night and continuing through early Wednesday morning. A disturbance over the Pacific is expected to develop into an upper-level low today and trek it’s way to the Oklahoma panhandle by tomorrow. By Tuesday night, a very strong 300 mb jet will convey this low upwards from the Southern Plains to the Great Lakes region. This fast upper level jet will help this system immensely from a meteorological standpoint with enhanced lift over the area. There are still some discrepancies and disagreement between the models this evening with the American GFS being a northern solution, the NAM being much slower and farther southeast, and the ECMWF/GEM slightly too far south. The forecast that we are currently using is ECMWF/GEM blend as the former two solutions are moreso on the “extremes” sides at this time.
We continue to have very high confidence with the timing of this storm. A light rain or snow is expected to begin falling across southern Iowa as early as the afternoon hours on Monday. Monday should be clear for any concerns with the exception of the night. By evening on Monday, snow will likely overspread most locations south of Interstate 80, with the heaviest being over southwestern Iowa. Snow should expand in coverage to the northern half and the entire state should be seeing snow by early Tuesday morning. Snow will continue heavily for the entire day before clearing out by Wednesday morning. However, blowing snow will continue to be a concern during the morning hours on Wednesday.
Speaking of winds, this will be one of the most significant threats with this storm. A tightening pressure gradient with the low will produce sustained winds of 25-30 MPH, the worst in the west, with gusts to over 40 MPH likely at times. This will lead to a lot of blowing and drifting of the falling snow and snow that has already fallen. Near-zero visibility and whiteout conditions can basically be written in pen if these winds verify. This is essentially a classic, and very dangerous, blizzard situation, with high snowfall accumulations and strong winds. If this holds out… travel will be impacted on a large scale, and may be impossible for some. It will be even worse in rural/open areas. Road closures can be assumed. The evening commute on Tuesday is right in the path of the worst northerly winds winds. Please try to make precautions if at all possible during the day Tuesday.
Detailed amounts is one of the areas of lower confidence at this time. Models are not exactly in agreement fully with amounts and it’s still important to note at the time of writing this post, the storm was still not fully into the United States yet and full upper-air network and observational network. Hopefully when that occurs, models should begin to come in more of an alignment and we’ll be able to give a more confident report. But let’s get to what our current thinking is right now. A lot of precipitation is available alongside this system and snow-to-liquid ratios will be in the 15:1 range on average. This will lead to a good snowfall across the area with the quality life aforementioned above. While we aren’t for sure of detailed amounts, we are highly confident that this will be a significant snowfall.
One-to-two inches of snow per hour look likely with this storm. Heavy snow will fall throughout the day and for an extended amount of time. Snowfall amounts could be locally higher, especially when considering potential convective banding, which can lead to even more sharp bursts of quick snow for some areas (oh, and thundersnow). Another issue that we’re currently dealing with is a dry slot expected over south central and southeastern Iowa by the afternoon Tuesday. Where this dry slot sets up can considerably cut down totals to the north. This is something that we will have to monitor over the next couple of days, and especially as we get new data. There isn’t much concern for a mix either with the rain/snow line likely being a sharp cutoff somewhere over the southeastern half.
Eight-to-ten inches is currently anticipated over the majority of the state, along and northwest of a line from Prairie Du Chien to Des Moines to Clarinda, and along and southeast of a line from Sloan to Northwood. There is potential for locally higher amounts in this area, especially in west central Iowa where 10-12+” is expected. Carroll, Fort Dodge, and Omaha are in this high end of things; Des Moines, Ames, Clarinda, Waterloo, Decorah, Mason City, and surrounding communities are looking at eight-to-ten inches; Cedar Rapids, Dubuque, Creston, Marshalltown, Spencer, Sioux City, Sheldon, Estherville and surrounding communities are looking at six-to-eight inches. The cutoff is sharp beyond that with Iowa City, Ottumwa, and Lamoni seeing four-to-six inches, the Quad Cities at two-to-four inches, and Burlington and Keokuk in southeast Iowa potentially getting an inch or two.
Due to all of this, the National Weather Service has issued a Blizzard Watch for generally the northwestern half of the state, which is in effect from late Monday night to early Wednesday morning. A Winter Storm Watch is in effect for northwestern Iowa where winds will not be strong enough for it to be considered a blizzard. You should begin preparing now…. ask yourself the general questions: do you have a winter survival kit in your car (if you must travel) and enough gas in your car if you get stranded? Do you need prescriptions refilled before Tuesday? Do you have enough food, diapers, etc. in your home to last you a few days? Do you have what you need if the power goes out? How will you check on the elderly and friends in need? These are all some basic things that you can ask yourself before the event. It is highly recommended to begin preparing now for this event and try your best to postpone or cancel your plans Tuesday and simply stay home. To repeat, travel will be extremely dangerous to impossible. You do not want to be out and about during this event. I know that some schools have already began moving activities around from Tuesday and cancellations likely will begin flooding in all over the state sometime Monday.
Bottom line: A Blizzard Watch has been posted for the potential of 8-12″ inches of snow over much of the state. The bigger threat is blizzard conditions with 25-35 MPH sustained winds (gusts to 45 MPH). Major travel difficulties will be a result of this. You need to take appropriate precautions now.
Stay tuned to the Iowa Weather Network for the latest up-to-the-date information during this event!