Thursday, December 5, 2013
FAQ on this weekend's winter weather
1. When is the ice going to start and how much will we get?
This varies a bit depending on where you are in the metro. The rain to freezing rain transition will occur from northwest to southeast. Thus, Crittenden and Tipton Counties will transition first, probably between 3-6am; Shelby, Fayette, DeSoto, and Tunica Counties will probably transition between 7-10am; Tate and Marshall Counties between 10am-1pm. Transition time will also affect total ice accumulations, as earlier transition will mean more time below freezing and likely higher amounts. For most of the metro, though we expect average amounts to be around 1/2" of ice - perhaps a little more to the northwest and maybe a quarter inch over northwest MS. All precip should come to an end by earlier evening, with the last few hours possibly seeing a little sleet or snow flurries.
2. Are you sure this won't turn out to be one of "those" events where it goes by to our north/south? What about the bluffs and Pyramid?
Confidence is high that the entire metro will see Ice Storm criteria met (0.25" of ice). While exact transition times and amounts may vary, this is not an event that will miss the metro. It's been consistently forecast by the computer models for 5-6 days now. The bluffs will have no effect on this storm (or any other one for that matter). The Pyramid has lost it's superpowers since the move of the pharaoh to the University of Memphis.
3. What kind of impacts could we have from that much ice?
The main effects will be on trees and power lines, as well as elevated roads, bridges, and overpasses. The weight of the ice will likely be enough to snap tree branches by afternoon (especially when combined with a 20-25 mph wind), which could fall on power lines weighted by ice. Some power lines will also succumb to the ice by themselves. The NWS is using an experimental "Ice Storm Index" this winter and it places the metro in the range of a category 2-3 (out of 5) in the southeast metro to a 3-4 in the northwest metro. The indicates that a combination of expected ice and wind could cause numerous utility interruptions, some of which could be prolonged (up to 5-10 days), and some damage to main feeder lines.
As for road travel, any road that has air flowing beneath it will be subject to freezing up early on after the ice begins. It just doesn't take more than a few hundredths of an inch of ice to make a skating rink on a bridge or overpass. Avoid known danger spots: most of 385/Nonconnah, I-40/240 overpasses/flyovers, Jackson Ave overpass off I-40, Mississippi River bridges, etc., etc.
As for primary roads and non-elevated interstates with high traffic volumes, it will take much longer for freezing to take place. On these roads, sleet usually causes more problems than freezing rain. However, prolonged heavier freezing rain can also create ice on these thoroughfares, especially after several hours of ice. Afternoon travel will be more hazardous that morning travel.
4. Why isn't the state DOT pre-treating the roads?
The salt brine that is used to pre-treat washes off in rain. Since rain will occur up until the freezing rain starts, there's no time to do that. All treatment efforts will be directed to post-freeze traction control and melting. In other words, the elevated roadways will likely freeze BEFORE they are treated. Expect significant delays as these areas are shut down to allow treatment and hazardous conditions otherwise! Our guidance is "if it isn't necessary, don't get out."
5. Any other impacts I should know about?
Certainly there are MANY activities that are subject to weather conditions this weekend. Check with officials for that event on details. The Marathon officials have indicated a desire to race, but have reserved the right to call it off up to 5am Saturday. Some Christmas parades have been cancelled or rescheduled - check with your city/town. Watch local news outlets for the latest cancellations or postponements.
Air travel could also be disrupted. Aircraft can still fly (with a good de-ice job before take-off) but many airlines choose to preemptively cancel flights to avoid getting planes stuck in bad weather. Check with your airline. The airport is equipped to maintain operations throughout the event (especially given the reduced passenger flight schedules).
Many schools/colleges/educational institutions have also preemptively cancelled classes. These include Shelby County, Memphis Catholic, Tipton County, Fayette County, DeSoto County (half day), University of Memphis, and a host of others. Check with local news outlets or your school's website or social media feeds for the latest info.
There will be lots of other residual impacts, lasting throughout the weekend. We couldn't possibly get into them all.
6. How does this storm rate against the Great Ice Storm of 1994?
7. You mentioned "round 2" on Saturday night. What's that all about?
The "Forgotten Ice Storm" may be the one on Saturday night. Another round of freezing rain, with maybe a little sleet, will move through on Saturday night into Sunday morning. With all the attention on Friday's storm, this one will get overlooked until Saturday and will catch many off guard. Potential exists for another 1/4"-1/2" of ice from late Saturday evening until mid-morning Sunday before changing to rain for the remainder of the day Sunday. By itself, this would get as much attention as Friday's storm.
The real issue with this storm will be the CUMULATIVE effect of it being the second storm. If 1/2" of ice accumulates on Friday and very little melts on Saturday, then another 1/4" falls Saturday night, then you have nearly 3/4" of ice on trees and power lines Sunday morning. Anything weakened by the first round could be severely damaged by the second. This is why we are recommending preparing for multiple days of impacts. Many could lose power on Friday; many more could be added to the list Saturday night.
8. So how should I prepare?
Make it an adventure by breaking out some family games if power goes out! Don't forget about your outdoor pets either! Make sure they have a warm place to stay where their water won't freeze. Remember that a full tank of gas and a car charger can keep your cell phone going as long as cell towers are working. Additional tips can be found on this Red Cross flier (PDF). The Red Cross also provides this power outage info sheet (PDF), including what to do before, during, and after a prolonged outage. Never run a car in a garage with the door completely closed and keep space heaters away from flammables, curtains, etc.! Finally, be prepared to restrict travel to only necessary and vital trips if conditions get bad.
9. How can I stay up on the latest information about local weather, preferably from a very reliable local source?
main website has everything you need to stay in touch with current conditions, forecast conditions, radar with precipitation type, and much more. Our mobile site and mobile apps for Android and iPhone also have the same information. The mobile apps also provide our StormWatch+ push notification-based weather warning system. For about 1/3 the cost of a low budget weather radio, we can provide instant notification of changes in weather warnings, watches, and advisories from the NWS for YOUR location, not your county.
Finally, we're all over social media and provide the most current information, including nowcasting of local conditions and imminent hazards, via our social channels. They are all linked from our websites, as well as at the bottom of this post. Facebook and Twitter are your best sources of local weather info from MWN, specifically for the Memphis metro. Nearly every piece of information we provide has a backup method or source in case the primary fail,s including updating the social feeds from a remote location that will not get ice (thanks to awesome interns in Starkville, MS!).
10. Anything else I need to know?
Just this, if you haven't stocked up yet:
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!