Sunday, March 2, 2014

Winter storm still on track - latest information from MWN

Auto-updating current temperatures across the metro.
Auto-updating radar imagery. Click here for precip-typed loop from MWN (or here for mobile users).

9:15pm Sunday:

Temps are finally starting to get to the freezing point in Shelby County, and as regional radar shows, there is still several hours of precipitation to go. The Storm Prediction Center issued a "mesoscale discussion" a bit ago highlighting the I-40 corridor from Little Rock to Memphis to Nashville and indicating that they are still expecting accumulating freezing rain and sleet to continue, as well as the thunder, into the nighttime hours (click the link above for the admittedly-technical details). We have backed off our ice accumulation totals a bit due to the latest changeover to ice, but maintain a good 1/2" of sleet with a little snow late tonight in the forecast.  We expect all precip to be tapering off by 2-3am with just a chance of light snow or freezing drizzle after that time.

Anything that falls from here on has the ability to stick to anything, including roadways. Temperatures WILL still fall into the teens late tonight and whatever is on the roads can and will freeze.  Monday morning's commute could be tricky, but should be made easier by the decision of Shelby County Schools to close, reducing the traffic on the roadways.

This will probably be our last blog update of the night.  Stay with our Facebook and Twitter feeds for ongoing details and continuous nowcasting into the night.  If you must travel overnight or in the morning, allow plenty of time, room between you and the car in front of you, and take it easy!

Area of concern for SPC for freezing rain and sleet over the next few hours.

7:15pm Sunday:

Crazy amounts of rain have fallen in the past few hours, especially north of I-40. As of 6:30, MWN in Bartlett has totaled 1.79" mainly in the past few hours with temps in the low to mid 30s.  We have minor ice accumulation on trees and other exposed objects and a lot of running water across the ground.  The rain total here is already more than I expected for the entire event and we have several hours left to go.

The big question everyone is asking is whether this winter event will materialize at all or if we'll end up with lots of 33-degree rain and no ice to show for it despite the forecast.  And trust me, we understand.  Our sector's track record hasn't been stellar this winter.  (I will say that it's been the most difficult winter of my 17 years of forecasting Memphis winter weather.)

We've mentioned on social media that the next couple of hours are critical.  Here's why: as the upper-level disturbances responsible for today's precipitation move closer, cooling typically results, especially at the upper levels.  In normal circumstances, the lowest levels follow suit.  In addition, the cold front is continuing to sink slowly to the south allowing colder air (in the 20s just 50 miles to our northwest) to move in.  We're well into the period that freezing rain was expected and yet we sit at 33 degrees south of the Shelby/Tipton line. If we don't drop to freezing at the surface in the next couple hours, the colder air overhead (which is more predictable) will move over and we may end up with little freezing rain. HOWEVER, that cold air aloft will put us in a sleet/snow regime. Precipitation is expected to continue into the wee hours of the morning. So while we may miss our window of opportunity for ice (and is that REALLY a bad thing?), sleet and possibly snow are still expected. Totals for the event may not jive with the forecast, but again, is that really a bad thing?

For those that want ice and snow I say "it ain't over."  For those who would rather avoid disaster, there's still a chance.  And for those who would rather throw darts at the weather people, you'll find a way no matter what happens.  We've got thick skin or we wouldn't be in this business.

4:00pm Sunday:

Forecast remains on track with no changes to Winter Storm Warnings. The first steady batch of precip has moved through much of the area, dropping temps to the freezing mark across Tipton, Crittenden, and northern Shelby County. Light icing has been reported in Marion, Millington, and Munford.  We've also gotten some tiny icicles on trees here in Bartlett at the MWN office.

The heaviest precipitation is expected after dark until 2-3am when the most significant ice is expected and temps will be in the 20s.  Travel is not recommended after dark unless absolutely necessary. Power outages and hazardous roads remain the main concerns with some outages possibly lasting a few days depending on infrastructure damage due to the weight of the ice.

In addition, wind gusting to 30+ mph overnight will  make power outage issues worse as lines weighted with ice are broken by strong wind.  The wind and cold temperatures have also prompted a Wind Chill Advisory to be issued for the overnight hours as lows fall to the mid teens and wind chills drop to near zero.

All preparations should be complete, including preparing for possible long-duration power outages.  Be sure all devices are charged and all outdoor pets are brought in or appropriately sheltered with a water source that won't freeze.

We'll continue to update as conditions necessitate.  Get the latest on our Facebook and Twitter feeds.

12:55pm Sunday:

The Winter Storm Warning has been officially extended and starts now, ending at 6am Monday. Temps are still sitting in the mid 30s and will remain there for a couple of hours, likely until the first round of steady precip arrives after 3pm.  It's showing up now on radar above.  Forecast precip amounts remain unchanged and, in the immediate metro, look to be up to 3/4" of ice (freezing rain), transitioning to sleet later this evening (up to 1/2") and then ending as light snow (up to an inch).  Sounds like a frozen treat that Blue Bunny might want to consider!  North of the metro, more sleet/snow is expected with slightly lower freezing rain amounts, while north MS, especially south of DeSoto County, overall ice amounts will be a bit lower, and little if any snow is expected.

We'll continue to update as conditions necessitate.  Get the latest on our Facebook and Twitter feeds.

11:45am Sunday:

The forecast is still on track.

Temps fell about 25 degrees very quickly behind the cold front this morning and now sit in the mid 30s (always current metro temps above). With the initial push of cold air to the south and just light rain/mist around, we expect to stay just above freezing for a couple of hours until the deeper cold air trailing the front and escorted by upper-level disturbances arrives by mid-afternoon, which will also coincide with when the first good round of precipitation reaches the metro (latest radar loop also shown above).  That precip is originating in eastern OK and western AR and will move in from the west.  There is still the possibility of thunder late this afternoon and evening, which would enhance precipitation rates.

The NWS has indicated it will start the Winter Storm Warning at noon along the I-40 corridor vs 3pm, but the official bulletin has not been sent yet.  Everything remains on track for a prolonged period of icing from late afternoon through the wee hours Monday morning.  Precip may start as rain but should quickly change to freezing rain after onset around mid-afternoon.  We still expect to see a period of sleet as well, sometimes mixed with the freezing rain, but as the predominant precip type later this evening.  Then, light snow will likely fall late tonight on top of the ice.  Precip amounts still appear to be on track for up to 3/4" of ice/freezing rain, 1/2"+ of sleet and a dusting of snow (more from Tipton County north).  These amounts are not as much as 1994 but are more than enough to cause major issues for travel, commerce, and infrastructure (power).

Preparations for a significant ice event, possibly with lengthy power outages and dangerous travel conditions should be complete within the next couple of hours.  Roads will initially be warm enough to stay just wet, but after sunset, especially during periods of sleet/snow, they could get very hazardous.  Elevated roadways (Hwy 385, I-40/240/55 overpasses and flyovers, and bridges over water or other roads) should be avoided as soon as the air temperature reaches 32 degrees.

We'll update again as conditions warrant. The best way to see the latest info is via our Facebook and Twitter feeds.

7:30am Sunday:

We'll try and update this a few times today to provide the latest information regarding the impending winter storm that will affect the entire metro beginning later this afternoon and continuing overnight.  The first question to answer is "what is the chance this will miss us altogether?"  The answer is "near zero."  The second one is, "what is the chance that we won't get much of anything, with only minor impacts?"  The answer: "very low."

In sum, everyone in the Memphis metro is expected to see an amount of ice and sleet that will cause significant impacts to their normal routine, make travel dangerous, and could result in power outages that last multiple days in some areas.  The latest graphics from the NWS on timing and accumulations are below.  Winter Storm Warnings go into effect for most of us at 3pm (6pm for far southeast metro counties).

Timing of the winter storm warnings and advisories

NWS forecast ice accumulations for this event, beginning after the start time of the warnings indicated above. (+1/2" indicates greater than 1/2" of ice).

Probability of more than 1/2" of ice through 6am Monday.  The metro has a 50-60% chance.  This does not take into account sleet, which is expected to top the ice, followed by a layer of light snow of up to 1".
At 7am, temps across Shelby County ranged from  63 at Memphis International to 49 at MWN in Bartlett. It's now 7:30 and we've dropped another 6 degrees in Bartlett. [8:15 update: Memphis dropped 20 degrees last hour, now at 43 and falling. At 8:15 in Bartlett it was 38.] Given the latest forecast models and data from the NWS, we expect the transition to freezing rain to occur around 3pm in Tipton County, 4pm in Shelby County, and 5-6pm across north MS, including DeSoto, northern Tunica, Tate, and northern Marshall Co.

Once the temp hits 32 and freezing rain begins, temps will continue to fall into the 20s. Freezing rain of 1/2" or more (possibly up to an inch) will transition to sleet, then finally after midnight, light snow, as temps fall well down into the 20s.  A dusting to 1" of snow is expected (more north, less south).  Wind will be another factor overnight that could exacerbate power outages as frozen lines swing in 20-30 mph wind.  Power outages are expected in many areas and could last for a few days in some areas.  Road conditions will initially be OK, but within a couple hours of reaching 32 will become slick to dangerous.  Elevated bridges/overpasses should be avoided after freezing rain begins.

Temperatures will remain in the 20s Monday.  Hazardous driving conditions will likely continue into the day Monday.  Have an alternate plan for work if you are able and certainly allow plenty of extra time if you can't.  Other preparations, which should be complete by early afternoon, include charged cell phones/devices, flashlights with extra batteries, pets taken care of (no frozen water dishes outside and bring them in), placing cars under cover if able and ice scrapers NOT inside the car (if the doors freeze shut) if they are parked outside, a full gas tank, whatever bread and milk and other staples you think you need for a couple of days (and don't forget water).

We'll continue to post the latest throughout the day on our social media feeds linked below, as well as here as able.  Visit on the web or mobile device for the latest radar, current temps, etc.  Stay safe and be prepared!

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1 comment:

Anonymous said...

Great Update. Everything you need to know about the Storm. Thanks