Archive for January, 2011

10:45 Update
January 31, 2011

Precipitation has already started to break out across portions of eastern and central Oklahoma this evening.  Thunderstorms are also being reported in those areas.  That shield of precipitation will continue to move east-northeast tonight.

The bulk of the heavy precipitation will likely move in after 2 a.m.  Isolated showers and sleet will be possible through midnight.  We did get a report near Bentonville of sleet and rain.

The 0Z data continues to support the chances for major ice and snow accumulations across our area.  I’m not really adjusting the forecast per the 0Z data; there’s been enough consistency with the runs to keep with our going forecast.

Drew Michaels

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18Z NAM Update
January 31, 2011

Well after looking over the 18Z data we really don’t have a lot of changes to the forecast.  I noticed the Fayetteville bufkit sounding wanted to paint a lot of sleet across northwest Arkansas than freezing rain.  Sleet is such an unstable precipitation type.  The slightest amount of warming or cooling can change the type of precipitation.  I think we’ll have more freezing rain than sleet with this event.

 The Fort Smith data was supportive of more snow and sleet with this event.  The model had increased the totals to 5″ to 6″ of sleet and snow.  I will look at the 0Z to see if we need to increase the totals; otherwise, we’re not going to mess with the forecast at this point.

Drew Michaels

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3:30pm Update: Blizzard Warning Issued
January 31, 2011

The National Weather Service has issued a blizzard warning for all of southern Missouri and parts of Northeast Oklahoma including McDonald, and Delaware counties. Snowfall will top 12″ in those areas with winds gusting to 40 mph later tomorrow.

Ross Ellet

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3pm Update: Winter Storm Timelines
January 31, 2011

We will have your updated snowfall totals coming up in the next couple hours.

Ross Ellet

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Noon Update
January 31, 2011

We are just starting to go over the newest computer models right now. The storm has remained intact but the overall precipitation is increasing. This will lead to both significant icing and snowfall through the day tomorrow. We have yet to go through the thermal layer on both the NAM and GFS to see if the ice and snow totals will have to be adjusted. I am starting to go through your comments and will do my best to answer them, but it may take a little time. I will get a couple more updates up early this afternoon with the winter storm timelines and also an entry about the engine driving this historic winter storm.

On a more serious note, if you do have plans through the day tomorrow in northwest Arkansas or northeast Oklahoma please think of a back up plan just in case. Also, it would be a good idea to make sure your emergency supplies are stocked such as flashlights, batteries, water, medication and non-perishable foods just in case power goes out or you are shut in for a couple of days.

Ross Ellet

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Monday 6am Update: Historic Storm On Track
January 31, 2011

A massive winter storm is on track, and for areas in northeast Oklahoma this storm may stick out in the history books. Lets get right down to it. There will be 4 threats with this storm and they will arrive in this order 1) ice, 2) snow, 3) winds, 4) cold.

Here are the expected ice accumulations

Here are the expected snow totals

Near Blizzard Conditions

Winds are expected to be sustained between 20 to 30 mph with wind gusts to 40 mph on Tuesday afternoon and evening. Wind combined with heavy snow will create significant blowing and drifting of snow. The combination of the wind and snow could create near blizzard conditions in northwest Arkansas with the possibility of blizzard conditions near I-44 in Oklahoma. The National Weather Service is currently monitoring the wind potential and could upgrade to a blizzard warning for areas in northeast Oklahoma late today or overnight tonight. It is unlikely that a blizzard warning would be issued for any Arkansas counties.

Cold

Temperatures will free fall dropping to sub-zero levels by Thursday morning. This will likely be one of the coldest blasts that we have seen in the past decade. Temperatures may not rebound to freezing until Friday or Saturday.

Behind The Forecast

I will elaborate more on these totals and fine details in another update later this morning. The major winter storm has initialized extremely well in the 00z model runs with not only the GFS and NAM but also the European model as well. In fact the 00z NAM was the outlier keeping the storm a little further north. In the 06z run the NAM has shifted in line with the other two models with higher precipitation and colder air. At this time, we feel that around 1.4″ of total precipitation could fall along I-40 mixed with rain, freezing rain, sleet, and snow. About 1.6″ of total precipitation could fall in northeast Oklahoma and northwest Arkansas most of which will fall as freezing rain and snow. The 00z GFS and European were painting 1.5-2.5″ of total QPF, the 00z NAM was lower but the 06z has bounced back up. We are concerned the storm could inch a bit further south. The 12z model runs should help to answer that question.

Ross Ellet

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Monday 2am Update
January 31, 2011

I am going through the 00z GFS and NAM in-depth as we speak. I will have a new update by 5:30am with the latest maps and forecast at the latest. As Damon mentioned there will be an extremely sharp cut off in ice and snow totals with this storm. Which also means there will be big bust potential with our forecast unfortunately. My other concern is the wind speeds on Tuesday, which now look like they will be sustained between 25 to 30 mph with wind gusts near 40 mph. This could create blizzard to near blizzard conditions for northeast Oklahoma and extreme northwest Arkansas. For areas in northeast Oklahoma, and extreme northwest Arkansas this is the real deal…could be a historic storm. More to come in a few hours.

Ross Ellet

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Preliminary Ice and Snow Forecast
January 30, 2011

A rather difficult two-fold forecast.  After starting as rain, first will come the risk of ice.  Then the ice will be followed by the snow.  Here is a preliminary ice and snow accumulation map.  The gradient across our viewing area of only a little ice/snow will be close to areas that see a lot of ice and snow, so it is difficult to draw such tight gradients.  However, here is an initial look to give you a general idea where the higher totals are expected to be.  The heaviest ice and snow totals for our area will be in northern and western Benton County and adjacent areas into Oklahoma and Missouri, with many areas of Northwest Arkansas seeing near or over a 1/2″ of solid ice.  This will be enough to pose a risk to power outages.  On top of that ice will be a layer of snow.   Lesser amounts of ice and snow are expected for the Fort Smith area, and it appears that Eastern Oklahoma will see more ice and snow than Western Arkansas.  By the time the enitre atmosphere becomes cold enough for snow, a layer of dry air aloft will come in (what we call the dry slot). This is expected to limit ice and snow amounts from Fort Smith to the south and east. 

Slight changes in path of the low and a couple of degrees of change at the ground and just above the ground will make a large differences in the varying amounts of ice and snow.  Ross and Drew will have further updates on possible changes on Monday. 

Damon Shaw, 40/29 Meteorologist

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Tuesday Timelines
January 30, 2011

Our viewing area will be a battleground between significant ice with snow for some and little more than just a cold rain for others. 

Benton County:  Initially starting as rain, but quickly changing to freezing rain.  Because temperatures will be close to or below the freezing mark while the heaviest precipitation is falling, this is where the most significant icing is expected.  This is where we will have the highest risk of ice accumulations over 1/2″ as well as a higher risk of power outages.  A changeover to snow will also be a little sooner here, with about 2-4″ of snow on top of the ice.  Some spots on the Oklahoma or Missouri border could exceed 4″. How much snow that falls is still a bit in question, but confidence is high that icing will be a problem. 

Fayetteville area:  Temperatures will be above freezing a little while longer than Benton County, so ice accumulations probably not quite as high, but it will still be a problem both on the roads and powerlines as temperatures drop below freezing by the middle of the day.  Lesser amounts of snow accumulations are expected, around 1-2″ on top of the ice.  Again, how much snow that falls is still a bit in question, but confidence is rather high that at least freezing rain will create problems. 

Fort Smith area:  It is expected to remain above freezing Tuesday morning while the heaviest rain falls.  The subfreezing air will come in about the same time the heaviest precipitation begins to lessen, thus reducing the ice accumulations compared to areas just the north and west of Fort Smith.  There still will be a narrower window of some freezing rain or a brief wintry mix before precip tapers to flurries.  However, the bust potential is a lot higher for Fort Smith.  It is important to point out that Eastern Oklahoma (Sallisaw, Stigler, Vian, etc.) will probably see more ice and snow than Fort Smith.   The risk of accumulating ice and snow decreases even more as you head further south and east of Fort Smith.

Damon Shaw, 40/29 Meteorologist

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12Z GFS & NAM Thoughts….Noon Update
January 30, 2011

Thanks again to everybody posting your thoughts and comments on the blog.  Ross, Damon, and I are all taking time during the weekend to answer questions on the blog.  Please be patient if you’re waiting for an answer.

I’m going to piggyback off of Ross’ blog entry from earlier this morning.  I just looked at the 12Z GFS Bufkit data and really there are a lot of similarities with the 12Z NAM.  The placement of the surface low is pretty close between the two models.  The timing of the precipitation is very similar as well.  As a forecaster it’s easier to build a forecast when you have consistency with the models.  We will likely experience some more changes and wrinkles over the next 24 to 48 hours before the event occurs, so I want to caution everybody. 

If you’re a snow fan than Benton county will be the spot for this event.  Other than minor freezing rain early Tuesday morning, the cold air will likely be in place to see mostly snow and sleet.  Accumulations of 4″ to 8″ seems very possible.  Northwest of Benton county snow totals will likely total over 12″.

As Ross mentioned, where it gets tricky is across Washington, Crawford, Sequoyah, Madison, and Carroll counties.  The freezing rain icing threat is very real with this event.  We’re thinking the freezing rain will start after 4 a.m. and last through 10 a.m.  While it’s possible for the terrain to slow some of the surface cold air, the strength of this storm will likely overcome the terrain.   0.25″ to 0.75″ of ice is very realistic before it changes over to sleet and snow during the late afternoon.  Snow and sleet accumulations of 2″ to 4″ will be possible.

The River Valley will likely see rain through Noon on Tuesday.  Early afternoon will likely support a mix of freezing rain and sleet with minor ice accumulations below a tenth of an inch.  Sleet and snow totals will likely remain below 2 inches.

Drew Michaels

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