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Winter Weather Awareness Week
 
Introduction
 

Winter can bring a variety of conditions, including heavy snow, ice, and cold temperatures. These conditions can make driving conditions hazardous, with power outages occurring at times. In the end, you may become exposed to the elements...with your life threatened.

To help the citizens of Arkansas prepare for these conditions, a special week has been set aside to review safety rules and to understand the hazards of winter. This year, Winter Weather Awareness Week runs from December 3-8, 2017For a video introduction to Winter Weather Awareness Week click here.

 

Important Information
 
Winter Weather Awareness Week is a joint effort between the National Weather Service and several partners across Arkansas including the Department of Emergency Management, the Department of Transportation, and the Department of Education.
In the picture: Winter Weather Awareness Week is a joint effort between the National Weather Service and several partners across Arkansas including the Department of Emergency Management, the Department of Transportation, and the Department of Education. Click to enlarge.
 

The NWS will transmit winter weather safety information on the NWS Weather Wire and on NOAA Weather Radio All Hazards during this week. You can also acquire weather information from NWS Little Rock on the Internet!

 

Information Sent During Winter Weather Awareness Week, 2017
 
Sunday, December 3, 2017...Introduction...click here.
Monday, December 4, 2017...Outlook for the Upcoming Winter...click here.
Tuesday, December 5, 2017...Winter Precipitation Types...click here.
Wednesday, December 6, 2017...Winter Weather Watches, Warnings and Advisories...click here.
Thursday, December 7, 2017...Winter Weather Safety Rules...click here.
Friday, December 8, 2017...The Cold of Winter...click here.

 

Winter Forecast
 
The outlook for this winter (December, 2017 through February, 2018) is for milder and drier than average conditions across the southern United States, including Arkansas. The outlook is courtesy of the Climate Prediction Center.
Temperature Outlook  |  Precipitation Outlook
In the pictures: The outlook for this winter (December, 2017 through February, 2018) is for milder and drier than average conditions across the southern United States, including Arkansas. The outlook is courtesy of the Climate Prediction Center.
 

One of the most reliable long-range predictors deals with monitoring water temperatures along the equator in the Pacific Ocean. If the water cools, we trend toward La Niña conditions. If warming occurs, we are headed for El Niño. Both variables have a say in how the weather behaves across the country, especially when they become dominant. This winter, the pendulum will sway toward La Niña.

When La Niña becomes the primary variable in winter, the expected outcome is warmer/drier than usual conditions in portions of the southern United States, with colder/wetter than average weather in parts of the north.

 

 

Big Winter Events
 
There were ruts in a few neighborhood roads in Sherwood (Pulaski County) to start the morning on 12/26/2012. Otherwise, most roads were snow covered and hazardous.
In the picture: There were ruts in a few neighborhood roads in Sherwood (Pulaski County) to start the morning on 12/26/2012. Otherwise, most roads were snow covered and hazardous. Click to enlarge.
Along U.S. Highway 167 to the south of Cave City (Sharp County), there was ice on the lines and some snow on the ground on 01/28/2009.
In the picture: Along U.S. Highway 167 to the south of Cave City (Sharp County), there was ice on the lines and some snow on the ground on 01/28/2009. Click to enlarge.
 

Even if it is a mild and dry winter locally, that does not mean these conditions will hold the entire time. Temperatures will fluctuate, sometimes wildly, and there will be precipitation. If cold air arrives, and sticks around as moisture increases, that is when big snow or ice storms often unfold. Major winter events have affected Arkansas in recent years. On Christmas in 2012, much of the region was buried under a thick blanket of heavy snow, with accumulations over a foot in some areas. At Little Rock (Pulaski County), 10.3 inches of snow piled up. The last time it snowed (more than a trace) in the city on Christmas was 1926! In late January, 2009, one to two inches of freezing rain (and locally more) accrued on trees and power lines in roughly the northern two rows of counties. More than 300,000 utility customers lost power. Tree damage was extensive, and at least 30,000 power poles were downed or snapped.

 

 

Precipitation Types
 
In Arkansas, it is not uncommon for subfreezing conditions to arrive from the north (provided by a large area of Arctic high pressure), and then warm/moist air tries to build into the state from the Gulf Coast (provided by low pressure to the southwest) before the cold air retreats. That is a recipe for a wintry mess. Clouds and precipitation often result, with snow where cold air is deepest, and rain where it is shallow. Sleet and freezing rain are found somewhere in-between.
Winter Precipitation Types (Part 1)  |  Winter Precipitation Types (Part 2)
In the pictures: In Arkansas, it is not uncommon for subfreezing conditions to arrive from the north (provided by a large area of Arctic high pressure), and then warm/moist air tries to build into the state from the Gulf Coast (provided by low pressure to the southwest) before the cold air retreats. That is a recipe for a wintry mess. Clouds and precipitation often result, with snow where cold air is deepest, and rain where it is shallow. Sleet and freezing rain are found somewhere in-between.
 

Forecasting precipitation types in Arkansas is challenging. When cold air dives southward from Canada, it is usually shallow by the time it reaches us. Think of it as an upside down bowl of subfreezing conditions, and we are toward the southern edge of the bowl. If temperatures are above freezing over the bowl, and there is precipitation falling, there will likely be melting followed by refreezing. This is a typical ice (freezing rain or sleet) scenario. If the edge of the bowl extends all the way into the clouds, and no warm layer exists, then melting would not occur and here comes the snow!

 

Watches, Warnings, and Advisories
 
Winter weather headlines were posted from Arkansas to the mid-Atlantic states at 300 pm CST on 01/06/2017.
In the picture: Winter weather headlines were posted from Arkansas to the mid-Atlantic states at 300 pm CST on 01/06/2017.
 

When a winter event is on the horizon, the National Weather Service will usually have a headline in place. There could be a Watch followed by a Warning and/or Advisory, but what does it mean? 

If there is a possibility of heavy snow and/or ice, a Winter Storm Watch will be issued. In the Little Rock County Warning Area, this would be at least 4 inches of snow in 12 hours, 6 inches of snow in 24 hours, a quarter inch or more of freezing rain, and/or a half inch of sleet or more. If the heavy snow and/or ice becomes imminent, a Winter Storm Warning or Ice Storm Warning will be posted. On very rare occasions, it there is a lot of wind (at least 35 mph), and blowing/drifting snow creates very low visibility (less than a quarter mile), a Blizzard Warning will go out. Anything less than warning criteria will be a Winter Weather Advisory.

 

 

Check the Roads
 
Roads were snow covered (at least partly) in much of northern and central Arkansas at 930 am CST on 01/06/2017.
In the picture: Roads were snow covered (at least partly) in much of northern and central Arkansas at 930 am CST on 01/06/2017. The image is courtesy of IDriveArkansas.
 

Following a winter event, sometimes it is not a good idea to venture out onto the roads. From a safety standpoint, you are putting yourself at risk of having an accident. Also, you may get in the way of crews trying to treat and clear the roads. If you must drive, please slow down and take it easy! Before you start the vehicle, check the roads at IDriveArkansas. Maps are available to show the status of major thoroughfares; that is; what is on the pavement (such as snow, ice/ice patches, or slush) and how much (such as mostly clear, partly covered, or covered). This information is updated often, especially when there is wintry precipitation. 

 

Links of Interest
What is on the Road? (examples: slush, ice or snow)
How Much is on the Road? (examples: mostly clear, partly covered or covered)
Understanding Route Conditions (determining snow/ice coverage on roads)

 

Factoring in the Wind
 
WIND CHILL INDEX °F
  WIND SPEED (MPH)
TEMP (°F) 5 10 15 20 25 30 35 40
-25 -40 -47 -51 -55 -58 -60 -62 -64
-20 -34 -41 -45 -48 -51 -53 -55 -57
-15 -28 -35 -39 -42 -44 -46 -48 -50
-10 -22 -28 -32 -35 -37 -39 -41 -43
-5 -16 -22 -26 -29 -31 -33 -34 -36
0 -11 -16 -19 -22 -24 -26 -27 -29
5 -5 -10 -13 -15 -17 -19 -21 -22
10 1 -4 -7 -9 -11 -12 -14 -15
15 7 3 0 -2 -4 -5 -7 -8
20 13 9 6 4 3 1 0 -1
25 19 15 13 11 9 8 7 6
30 25 21 19 17 16 15 14 13
35 31 27 25 24 23 22 21 20
In the table: The wind chill index is determined by combining the temperature and wind speed. Given a temperature, the wind chill index will decrease as the wind strengthens.
 

Have you noticed that it feels colder on a winter day when the wind is blowing? This is not your imagination. On a 30 degree afternoon, if there is a 20 mph sustained wind, it feels like 17 degrees to exposed skin. This apparent temperature is the Wind Chill Index, and it can be dangerous as values approach 0 degrees. Given such values, the National Weather Service will often issue a Wind Chill Advisory so that people can adequately prepare for the elements. This includes wearing several layers of loose-fitting, light-weight clothing. The layers actually trap warm air, and keep the cold air out. In addition to a coat and scarf, a hat and mittens are recommended (since more than half of your body's heat escapes through your head and hands).

 

Link of Interest
More About the Wind Chill