Monthly Storm Reports and Storm Data
Storm Reports
Are you interested in what happened during a recent event? Check out the report below.
 
Winter Weather on January 14-15, 2013
 
Temperatures at 600 pm CST on 01/12/2013.

A cold front pushed through Arkansas on January 12th. Behind the front, temperatures plummeted into the 30s in the northwest by sunset. 
In the picture: Temperatures at 600 pm CST on 01/12/2013. There was a forty degree difference across the front. The front stalled for awhile and waited for a storm system ("L") to pass before progressing through southern and eastern Arkansas during the overnight hours. 

 

The front eventually stalled over the southeast United States as it encountered a ridge of high pressure off the Florida Coast. Well below normal temperatures existed behind the front on the 14th. Areas of light freezing rain and sleet developed from Little Rock (Pulaski County) southeastward.
The pattern at 1200 pm CST on 01/14/2013.
In the picture: The pattern at 1200 pm CST on 01/14/2013. Precipitation broke out north of a stalled front in the southeast United States. Where it was cold enough, including southeast Arkansas, there was a light wintry mix.

 

In the far southeast, quarter to half inch ice accruals were reported on elevated surfaces (trees, power lines, bridges/overpasses, etc) in Ashley and Chicot Counties. This created hazardous driving conditions.

 

There was greater than a 90 percent chance of 0.01 inch to 0.10 inch of freezing rain in southeast Arkansas in the twenty four hour period ending at 600 am CST on 01/16/2013.

The front did not move much on the 15th, with chances for icy precipitation continuing in the south/east.
In the picture: There was greater than a 90 percent chance of 0.01 inch to 0.10 inch of freezing rain in southeast Arkansas in the twenty four hour period ending at 600 am CST on 01/16/2013. The graphic (made on 01/15/2013) is courtesy of the Hydrometeorological Prediction Center.

 

Preliminary snow/ice totals on 01/15/2013.
In the picture: Preliminary snow/ice totals on 01/15/2013.
 

Additional amounts were generally under a quarter of an inch. Ice caused the most problems in the extreme southeast, with an ice storm from there into northeast Louisiana, northern and western Mississippi and parts of western Tennessee.

Farther north/west, there was some light snow in the Ozark and Ouachita Mountains and into northeast Arkansas.

 

Two to four inch accumulations resulted from Jasper (Newton County) and Russellville (Pope County) northeast to Mountain Home (Baxter County), Mountain View (Stone County), Batesville (Independence County) and Pocahontas (Randolph County). The 300K isentropic surface showed moisture transport vectors (in blue) blowing from higher to lower pressure (dashed yellow lines) on 01/15/2013.
In the picture: The 300K isentropic surface showed moisture transport vectors (in blue) blowing from higher to lower pressure (dashed yellow lines) on 01/15/2013. This created lift across much of Arkansas in the mid-levels of the atmosphere, and moisture (in green) was taken skyward along the surface to make clouds and precipitation. What is a 300K isentropic surface? This is a level aloft where, if air parcels were brought close to the ground (1000 mb) adiabatically (without gaining/losing heat), they would reach a temperature of 300 Kelvin (around 80 F). In northwest Arkansas, that level was anywhere from 600 to 650 mb (roughly 12,000 to 14,000 feet), and closer to 800 mb (around 6,500 feet) in the southeast. So, moisture transport vectors (wind moving water vapor) from the south/southwest were generally going uphill (rising motion). By the way, at the top of the hill (across the northern counties), moisture was very close to the dendritic growth zone (temperatures between 0 F and 10 F). This is where the fastest accumulating fluffy flakes are born (high snow to water ratios).

 

Forecasting This Event

There was no doubt that ice would be an issue in southeast Arkansas on January 15th. Ice Storm Warnings (for significant icing) were posted for a dozen counties in the southeast, with Winter Weather Advisories (for minor icing) farther northwest toward Little Rock (Pulaski County) but not including the metro area. That forecast worked out. If anything, ice totals were a little less than expected.

Moisture was even more limited in the northern and western counties where it was cold enough for snow. Models indicated shallow moisture aloft, and it would have to fall (and evaporate) through a dry layer near the ground. With only enough moisture for a dusting, no weather headlines were necessary...or so it was thought.

While trace amounts were projected in the north/west, liquid added up to as much as a tenth of an inch. In Arkansas, a snow to water ratio is normally 10 to 1; that is, .05" of water will net a half inch of snow. But this was a 20 or 30 to 1 snow (dry and powdery), which explains the 2 to 4 inch accumulations in the Ozarks.

As reports of accumulating snow/sleet came in, Winter Weather Advisories were issued all the way to the Missouri border.

Slow warming was expected during the event, with a gradual changeover from solid (snow/sleet) to liquid (rain/freezing rain). While temperatures did warm a few degrees in the afternoon, it was mainly after precipitation ended.

The moral of the story: Anytime mixed precipitation is in the forecast, it can get complicated. How deep is the cold air? How much moisture is coming? What will fall where and how much? These are the challenges faced every winter in Arkansas. This event was no different.

 

The particular model (North American Mesoscale Model or NAM) showed no precipitation (less than 0.01") in the northwest half of Arkansas on 01/15/2013.

In the transition zone between snow and ice (central sections), mainly sleet fell with less than a half inch common.
In the picture: The particular model (North American Mesoscale Model or NAM) showed no precipitation (less than 0.01") in the northwest half of Arkansas on 01/15/2013. A forecast sounding (inset) around Mountain View, AR shows why. While the atmosphere was expected to become saturated in the mid-levels of the atmosphere (between 10,000 and 18,000 feet), any precipitation would have to fall through a dry layer closer to the ground. This would lead to evaporation and nothing measurable. Of course, this did not happen.

 

Roads across the area were snow and ice covered during the afternoon hours, with temperatures mostly at/below freezing. A warm ground caused some melting, with slowly improving conditions. However, some refreezing happened after dark, with icy patches on paved surfaces and hazardous travel on bridges and overpasses.

 

Storm Reports
There were numerous reports of light snow, sleet and freezing rain on January 15, 2013. For a look at some reports, click here.
 
Link of Interest
Plot Reports
Preliminary reports of wintry precipitation in the Little Rock County Warning Area on January 15, 2013 (in red).
Submit a storm report.
In the picture: Preliminary reports of wintry precipitation in the Little Rock County Warning Area on January 15, 2013 (in red).
USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.