April 2013 Weather Highlights for West-Central Texas
Precipitation for April varied from well-above to well-below normal across west-central Texas (Figure 1).
Figure 1: Percent of Normal Precipitation for April, 2013.
The monthly precipitation was above normal across parts of the Northern Edwards Plateau, and in scattered pockets of the Concho Valley and Big Country. These locations received received 2-4 inches of rainfall during the month. For a few locations in the western Concho Valley and western Big Country, the monthly amounts were less than 25 percent of normal.
Temperatures averaged above normal for the month, although to a lesser extent at Abilene.
At Abilene Regional Airport, the average temperature for April was 63.9 degrees. This was 0.7 degrees above the normal average temperature of 64.6 degrees. Total precipitation for Abilene in April was 1.72 inches. This was 0.08 inches above the normal of 1.64 inches.
At San Angelo Regional Airport, the average temperature for April was 67.3 degrees. This was 1.3 degrees above the normal average temperature of 66.0 degrees. Total precipitation for San Angelo was 0.98 inches. This was 0.44 inches below the normal of 1.42 inches.
The April weather highlights for west-central Texas featured a rollercoaster pattern in temperatures, and several strong to severe thunderstorm events. This began in the first week of April.
Temperatures were warm on the 1st with highs in the 80s. With the approach of a strong cold front from the north, a severe thunderstorm affected the far northern Big Country during the late evening. This storm produced wind gusts of 60-65 mph as it tracked southeast across Haskell and Thockmorton Counties. Nickel size hail was reported in Haskell. Parts of the southern half of Throckmorton County received 1.5 to 3 inches of rainfall from this storm.
The strong cold front advanced south across the Big Country on the early morning of the 2nd. This front pushed south and reached the Interstate 10 corridor on the evening of the 2nd. Following the cold frontal passage, temperatures remained in the lower 40s across the Big Country, with light fog and occasional light rain. Across the southern half of west-central Texas, temperatures reached the 70-75 degree range during the afternoon.
With the approach and arrival of an upper level disturbance from the west, a large area of showers and thunderstorms developed during the evening of the 2nd, and moved east across a large part of west-central Texas (south of Interstate 20). Frequent lightning and locally heavy rainfall accompanied the storms, but no severe weather was reported. This was a beneficial rainfall event (Figure 2).
Figure 2: Rainfall for the 24-hour period, ending 7 AM CDT, on Wednesday, April 3, 2013.
Rainfall amounts between 0.5 and 1.5 inches were common, with a few locations receiving more than 1.5 inches. Temperatures were rather chilly areawide on the 3rd, and were mostly in the 40s with cloudy skies. Scattered showers and thunderstorms occurred across the eastern half of west-central Texas, as another upper level disturbance entered the southern Plains. With the exception of southern Kimble County (which received one half to one inch), rainfall amounts varied under one half inch. With the departure of the upper level disturbance, temperatures moderated on the 4th, as skies gradually cleared from west to east across the region.
In the following days (April 5-7), a substantial warming trend in temperatures occurred. With gusty south winds, temperatures warmed into the 80s for highs on the 6th. Abilene recorded a peak wind gust of 46 mph. On the 7th, a dryline advanced east across parts of west-central Texas, to just east of a line from Millers Creek to Abilene to Sonora by late afternoon. The dryline marked the separation of very warm and dry air to the west, and warm and more humid air to the east. High temperatures reached the 90-95 degree range across most of the area west of the dryline, and were combined with minimum relative humidity values of less than 20 percent. At Sweetwater, the relative humidity value dropped to less than 10 percent during the late afternoon.
Low clouds developed north into west-central Texas on the early morning of the 7th, and to a greater extent on the 8th. This was indicative of a low-level moisture return to the area. With the low cloud presence and continued south winds, a record high minimum temperature (65 degrees) was tied at San Angelo on the 8th.
A major change of events on the 9th and 10th included hot and dry conditions, severe weather, and some winter weather.
A dryline advanced east across parts of west central Texas on the 9th, and marked the boundary between hot and dry air to the west, and warm and humid air to the east. Afternoon high temperatures were in the lower to mid 90s west of the dryline. A strong, Canadian cold front surged south and arrived in the Big Country during the evening hours of the 9th. As the dryline retreated to the west and intersected the southward moving cold front, scattered strong to severe thunderstorms developed and affected the Big Couontry. Golfall size hail was reported 10 miles west of Throckmorton, while hen egg size hail occurred around Elbert (Throckmorton County).
The below radar animation (Figure 3) shows the development and coverage of storms across the Big Country, between 4:30 PM and 8:30 PM CDT, on April 9th.
Figure 3: Animated National Weather Service San Angelo Radar Imagery, for April 9.
The westward retreating dryline and the southward moving cold front can be seen in Figure 3. The cold front continued to move south through the rest of west-central Texas during the night. Strong, gusty north winds followed its passage. Peak wind gusts of 47 mph at San Angelo, and 41 mph at Abilene, were recorded.
Additional thunderstorms occurred during the post-Midnight hours of the 10th, with the approach of an upper level storm system from the west. Some of these storms contained hail. Dime to quarter size hail was reported at Potosi (Taylor County), and nickel size hail occurred at Roscoe (Nolan County).
As much colder air poured into the area, some of the precipitation became mixed with light sleet and freezing rain across the Big Country. A trace of ice accumulation was reported at some locations, but with warm ground conditions, no travel problems occurred. Temperatures dropped into the upper 20s to lower 30s across the Big Country, and into the 30s farther to the south.
Temperatures were much cooler on the 10th, most noteably across the Big Country. A new record low maximum temperature of 50 degrees was set at Abilene.
Another significant warmup occurred in the following days.
A dryline advanced east across west-central Texas on the 14th. Hot and dry conditions with gusty southwest (or west-southwest) winds occurred behind the dryline. Temperatures reached the lower to mid 90s for highs, and relative humidity values dropped to between 5 and 15 percent. A peak wind gust of 41 mph was recorded at San Angelo. Temperatures were well-above normal on the 15th, when a dryline advanced into eastern parts of west-central Texas. Afternoon highs were mostly in the lower to mid 90s. Across much of the area behind the dryline, relative humidity values dropped to less than 15 percent. A new record high minimum temperature (70 degrees) was set at San Angelo on the 15th.
On the 16th, very warm and more humid conditions occurred, with the exception of the northern and western Big Country, where a cold front entered the area before stalling. A record high minimum temperature was tied at San Angelo. Very warm and humid conditions occurred areawide on the 17th. The low temperature of 73 degrees at San Angelo not only set a new record high minimum temperature for that date, but also tied the record high minimum temperature for the month of April. This record was previously set on April 26, 2012 and April 30, 2002. In addition, a new record high minimum temperature for April 17 was set at Abilene.
Gusty south to southeast winds occurred on the 17th, with peak wind gusts of 46 mph at San Angelo and 43 mph at Abilene.
With the approach of an upper level storm system from the central and southern Rockies, along with the arrival of a strong cold front, a band of thunderstorms developed and moved southeast across west-central Texas, between Midnight and 6 AM on the 18th. Several of the storms were severe. Quarter size hail was reported at Hariett, and wind gusts to 60 mph were reported 2 miles northeast of Wall (both locations in Tom Green County). Wind damage was reported at several locations across the Big Country. Peak wind gusts of 54 mph at San Angelo, 47 mph at Abilene, and 40 mph at Junction, were recorded.
Figure 4 (below) shows a radar animation with this line of storms, between 1 AM and 5 AM on the 18th.
Figure 4: Animated National Weather Service San Angelo Radar Imagery, for April 18.
Rainfall amounts of one quarter to one half inch occurred across much of west-central Texas, while scattered locations received between one half and one inch.
In the wake of the strong cold frontal passage, much cooler and drier air overspread the region, accompanied by gusty north winds. Afternoon highs on the 18th (in the upper 50s to mid 60s) were 25-35 degrees cooler than on the 17th. Clear skies and diminishing winds allowed temperatures to drop into the 30-35 degree range for early morning lows on the 18th, across much of west-central Texas. This occurred as high pressure developed south into Texas. A relatively late season light freeze was recorded several locations. Record low temperatures were set at Abilene and San Angelo (34 degrees at both locations). The cool airmass remained over the area on the 19th, as high pressure shifted southeast across Texas. Abilene and San Angelo both recorded record low temperatures on the 19th.
A warming trend in temperatures began on the 20th, with gusty south winds. A peak wind gust of 43 mph was recorded at the Abilene Regional Airport.
Following a warm day with highs in the 80s to near 90 on the 22nd, yet another strong cold front brought an abrupt change in temperatures on the 23rd. This was the 4th strong cold front to affect west-central Texas during April. This front surged south across the Big Country during the early morning hours of the 23rd, and continued south across the rest of west-central Texas during the morning. Temperatures were much cooler on the 23rd, and were accompanied by gusty north winds. Considerable cloud cover also helped to hold temperatures down across the region. Across the Big Country, temperatures were in the 40s through the day. Temperatures fell into the mid 40s to lower 50s across the Concho Valley and Heartland areas. Across far southern parts of west-central Texas, temperatures fell into the 50s.
Temperatures dipped into the 30s for early morning lows on the 24th. The coldest readings were across the Big Country, where skies partially cleared during the night. Some locations across the Big Country recorded a late season light freeze. For some locations, the latest freeze on record was avoided by a narrow margin. A new record low temperature of 33 degrees was set at Abilene.
The unusually cool airmass lingered over the region on the 24th, with high temperatures mostly in the 60-65 degree range. A new record low maximum temperature was set at San Angelo on the 24th. A warming trend in temperatures ensued in the following days.
With an upper level disturbance over the region, showers and thunderstorms occurred on the 28th. The coverage was scattered across the Big Country and Concho Valley during the afternoon and early evening hours. Later in the evening, a band of thunderstorms developed and moved slowly south across the Northern Edwards Plateau and Northwest Hill Country. This band of storms contained frequent lightning, small hail, gusty winds, and very heavy rain. Figure 5 (below) shows a radar animation with the storms across the aforementioned areas in the southern part of west-central Texas, between 6:48 PM and 10:48 PM CDT.
Figure 5: Animated National Weather Service San Angelo Radar Imagery, for April 28.
The orientation of this band of storms along the Interstate 10 corridor caused considerable difficulty for motorists, and traffic accidents were reported. Rainfall amounts of 1-2 inches were common across western Kimble County, and across much of Sutton and southern Crockett Counties. Despite the travel disruptions, the rainfall was of some short-term benefit for that area, which has been encompassed in severe to exceptional drought conditions.
Warm and dry conditions occurred during the last couple of days in the month. Between 8 PM and Midnight on the 30th, a cluster of strong thunderstorms moved southeast into the Big Country. Wind gusts to 53 mph were recorded at the Sweetwater Airport.