Weather conditions not at all typical of December continue across Central and South Texas. For the past few days, daily temperatures have been averaging between 10 and 20 degrees above normal! For most of our region and Texas as a whole, December 2021 is shaping up to be the warmest December on record.
In the big weather picture, the jet stream is currently flowing southeast from western Canada to the western Rockies, then northeast to Great Lakes and New England. To the south of the jet, a broad ridge of high pressure stretches from Texas to the Mid-Atlantic. This fairly stagnant pattern is bringing quite cold and unsettled weather to much of the western U.S. and dry, unseasonably mild weather to the South Central and Southeastern U.S. This pattern is forecast to breakdown late this week when the western trough moves to the east and the ridge retreats to the southwestern Atlantic. This will allow cold air to finally spread south into Texas.
A moderate wind flow off the Gulf of Mexico continues to bring unseasonably warm and humid weather conditions to Central Texas. Moisture trapped below a strong inversion has resulted in the development of widespread clouds, fog and patchy drizzle for the past few mornings. Mixing of the lower atmosphere in the late morning hours causes the inversion to weaken and mostly sunny conditions to develop in the afternoon. Similar conditions are forecast to continue this afternoon and Wednesday. Temperatures both days are predicted to reach near 78-80 degrees across the Hill Country and Central Texas regions and into the low 80s across the coastal plains. Lows Wednesday morning will range from the upper 50s to low 60s across the Hill Country to the mid and upper 60s across the coastal plains.
Some small changes in the pattern are forecast to take place Wednesday when a Pacific cold front slides southeast out of Northwest Texas. The front is forecast to move across the Hill Country Wednesday morning, reaching the Austin/Interstate 35 corridor about midday. The front is forecast to continue southeast and pull up stationary near the Interstate 10 corridor Wednesday evening. No rain is forecast with the front. However, northwesterly winds will increase to 10-15 mph behind the front. In addition, humidity levels will trend noticeably drier. The sky will be partly cloudy Wednesday night. Lows Thursday morning will include the upper 40s to low 50s across the Hill Country and the low and mid-50s across Central Texas. Across the coastal plains region, lows will continue in the low and mid-60s.
The dry and slightly cooler air Wednesday and Wednesday night will only be a quick tease as the cold front is predicted to move back to the north Thursday afternoon, bringing a return of the warm and humid Gulf air. Expect a mostly sunny sky. High temperatures Thursday will generally be in the mid-70s, with lower 80s expected across the coastal plains. The sky will become cloudy Thursday night. Lows Friday morning will range from the mid-50s across the Hill Country, to the upper 50s across Central Texas, to the mid-60s across the coastal plains.
For the last day of 2021, few changes are forecast. Morning clouds, fog and patchy drizzle Friday morning will give wary to mostly sunny and warm conditions in the afternoon. High temperatures are forecast to be near 78-80 degrees. The sky will turn cloudy Friday night and there will be a slight chance for a few light rain showers across much of the region overnight. Temperatures at midnight are forecast to be around 68-70 degrees. Lows Saturday morning will generally be in the low 60s, with upper 60s expected across the coastal plains.
New Year’s Day will feature morning clouds and mostly sunny conditions in the afternoon. Temperatures will be warm, with highs forecast to be around 78-80 degrees.
A strong Canadian cold front associated with the western trough is predicted to sweep southeast across the region Saturday evening and Saturday night, bringing much colder air! In fact, a light freeze is predicted across parts of the northern Hill Country Sunday morning. Lows Sunday will include to upper 20s to low 30s across the Hill Country, the low and mid-30s across Central Texas and around 38-40 degrees across the coastal plains. Expect northwesterly winds to increase to 15-25 mph behind the cold front Saturday night through Sunday.
There will be a slight chance for a few light rain showers along the cold front when it moves past the Interstate 35 corridor. Rain amounts should only average around a tenth of an inch. It should also be noted parts of North Texas, extending south to around Brownwood and Abilene, could see a mixture of light rain and snow after midnight Saturday night as a weak atmospheric disturbance tracks east across North Texas. No significant accumulations are forecast. Sunny, breezy and much colder conditions will develop Sunday in the wake of the cold front. High temperatures are forecast to be only in the upper 40s to low 50s.
A freeze is forecast for the entire region Sunday night into Monday morning as the wind decreases and the sky is clear. Lows Monday morning are predicted to be in the mid-20s across the Hill Country, near 28-30 degrees across the Austin/Central Texas area and in the low 30s across the coastal plains.
The outlook for next week calls for mostly sunny and dry weather throughout the week. The week will start off cold, but milder temperatures are forecast to make a quick return Tuesday, continuing through Thursday.
High temperatures are predicted to be in the mid-50s Monday, warming to the mid-60s Tuesday and into the low to mid-70s Wednesday. Highs are forecast to fall to the 60s for Thursday and Friday. Low temperatures Tuesday morning are predicted to be in the upper 30s, warming to near 50 degrees Wednesday and Thursday mornings.
Long-range forecasts do not show any arctic air headed to Texas through the middle of January.
Alignment of the Planets in the Evening Sky Continues
The line of Jupiter, Saturn, and Venus in the southwest at dusk continues to evolve. Venus, the lower right end of the line, is dropping away rapidly. And the whole line is sliding farther to the lower right. Meanwhile, Mercury down below is on its way up to pass Venus. On the 28th Mercury will be passing 4° to Venus’s lower left; and on the 31st you’ll find it 7° to Venus’s left or upper left. All week, Mercury remains a bold magnitude –0.7 magnitude.
Have a good week.