Updated 845am CT Wednesday / 4 December 2013
…. Unseasonable Warmth Continues ….
…. Massive Arctic High to Move into Texas by End of Week ….
…. Potential Winter Storm for Parts of Texas by Friday into the Weekend ….
On this Wednesday morning…. a southward moving strong cold front extends from Missouri southwestward into Oklahoma and northwest Texas then northwestward into New Mexico and Colorado where a low pressure storm system is developing. As a result of this surface weather pattern, surface winds are southerly across our area.
In the upper levels of the atmosphere… an intense upper level low moving slowly east southeastward over the western Dakotas and Wyoming as a trough deepens southwestward into California. As a result, the upper level winds over south central Texas and the Austin metro area about 18,000 feet above the ground are now west southwesterly 40 to 50 mph.
Weather is in a state of flux across the area. A southerly surface wind continues across the area with well above average temperatures expected today. With increased low level moisture, we’ve seen dense morning low clouds and fog this morning in areas along and east of the IH35 corridor.
By tomorrow, we’ll transition to a more northerly wind aloft as the area of low pressure moves from the northern Rockies into the plains states. A massive area of arctic high pressure.. now located over the northern USA as well as Canada and eastern Alaska with surface temperatures underneath the high as cold as -33 F over western Canada.. is breaking loose and surging southward into the western and central USA as the upper level low pressure moves to the east. By Friday into the weekend, the leading edge cold front will move well into the Gulf of Mexico and the arctic air mass will overtake much of the lower 48 states.
As the colder surface air moves in, the subtropical jet stream (higher in the atmosphere) off the tropical Pacific, will send disturbances overhead and will create an overrunning pattern where moisture comes back on top of the colder air. As the upper air disturbances move overhead, they will cause atmospheric lift with periods of precipitation possible back in the colder air. With temperatures expected to be near or even slightly below freezing, especially in the Friday night and Saturday night overnight hours and primarily north of the Austin area, we could see periods of freezing drizzle and freezing rain given the very shallow layer of surface based arctic air. I’ll continue to watch these precipitation prospects closely but, at this time, I think it’s a fair bet that the NWS will be issuing winter watches, advisories and warnings for parts of our area as this system gets better developed and the arctic cold air moves into our area.
The unseasonably cold weather pattern will likely persist for a few days with another surge of colder air moving into the area.. mainly reinforcing the colder air place.. by late next Monday into Tuesday. As we look ahead, under a clearing sky, we could see the coldest air of this fall season by Monday night and Tuesday night of next week with hard overnight freezes likely.
Regarding my forecast, my local forecast confidence: Very high forecast confidence through today and tonight.. then dropping to medium to high tomorrow (exact frontal passage time and rain chances along front being the question). For Friday through the weekend, my forecast confidence drops to low to medium with the main questions being the intensity of the cold air along with liquid/freezing precipitation chances.
Have a good Wednesday…
Meteorologist Troy Kimmel