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Why fronts don't always bring rain...

Posted: Tue Oct 01, 2019 3:09 am
by thunderchaser83
Below is the forecasted temperature for 07 October 2019. First, this is 192 hours out. So, take everything here with a grain of salt..
gfs_H192_Temp.png (146.84 KiB) Viewed 613 times
With a cold front being shown on the 2m Temp map, you might expect some kind of precipitation...but under this situation, none is forecasted by the GFS. Why?
sfcwind_mslp.us_sc.png (524.31 KiB) Viewed 613 times
Notice the iso bars (pressure), there is not any lower level support, and looking at the temperature profile, there is even a temperature inversion aloft. Sinking air that could prevent storms from developing. Second, aloft, at the 500mb level, there is a high pressure ridge. So this is a very shallow cold front. Not much in the way of lift to push a parcel of air passed its LFC. With sinking air, you'll see clear skies. No precip. I'd be willing to say, almost none.

Winds are straight from the north until you hit I-10 corridor where they turn and come out of the north east.
500wh.conus.png (246.58 KiB) Viewed 613 times
It will probably end up being a warm day, and that's it. Even with moisture in place.

For some kind of precip or storms, you'd really need an upper level trough that brings in a cold front from the Northwest, has a more defined area of low pressure with some vorticity maxima (jet streaks), a warm front, etc. This orientation of winds would bring in warm moist air from the gulf and draw cold dry air from the mountains and desert north and west of Central Texas. Such a cold front would be sufficient for storms, possibly even severe storms. Alas, we have no such situation this time around!