Friday afternoon and evening are looking more like May than late September. Showers and thunderstorms are expected to develop and some could be strong to severe with hail, damaging wind and an isolated tornadoes possible.
Scenario
As an area of low pressure to the northwest pushes through parts of Wyoming and Colorado, it will send a cold front through the Texas and Oklahoma panhandles. The front will dig under warm, moist air and being to fire showers and thunderstorms across the area starting around two or three o’clock Friday afternoon.
As mentioned above, some of these storms could be strong to severe. The main threats for most storms will be quarter-sized hail and gusty winds. But in the strongest storms things like pin pong ball sized hail, winds in excess of 60mph and an isolated tornado cannot be ruled out. Right now it is also looking like flooding rains will be a possibility due to “training” by storms – where storms initiate and move over the same areas.
A Quick Breakdown
Partly cloudy conditions this morning with a raindrop or two to the west will give way to increasing clouds and eventually showers and storms. The first storms will begin to initiate around 2pm or 3pm on a line from Boise City to Clovis. The general movement of these storms will be from southwest to northeast around 20 to 40 mph.
As storms develop they will have a tendency to be discrete – or isolated – in nature. It is in these isolated cells that heavier rains, stronger winds and larger hailstones will develop. Also in these types of storms – sometimes called them supercells – there is a higher probability of seeing an isolated tornado.
As of now it appears that a bulk of the weather will move through Amarillo between 6pm and 8pm. That means any plans for evening football should also include a “Plan B” and a NOAA Weather Radio.
After about 10pm most of the action is off to the east and southeast of Amarillo and by tomorrow morning we’ll be dealing with a few clouds and gusty north winds.
For the Wx Curious
As the aforementioned area of low pressure to our north pushes east, the winds aloft from the southwest will increase across the high plains. Meanwhile the winds at the surface will converge to form a weak pseudo-dryline. That dryline will be set up from roughly Goodwell, Oklahoma south to Hart, Texas. This will set up a fair amount of Surface-to-500MB crossover in some of the eastern counties of the Texas panhandle.
For the same area, here are some quick stats from the 6z RAP computer weather model:
LCL > 1500
CAPE < 1000
LI > -4
EHI > 1.50
Helicity > 150
While these numbers don’t look overly impressive there are a few things of note.
The LCL number is looking at roughly the altitude of the cloud base. At LCL around 1500 is often favorable for tornadic development. The CAPE – explained here – value is a measure of instability and is a good indicator of how severe the severe weather can get. Generally speaking, the bigger the number, the more severe the weather can become. With a CAPE around 1000, the severe threat is marginal.
The EHI and Helicity values are both capable of producing supercells and isolated tornadoes.
Also, the Texas and Oklahoma panhandles will be in the lower right quadrant which is the most favorable for precipitation development. In fact, already this morning with a southeast wind, there are showers and a few rumbles of thunder firing along the lee-side of the Rocky Mountains in eastern New Mexico.
Right now given PWAT values between 1.5 and 2.0, heavy rains and even flash flooding conditions will likely be realized in at least a few places.
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