Saturday, April 10, 2010

Severe Weather Potential 4/11-4/13

Sooooooo.....We have a large Pacific trough that sets up over the western U.S. This trough will swing pieces of energy that will allow thunderstorms to develop and potentially go severe...

Sunday-This is probably going to be the best day for tornadoes as this storm moves through the area. Latest NAM runs suggest a CAPE bomb of 2800-3000 j/kg in southern Kansas/northern Oklahoma with good directional wind shear, especially in the sfc-700 mb layer. However the speed sheer is not all that great due to a lack of a strong pressure gradient. Dewpoints look to be in the 60s across central Kansas/Oklahoma. NAM/WRF show a few discrete cells developing after breaking the cap. The cells will be slow moving to nearly stationary due weak flow aloft, but with them binge very isolated, they will be very photogenic. If enough convergence develops at the surface and winds at the surface can increase a bit, a tornado or two will be possible.

If I were going to chase I would stay in southern Kansas between Dodge City and Wichita.

Monday and Tuesday-The severe weather threat on these days will primarily be large hail and damaging winds and will be across the high plains and closer to home. Directional wind shear is really not all that impressive. A few isolated thunderstorms will be possible late Monday afternoon/evening. Shear is fairly unidirectional, except in the Dakotas where there is a little bit more of an easterly component to the surface winds. Dewpoints will be in the mid 40s and 50s from eastern Colorado through the Nebraska Panhandle. Southerly winds will aid in advecting moisture from the southern plains. A few storms will fire but shear is not favorable for tornadic supercells

Tri-State region

Across my viewing area, severe weather threat will be limited on Monday due to a dry lower atmosphere. Expect a few thunderstorms to fire in the afternoon and evening, but with a dry lower atmosphere and LCL's over 2500 m above the surface, the only threat from theses storms will be gusty winds from evaporating rainfall and downbursts.

Moisture advection will increase Monday night with a 5-15 mph southeasterly wind across the Panhandle and SE Wyoming. A cold front will move through the region on Tuesday which will be the lifting mechanism. Wind shear ahead of and along the cold front will be mainly unidirectional which would take out any threat of tornadoes. With that said large hail and damaging winds will be possible. CAPE values are really not all that impressive, but for the high plains the values are large enough for a few storms. Another issue will be the potential for heavy rainfall with precipitable water values approaching 0.8" The greatest tornado threat will occur over the Dakotas where there is a more easterly component to the surface winds, but with that said the shear is still not all that impressive.

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