Sunday, June 6, 2010

Severe Weather Threat For June 7th

A very interesting scenario is setting up for portions of the Tri-State region on Monday. A shortwave within the ridge of high pressure that is centered over the area will rotate over the area on Monday. ESE winds at the surface will advect more moisture in to the Tri-State region. Dew points look to be in the low to mid 60s by tomorrow afternoon across southeast Wyoming...WOW!! The result will be a huge amount of Cape along the Front Range (3000-4000 j/kg).

The one issue that looks like will be a big problem would be the very strong capping inversion that is going to be sitting above most of the area. 700 mb temperatures look to be in the 15-18 degree range through 6:00 PM, far to warm for initiation. The GFS continues to show the cap holding strong until the late evening hours when temps aloft finally cool while the WRF/NAM show some isolated development, mainly in Wyoming.
Have decided to side with the WRF/NAM on this one, although some of its coverage may be a little on the high end. 700 mb temperatures across east-central Wyoming are much cooler and thunderstorms should initiate up there. Outflow boundaries will move south out of those storms and will most likely collide with boundaries from storms on Sunday that will be pushed against the Laramie Range. These boundaries will be the focal point for storm initiation.
By 00Z, the capping inversion looks to weaken along the I-25 corridor in Wyoming. At this time, if the timing is correct, outflow boundaries from storms to the north will collide with other boundaries along the Cheyenne Ridge/Laramie Range giving updrafts a slightly stronger push up to potentially break the cap where it is weak enough in SE Wyoming.
Northern Colorado should stay capped through the afternoon as the cap is much stronger. I would expect the cap will weaken a bit between 00-03Z just in time for southbound outflow boundaries from storms in Wyoming to provide areas of convergence in northern Colorado, at which time CAPE values appear to be very impressive. Most of the convection should occur in Colorado after 3Z.
Whats the threat?!?!?!?!?
Strong CAPE values would indicate the potential for some very strong updrafts. Surface to 500mb bulk shear values appear to be in the 50-60 kt range, enough for the updrafts to remain rain/hail free. There are at times brief veering wind profiles across the area as a surface low in SE Colorado keeps winds at the surface in a ESE direction with winds aloft from the WSW in the quasi-zonal flow.

As of now feel the primary threat will be large destructive hail and damaging winds. However, if LCL's can remain in the 750-1000 m range a few isolated tornadoes can not be ruled out. The threat for severe weather will exist between 4:00 PM and 8:00 PM for SE Wyoming and will shift south and east between 8:00 PM and 12:00 AM for northern Colorado. I feel that storm chasers who park themselves in Cheyenne tomorrow afternoon/evening could enjoy a few very nice looking supercells....

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