Severe Weather Discussion 2007-5-2

Severe Weather Discussion for March 20 – 24, 2007.
Valid: 03/18/2007.

Highlights:

– Isolated severe thunderstorms are possible across north Texas into western Oklahoma on Tuesday. Primary threat is large hail.

– Severe thunderstorms are possible on Wednesday across the western parts of Texas into western Oklahoma.

– Heavy rain is likely region wide Thursday – Saturday with common 1-3 inches and isolated areas 3-5 inches. Severe thunderstorms are possible, but the specific location is difficult to pin down.

Discussion:

No changes to forecast reasoning from yesterday. GFS has trended towards the ECMWF regarding system evolution this week. System is still progged to close off and become cutoff from the mean flow on Wednesday. The system will then meander in the southwest U.S. for a few days before being kicked out on Saturday.

A front will enter Oklahoma on Monday and should stall somewhere in the state as a northern stream shortwave trof moves north of the region. This boundary will likely provide a focus for showers and thunderstorms Monday into early Tuesday. Dewpoints are already running in the low/mid 50s so there is sufficient moisture for precip.

Late Tuesday isolated severe thunderstorms may occur in north Texas into western Oklahoma as a surface low develops in Colorado. Current thinking is that this activity will be marginally severe with large hail the primary threat. Instability is not that impressive and moisture should be in the upper 50s at best.

Wednesday appears to be the best chance for widespread severe weather. However, this chance should be way west near I-27 between AMA and LUB. Additionally, Cirrus screw-us is going to be a big problem given the southern latitude of this system. Models seem to have picked up on the cirrus threat and have reduced instability factors as a result. However, given increasing flow aloft, deep layer moisture return, and some heating; favored areas will have to be monitored. Any storm that can develop will have the potential to be a supercell.

Wednesday convection should start what will be a heavy rain event for much of the region. GFS storm total precipitation is rather disturbing with a large part of Oklahoma in the 1.75 to 2.50 range and parts of central/southwest into the 3-5 inches range. Additionally, a large part of central Texas is also in the 3+ inches range. This will need to be watched as this system has the potential to produce widespread flooding.

Degree of moisture return and strong flow aloft would point to potential for severe weather. However, I think the best chance will be in central/south Texas Thursday and Friday. There may be a great chance region wide on Saturday as the upper system lifts out to the northeast across Kansas. Too many details and the lead time is rather large, for now need to be worried about the flooding potential. I do think the severe potential warrants a slight risk Tuesday and Wednesday for parts of Oklahoma. Thursday and Friday should see this threat south of Oklahoma with the threat returning on Saturday. Wednesday may get an upgrade to a moderate, but want to see what the cirrus is going to do first.

Probabilities:

Risk area for any part of OK/TX (valid: 03/19, Day 2, Day 3):

Slight: 100%, 100%
Moderate: 0%, 0%
High: 0%, N/A

Chase Status:

Level 1 – Normal

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of Hook-Echo.com. For his day job, Putnam works in emergency management for information technology.
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