Weekly Severe Weather Discussion

Severe Weather Discussion for November 26 – December 2, 2007.
Valid: 11/26/2007.

Highlights:

– Seasonable temperatures today through Friday with highs in the 50s. Temperature may take a down turn this weekend with highs in the 30s Saturday and/or Sunday.

– Winter Precipitation is possible this weekend. It looks like a rain/freezing rain setup at this point.

– Tropical Storm Season ends on Friday.

Probabilities:

– Severe Thunderstorms in Oklahoma: < 5%
– Storm Chase: < 5%
– Winter Precip: 15%

Discussion:

Much needed rain fell across Oklahoma yesterday with some snow Friday night into Saturday. Good that last night's precipitation was liquid as 0.62 inches fell. That would have been 4-6 inches of snow.

The next few days will be quiet with the only sensible weather being periodic airmass changes. Today – Wednesday will be quite nice with temperatures warming to the upper 50s on Tuesday and Wednesday. By late Wednesday a northern stream shortwave trof moves north of the region and pushes a cold front through Oklahoma. This will have a little Pacific air with it and should cool us down into the low 50s on Thursday. The mid-level flow is rather progressive so the cold down will be short-lived with temperatures warming into the mid 50s on Friday. There will be several reinforcing shots of cold air as the mid-level flow remains progressive and several northern stream shortwave trofs traverse east across the northern U.S.

Forecast for this weekend is once again a low confidence one as models are in poor agreement regarding the evolution of a western U.S. southern stream shortwave trof. 00z/06z GFS wants to phase the trof into a large full latitude system and move it across the region on Sunday/Monday. The 12z 11/25 GFS is less phased and a little quicker. The 00z ECMWF is somewhat in agreement with the 00z GFS. The difference is huge as the 00z/06z GFS would be an all rain event given strong southerly flow. The 12z GFS's weaker southern stream system, lagging a stronger northern stream system would allow for freezing rain potential. OUN has hinted at the accompanying airmass being of a shallow nature and that is certainly possible. I'm going 15% on the winter precip for CYA and will handle any developments with special discussion. While freezing rain events are possible and there is cold air loading in Canada, it is still a tough sell in late November. Freezing rain events are much more
likely in late December through early February. It will be something to watch as Canadian/Arctic air have a way of ignoring the models. Temperatures Saturday and Sunday are equally high bust potential with the range from the low 30s to upper 40s.

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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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