Severe Weather Discussion for March 10 – 16, 2008.
– Pleasant mid-March week ahead with temperatures around seasonable norms. The only “cool” day this week appears to be Saturday.
– Thunderstorms are possible across Texas on Monday, primary threat will be small hail.
– Slight chance of thunderstorms Wednesday night for Oklahoma, primary threat will be small hail.
– Thunderstorms are possible Sunday evening for parts of Texas and southern Oklahoma, with low-impact severe weather.
– Storm Season starts March 15th.
– Severe Thunderstorms in Oklahoma: 10%
– Storm Chase: < 5%
– Winter Precip: < 5%
The southern jet stream will be rather active this week, but sensible weather will be somewhat low. This is due to this past Thursday’s longwave trof and resultant Canadian high pressure intrusion into the Gulf. Effective push of Gulf moisture was past the Yucatan. While the Canadian high pressure is progressive, return flow will take several days along with strong cyclonegenesis.
While there will be several systems this week, the pattern will not be amplified and this should keep the cold air up north. The first system will be passing over Texas at the beginning of the period tomorrow. 12z NAM is robust with showers and some thunderstorms across central and north Texas on Monday. This appears reasonable given moisture return of 50-55F. 12z GFS agrees well also. Weak surface high pressure will be present with little change in temperatures expected once the system is east of the region.
Tuesday and much of Wednesday will be warm. Fire danger may be very high as moisture return remains limited. A northern stream system will be moving along the U.S./Canada border with a weaker southern stream system somewhat in-phase with it. The latter system should combine with modified moisture return around 50F to produce isolated thunderstorms. No impacts are expected as the primary threat should be small hail.
A Canadian cold front moves towards the region on Thursday but gets held up by another southern stream shortwave trof due in on Friday. This trof will be low amplitude with a small area of channeled vorticity moving through Oklahoma Friday afternoon. While moisture will be increasing, models develop very little QPF across the state. I’d think this system will produce some isolated showers and maybe a thunderstorm. Small time and spatial scale keeps this out of the general forecast. After this system passes the developing Canadian high will move through the region in a narrow channel of the central U.S. This front will go to the Gulf and cool OK/TX down on Saturday. Skies should be clear on Saturday, allowing for a decent warmup despite the Canadian intrusion with temperatures in the mid 50s in Oklahoma to 70s in central Texas.
A warmup is expected on Sunday with temperatures near climate norms of 64F in Oklahoma City. The real interest appears to be developing by Sunday as a highly amplified southern stream shortwave trof approaches the west coast. The 12z ECMWF/GFS runs are in agreement with placement of this thing, an odd item for 168 hours out. Going with the 12z runs, I would expected isolated thunderstorms Sunday evening as warm air advection increases across the region. GFS dewpoiints show 55F in central Texas at 7pm Sunday. I went ahead with 10% severe for this time period since there could be some isolated elevated hailers. Confidence is above normal that this system may produce a medium-end event across parts of the region on Monday. Climatology would favor eastern OK/TX and for now this is the most prudent forecast. Special discussions may be needed starting Thursday if current model trends continue.
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