Severe wx this weekend, potentially an outbreak on Sunday

[WXBUFFJIM]

Good afternoon and evening folks. Severe weather will likely increase over the next few days across the south central United States as a disturbance approaching from the west encounters a warm, moist, and unstable airmass. The threat for severe weather will begin later Saturday across western Texas before shifting east into the piney woods of east Texas and possibly into southeastern Texas as well.

Looking at the day 2 outlook issued by the storm prediction center shows a severe weather threat for western Texas late Saturday into Saturday night. In the upper levels of the atmosphere, expect a large cutoff low to develop and move eastward into the four corners region during the day Satyrdat. The flow aloft will become southwesterly over the great plains resulting in a high pressure ridge across the Ohio and Tennessee Valley. At the surface, expect a low pressure center to deepen across the high plain states. This will mean heavy snow potential on the backside of this surface low across the Rockies and the Black Hills later this weekend.

The question during the day Saturday will be how much moisture gets advected in from the southeast across western Texas where the severe threat resides later Saturday. At this point with dewpoints generally at 50 degrees or higher across west Texas, scattered showers and thunderstorms are expectd to develop later Saturday and particularly into Saturday night as the upper level low approaches from the west. However the other question is the timing of this upper low. Could it generate thunderstorms later Saturday night as opposed to Saturday evening across west Texas? While instability maybe just marginal for supercell development across west Texas, strong deep layer shear will be present. Thus conditions appear favorable for organized thunderstorms with potentially a mesoscale convective system later Saturday night across west Texas and into western Oklahoma as well. The main threats if severe weather were to occur late Saturday will be large hail and damaging winds.

On Sunday, (day3) a very strong mid to upper level trough situated over the southern Rockies early in the period will rotate northeastward across the central and southern Plains. At the same time, an upstream trough will drop southeastward into the Pacific northwest. Cyclogenesis or stronger surface low pressure system will deepen as it tracks northeastward across Kansas and into southeastern Nebraska. Trailing the low will be a dry line/cold front, which will surge rapidly eastward across Texas and into southern Oklahoma Sunday afternoon and evening as a 80-90 knot mid level jet crosses the southern plains. Moisture will also be present as a 50-60 knot low level southrly jet plows into Texas and Oklahoma Sunday morning and into and lower Missouri and southern Mississippi Valleys Sunday night in advance of the cold front. The big question is how much instability occurs ahead of the cold front? At this point, models show dewpoints into the 60s across central Texas by late Sunday with higher dewpoints along the Texas coast with 55 degree dewpoints advecting into the Red River. Strong wind max accompanied by steep mid level lapse rates will rapidly spread eastward across northern Texas and into southern Oklahoma. This will enhance the instability and severe thunderstorm potential.

During the early stage of severe thunderstorm development, expect supercells with possible tornadoes across east central Texas and into extreme southern Oklahoma by Sunday afternoon. Large hail and damaging winds are likely as well as shear profiles strongly favor supercell development. Shear from the surface up to 6 km above the ground are 50-60 knots, which favors supercells, some with possible tornadoes. Dallas/Fort Worth, Plano, and possibly into Ardmore may want to keep a close eye on this. Then expect a rapidly transition over to a squall line with large hail and damaging winds being the main threat. The potential does exist for widespread wind damage potential across east central Texas and extending eastward into parts of Louisiana and Arkansas later Sunday into Sunday night as dynamics continues to play a key role in addition to the still deepening cyclogenesis over the middle of the country Sunday night.

This situation will continued to be monitored over the next several days. However this could potentially be the biggest severe outbreak of 2004 so far, I'll say that now. More updates on this tomorrow.

Good evening.

Jim

[JCT777]

Good discussion, Jim. I guess it is severe weather season already!

[WXBUFFJIM]

Yup JCT, sure is. It's only the beginning too as severe weather becomes more of a frequent occurrance in the months ahead. With this event, will we see 50 tornadoes or 148 tornadoes?? No. Could we see wind damage, large hail, and isolated tornadoes though?? Yea, the potential does exist for that.

Bottom line, keep an eye on this across the lone star state this weekend and further east late Sunday into Sunday night. An active severe weather period is coming up.

Jim

[Guest]

Jim,

What do the convective chances look like further north into Kansas and southern Nebraska?

The NWS has a chance of storms for north-central Kansas and southward (NWSFO GID).

Just wondering! Thanks

[WXBUFFJIM]

For Sunday, expect showers with a chance of thunderstorms across northern kansas into southern Nebraska. However as colder air moves in Sunday night into Monday, expect rain to mix with or possibly change over to wet snow. Just about everything, you name it. Definitely something to be on the lookout for.

Jim

[Guest]

Thanks, Jim!