Severe Weather Discussion for April 24, 2015. Issued: 04/22/2015

Severe Weather Discussion for April 24, 2015.
Issued: 04/22/2015.

Highlights:

– A few severe thunderstorms are possible this afternoon and evening, mainly near the Red River and south. A tornado watch is posted for NW Texas, panhandle and a small part of far SW OK.

– Active severe weather day is still possible on Friday across much of Oklahoma. Forecast issues remain – dryline location, moisture quality and morning/Texas convection.

Discussion:

Forecast Changes: None

Today – Early morning convection greatly stabilized the atmosphere across Oklahoma. The greatest threat for severe weather is along the Red River and south.

Friday – 12z model suite in much better agreement re upper system moving into the region from the SW U.S. The general trend of all models has been to slow the ejection said upper system into the region on Friday. Despite this slowing trend, several of the models still punch the dryline to I-35 by 7pm. As stated yesterday, I am not convinced of this solution, it also leads many to think the best chance for thunderstorms will be east of I-35. The 18z 12km NAM has done the same trick it did yesterday, slowing the dryline Friday afternoon. It also lights off storms over central Oklahoma and moves them east. This scenario is very reasonable and I think far more likely than those pointing to eastern Oklahoma. A concern will be the dryline slowing even more as we get closer to Friday. Again, dryline movement is tied closely to speed of the ejecting upper system. Since this system is moving into the region from Baja Peninsula, it will not be sampled by the upper air network until Friday. Another note is that models have a bad habit of generating convection 30-40 miles east of where it actually will start, again another concern for storms developing along HWY 81 as noted in yesterday’s discussion. Wind fields will be impressive across the region, there is a little veering above 700mb than is expected. Not sure this is a big deal, so will just note and move on.

The primary issues impacting severe weather on Friday relate to moisture quality (hence instability) and morning convection. Lingering surface high from large closed low over the Great Lakes will be parked across the central U.S. Models struggle to return maritime moisture northward due to this feature and there are a variety of solutions on how much moisture will get north. 18z 4km NAM is reasonable in showing moisture trapped in central Texas by this feature and developing surface low over southeast Colorado late Thursday. Moisture return commences Friday morning with serious questions if enough can return for storms Friday afternoon. This trend will have to be monitored but if correct will greatly modulate Friday’s severe weather threat into the low category.

Sunday – technically outside the forecast period but models indicate another upper system moving towards the region. EC and GFS are completely different, with EC favoring cool/dry conditions and the GFS showing better chance for severe thunderstorms.

Probabilities:

Risk area for any part of OK (valid: 04/23, Day 2):

Slight: 100%
Enhanced: 75%
Moderate: 35%
High: 0%

Chase Status:

Level 3 – watching Friday.

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