Weekly Weather Briefing 2/24/2011 slides: srh.noaa/shv/briefing

1. Weekly Weather Briefing2/24/2011slides:www.srh.noaa.gov/shv/briefing Matthew Duplantis National Weather Service Shreveport, Louisiana

2. Overview Thursday Southwest AR: Severe threat greatest over this area. Under a Moderate Risk from the Storm Prediction Center for supercells capable of producing high winds, large hail and isolated tornados. Northern LA: Severe threat decent but could be just as great as SW AR if instability increases over this area…if and when cloud cover erodes and allows for temperature increases along and ahead of a pre-frontal trough. Could see temperatures in the lower 80s…if clouds break. Rest of 4 state area: Under a Slight Risk from the Storm Prediction Center for thunderstorms along a cold front/dryline capable of producing high winds, large hail and isolated tornados. Other Impacts: Rainfall/flooding threats are low as some areas could see roughly one inch of rainfall with some of the stronger storms. Sunday For areas along and north of I-20…another round of severe weather with a much more dynamic system moving across our northern areas. High wind and large hail are the primary threats with this next system…cannot rule out isolated tornados. National Weather Service Shreveport, Louisiana

3. Big Picture (9 AM) L National Weather Service Shreveport, Louisiana

4. Big Picture (9 AM) L WARM FRONT DRY LINE National Weather Service Shreveport, Louisiana

5. Radar (945 AM) National Weather Service Shreveport, Louisiana

6. Overall Categorical Threat • Moderate Risk of severe weather over SW AR and extreme northern LA. • Slight Risk of severe weather over the entire rest of the four state region. • One caveat is how much instability we receive in southern sections…

7. Wind Threat • Greatest threat over SW AR and northern LA. • Roughly 45% chance of seeing 50+ knots within 25 miles of a point. (Orange area) • Roughly 30% chance of 50+ knots. (Purple area) • 15 % elsewhere.

8. Hail Threat • Greatest threat over east TX, NW LA and SW AR. • Roughly 30% chance of seeing 1” hail or larger within 25 miles of a point. (Yellow area) • Roughly 15% elsewhere.

9. Tornado Threat • Greatest threat over SW AR • Roughly 15% chance of seeing a tornado within 25 miles of a point. (Dark green which = Purple area) • Roughly 10% chance of seeing an EF2-EF5. (Purple area)

10. Timing: 12 PM Thursday • Dryline/front approaching our western areas. • Pre-frontal trough beginning to initiate development. GFS Model (Dewpoints in yellow) DRY LINE/FRONT PRE-FRONTAL TROUGH

11. Timing: 6 PM Thursday • Dryline/front has moved through about half of four state region. • Pre-frontal trough continuing and expanding convection and supercells. GFS Model (Dewpoints in yellow) DRY LINE/FRONT PRE-FRONTAL TROUGH

12. Timing: 12 AM Friday GFS Model (Dewpoints in yellow) • Dryline/front has moved through all of the area. • Severe threat ending. DRY LINE/FRONT

13. Sunday Severe Threat • More dynamics with upper level system moving out of the 4 corners region in SW US. • Will have more instability with this system…

14. Sunday Severe Threat • Storm Prediction Center has already mentioned the area in their Day 4 Outlook.

15. Timing: 6 PM Sunday – 12 AM Monday GFS Model (Dewpoints in yellow) • Cold front will push through the four state region during the late evening hours on Sunday. • Should be through the entire area by daybreak on Monday. • Greatest threat along and north of I-20. COLD FRONT

16. Bottom Line • Severe weather threat in southern AR, northern LA, and east TX. • Damaging Winds • Large Hail • Isolated Tornadoes possible along and ahead of pre-frontal trough…cannot rule out along dryline/front but chances are low… • Widespread Severe threat for areas in east Texas and Northern Louisiana if instability increases! • Another Severe threat looming for Sunday evening…

17. NEXT CONFERENCE CALL: Thursday 10 AM (regular briefing) 03/03/2011 www.srh.noaa.gov/shv/briefing National Weather Service Shreveport, Louisiana