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Special Winter Weather Briefing 1/8/2010 slides: srh.noaa/shv/briefing

This briefing provides an overview of a winter weather system moving across Texas, bringing precipitation to Louisiana. There is a potential for heavy snow and freezing rain, especially in northern parts of the state. Travel and power outages are expected. Stay updated for the next conference call.

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Special Winter Weather Briefing 1/8/2010 slides: srh.noaa/shv/briefing

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  1. Special Winter Weather Briefing1/8/2010slides:www.srh.noaa.gov/shv/briefing Keith Stellman National Weather Service Shreveport, Louisiana

  2. Overview Sunday Low pressure system moving across Texas will bring precipitation to the region as early as Saturday night/Sunday May start as rain, but will transition to a mix of sleet and freezing rain by Sunday AM (West) Sunday noon (East). Then sleet/snow to all snow by Late Sunday…after 3 PM Accumulations of 4 or more inches snow/sleet possible especially I-30 and possibly down to I-20 Ice accumulations of 0.5 inch is possible..especially in northern LA Monday Precip ends before dawn at most locations Light flurries early AM across I-30 corridor AM Temperatures ≤ 32 I20 north, Upper 20’s along/north US 82 (Clarksville ->El Dorado) National Weather Service Shreveport, Louisiana

  3. Scenario H L Strong Upper Level Low Pressure Area L Mon L L Sun Today Tonight National Weather Service Shreveport, Louisiana

  4. Winter Storm Watches • Expanded to include all counties/parishes • Due to the threat of freezing rain/sleet accumulations in the south

  5. Sleet/snow/Freezing rain DilemmaTemperature profile at 3 PM Sunday - Shreveport • High Res models suggest a warm nose ~2500-5000kt ranging 34-35 ºF • If that occurs sleet or Freezing Rain is more likely • If the precip melts in that layer…Ice • If the precip is able refreeze, sleet Surface Tempeatures 28-31 Freezing line Height

  6. Sleet/snow/Freezing rain DilemmaTemperature profile at 6 PM Sunday - Shreveport • Warm Nose disappears • Precip would become all snow after 3 PM • Snow would fall onto any ice/sleet accumulations • Northern LA Surface Tempeatures 28-31 Freezing line Height

  7. Ice Accumulation Probabilities • *** If the warm nose materializes *** • Could be all sleet if it re-freezes in the lowest 2000 feet. • Greatest chances mainly in North LA • Amounts generally 0.25-0.50”…some models suggest slightly higher • Late AM->3/4PM • Changeover to snow occurs after ~4 PM

  8. Timing: 6 AM NAM Model • Light rain…mixing with sleet across deep east TX • Surface low near Corpus

  9. Timing: 9 AM Purple = sleet/snow/fzra Lt Blue = mix NAM Model • Rain becoming more sleet and/or freezing rain • Surface low shifting NE

  10. Timing: Noon NAM Model • Mixed precip likely everywhere • Surface low shifting south of Lake Charles

  11. Timing: 3PM NAM Model • Changeover to all snow across TX • Sleet/FZRA beginning to change in LA..but still falling

  12. Timing: 6PM NAM Model • Changeover to all snow most areas • Upper low centered near SHV • Surface low well to the SE • NE winds brining enough cold air to change type Blue = snow Lt Blue = mix

  13. Snow Forecast (issued 6 AM Saturday) • Higher amounts north where warm nose keeps precip mostly snow • Main axis may vary depending on freezing line and exact track

  14. **If we see Ice*** • Greatest chances mainly in North LA • Amounts generally 0.25-0.50”…some models suggest slightly higher • Will tend to decrease snow amounts • Snow will fall on any ice by late afternoon

  15. Monday (with snowpack, highs/lows could be colder Lows Highs Arctic Air Moving In

  16. Impacts • Heavy snows possible late Sunday AM through early Monday AM (I-20 north) • Lower visibilities • Slushy roads in heavier snows • Heavy wet snows can weigh on pine trees and come down on powerlines • Cold temperatures through mid-week keep snows around • Pipe freezing issues, if temperatures remain <35 through mid week • If Freezing rain materializes, could be talking about 0.25-0.50” • Snow will fall onto FZRA late Sunday • Mainly North LA, but could spill into NE TX and Southern AR • Obvious travel issues • Power outages

  17. NEXT CONFERENCE CALL: TBD….Sunday www.srh.noaa.gov/shv/briefing National Weather Service Shreveport, Louisiana

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