special winter weather briefing 1/7/2010
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Special Winter Weather Briefing 1/7/2010. Keith Stellman. National Weather Service Shreveport, Louisiana. Overview. Sunday Low pressure system moving across Texas will bring precipitation to the region as early as Saturday night/Sunday - PowerPoint PPT PresentationTRANSCRIPT
Special Winter Special Winter Weather BriefingWeather Briefing
1/7/20101/7/2010
Keith StellmanKeith Stellman
National Weather Service Shreveport, LouisianaNational Weather Service Shreveport, Louisiana
Overview SundaySunday
Low pressure system moving across Texas will Low pressure system moving across Texas will bring precipitation to the region as early as bring precipitation to the region as early as Saturday night/SundaySaturday night/Sunday
May start as rain, but will transition to a mix of May start as rain, but will transition to a mix of sleet/snow rain by Sunday AM (West) Sunday PM sleet/snow rain by Sunday AM (West) Sunday PM (East)(East)
Accumulations of 4 or more inches snow/sleet Accumulations of 4 or more inches snow/sleet possible especially I-30 and possibly down to I-20possible especially I-30 and possibly down to I-20
MondayMonday Precip ends before dawn at most locationsPrecip ends before dawn at most locations Light flurries early AM across I-30 corridorLight flurries early AM across I-30 corridor AM Temperatures ≤ 32 I20 north, AM Temperatures ≤ 32 I20 north, Upper 20’s along/north US 82 (Clarksville ->El Upper 20’s along/north US 82 (Clarksville ->El
Dorado)Dorado)National Weather Service Shreveport, LouisianaNational Weather Service Shreveport, Louisiana
ScenarioScenario
National Weather Service Shreveport, LouisianaNational Weather Service Shreveport, Louisiana
Today Sat
Sun
Strong Upper Level
Low Pressure Area
Mon
HH
Sleet/snow/rain DilemmaSleet/snow/rain DilemmaTemperature profile at 6 PM SundayTemperature profile at 6 PM Sunday
Model #1Model #2
Free
zing
line
Some Some models models suggest a suggest a warm nose warm nose ~4-5kt ~4-5kt ranging 33-ranging 33-35 ºF35 ºF
If that If that occurs sleet occurs sleet is more is more likely likely (model 1). (model 1).
If not, snow If not, snow (model 2).(model 2).
Different Different sites vary in sites vary in this profilethis profile
Note the Note the winds winds advecting advecting colder air colder air from the NEfrom the NE
Height
Scenario #1 (noon – 6 Scenario #1 (noon – 6 PM) PM)
NAM Model NAM Model
Snow/slee
t lin
e
Snow/slee
t lin
e
Liquid Liquid equivalenequivalent t amounts amounts 0.25-0.25-0.50” 0.50” behind behind the snow the snow lineline
Scenario #1 (6 PM - Scenario #1 (6 PM - Midnight) Midnight)
NAM Model NAM Model
Snow/sleet lineSnow/sleet line
Liquid Liquid equivalenequivalent t amounts amounts 0.25-0.25-0.50” 0.50” north of north of the snow the snow lineline
Scenario #2 (6 PM) Scenario #2 (6 PM)
Euro Model Euro Model
Snow/sleet lineSnow/sleet line
Coldest Coldest model, model, worst case worst case scenarioscenario
Liquid Liquid equivalent equivalent amounts amounts 0.50 – 0.50 – 1.25” 1.25” north of north of the snow the snow lineline
Heaviest Heaviest swath swath from Tyler from Tyler - > El - > El DoradoDorado
National Center Snow National Center Snow Forecast Forecast (Friday Afternoon)(Friday Afternoon)
Swath of Swath of heavier heavier snows from snows from Tyler -> NW Tyler -> NW LA/ LA/ Southern ARSouthern AR
Generally Generally along I-20 along I-20 except TXexcept TX
We think the We think the extent is too extent is too far south…far south…but under but under worst case worst case scenario scenario some could some could extend extend further further south south
Previous Forecast Previous Forecast (issued 6 AM Friday)(issued 6 AM Friday)
Less in Texas, Less in Texas, focus more in focus more in southern ARsouthern AR
Forecast, for nowForecast, for now
Forecast amounts, for Forecast amounts, for nownow
**This is a **This is a conservative conservative forecast forecast based on the based on the uncertainties uncertainties in the in the temperature temperature profilesprofiles
IfIf an an all all snow snow event… event… amounts amounts could be could be doubleddoubled
Monday Monday (with snowpack, highs will be colder than (with snowpack, highs will be colder than
this forecast this forecast
Arctic Air Moving In
Lows Highs
ImpactsImpacts Heavy snows Heavy snows
possible late possible late Sunday AM Sunday AM (west) through (west) through early Monday AM early Monday AM (north)(north)
Lower visibilitiesLower visibilities Slushy roads in Slushy roads in
heavier snowsheavier snows
Heavy wet snows Heavy wet snows can weigh on pine can weigh on pine trees and come trees and come down on powerlinesdown on powerlines
Cold temperatures Cold temperatures through mid-week through mid-week keep snows around keep snows around
pipe freezing issues, pipe freezing issues, if temperatures if temperatures remain <35 through remain <35 through mid weekmid week
NEXT CONFERENCE CALL:
TBD….Possibly Sat AMTBD….Possibly Sat AM
www.srh.noaa.gov/shv/www.srh.noaa.gov/shv/briefingbriefing
National Weather Service Shreveport, LouisianaNational Weather Service Shreveport, Louisiana