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