Posted by:Drakoen, 12:53 AM GMT on February 12, 2010
At the surface, radar imagery from the Dallas-Fort Worth area depicts a large swath of snow with the rain/snow line south of interstate-20 just north Waco and extending eastward towards Big Spring, Texas and westward into the northern Louisiana just south of Shreveport. A band of heavy snow up through Dallas and Fort Worth with rates between near 1in/hr will likely produce an additional 2-4 inches of snow in and around the metroplex; 700mb progs are show omega forcing/mid level uplift and 850mb temps of -3C in the snow growth region. Snowfall totals in and around the Dallas metroplex will range from 8-12 inches and areas further north and west will see totals between 10-14 inches as the heavier bands of snow quickly produce accumulating snowfall. All of the snow taper of in Texas to light snow and flurries into the late evening hours. Down towards Waco could see around 1-3 inches of snow. Expect this rain/snow line to advance south and eastward as temperatures dive as we approach the evening hours towards Austin and Bryan in central Texas where trace amounts of snow mix with rain is expected. The best chance of snow in those areas will be late in the evening hours and into the early morning hours after midnight when the 850hpa low moves over eastern Texas and into Louisiana with low level cooling and uplift. South of the rain/snow line rainfall totals of 1-3 inches are possible down towards Houston and Port Arthur. Sleet is affecting portions of central and southern Louisiana and into southern Mississippi, Alabama, and the western panhandle as temperatures are dropping off and due to the isentropic lift generated showers over these areas.
Forecast: Low level cyclogenesis is taking shape over southern Texas; numerous buoy reports indicate rapidly falling pressures over the region. This low is expected to intensify over the evening hours and progress eastward as the mid level trough behind the system advects eastward. The rain/snow line over northern Louisiana will advance south east eastward Thursday night and into Friday. Friday morning at 7:00am the low will be south and east of Louisiana. The 850hpa low out to the north of the surface low will result in dynamic cooling and mid level forcing for the areas north Interstate-10. 1000mb-850mb thickness sub 1290gpm and 850mb-700mb thickness running 1540 gpm along the I-10 corridor. 850mb temps between 0 to -3C.
Things will start out as sleet in central and southern Louisiana Thursday evening and then change over to snow completely on Friday. The rain/snow line appears to extend down towards New Orleans with the NAM, GFS, and CMC unanimously extending the 850mb 0C line isothermal south of I-10 with wet snow up to an inch. Areas north of I-12 will likely receive significant snowfall accumulations from this winter snow storm.
The GFS, NAM, and Hiresolution NMM show a wide swath of .5-1 inches of liquid precip which would equate to 5 to 10 inches of snow for some areas across Central portions of Louisiana, Mississippi, and Alabama with mid level energy support by a mid level trough axis and its amplification over the region support a snow growth zone. By Friday afternoon the low will continue eastward dumping moderate to heavy snow southern portions of Mississippi, Alabama and Georgia as well as the Florida panhandle possibly back towards Tallahassee. Models have come in much colder with the result the result being 850mb temps ranging from -1 to -4C; models have also come in wetter to yield significant snowfall accumulations supported by mid level dynamics with snowfall ratios at a standard 10:1. Snowfall accumulations will be possible all the way to the coast with snowfall 8:1 ratios.