Posted by:Drakoen, Saat: 11:32 PM GMT Tarih: 22 Şubat 2010
As much advertised over the past week, a Winter Storm is setting its sights on Texas and portions of the southeast. The RUC 20z analysis reveals are large negative EPO western ridge and to the east of the ridge a strong trough of low pressure with the shortwave energy heading into the four corners region. A pair of low pressure centers at the surface is delivering snow into portions of Arizona and New Mexico. Surface observations and radar imagery shows light snow affecting portions of northern Texas around Interstate-40. These snow showers should continue into the evening hours and proliferate heading into the early morning hours on Tuesday as the low pressure center slides eastward along with the shortwave trough. Models indicate total snowfall accumulations between 2-5 inches with the highest totals just south of Interstate 40. Snow should taper off in the early afternoon hours.
Guidance indicates the positively titled upper trough axis to be just east of Texas Tuesday morning with widespread snow showers (initially starting off as a rain/snow mix) will be impacting areas in western and central Texas down towards the Texas/Mexico border with MOS surface temperatures in the lower 30s to upper 20s around I-20. Significant snowfall accumulations will occur between I-20 and I-10 during the day on Tuesday especially heading into the afternoon hours perhaps between San Angelo eastward towards Waco with totals 6-9 inches possible with estimated snowfall ratios around 12:1. Around I-20 and to the north of accumulations of 1-2 inches will be possible depending on if moderate or heavy snow bands manage to penetrate the area.
Aiding in the development of heavy snow bands will be a dendritic growth zone with temperatures between -12C and -18C up near 13,000-14,000ft supported by omega maxima within the snow growth zone. In addition a deep saturated layer with 500mb-700mb lapse rates near 7.5C/km and mid level frontogenetical forcing as the 700mb trough axis positions itself over central Texas will support the falling of heavy snow to cool the surface when temperatures are in the lower to mid 30s. 110-130 knot winds in the right entrance region of jet stream favors forcing for vertical ascent over a large region of central Texas isentropically from the surface.
The GFS 12z shows the moisture spreading much farther north than the rest of the computer model guidance with substantial QPF amounts too far east in areas where it shows the omega values highest below the dentritic growth zone according to bufkit analysis. The rest of the guidance (UKMET/ECMWF/CMC/NAM) favors central Texas as the focal point of significant snowfall accumulations. The rain/snow line should extending just south of San Antonio. A sharp cut off should be expected but snowfall could extend all the way to Houston in trace amounts as the 1000mb-500mb progs show a thickness of 540dm over the area along with lingering low level moisture as the upper level trough slides eastward and the vorticity shears ENE into the southeast.
Rough estimate of snowfall totals:
Forecast for the Southeast (Louisiana, Mississippi, Alabama, and Georgia) coming soon.