Morning briefing from Jeff:
Colder air mass has moved in faster than expected requiring changes to Freezing Rain Advisory start times.
Freezing Rain Advisory will begin at noon today-600am Tuesday for: Burleson, Brazos, Madison, Walker, Houston, Trinity, and Polk Counties
Freezing Rain Advisory will begin at 600pm today-600am Tuesday for: Washington, Grimes, Montgomery, San Jacinto, and Liberty Counties.
600am temperatures range from 35 at College Station to 43 at BUSH IAH to 27 at Dallas. Freezing line currently extends from near Austin to Texarkana and has been steadily progressing southward this morning. High temperatures for today have already been reached and temperatures will continue to slowly fall into the 30’s area wide by early afternoon. Freeze line will move into our northern counties between noon and 200pm and then progress southward to a Brenham to Conroe to Cleveland line by 600pm.
Regional radars show extensive freezing rain and sleet across much of N TX into the Hill Country and this is confirmed by hazardous road conditions in those areas. Short wave in the flow aloft over New Mexico will move across TX today helping to enhance the precipitation across the region. Where surface temperatures fall to freezing, light rain and drizzle will change to light freezing rain and freezing drizzle. Elevated objects such as trees, power lines, and bridges/overpasses will be cooling to freezing with the air temperature allowing ice accumulation on these surfaces. Soundings and profilers show the forecasted strong warm layer aloft in place with temperatures above 40 degrees a few thousand feet above the surface. Since rainfall is expected to be very light, not sure much if any of the warm layer aloft will mix down helping to offset the cold air advection…this was a concern yesterday that would prevent temperatures from falling as much…but this does not appear to be the case today. Fairly high confidence that the ongoing strong cold air advection will push the freezing line into the area this afternoon.
Question then becomes how far south does the freezing line progress tonight into Tuesday morning and how much precipitation falls during this period. 00Z model guidance has trended a degree warmer for tonight even though all guidance is running about 3-4 degrees too warm at the moment. Expect the freezing line tonight to move as far south as a Columbus to Waller to The Woodlands to Splendora line. Forecast models show the best precipitation chances in the noon-midnight time period today with chances decreasing between midnight and 600am on Tuesday.
Accumulations:
Ice accumulations in the advisory area will average .01 to .05 of an inch with possibly higher amounts in the Huntsville to Livingston area where temperatures will be below freezing the longest. Road temperatures are fairly warm from the 80 degree highs yesterday and will slowly cool through the day. Suspect surface air temperatures will need to reach at least 30-31 for ice formation on bridges and overpasses. With that said, freezing drizzle is historically the most dangerous of winter precipitation as roadway surfaces can appear dry, but actually have a thin coating of ice…so caution is advised even if the bridge deck appears dry.
Wednesday Morning:
Forecast models show the main upper level storm system moving nearly overhead early Wednesday morning with rapid cooling of the warm layer aloft. While surface temperatures will have warmed into the mid 30’s by this time early Wednesday, sounding profiles suggest rain may change to or mix with sleet. Precipitation in this time period looks much heavier than today. Not expecting any accumulations with surface temperatures above freezing, but will need to monitor for any additional P-type changes or changes in surface temperatures.
Freezing Rain/ice accumulation (>.01 of an inch) threat probabilities:
http://www.hpc.ncep.noaa.gov/pwpf/wwd_a ... babilities
Decision Support Matrix:
Burleson, Houston, Madison, Walker, Trinity, San Jacinto, Polk:
Ice Accumulation: .03-.06 of an inch
Timing: noon Monday-600am Tuesday
Temperatures: 28-30 degrees
Winds: NNE 15-20mph
Confidence: high
Transportation: anti-ice operations likely
Education: delays and cancellations possible
Aviation: anti-ice operations likely
Power: isolated outages possible
Brazos, Grimes, Washington, Montgomery, Waller, northern Liberty:
Ice Accumulation: .03-.05 of an inch
Timing: 600pm Monday-600am Tuesday
Temperatures: 30-32 degrees
Winds: NNE 10-15mph
Confidence: moderate
Transportation: prepare for anti-ice operations
Education: delays possible
Aviation: anti-ice operations likely
Power: isolated outages possible
Austin, Colorado, north Harris (Cypress-Spring-Kingwood), central Liberty:
Ice Accumulation: patchy ice accumulation possible
Timing: 1000pm Monday-600am Tuesday
Temperatures: 32-33 degrees
Winds: NNE 10-15mph
Confidence: moderate
Transportation: monitor trends/standby equipment and personnel
Education: delays possible
Aviation: anti-ice operations possible at Hooks and IAH
Power: None
Fort Bend, southern Harris, Wharton, Jackson, Matagorda, Brazoria, Galveston, Chambers:
Ice Accumulation: None expected at this time
Timing: N/A
Temperatures: 33-35 degrees
Winds: NNE 14-18mph
Confidence: moderate
Transportation: None
Education: None
Aviation: None
Power: None
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or 
