jeffl
12-22-2004, 04:21 PM
Have your cameras ready, its has never snowed in Houston on Christmas Eve or Christmas Day, but this year it will be dang close.
Extended period of freezing temps (36 hours below freezing) and winter precip. heading for SE TX
Travel conditions will be going downhill starting Thursday night and into Christmas Eve.
Will go with P-type of all frozen in the forecast as the models confirm this with very cold soundings. Amounts will vary over the region from a dusting to maybe 2.0 inches around Matagorda Bay.
Warm ground may result in melting upon contact limiting significant accumulations. Bridges and overpasses will have problems with glazing as temps. will not get above freezing from Thursday night through Christmas Day.
Setup:
Strong 500mb short wave within the polar jet will approach TX late Thursday. Impressive isentropic lifting will begin around midday and spread north and northeast from the middle TX coast. Secondary surge of very cold arctic air will enter TX midday Thursday and spread across the state. Temps. will once again fall during the afternoon to below freezing. Moisture increases as dynamical lifting increase ahead of the upper level energy. 150kt jet right over and just north of the area will help increase the moisture profile. Deepest moisture is along and south of I-10 and that is where the best precip. chances will be.
Precip. should start by late Thursday night as a rain/snow/sleet mix and change to all snow by early Friday as deeper arctic air moves southward. Critical thickness and 850mb 0C lines confirm a frozen profile with a winter mix even over the open Gulf.
Accumulations:
Meso-scale bands and enhanced lifting could result in snow and sleet burst more typical of the lake effect snow gun regions. Locations under such burst cold easily received 1-2 inches in an hour or so. Ground temps. remain in the 60's and should fall into the 30's by Friday morning. Much of what falls will melt on contact with concrete surfaces. Rooftops and grassy areas should see a dusting to 1.0 inch of accumulation. Jackson, Matagorda, and Wharton counties may see accumulations of 1.5 -2.0 inches. Bridges and overpasses will become ice covered and frozen by Friday morning, with travel extremely hazardous over the region. Expect major airport delays and flight cancellations as both airports will enact rigorous de-icing procedures.
Winds will remain strong through the period with wind chills falling into the lower teens and single digits Thursday night through Christmas Day.
Forecast (moderate confidence):
Tonight: some clearing and cold with lows near freezing. North winds 15-25mph and gusty.
Thursday: partly cloudy early with increasing clouds late. Highs near 40. North winds 15-25mph and gusty. Wind chills in the lower 20's.
Thursday night: cloudy with a winter mix developing after midnight. A 40% chance of snow and sleet. Cold with lows in the mid to upper 20's. Winds N 15-25mph and gusty increasing to near 30-40mph along the coast. Wind chills lower teens. Accumulations of .5 to 1.0 inch on grassy surfaces and rooftops.
Chirstmas Eve: Cloudy and very cold with snow and sleet through early afternoon. Chance of precip. 50%. Highs near 30. N winds 20-30mph and gusty. Accumulations of 1.0 in on grassy surfaces south of I-10.
Christmas Eve night:cloudy and very cold with flurries in the evening. Lows in the upper teens and lower 20's. North winds 5-10mph. Winds chills below 10.
Christmas Day: cloudy early with decreasing clouds late. Cold with highs in the upper 30's.
Extended period of freezing temps (36 hours below freezing) and winter precip. heading for SE TX
Travel conditions will be going downhill starting Thursday night and into Christmas Eve.
Will go with P-type of all frozen in the forecast as the models confirm this with very cold soundings. Amounts will vary over the region from a dusting to maybe 2.0 inches around Matagorda Bay.
Warm ground may result in melting upon contact limiting significant accumulations. Bridges and overpasses will have problems with glazing as temps. will not get above freezing from Thursday night through Christmas Day.
Setup:
Strong 500mb short wave within the polar jet will approach TX late Thursday. Impressive isentropic lifting will begin around midday and spread north and northeast from the middle TX coast. Secondary surge of very cold arctic air will enter TX midday Thursday and spread across the state. Temps. will once again fall during the afternoon to below freezing. Moisture increases as dynamical lifting increase ahead of the upper level energy. 150kt jet right over and just north of the area will help increase the moisture profile. Deepest moisture is along and south of I-10 and that is where the best precip. chances will be.
Precip. should start by late Thursday night as a rain/snow/sleet mix and change to all snow by early Friday as deeper arctic air moves southward. Critical thickness and 850mb 0C lines confirm a frozen profile with a winter mix even over the open Gulf.
Accumulations:
Meso-scale bands and enhanced lifting could result in snow and sleet burst more typical of the lake effect snow gun regions. Locations under such burst cold easily received 1-2 inches in an hour or so. Ground temps. remain in the 60's and should fall into the 30's by Friday morning. Much of what falls will melt on contact with concrete surfaces. Rooftops and grassy areas should see a dusting to 1.0 inch of accumulation. Jackson, Matagorda, and Wharton counties may see accumulations of 1.5 -2.0 inches. Bridges and overpasses will become ice covered and frozen by Friday morning, with travel extremely hazardous over the region. Expect major airport delays and flight cancellations as both airports will enact rigorous de-icing procedures.
Winds will remain strong through the period with wind chills falling into the lower teens and single digits Thursday night through Christmas Day.
Forecast (moderate confidence):
Tonight: some clearing and cold with lows near freezing. North winds 15-25mph and gusty.
Thursday: partly cloudy early with increasing clouds late. Highs near 40. North winds 15-25mph and gusty. Wind chills in the lower 20's.
Thursday night: cloudy with a winter mix developing after midnight. A 40% chance of snow and sleet. Cold with lows in the mid to upper 20's. Winds N 15-25mph and gusty increasing to near 30-40mph along the coast. Wind chills lower teens. Accumulations of .5 to 1.0 inch on grassy surfaces and rooftops.
Chirstmas Eve: Cloudy and very cold with snow and sleet through early afternoon. Chance of precip. 50%. Highs near 30. N winds 20-30mph and gusty. Accumulations of 1.0 in on grassy surfaces south of I-10.
Christmas Eve night:cloudy and very cold with flurries in the evening. Lows in the upper teens and lower 20's. North winds 5-10mph. Winds chills below 10.
Christmas Day: cloudy early with decreasing clouds late. Cold with highs in the upper 30's.