jeffl
12-23-2004, 09:49 AM
Extended period of freezing temps expected
We should fall below freezing tonight and not get back above until midday Saturday.
Cold arctic air firmly entrenched over the region with temps at or below freezing from I-10 northward. Secondary surge over OK with bitter cold temps in the single digits. The secondary surge will arrive this evening with north winds increasing and temps falling well below freezing.
Now to the much talked about snow chances:
Upstream dewpoints this morning are in the single digits as far south as Dallas with teens from College Station to Huntsville, 20's over the Houston area, and near 30 along the coast. Secondary arctic surge will only reduce these numbers more this afternoon and tonight creating a very dry layer from 850mb to the surface. Strong short wave advertised in the models is currently shown in the water vapor over the SW US with strong upper air lifting spreading east into W TX. Sub-tropical plume is spreading mid and high level moisture toward TX from the deep Pacific. Visible images are showing the eroding cloud deck slowing its southward progression with increasing mid and high clouds from the SW. I think we will have a tough time breaking out of the low deck today, which will result in temps only warming into the mid or upper 30's instead of mid 40's.
Tonight:
Forecast models show strong isentropic lifting in the 295K to 300K level from Corpus Christi to Conroe. Forecast PWS are in the .3 to .4 range, but surface dewpoints fall into the teens. The moisture will be based in the mid level from the sub-tropical jet. The profiles are frozen from the surface upward with indications of decent crystal formation near the 700mb level. The amount of dynamical lifting may be enough to overcome the lack of moisture, however the dry layer near the surface may evaporate anything that falls from the mid level deck. Will be closely watching the wet bulb temp for any indication of saturation near the surface.
Friday:
Upper level energy arrives from the west with a vort max moving over the area. Moisture remains limited, but the lifting near the cold core center may be enough for a few bands of precip. Highs will go nowhere under continued strong cold air advection and should top out in the 30-32 degree range.
Christmas Day:
Very hard freeze in the morning with lows in the upper teens and low 20's. Upper level trough pulls east with warming conditions. Highs should finally rise above freezing around midday.
Accumulations:
Given that the ground conditions remain warm and the expected precip will be light. Very light accumulation is expected as whatever falls should melt on contact with the ground. Exceptions will be rooftops, bridges, and open grassy areas where some minor accumulation is possible. Should the moisture be greater, or meso-scale snow bands develop, then accumulations could easily approach 1 inch. 0C 850mb temp and 32 degree wet bulb line cuts the coastal counties in half around 600am Friday morning. Will have to go with a rain/snow mix south of this line then change to all snow by mid morning. If it falls inland it will be all snow.
Forecast:
Today: partly to mostly cloudy this morning with increasing clouds late. Highs in the upper 30's. North winds 5-10mph
Tonight: cloudy and cold with a 30% chance of snow after midnight. Little accumulation is expected. Lows in the mid 20's. N wind increasing 15-25mph and gusty.
Christmas Eve: cloudy and cold with a 40% chance of snow. Some light accumulation is possible. Highs near freezing. N winds 10-20mph and gusty. Wind chills in the 5-15 degree range.
Friday night: cloudy early with flurries, becoming partly cloudy late. Very cold, with lows from the upper teens north to low 20's Houston area to upper 20's coast.
Christmas Day: decreasing clouds with highs near 50.
Jeff L
We should fall below freezing tonight and not get back above until midday Saturday.
Cold arctic air firmly entrenched over the region with temps at or below freezing from I-10 northward. Secondary surge over OK with bitter cold temps in the single digits. The secondary surge will arrive this evening with north winds increasing and temps falling well below freezing.
Now to the much talked about snow chances:
Upstream dewpoints this morning are in the single digits as far south as Dallas with teens from College Station to Huntsville, 20's over the Houston area, and near 30 along the coast. Secondary arctic surge will only reduce these numbers more this afternoon and tonight creating a very dry layer from 850mb to the surface. Strong short wave advertised in the models is currently shown in the water vapor over the SW US with strong upper air lifting spreading east into W TX. Sub-tropical plume is spreading mid and high level moisture toward TX from the deep Pacific. Visible images are showing the eroding cloud deck slowing its southward progression with increasing mid and high clouds from the SW. I think we will have a tough time breaking out of the low deck today, which will result in temps only warming into the mid or upper 30's instead of mid 40's.
Tonight:
Forecast models show strong isentropic lifting in the 295K to 300K level from Corpus Christi to Conroe. Forecast PWS are in the .3 to .4 range, but surface dewpoints fall into the teens. The moisture will be based in the mid level from the sub-tropical jet. The profiles are frozen from the surface upward with indications of decent crystal formation near the 700mb level. The amount of dynamical lifting may be enough to overcome the lack of moisture, however the dry layer near the surface may evaporate anything that falls from the mid level deck. Will be closely watching the wet bulb temp for any indication of saturation near the surface.
Friday:
Upper level energy arrives from the west with a vort max moving over the area. Moisture remains limited, but the lifting near the cold core center may be enough for a few bands of precip. Highs will go nowhere under continued strong cold air advection and should top out in the 30-32 degree range.
Christmas Day:
Very hard freeze in the morning with lows in the upper teens and low 20's. Upper level trough pulls east with warming conditions. Highs should finally rise above freezing around midday.
Accumulations:
Given that the ground conditions remain warm and the expected precip will be light. Very light accumulation is expected as whatever falls should melt on contact with the ground. Exceptions will be rooftops, bridges, and open grassy areas where some minor accumulation is possible. Should the moisture be greater, or meso-scale snow bands develop, then accumulations could easily approach 1 inch. 0C 850mb temp and 32 degree wet bulb line cuts the coastal counties in half around 600am Friday morning. Will have to go with a rain/snow mix south of this line then change to all snow by mid morning. If it falls inland it will be all snow.
Forecast:
Today: partly to mostly cloudy this morning with increasing clouds late. Highs in the upper 30's. North winds 5-10mph
Tonight: cloudy and cold with a 30% chance of snow after midnight. Little accumulation is expected. Lows in the mid 20's. N wind increasing 15-25mph and gusty.
Christmas Eve: cloudy and cold with a 40% chance of snow. Some light accumulation is possible. Highs near freezing. N winds 10-20mph and gusty. Wind chills in the 5-15 degree range.
Friday night: cloudy early with flurries, becoming partly cloudy late. Very cold, with lows from the upper teens north to low 20's Houston area to upper 20's coast.
Christmas Day: decreasing clouds with highs near 50.
Jeff L