A rare, weak cold front is predicted to sink south through our region this afternoon and tonight, providing a focus for the development of scattered rain showers and thunderstorms.  Friday morning’s weather maps showed the persistent ridge of high pressure in the upper atmosphere has shifted away from Texas and the south central U.S to the western US.  This has allowed an unusually strong trough of low pressure to develop south into Texas out of southern Canada.  A cold front associated with the trough pushed into Texas Thursday night.  As of early Friday afternoon, the cold front stretched from Longview, to Temple to near Fort Stockton.  While certainly not a “blue norther”, the air behind today’s cold front is drier and just slightly cooler.  Forecasts call for the front to reach the Austin/Interstate 35 corridor region around mid-afternoon Friday and the Interstate 10 corridor Friday evening.  The front is predicted to stall across the coastal plains region Saturday, then weaken and wash out on Sunday.

As temperatures warm into the 90s this afternoon, scattered rain showers and thunderstorms are forecast to develop along and to the south of the cold front.  The probability for rain will be near 40-50 percent across the Hill Country and Central Texas regions and be less than 20 percent across the coastal plains.  Today’s atmosphere will be structured in such a way that some of the developing storms may become strong to marginally severe.  Today’s primary severe weather threat will be strong, potentially damaging winds.  The Storm Prediction Center has placed the area north of Interstate 10 under a Marginal Risk for severe thunderstorms this afternoon and evening.

Widespread rainfall is not expected.  However, spotty totals of 0.25 to 0.50 inches are forecast across the Hill Country and Central Texas regions through midnight.  Isolated totals of 1-2 inches will be possible.  High temperatures this afternoon will be in mid and upper 90s.  Lows Saturday morning will include the low 70s across the Hill Country with middle 70s at most other locations.

On Saturday, the chance for rain and scattered thunderstorms will shift to the coastal plains region, in the vicinity of the stationary front.  The probability for rain will be near 30-40 percent.  Spotty totals of 0.25-0.50 inches are forecast.  Further inland, there will be just a slight chance for a few scattered rain showers across Central Texas through the afternoon.  Little to no rain is forecast across the Hill Country.  Expect a mostly sunny to partly cloudy sky.  High temperatures are forecast to be in the mid and upper 90s, with lower 90s expected towards the coast.

Sunday’s weather is shaping up to be mostly sunny.  There will be a slight chance for a few spotty rain showers across the coastal plains while most other areas will remain dry.  High temperatures are predicted to be in the upper 90s.

Forecasts call for a second cold front to sink south out of North Texas Monday, pulling up stationary across Central Texas Monday afternoon into Tuesday.  This next front is expected to cause a slight chance for rain showers and thunderstorms across the region both days.  For locations that do happen to see rain, totals should average around a quarter inch or less.  Otherwise, weather conditions will be mostly sunny to partly cloudy and hot.  High temperatures both days will be near 98-100 degrees, with mid-90s expected towards the coast.

Sunny, dry and hot weather is forecast Wednesday through next weekend as the trough of low pressure exits east and the ridge of high pressure over the Southwest begins to spread back over Texas.  Fortunately, the ridge is predicted to only be moderately strong, so extreme temperatures are not expected.  A few isolated rain showers will be possible towards the coast, but areal coverage will be less than 20 percent.  Daily high temperatures are forecast to be close to 100 degrees, with middle 90s expected towards the coast.

The outlook for the week of August 10th calls for little change as the center of the high pressure ridge remains parked over New Mexico.  Sunny, hot and dry weather will continue with daily high temperatures staying close to 100 degrees.

Tropical Weather Outlook

As of 1 pm Friday, the center of Hurricane Isaias was located by an Air Force Reserve Hurricane Hunter aircraft and Bahamas radar about 245 miles southeast of Nassau, Bahamas.  Isaias was moving toward the northwest near 16 mph, and a general northwestward motion with some decrease in forward speed is expected for the day or so followed by a turn toward the north-northwest.  On the forecast track, the center of Isaias will continue to move near or over the Southeastern Bahamas today.  Isaias is forecast to be near the Central Bahamas tonight, and move near or over the Northwestern Bahamas Saturday and near the east coast of the Florida peninsula Saturday afternoon through Sunday.

Data from the reconnaissance aircraft indicate that maximum sustained winds are near 75 mph with higher gusts.  Strengthening is expected later today and tonight, and Isaias is forecast to remain a hurricane for the next few days.

Isaias poses no threat to the Gulf of Mexico.

National Hurricane Center forecasters are keeping an eye on a tropical wave in the west-central tropical Atlantic, located about 950 miles east of  the Lesser Antilles.  This system is producing disorganized showers and thunderstorms as it moves to the west.  Some slow development of this system is possible while it turns northwestward over the western Atlantic by early next week.  NHC forecasters are giving the wave a 30 percent chance for development over the next 5 days.

NHC forecasters are also monitoring an area of showers and thunderstorms that remain separated from the center of a small area of low pressure located in the far eastern tropical Atlantic, a couple of hundred miles east of the Cabo Verde Islands.  The system is moving northward toward less favorable environmental conditions, and significant development of this system appears unlikely.  NHC forecasters are giving this system just a 20 percent chance for development over the next 5 days.

Elsewhere, tropical cyclone development is not expected over the next 5 days.

Catch Mars in the Late Evening Sky

Brilliant Jupiter and Saturday are now quite visible in the eastern evening sky.  But now, the planet Mars rises in the eastern sky around 11 pm CST.  It will be quite bright (magnitude –1.2).  It will appear yellow-orange in the constellation Pisces, like a far-off bonfire.   Where will it come up?  Watch the eastern horizon below the Great Square of Pegasus.  By dawn Mars shines grandly high and bright in the southern sky.

In a telescope this week Mars grows from 14½ to 15½ arcseconds in apparent diameter, as big as it appears at some oppositions!  But we’re still speeding toward it along Earth’s faster orbit around the Sun, and we have a long way to go. Around this year’s opposition in early October, Mars will be 22.6 arcseconds wide!

Have a good weekend.