Launch Forecast: 70 Percent Chance Weather Will Be 'Go"

NASA is gearing up today for the start of a three-day countdown to the planned launch Wednesday of shuttle Discovery's final flight, and the weather appears as if it will cooperate.

Meteorologists at the U.S. Air Force 45th Space Wing Weather Squadron say there is a 70 percent chance conditions will be acceptable for an on-time liftoff at 3:52 p.m. Wednesday. The only concerns are a chance of low-level clouds or rain within 20 nautical miles of the Shuttle Landing Facility at Kennedy Space Center.

Here is the detailed forecast:

A high pressure ridge is migrating into Central Florida providing favorable weather conditions. Tuesday and Wednesday, an upper level trough will deepen and cut-off over the Western Gulf of Mexico. By launch day, moisture will migrate from the south into Central Florida causing a chance for low clouds and isolated showers. Our primary concerns for launch are a low-cloud ceiling and showers within 20NM of the Shuttle Landing Facility (SLF). Thursday, a cold front will move into Florida as a strong upper level trough deepens in the Eastern US. The trough may push the cut-off low in the Western Gulf toward Florida, although meteorological models differ on the timing of the front and movement of the low. With this, there is an increased
chance of a low-cloud ceiling, showers, and even a possibility of thunderstorms in Central Florida on Thursday. As a result, the probability of KSC weather prohibiting launch increased to 40%. The front will move through Central Florida Thursday evening, and Friday, strong northerly winds are expected behind the front.

Tropical Discussion: Tomas is now a category 2 hurricane entering the Eastern Caribbean moving west- northwest. The National Hurricane Center expects Tomas to be passing south of Hispaniola by launch day still at category 2 strength.

Countdown is set to begin at 2 p.m. today.