Weather Underground Forecast for Saturday, November 21, 2009.

While tropical storm development is not expected on Saturday, a strong system will bring wet weather to the Gulf of Mexico. A low pressure system that developed in the Southern Plains of the US will strengthen as it picks up additional moisture and energy from the Gulf. Flow around this system will push strongest storms and heaviest rains over the Gulf States, while a front will extend southward. This front will sweep through eastern Mexico and move into the Yucatan Peninsula by evening. Light showers are expected over these ares with less than a half of an inch of rainfall. As this system pushes eastward, high pressure with dry and sunny conditions will build over the rest of Mexico.

Meanwhile, the rest of the Caribbean Sea will see mild weather. Onshore flow will allow for light coastal sprinkles to persist over Costa Rica and Panama. Also, light and scattered afternoon showers may develop over the Lesser Antilles, while the Greater Antilles remains mainly dry and sunny throughout the day.

In South America, wet weather persists on the western coast due to strong onshore flow. This will trigger strong storms over Colombia, while lighter showers are expected to extend well into western Brazil and down the coast into Ecuador and Peru. To the south, a strong low pressure system will continue spinning over Paraguay, Uruguay, and southern Brazil. Strong storm development is anticipated as this system is associated with ample moisture. Another low pressure system tracking past the southern tip of the continent will bring periods of heavy rainfall, while most of central and northern Chile and Argentina will remain dry and sunny. Expect another day of scattered showers and thunderstorms in Sao Paulo with highs near 80(F)/ 26(C), while Santiago will see a few clouds with highs also near 80(F)/ 26(C).