A shortwave trough will move through southern South America during the days Monday 18 and Tuesday 19. This system will interact with a very hot, moist and highly unstable air mass already in place and lead to the development of bad weather conditions over central, eastern and northern Argentina, as well as over Uruguay and extreme southern Brazil.

The Argentine provinces of Córdoba, La Pampa, Buenos Aires, Santa Fe and Ente Ríos will register very high temperatures and dew points during Monday, but the approaching of the disturbance from the West will trigger thunderstorms and showers there. Given the very high instability already dominating the area, with Lifted Indices of -6 to -8, an upper level jet blowing at 70/80 knots and the intensification of a low level jet (with maximum velocities of about 35 knots), some if these thunderstorms will likely develop into supercells, with the main threat becoming big hail (1 to 2 inches) and strong wind gusts. One or two isolated tornadoes can not be totally ruled out, especially over Córdoba and late in the afternoon, when the low level jet becomes more intense.

On Tuesday, all this activity will become organized into a mesoscale convective system over eastern and northeastern Argentina, increasing the potential for very heavy rains and storm totals locally surpassing 4 inches over Entre Ríos, Corrientes and northeastern Buenos Aires, as well as over western and northern Uruguay. The development of this system will be accompanied by the formation of a surface low pressure near Buenos Aires City... something very rare for this time of the year. This low will tend to move east and southeast during the day Tuesday. A cold front will then develop in association with this low pressure area and it will tend to affect northeastern Argentina and southern Brazil later on, bringing heavy rains and thunderstorms. A highly unstable environment along with 50 knots at low level will increase the chance for severe weather over that area, including the chance for some isolated tornadoes.

A multiple number of storm systems are lining up in the Pacific, and according to the latest weather models California is forecasted to take the main brunt of these storms! We've already seen copious amounts of rain and snow in the state within the last few days, and the precipitation does not look like it will end any time soon! At this time there are a number of issues to address... along the coastal ranges mudslides are beginning to become a problem, where tremendous rainfall has loosened the ground that many houses are built on. Flood advisories are posted for a good portion of the Central Valley. The higher elevations are getting pounded by snowfall rates in excess of 2 inches per hour, and subsequently winter storm warnings have been issued along the spine of the Sierra Nevada range. Somewhat of a rarity in California, severe storms are also being reported! Storms embedded in heavy rain are causing some extreme wind gusts, with a report of a 75 mph wind on the Golden Gate Bridge! This is turning into a dangerous situation and residents of the state need to monitor the weather closely!