A warm front will be followed by a cold front tomorrow in Rio Grande do Sul. The two systems will be responsible for causing instability in the state with rain that will be locally heavy and with the risk of isolated thunderstorms as the territory of Rio Grande do Sul will be in the transition between masses of hot and cold air.
The hot front advances in Rio Grande do Sul from North to South today and brings rain at least part of the day to parts of the West, Center, South and East of the state, including the capital. There is a risk of heavy rain in some places with lightning and occasional isolated hail. There are periods with sunny spells. In the South, the heaviest rain occurs in the second half of the day.
On the West, North and Northwest Borders, on the contrary, hot air enters and the sun appears hot throughout the period. Firm weather prevails and in most cities in these regions it should not rain this Friday. The maximum temperatures rise and will exceed 30ºC in the Northwest of Rio Grande do Sul, where the afternoon will be very hot and stuffy with wind from the North quadrant.
Tomorrow, Saturday, the front will be over Uruguay and the extreme south of Rio Grande do Sul at the beginning of the day causing rain, locally heavy, and isolated thunderstorms. It turns out that it will no longer be moved by hot air and will start being driven by colder air that will advance through Argentina. As a result, the warm front will stop being hot and become cold.
The sun appears in most of Rio Grande do Sul during Saturday accompanied by clouds, but throughout the day the cold front advances to the North and brings rain to most of the state of Rio Grande do Sul. In the West and South, rain already occurs in the morning. From afternoon to night, instability affects most areas of the state. Sectors further north in Rio Grande do Sul may be without rain on Saturday.
As it advances across the state this Saturday, the cold front will encounter very warm air in front of it, which will favor heavy clouds with the potential for heavy rain and isolated thunderstorms with lightning, occasional hail and gusts of strong wind.
Warm front brings rain today more in the South and East of the state | METSUL
Front becomes cold tomorrow and will advance from South to North | METSUL
The temperature will be very high for this season’s standards from the Center to the North of Rio Grande do Sul before the arrival of the front with maximums between 31ºC and 33ºC in cities such as Greater Porto Alegre, the valleys and the Northwest, but in some points they should be even higher high.
Understand the difference between a warm front and a cold front
Unlike a cold front, which is driven by cold air, a warm front has its movement dictated by the advance of warm air. Therefore, its movement in the state is from North to South, unlike cold frontal systems that advance from South to North. This is also why after the passage of the warm front it heats up a lot, unlike the cold front which brings a drop in temperature.
Warm fronts traditionally occur in autumn and winter, especially in June, and usually bring locally heavy to intense rain, lots of lightning and hail. Although isolated thunderstorms with wind may occur, heavy rain, lightning and hail are more common than wind on warm fronts.
Lots of rain yet to come
The rain in Rio Grande do Sul will not be limited to today and tomorrow. The instability is part of a scenario of many days in a row with rain that is expected for the state until the beginning of May, although there are moments of improvement. Excessive volumes of rain and isolated thunderstorms can be expected in the state at the end of April and the beginning of May.
Numerical models analyzed by MetSul and updated in the early hours of this Friday continue to indicate precipitation above 100 mm for most of the state over the next seven days, but with accumulations in different points that could exceed 150 mm or 200 mm, creating risk of flooding, flooding and river flooding.
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