48C = 118.4 F

from Bob Henson ·shared with thanks. The intense heat that has waxed and waned across various parts of Europe this summer is on the move once again, and residents of Spain and Portugal need to be prepared.

Temperatures could approach or exceed all-time highs across parts of the Iberian Peninsula from Thursday to Saturday.

A ridge of high pressure that’s been lodged over and near northern Scandinavia will be eroding later this week, as a separate ridge builds northward from Africa and a trough approaches Europe from the northwest.

This pattern will pull hot, dry air from Algeria and Morocco into the Iberian Peninsula (Spain and Portugal), along with some Saharan dust. By the weekend, a building surface high across Ireland and Britain will help push the scorching air mass back southward across the higher terrain of central Iberia. This will lead to downslope flow across parts of Portugal and southwest Spain that could heat the air even further.

The expected pattern is so extreme that the surface-temperature predictions of forecast models have to be approached with a grain of salt. Such models often struggle when trying to get a handle on the most unusual situations, especially when surface temperatures have a chance of going “ superadiabatic .”

A superadiabatic lapse rate means that conditions are warming the surface air even more than one would expect simply from bringing air of a certain temperature down to the surface from aloft. By itself, that descent produces a warming of 10°C per kilometer, or about 5.4°F per 1000 feet.

With that caveat in mind, some of the model forecasts are jaw-dropping. Highs are projected in some model output to approach the neighborhood of 50°C (122°F) across parts of central Portugal northeast of Lisbon. For context, the hottest temperature ever reliably recorded in Portugal is 47.4°C (117.3°F), which was notched at Amareleja on August 1, 2003, near the peak of Europe’s infamous and deadly heat wave of that year.

Spain’s all-time heat record of 47.3°C (117.1°F), set in Montoro on July 13, 2017, may also be in jeopardy. Forecasts from the UK Met Office suggest that 48°C (118.4°F) is possible in Iberia. The Weather Company is predicting that temperatures could reach 47°C by Saturday in the Alentejo and Tejo regions of Portugal, with readings of 40°C (104°F) possible in southern France.

Fire weather outlooks issued by Portugal’s national weather agency, IPMA, show increasingly dire conditions spreading across most of the country as the week unfolds. issued by Portugal’s national weather agency, IPMA, show increasingly dire conditions spreading across most of the country as the week unfolds.

By Saturday, more than half of Portugal is predicted to be in very high wildfire danger, and roughly 20% of the nation is in the highest risk category.

For example, the Abrantes municipality in central Portugal is projected by IPMA to hit 45.1°C (113.2°F), with relative humidity dipping to as low as 13%.

At higher terrain, such as the Sistema Central range that extends from central Portugal into northwest Spain, models suggest there could be just enough moisture through the depth of the atmosphere to support “dry” thunderstorms—those that produce lightning but very little rain.

believed to have triggered at least some of the blazes in the June 2017 disaster.For more on the avalanche of heat records set across the Northern Hemisphere in recent weeks—including the all-time records in both North and South Korea set on Wednesday, as discussed by Jeff Masters in our Such storms areat least some of the blazes in the June 2017 disaster.For more on the avalanche of heat records set across the Northern Hemisphere in recent weeks—including the all-time records in both North and South Korea set on Wednesday, as discussed by Jeff Masters in our last post —see the roundup from Jon Erdman at weather.com.