Hurricane Hilary has now turned north-northwestward and is forecast to track near Baja California before making landfall near the U.S.-Mexico border later this weekend.
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Heavy rainfall associated with the system is forecast to develop across the southwestern U.S. today, well in advance of the storm's center, and continue through the weekend, with the heaviest amounts expected on Sunday.
Highly anomalous moisture transport into the region will support rainfall amounts exceeding the average annual totals for some locations in the Southwest.
Flash, urban, and arroyo flooding is expected, with dangerous and locally catastrophic impacts likely.
In addition to flooding rains, Hilary is forecast to bring tropical storm conditions to portions of southern California on Sunday.
Large swells will affect portions of southern California over the next few days.
These swells are likely to cause life threatening surf and rip current conditions.
Widespread cloud cover will keep temperatures below average, with unseasonably cool temperatures forecast to expand northward from southern California and western Arizona into the Sierra Nevada and the Great Basin through the weekend.
In contrast to the temperatures in the West, dangerous heat will continue to intensify and expand, with well above normal to record temperatures forecast across the Plains and lower Mississippi Valley today.
The heat wave will continue to expand on Sunday to include more of the Midwest on Sunday.
This weekend, some locations in the Midwest may experience their hottest day of the year.
The prolonged nature of the heat wave, combined with very warm overnight temperatures, will limit relief from the oppressive daytime temperatures and compound the overall heat impacts.
A relatively quiet period is expected for much of the eastern U.S., with shower and thunderstorms confined mainly to Florida and the Southeast coast.
After another day of seasonal to below-average temperatures today, summer heat is forecast to return to much of the Northeast and Mid-Atlantic states on Sunday. ■
A very active and complex mid-May weather pattern is set to produce numerous areas of severe weather, heavy rain, high winds, and anomalous temperatures through this weekend.