Late-Week Pattern Change a Southwest Sizzler, Comfortable in the East

Lightning Fact or Myth?

As we approach Father's Day weekend, a shift in the jet stream pattern will bring dangerous heat to the West, but also keep much of the East's heat relatively in control.

This highly-amplified jet stream pattern will feature a ridge of high pressure stretching from the Southwest into the Great Lakes, as well as upper-level troughs, or southward dips in the jet stream, over both the East Coast and Pacific Northwest.

(MAPS: Weekly Planner)

First, we'll take a look at changes coming to the East and then we'll look at some of the details for the West.

East Heat Controlled, Low Pressure Offshore

Changes are ahead for portions of the East as an upper-level trough will drive a strong cold front for mid-late June through the Southeast late this week and into the weekend. This is the same system that is slowly pushing through the Midwest this week.

(MORE: Severe Storms, Heavy Rain in the Midwest)

The Southeast will finally get some relief from the heat, as highs well into the 90s will be replaced with temperatures in the 80s this weekend. Lows will also drop into the 60s by late this weekend, instead of the 70s, providing an opportunity to give the A/C a rest at night.

High pressure will build in behind this system, bringing drier conditions and keeping temperatures near to slightly below average Friday through the weekend.

High temperatures in portions of the Northeast and mid-Atlantic will drop to the 70s and lower 80s Thursday and Friday before warming up well into the 80s over the weekend.

(FORECAST: New York | Baltimore | Charlotte, North Carolina | Louisville, Kentucky)

In addition, an area of low pressure will move well off the coast of the mid-Atlantic or Southeast by the weekend.

While high pressure will keep the Northeast relatively nice, in concert with this offshore low, it may produce stiff east-northeast winds from Virginia Beach possibly as far south as Florida's First Coast, giving rise to a threat of rip currents and high surf.

(MORE: Will East Coast Low Be a Father's Day Weekend Beach Bummer?)

With the frontal system eventually stalling out, a chance for rain and a few thunderstorms could hug the Southeast coast, Florida peninsula, perhaps as far west as the northern Gulf Coast this weekend. 

(WEEKEND FORECAST: Hatteras | Myrtle Beach | Daytona Beach | Orlando | Destin)

Be aware, however, of the potential for high surf and rip currents, even if the weather doesn't look so threatening at the time.

(WATCH: The Dangers of Rip Currents)

Excessive Heat in the Southwest

An intense upper-level high pressure system will expand from the Desert Southwest into the central Plains.

The result of this will be a searing heat wave, even by Desert Southwest standards.

(MORE: Dangerous Heat in Southwest, Plains)

High temperatures are expected to soar into the 100s, 110s and 120s for portions of the Southwest this weekend and into early next week. This isn't necessarily all that unusual in the Southwest in the weeks before the wet phase of the North American monsoon (translation: increased humidity and more frequent afternoon/evening thunderstorms) kicks in.

However, Phoenix may approach 120 degrees, something done only three times on record, there. Temperatures will climb into the 90s to near 100 degrees in southern California as well, including Los Angeles. 

Not only will high temperatures be up to 20 degrees warmer than average, but lows will be 5 to 15 degrees above average across the region. Lows will only drop into the 80s for much of the Desert Southwest, while downtown Los Angeles will see temperatures only dip into the 70s, about 10 degrees warmer than average.  

Excessive heat watches have already been posted for this weekend in parts of the Southwest and southern California, including the Tucson and Phoenix areas, due to the dangerous heat expected. 

Heat advisories have also been posted for portions of the central and southern Plains, along with portions of the lower and middle Mississippi Valley. This includes Little Rock, Arkansas, and Dallas.

(FORECAST: Los Angeles | Las Vegas | Phoenix | Denver)

The upper-level ridge of high pressure is expected to expand into the Northwest by late in the weekend, bringing drier conditions and warmer temperatures to the region.

Temperatures will also remain hot in the central and southern Plains through this weekend. Highs will typically top out in the mid to upper 90s, with a few lower 100s possible.

MORE ON WEATHER.COM: TripAdvisor Best Summer Destinations 2016 (PHOTOS)