While polar air offers an early taste of fall in the Midwest and eventually the East, hotter than average temperatures are cooking the western U.S. An amplified jet stream pattern is behind this split of opposing weather extremes.

The fall-like July temperatures in the middle of the country have captured most of the attention, but the West is experiencing a notable heat wave. As the dip in the jet stream or trough over the central and eastern U.S. digs deep, a ridge is pushing north over the western states, bringing warm temperatures climbing as much as 20 degrees above normal.


200mb winds and heights from the GFS model, valid Monday morning. A ridge of high pressure in the West balances out the eastern U.S. trough. (WeatherBell)

In the Midwest, the cool air  arrived as advertised Monday. In the  morning. Eagle Mountain bottomed out at 46 °F, and International Falls dipped to 47 °F. Several record low daily maximum temperatures were also established. The Twin Cities set a record low maximum temperature of 65 °F on Monday. St. Cloud, Minn. and Eau Claire, Wisc. broke cool records, as well.

Temperatures today are forecast to be more than 20 degrees below average in parts of the Midwest.


Tuesday afternoon temperature anomaly or difference from average from the GFS model. (WeatherBell)

 

The Major League Baseball All-Star game being played in Minneapolis may be the coldest in several decades, according to Paul Douglas of the Minneapolis Star Tribune. “It may, in fact, be the coolest MLB All-Star Game since 1980 (if the first-pitch temperature is cooler than 68F). No haze, no smog. No raging storms – just popcorn cumulus clouds and a sprinkling of stars by 10 PM,” Douglas writes. “Baseball the way it was meant to be.”

Green Bay’s record low maximum today is 66 °F , and the forecast high for Green Bay from the National Weather Service is 65 °F. Rhinelander, Wisc. may also break its record low maximum temperature (65 from 1981).

While the coolest temps will be restricted to the Midwest, early morning lows will feel more like early autumn as far south as Georgia where dew points will dip into the 50s Wednesday.

However, while cool, dry air plunges south in the Midwest, the Northwest is getting the hot end of this deal, as the ridge pushes temperatures to as much as 20 degrees above normal. While the state of Washington will take the warmest hit, these toasty temperatures will be felt as far south as central and southern California, with much above normal overnight temperatures.


This record heat warning graphic was issued by the National Weather Service in Medford, Ore. on Tuesday. (NWS)

Heat advisories have been issued in Washington, Oregon, and Nevada. High temperatures are expected to top 100 in these areas. In northwest California, the National Weather Service is expecting highs to reach 106 to 110 °F on Tuesday, and 105 °F on Wednesday.

According to The Weather Channel, this record-breaking heat puts Seattle in position to break its record for warmest July:

A heat wave is expected for Seattle where the current forecast calls for five days of 90+ degree temperatures, which would tie the record (set in August 1981) for consecutive days of 90+ degree temperatures. Seattle has an average of three 90 degree days per year.

The heat has also turned up the dial on the fire weather risk. In Washington, the threat of thunderstorms and lightning in combination with the hot, dry conditions has prompted a red flag warning. A fast-growing fire has already erupted in southern Oregon on Sunday night, fueled by high winds and dry air. 100 people were evacuated from the area soon after the fire began, and crews are still waiting to access the area an assess the damage.

This bi-polar pattern was initiated, in part, by Super Typhoon Neoguri, which brought strong winds and heavy rain to southern Japan last week.  According to Weather Underground’s Jeff Masters:

[Neoguri] set in motion a chain-reaction set of events that has dramatically altered the path of the jet stream and affected weather patterns across the entire Northern Hemisphere. Neoguri caused an acceleration of the North Pacific jet stream, which amplified a trough low pressure over Alaska, causing a ripple effect in the jet stream over western North America, where a strong ridge of high pressure developed.