After an extraordinarily quiet period devoid of tropical storms and significant tornado activity, dangerous weather extremes are impacting or closing in on the U.S., from coast to coast.
“There are multiple hazards in multiple regions that warrant the highest level of awareness,” said National Weather Service spokesman Chris Vaccaro.
This combination of threatening weather – occurring simultaneously – may be unprecedented.
“Wunderground weather historian Christopher C. Burt has done some research to see the last time a blizzard, major severe weather outbreak, tropical storm, and extreme fire danger all threatened the U.S. at the same time, and has not been able to find such an event in past history,” writes wunderground meteorologist Jeff Masters.
Here’s a guided tour of what’s happening, starting in the center of the country…
Blizzard socking the western Plains
Raging winds and blinding snow are crushing portions of western South Dakota, eastern Wyoming, and northwest Nebraska, as a vigorous fall storm deepens in the northern Plains.
The mid-latitude cyclone over the Great Plains is deeper than Tropical Storm Karen in the Gulf… pic.twitter.com/wBUFOuqj7D
— James Spann (@spann) October 4, 2013
In Lawrence County, South Dakota, law enforcement is warning locals to stay off the roads.
A BLIZZARD IS ONGOING ACROSS LAWRENCE COUNTY. NO TRAVEL IS ADVISED ANYWHERE IN THE COUNTY. TREES AND POWER LINES ARE DOWN…MAKING IT DIFFICULT FOR SNOW PLOWS TO CLEAN THE DEEP SNOW OFF THE ROADS.
— Mark Tarello (@mark_tarello) October 4, 2013
Snowfall totals exceeding 20 inches have been reported in the region, with more to come. 22 inches were reported in Lead, South Dakota, according to the National Weather Service.
Snowfall rates are currently near or exceeding 1 inch per hour. The heavy snow combined with winds sustained from the north at 30 to 50 mph and gusts as high 70 mph are creating dangerous, white-out conditions.
— David Bernard (@DavidBernardTV) October 4, 2013
Severe thunderstorm outbreak possible in Midwest: Iowa most at risk
On the warm side of the potent storm in center of the country, severe thunderstorms are likely to break out this afternoon.
Over 13 million people from southern Oklahoma to western Wisconsin are under an elevated risk of violent thunderstorms, with central and northern Iowa facing the greatest odds – in the so-called “moderate risk” zone. A combination of instability and low-level swirling winds may conspire to spawn a few tornadoes in this area.
Lots of tornado potential today but seems like a pretty small area/timeframe of such. New NAM: pic.twitter.com/haLTvujHh3
— Ian Livingston (@islivingston) October 4, 2013
The most common risk for storms that develop in the Heartland today is from straight line damaging winds – mainly late this afternoon into this evening.
West Coast: Significant wildfire threat
Large areas of California, including around Los Angeles and near San Francisco, have “critical” fire risks today and tomorrow as strong offshore winds blow across adjacent mountain ranges. As these so-called “Santa Ana” (in southern California) winds whip across the mountains, air is forced downward causing it to heat up and dry out. Writes the National Weather Service:
WARM TEMPERATURES IN THE 80S TO NEAR 90 DEGREES ARE EXPECTED DURING THE AFTERNOON … LEADING TO MINIMUM RELATIVE HUMIDITY VALUES IN SINGLE DIGITS TO NEAR 15 PERCENT.
This hot, dry air coupled with winds accelerating down the mountain slopes – exceeding 50 mph in some spots would aid any fire – natural or manmade – in spreading hastily.
Observed gusts just east of the San Francisco Bay area have already reached 30-45 mph.
In Southern California, some of the strongest winds should arrive Saturday morning.
This Santa Ana is just getting started. Here’s a numerical model forecast of wind gusts tomorrow morning (7 am PDT). pic.twitter.com/bWdZBF4p4L
— NWS Los Angeles (@NWSLosAngeles) October 4, 2013
The National Weather Service office in Los Angeles is calling the fire danger “extreme” and the “highest in five years.”
Tropical storm Karen
For only the second time this hurricane season, a tropical weather system will make landfall on the U.S. coast. Karen – forecast to make landfall along the northern Gulf coast Saturday night or early Sunday morning – has maximum sustained winds of 50 mph, and warnings and watches have been issued. After Karen moves ashore, it is expected to bring very heavy rains up the East Coast.
For more information, see: Weakened tropical storm Karen heading for Gulf coast, landfall likely Saturday night