Over 100 million Americans are currently under winter-related watches, warnings, or advisories as a significant winter storm moves out of the Pacific Northwest and across the Rockies. This system will be diving through the Plains and Deep South and then moving up through the Ohio Valley and into the Northeast.  The Arctic air mass we talked about in last week’s Meteo Monday continues to penetrate further southeast, so not only are we dealing with accumulating snow and ice for several areas across the country but the potential for record-breaking cold.

This storm has packed a punch across parts of the Pacific Northwest. Portions of Oregon have picked up over an inch of ice-accretion, which has led to nearly 300,000 power outages. 8-10” of snow has fallen across the Seattle Metro Area, and over a foot has fallen across the Vancouver, WA metro.

CRAZY! The weight of the snow collapses the roof of this boat dock in the Willamette River. House boats tipping, too. At the end of the vid, one man is escaping w/ what looks like a pet kennel! I hope everyone is safe. Caution: language

📷: John Kinsman around 4AM@fox12oregon pic.twitter.com/fETGx8YNzA

— Brenna Kelly (@BrennaKellyNews) February 13, 2021

The National Weather Service in Dallas, TX, is calling this a historic storm. “Major impacts resulting in severe stress to the region`s infrastructure (particularly power, water, and highways) are likely. Regional travel will be crippled for days.” They are also saying that these will be some of the region’s coldest temperatures since the December 1989 Arctic Outbreak. 

Portions of Louisiana that are still recovering from the devastating 2020 hurricane season will now have to go through a significant ice storm late Sunday night into Monday. NWS Lake Charles is projecting 0.10” to 0.30” of ice accretion across their County Warning Area (CWA). This will lead to tree damage, power outages and make driving impossible.

Below are the Weather Prediction Center (WPC) Winter Precipitation Guidance maps. These maps are valid from 7:00 AM EST Saturday through 7:00 AM EST Tuesday. They show the probability of greater than 4” of snow accumulation and ice accumulation greater than a quarter inch. 

Not only are we dealing with this winter storm, but there is also a severe weather threat. The Storm Prediction Center has a slight risk (level 2 out of 5) of severe thunderstorms across portions of the Florida Peninsula for Sunday.  The main threat is damaging winds, but isolated tornadoes are possible. 

Sources:

NOAA

Pivotal Weather

A frigid air mass has been pushing into parts of the country and you may have heard some rumblings in the news that even more cold air is on its way!  Here are some of the headlines that may have graced your social media feed. 

“Coldest Air of the Season Plunges into the U.S.” 

“An Arctic Air Mass Will Invade the Country”

“Chunks Of The Polar Vortex Will Bring Bitterly Cold Wind Chills”

Oh no!  The Polar Vortex!  Is it here?  AGAIN?!  Run for your lives!

Yes!  The Polar Vortex is here, and it is real!  And we are going to talk about it in this latest version of Meteo Monday!

So, what is a polar vortex?  Per the National Weather Service (NWS), “The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.”  The vortex always exists, and it is not a new phenomenon.

Winter for a good part of the United States is…cold. However, there are times where it gets much colder than average. Plunges of arctic air masses are caused when the jetstream links up with a piece of the polar vortex and pulls the frigid air southward into the lower 48. Using the term polar vortex to describe these cold shots became mainstream in the winter of 2013/2014 when the national media ran headlines about it. Since then, every cold snap has been labeled “polar vortex.”  It is important to stress that this is not a new term and that meteorologists started using the phrase in 1853!

Why do you see these news headlines about the polar vortex? First of all, The Climate Prediction Center (CPC) 6-10 day outlook over the past few weeks, has consistently shown temperatures across a good part of the country well below average.

Current weather computer models show that the coldest temperatures will likely occur just before sunrise on Valentine’s Day. We want to stress that this is not a forecast, it is a model’s interpretation, and things have changed and will continue to do so as we are still several days away. It is difficult to forecast who will get the coldest air. We have been looking at the model runs for the past several days. They continue to show that frigid temperatures will seep further south. But where exactly will this set up? 

Take a look at the Global Forecast System (GFS Model) slated for 12z (7:00 am EST on the 14th). The image at the top shows the forecast from Saturday, February 6, and the image at the bottom shows the forecast from today (February 8). Notice a shift in where the coldest air will be based on the model runs.  Saturday’s run had the arctic air stretching from the Northern and Central Plains eastward into the parts of the Ohio Valley and the Northeast. Today’s model interpretations are showing the coldest air much further west. This air mass is forecast to stay from west of the Mississippi River through the Northern and Central Plains and over the Rockies. Also a nose of colder air could settle into Texas and New Mexico. 

No matter how cold it gets, it is essential each winter season to review your safety plan. Arctic blasts typically occur each season, some worse than others.  And some lasting longer than others.  Arctic air combined with brisk winds can lead to extremely cold wind chill temperatures. Per the NWS, “The wind chill temperature is based on the rate of heat loss from exposed skin caused by wind and cold and is to give you an approximation of how cold the air feels on your body.” The NWS issues Wind Chill products to alert the public of dangerous cold.  

When venturing outside in the extreme cold, make sure to dress in layers. One of the dangers of the bitter cold is frostbite. Per the NWS, “Frostbite happens when the body’s survival mechanisms kick in during extremely cold weather. To protect the vital inner organs, the body cuts circulation to your extremities: feet, hands, nose, etc., which eventually freeze.” If you have to go out, make sure to cover every part of your body.  Stay out of the wind and limit your time outside.  Frostbite can occur within five minutes when wind chill values are -50°F or below. If your body temperature lowers to below 96°F, you have hypothermia. This is a severe health condition, and you must seek medical attention immediately. 

Other things to consider when an arctic air mass is on its way:  Protect your pets or farm animals.  Limit their exposure to the cold and make sure they have plenty of food and water. Take precautions to keep the pipes at your home or business from freezing. Keep at least a half tank of gas in your vehicle and prepare a winter car survival kit.  Items to include: jumper cables, a flashlight, first aid kit, a shovel and ice scraper, extra clothes, and blankets. 

So, whether the headline includes the words “polar vortex” or some other frigid phrase, remember it is winter, and periods of extreme cold are nothing new.  The goal is to be prepared and stay safe.  Think warm! Meteorological spring is only a few weeks away!

Sources:

Cold Weather Safety

What is the Polar Vortex? – Weather.Gov

Polar vortex

WeatherBELL Analytics

Climate Prediction Center – 6 to 10 Day Outlooks

2020 supplied us with at least three large derecho events. What is a derecho? Per the Storm Prediction Center, “A derecho is a widespread, long-lived wind storm. Derechos are associated with bands of rapidly moving showers or thunderstorms variously known as bow echoes, squall lines, or quasi-linear convective systems. By definition, if the swath of wind damage extends for more than 250 miles (about 400 kilometers), includes wind gusts of at least 58 mph (93 km/h) along most of its length, and also includes several, well-separated 75 mph (121 km/h) or greater gusts, then the event may be classified as a derecho.” In our overview, we are delving into the details of the most impactful derechos of the year.

June 3, 2020: Philadelphia Derecho

During the morning and early afternoon hours of June 3, 2020, a derecho marched across Pennsylvania, into New Jersey.  The damage was first reported in Beaver Township, Clarion County, PA where it knocked down several trees. The bow-echo started to grow in size as it marched across Central Pennsylvania, downing trees and power lines across Clearfield, Tyrone, State College, Lewistown, and Hershey. As it moved into the Lehigh Valley, across the Philly Metro Area, and NJ, it was at its strongest and was very destructive. 

• Length of Damage: 305 miles
• Highest Measured Wind Gust: 93 mph at Beach Haven, NJ. 
• Fatalities: 4. 
• Extensive tree and roof damage reported across highly populated areas of southeastern PA, and NJ. 
• Later in the afternoon, another round of severe storms hit this same area, prompting a tornado warning for Philadelphia. 
• Several homes that were under construction were destroyed. 
• Deadliest derecho to affect this region since 1950. 

Homes under construction in Philadelphia’s Port Richmond neighborhood were toppled by Wednesday’s strong derecho. A resident’s security camera caught the collapse as it happened. More: https://t.co/gg2Fx3um5X pic.twitter.com/gSWrAUd9Bd

— NBC10 Philadelphia (@NBCPhiladelphia) June 3, 2020

June 3, 2020: Central Rockies – Northern Plains Derecho

Rare derecho stretching from Utah to the Dakotas today.

A Rocky Mountain special. pic.twitter.com/tkNC8lLRmj

— Dakota Smith (@weatherdak) June 7, 2020

A very strong upper-level area of low pressure moved through parts of the Rockies and the Plains region on Jun 6-7, 2020.  It triggered a line of storms that brought widespread damaging winds and even a few brief tornadoes to parts of Utah, Colorado, Wyoming, and the Dakotas.  This event was classified as a derecho by the Storm Prediction Center.  This was a rare event for this part of the country. Per a post from meteorologist Elizabeth Leitman on Twitter, there have only been two other derecho events recorded in the Western U.S:  May 31, 1994, and June 1, 2002.

I put together some quick info on Saturday’s derecho event. Only two other derechoes in the Great Basin are well noted in literature. I’ve included storm reports for those events, as well as a derecho frequency map for comparison. Pretty remarkable event! #derecho #wxtwitter pic.twitter.com/d2KZk1Gvmk

— Elizabeth Leitman (@WxLiz) June 7, 2020

• Severe wind reports expanded 750 miles from far southeast Utah to southwest North Dakota. 
• For nearly 12 hours, severe winds were produced.
• Derecho tracked to the northeast at approximately 60 mph.
• Highest gust was 110 mph at Winter Park Ski Area in Grand County, CO.
• A peak gust of 78 mph at the Denver airport.
• 94 mph gust at Butte, SD.
• NWS Rapid City confirmed two brief tornadoes.  One was near Billsburg, SD and the other hit the Badlands/White River KOA campground in Jackson County.

#sdwx #cows Was pretty mesmerizing watching this shelf cloud with QLCS circulations embedded in it come at us. The cows were looking to us for shelter I think! pic.twitter.com/6gRhaxvuvB

— Michael Snyder (@SeattleWXGuy) June 7, 2020

August 10, 2020: Midwest Derecho

This derecho was by far the worst of the year.  It was also the worst one to occur in eight years. It began in eastern Nebraska and dissipated in southern Michigan/northwestern Ohio.  Iowa was by far the hardest hit, where estimated wind gusts of 140 mph caused major damage to homes, trees, corn crops, and cellphone towers. This derecho was the costliest severe thunderstorm event in US history, causing an estimated $7.5 billion in damage! It was also the second-costliest natural disaster to impact the US in 2020, falling behind Hurricane Laura, which produced $14.1 billion in damage. Cedar Rapids, IA  was the hardest-hit area. It was here where the 140 mph winds tore apart a large apartment complex, destroyed half of the trees in town, and caused extensive damage to many buildings. 

• Length of Damage: 770 miles
• Highest Measured Wind Gust: 126 mph in Atkins, IA. 
• 25 tornadoes confirmed. 
• 14 million acres of crops destroyed in IA. 
• 100 million bushels (3.52 million cubic meters) worth of grain storage and processing infrastructure destroyed. 
• Fatalities: 4, Injuries: 115.
• $7.5 billion in damage. 
• 150-foot communications tower collapsed.

Sources

3 June 2020 Derecho

Derecho slams Philadelphia area with destructive 80 mph winds

Iowa derecho in August was most costly thunderstorm disaster in U.S. history

Midwest Derecho – August 10, 2020, Updated: 10/8/20 12 pm (NWS Quad Cities)

August 10, 2020: Derecho Brings Widespread Severe Wind Damage Along with Several Tornadoes (NWS Chicago) 

https://en.wikipedia.org/wiki/August_2020_Midwest_derecho

Derecho Facts from The Storm Prediction Center

June 6 2020 Derecho (NWS Denver) 

June 6, 2020 Derecho (NWS Cheyene) 

June 6, 2020 Derecho (NWS Rapid City)

Derecho in South Dakota « CIMSS Satellite Blog 

Was Saturday’s Wind Storm Colorado’s First-Ever Derecho? via The Denver Post