NATIONAL STORM SUMMARY

 

APRIL 2013

 

1^st-6^th…A cold upper trough of low pressure from the North reached southward into the Central and Eastern U.S. and ushered another shot of arctic air into the north-central regions of the nation on Wednesday. This translated into well below average temperatures that seemed more reminiscent of winter than spring. As cold northwesterly flow spread into the Midwest, light to moderate lake effect snow showers developed downwind of portions of the Great Lakes. A Lake Effect Snow Warning and Winter Weather Advisory continued for areas of northern Michigan through the afternoon in anticipation of 2 to 4 inches of snow and strong northwest winds. South of this cold front, a second cold front became nearly stationary from the Lower Mid-Atlantic through the Deep South. Rain showers and isolated thunderstorms continued along and ahead of this cold front through the afternoon. Further south, impulses streaming across the southern Florida Peninsula created a slight risk of severe thunderstorm activity during the late afternoon. While the main concern with these storms were severe hail, tornadoes were not ruled out.

 

7^th-13^th…A significant snowstorm continued in parts of the West and Plains on Tuesday, while chances of severe weather activity heightened in the Great Plains. A strong storm system over the Intermountain West shifted eastward on Tuesday as a strong cold front reached from the central Plains across the central and southern Rockies and a strong low pressure system moved into Texas. Heavy snow showers fell across areas of Colorado, Wyoming, western Nebraska, and South Dakota, while strong winds gusting in excess of 50 mph picked up across the region through the day. This combination of snow and wind translated into blizzard conditions in parts of eastern Colorado through Tuesday night with lowered visibility, high snow drifts, icy roads, and hazardous travel conditions. Much of this wintry weather region and portions of southwestern Minnesota remained under Winter Storm Warnings and Winter Weather Advisories in anticipation. Blizzard Warnings continued for the mountains of Colorado through Tuesday evening. In addition to snow and wind, areas of morning freezing rain and sleet in Nebraska and parts of South Dakota led to possible ice accumulations of up to an inch. Meanwhile, warm and moist air from the Gulf of Mexico streamed northward and supported more rain and thunderstorms from the central Plains into the Ohio Valley and Great Lakes. This moisture tap continued the threat of severe weather development from the southern Plains through the Mid-Mississippi Valley.

 

In Colorado up to around 10 inches of snow had fallen in Colorado's mountains by dawn Tuesday (10^th). High winds and snowy conditions led to more than 500 flight cancellations in Denver on Tuesday, according to Denver International Airport. Several school districts canceled classes for Tuesday. Before the snow arrived, it was 70 degrees at the Denver airport at midday Monday, and a grass fire burned about 2 square miles in eastern Colorado. No structures burned.

Severe weather was reported before temperatures began to fall. Northeast of Denver, the town of Akron reported damage from a possible tornado on

Monday night. According to authorities, three structures were damaged, including a mobile home that was destroyed. Washington County Emergency

Management said the mobile home's occupant was displaced but not injured.

Loveland Pass, west of Denver, was closed to traffic on Tuesday morning due to poor conditions. The storm could boost mountain snowpack, which helps provide water through the summer. Colorado's snowpack was at 69 percent of average Monday.

In Wyoming, section of I-80 between Cheyenne and the Nebraska state line is closed, a stretch of about 45 miles. More than a foot of snow had fallen as of midmorning in Lander. In Pine Bluffs, near the Nebraska border, wind has created 1- to 2-foot drifts out of the snow that has fallen there.

Wind gusts up to 71 mph damaged a marina and windows in Sweetwater County. With hazardous conditions expected throughout the day, drivers were urged to keep a close eye on additional road closures.

In South Dakota, snowfall totals from Walda are expected to be highest in South Dakota, where snow is already falling in some areas, while other parts of the state are expected to receive moderate, possibly-crippling freezing rain. The National Weather Service in Sioux Falls was reporting power outages due to high winds downing power lines on Tuesday morning.

Approximately a half-foot of snow has fallen in Rapid City, and social media reports said there was extremely limited visibility in town. Schools were expected to remain open in Sioux Falls while the city received a cold rain in the morning, though some local elections were canceled. Conditions are expected to worsen as the day progresses, with rain turning into freezing rain and wind-blown snow in a matter of hours.

In Nebraska, while eastern Nebraska dealt with severe storms overnight Monday and into Tuesday morning, the western and central portions of the state began to see snow and wintry mix, with a foot or more in the forecast for parts of north-central Nebraska. Some of Walda's strongest winds were being observed in Nebraska on Tuesday afternoon, and wind chills were in the single-digits or below across a large chunk of the state. Eastern Nebraska will remain under the threat of severe weather through Tuesday evening.

In Minnesota, schools are closing in southwestern Minnesota as Walda moves into the region. Marshall Public Schools are among those dismissing early as travel conditions deteriorate. The National Weather Service has issued a storm warning for southwestern Minnesota through Thursday.

A large chunk of southern Minnesota is already reporting snow, but other areas that are seeing rain or freezing rain will see a changeover later on Tuesday afternoon or evening. The Minnesota Department of Transportation says roads in much of southwestern Minnesota are in difficult driving condition.

In Utah, wind gusts as high as 70 mph were reported in Utah as well, where conditions were life-threatening early Tuesday morning. The state avoided the brunt of the snow, although some higher elevations received significant accumulations. A few thousand residents lost power due to the high winds in the northern part of the state.

Rain moved through the Northeast, while rain and snow persisted for the Upper Midwest, and showers and thunderstorms diminished across the Southeast. A strong low pressure system that created a strong winter storm for the Plains and Upper Midwest continued to move northeastward and over the Great Lakes. This brought snow showers to the Great Lakes and Upper Midwest, which turned to rain showers as temperatures warmed throughout the day. The leading edge of this system pushed a warm front northward through the Northeast, creating heavy rain and periods of freezing rain from New Jersey and New York through Maine. At the same time, a strong cold front extended southward from this system and advanced eastward across the Eastern Valleys. This system has brought severe thunderstorms to the South the past three days, and finally started to push offshore and into the Atlantic Ocean. A few widespread scattered showers and thunderstorms developed from Maryland, through the Carolinas, and into Georgia. Some of these storms turned severe with strong winds and large hail.

 

14^th-20^th…A dangerous day was set up for the middle portion of the country Wednesday as a powerful storm brought a variety of significant weather events to the region. The associated cold front produced heavy rain for Iowa and Illinois. Some areas in Iowa had reported up to 3 inches of rain by the early afternoon, prompting flooding concerns due to surging rivers and streams. The second effect of the storm was the winter conditions it provided from the Northern Rockies through the Northern Plains. An area of showers and thunderstorms developed over the Appalachians.

A strong winter storm lingered over the Great Lakes on Friday, while the associated cold front brought severe thunderstorms to the Eastern states. A low pressure system continued moving northeastward, over the Great Lakes and toward eastern Canada. The back side of this system allowed for cool air from Canada to pour across the Upper Midwest, allowing for a few more snow showers to persist for northern and eastern Minnesota, as well as most of Wisconsin and the Upper Peninsula of Michigan. Most of the heaviest snowfall came to an end early Friday morning with record breaking snowfall totals for many areas of northern Minnesota and Wisconsin. Storm totals since Wednesday reached up to 20 inches for some areas, with 17.70 inches of snow reported at Duluth, Minnesota. This past snowstorm created the snowiest April on record for Duluth at 41.7 inches.

At the same time, the strong low pressure system continued pushing a cold front through the Eastern states. This system has a history of producing multiple tornadoes with many reports of strong winds and large hail. By mid-day Friday, one tornado was reported in Mansfield, Georgia with many reports of damaging winds across Alabama and Georgia. Severe flooding continued for the Ohio River Valley and Mid-Mississippi River Valley as the cold front created heavy rains for the region yesterday. Two day rainfall totals for much of Illinois ranged from 5 to 7 inches. This created major flooding concerns for the region, with many areas experiencing record flood levels.

A strong cold front brought showers and thunderstorms to the Eastern Valleys on Wednesday, while scattered snow showers moved across the Northern Plains. A low pressure system that brought a strong winter storm to the Upper Midwest early this week has moved eastward over the Great Lakes. The back side of the system continued pushing a cold front eastward, kicking up showers and thunderstorms from the Great Lakes through the Gulf coast. Some of these storms have turned severe with heavy rainfall and strong winds. A threat for large hail and tornadoes persisted for the Lower Mississippi River Valley as the system pulled moisture and energy in from the Gulf of Mexico. There have been multiple reports of trees and power lines blown down across Louisiana and Tennessee. Rainfall totals reached over an inch in these areas which allowed for flooding to remain a concern for the Ohio River Valley and Mississippi River Valley. Record level flooding was reported at Peoria, Illinois where the Illinois River was up to 29.35 feet on Wednesday morning. Since the rain last week, at least 20 locations in the Midwest have reached record flood levels.

Severe showers and thunderstorms developed across the South on Friday. A trough of low pressure moved off the Southern Rockies and into the Southern Plains, which pulled moisture in from the Gulf of Mexico. This system allowed for showers and thunderstorms to develop from Texas through Oklahoma that advanced eastward across the Mid-Mississippi River Valley and into the Tennessee Valley throughout the day. Rainfall totals in these areas ranged around an inch by mid-day on Friday. Some areas saw periods of heavy rainfall and gusty winds.

 

Jim G. Munley, jr.
http://www.jimmunleywx.com