STORMS RUMBLE ACROSS THE NATION'S MIDSECTION -- An intense low pressure system in the upper Midwest dominated the weather across much of the central portion of the country on Monday evening. The primary center of the low pressure system as of late Monday night was located in northwest Iowa near Sioux City. An occluded front extended eastward across Iowa to a point of occlusion near Cedar Rapids. A warm front continued southeastward from this occlusion across the Ohio and Tennessee Valleys to northern Georgia. A cold front extended southward and southwestward along the Mississippi Valley to southern Arkansas.
This system has had a history of severe weather as it intensified and moved toward the northeast from south central Kansas during the day on Monday. Early on Monday morning, severe thunderstorms associated with the cold front spawned a tornado that caused significant damage near Wichita, KS, including damage to portable classrooms in trailers at a school. No injuries were reported. Other tornadoes were reported across southeast Nebraska and eastern Oklahoma. Kansas, Arkansas and western Iowa. Damaging winds and large hail were also produced by these systems across Iowa, Missouri, Illinois, western Kentucky and Arkansas. Heavy rain was also reported. By Monday evening , several locations in Nebraska had set new 24 hour precipitation totals for the date. Grand Island had received a record 1.64 inches of rain, Hastings had 1.62 inches and North Platte, NE had received 0.62 inches.
As of late Monday night, severe thunderstorms continued to develop along a squall line through the lower Mississippi Valley to the east of the cold front. This squall line represents an organized line of strong to severe thunderstorms that typically develop well ahead of the advancing cold front. This squall line ran from northern Louisiana northward into central Illinois. These thunderstorms were fed by the warm humid air that streamed northward in the warm sector to the southeast of the low between the surface warm and cold fronts. Dewpoints in the warm sector reached the low 70s, providing the low level atmospheric moisture needed to fuel the thunderstorms.
A large area of precipitation, to include non-severe thunderstorms spread northward across northern Illinois, Wisconsin and Michigan's Upper Peninsula. To the north of the storm, sufficient cold air was being brought into the system on northerly or northeasterly winds to permit snow to fall from the Arrowhead of Minnesota through eastern South Dakota.
This system is forecast to continue moving toward the northeast, with the surface low being situated over eastern Wisconsin by Tuesday morning and near eastern Lake Superior by evening. A slight risk of severe thunderstorms remained until Tuesday morning in an area of the Mississippi Valley extending from southern Mississippi north to southern Wisconsin. Snow advisories continue for Minnesota through mid morning for accumulations of 3 to 5 inches of snow.
STORMY WEATHER ALONG THE CALIFORNIA COAST -- A storm system, packing gale winds, was poised to move onshore along the northern California coast. As of late evening, the center of this low pressure system was just south of Cape Mendocino, with a cold front that extended south to the San Francisco Bay area before turning to the southwest and heading out to sea. A wide area of precipitation extended across California.
This storm system is expected to move southeastward along the coast on early Monday. Precipitation is anticipated to continue to spread southward across California south of San Francisco. A winter storm warning was in effect for portions of the Sierras, where as much as two feet of snow are expected at elevations above 7000 feet. Winter weather advisories were also issued for Southern California mountains surrounding the Los Angeles Basin. Snow was forecast to spread across the Intermountain West on Tuesday. Snow advisories were posted for Nevada.
Moored buoys along the California coast reported ocean swells to as high as 30 feet. As a result, heavy surf advisories were posted along the California coast through Tuesday from Point St. George to Point Piedras Blancas.
The low also helped suppress the daily afternoon temperatures over California. Stockton had an afternoon high temperature of 49 degrees, while Redding and Red Bluff both had afternoon highs of 50 degrees, which either tied or set the record lowest high temperature for the date.
Record low temperatures were either tied or set across southern California on Monday morning, to include Big Bear Lake (16 degrees), San Luis Obispo (36 degrees) and Burbank (40 degrees).
A CHILLY START IN THE EAST -- A large elongated ridge of high pressure centered on the Virginia Capes brought tranquil weather to the East on Monday. However, with dry air, clear skies and light surface winds, cold overnight low temperatures are expected. Freeze warnings were posted for southern New Jersey.
Elsewhere, record high temperatures were set on Monday at Orlando, FL (91 degrees) and Beckley, WV (76 degrees).
UPPER AIR -- The mid and upper tropospheric charts of the 500 mb and 300 mb constant pressure surfaces for 00Z Tuesday continue to show the effects of a warm East and a cold West. A large height ridge continues to appear on both charts where the respective pressure surface stands higher above the warm lower troposphere from the eastern Great Lakes.. A height trough, with lower heights of the pressure surface, remains across the Rockies and the high Plains. On the 500 mb surface a closed height contour and nearly closed circulation appears over eastern Nebraska. This distinct feature reflects the cold low at the earth's surface one hundred miles to the north. At 300 mb, a region of strong southerly winds with speeds ranging between 80 and 100 knots over the eastern Plains provide a mechanism for maintaining the surface low. Acceleration of air passing through this region contribute to the production of upper level divergence needed to compensate the near-surface convergence in the surface low pressure system.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature in the lower 48 states on Monday was 7 degrees at Durango, CO. Monday's highest temperature was 94 degrees at McAllen, TX.
ALASKAN WEATHER -- Several low pressure systems over mainland Alaska spread clouds and precipitation across the state on Monday. Much of the precipitation fell as snow. One low pressure center was located near Valdez, with a front that extended southeastward into the northern Gulf of Alaska before curving southwestward into the North Pacific Ocean. A second low pressure system was situated northwest of Nome, with a front that extended eastward across northern Alaska into the Yukon Territory. A third low near Hooper Bay in the Yukon-Kuskokwim Delta had a front that extended southwestward across the Bering Sea toward Adak. Earlier, this storm had brought wintry weather in the form of snow, blowing snow and blizzard conditions across much of western Alaska to include coastal locations along the Bering Sea and the Alaska Peninsula. Measurable precipitation was reported at Seward, Kenai, Homer, Cordova, Cold Bay, Kodiak, King Salmon, Saint Paul Island, Nome, Kotzebue
The state's lowest overnight temperature as of Monday was 20 degrees below zero at Deadhorse. The highest temperature in the state by midafternoon was 48 degrees at Annette.
HAWAIIAN WEATHER -- Northeast trade winds were beginning to return to the islands on Monday as a low pressure system located to the northwest of the islands continued to weaken and move toward the west. This low had disrupted the typical northeast winds and had increased showers over the weekend. Showers continued to affect the windward slopes and the mountainous areas of the islands into early Tuesday. A ridge of high pressure to the northeast of the islands moved closer toward the islands. This high should be reinforced with another high by midweek. High surf advisories continued for the north shores of the islands and advisories have been added for the south shores.
ATMOSPHERIC SCALES -- For more detail on the traditional arrangement of the subdivisions according to space and time scales, together with their observation strategies, see the Tuesday optional Supplemental Information.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 1999, The American Meteorological Society.