WELCOME TO THE PREVIEW WEEK FOR ONLINE WEATHER - The Daily Weather Summary file will describe the current weather pattern across the U.S. Additional Supplemental Information Files will provide optional background material when appropriate.
Sincerely,
Ed Hopkins
The following discussion was based upon the major features appearing on the surface weather maps of late Sunday night. Three storm systems brought inclement weather over the continental US.
A MAJOR STORM SYSTEM DEPARTS THE EAST COAST -- A slow moving storm system that had been responsible for an episode of deadly severe weather across the Southern states at the end of last week was finally moving out to sea along the Eastern Seaboard. As of late Sunday night, the storm system consisted of one low pressure system located over the lower St. Lawrence Valley in New Brunswick with a cold front that trailed southward to a second low pressure center located to the east of the Delmarva Peninsula. A cold front continued southward over the open waters of the Atlantic to the Straits of Florida.
Ahead of this advancing cold front, winds from the south brought unseasonably warm, moist air northward into New England and Upstate New York. Daily record high temperatures were set on Sunday at Boston, MA (62 degrees); Albany, MY (54 degrees) and Portland, ME (53 degrees). Interestingly, the record at Boston was set in mid morning.
An extensive band of precipitation, mainly in the form of rain, accompanying this front extended from the Canadian Maritimes and New England southward to the Middle Atlantic States. Most of this precipitation was found in the warm air to the east of the front. Flooding of area rivers occurred over the weekend as a result of the heavy rains and the snowmelt accelerated by the warm weather. Flood watches and warnings remained for some river basins.
WINTRY WEATHER MOVES ACROSS THE MIDWEST -- A large band of snow moved eastward across the Mississippi Valley into Wisconsin on Sunday evening. Accumulations were on the order of an inch across southern Wisconsin. This snow was associated with a low pressure system that was located over northern Missouri. A warm front extended eastward across the Midwest toward the southern Great Lakes. Close to the front, some of the precipitation fell in the form of freezing rain, as warm air from south of the front was lifted over the colder air to the north of the front. By late night the snow had spread east to Michigan's Lower Peninsula. A cold front trailed to the southwest of the low. However, little precipitation was found along this front that marked the leading edge of colder air moving southward across the Plains.
The low pressure system is expected to move quickly northeastward on Monday. The accompanying snow is also anticipated to reach the eastern Great Lakes and Middle Atlantic States by afternoon. Several inches of snow, enhanced by Lake Michigan, are expected over Lower Michigan. Fortunately, little additional precipitation should fall to portions of the Midwest to the south, such as in Illinois, Indiana, Kentucky, Ohio and West Virginia, where flooding has been the result of a combination of heavy rains and recent mild weather that has melted the snow pack.
A WINTER STORM AFFECTS SOUTHERN CALIFORNIA -- A storm system accompanied by widespread precipitation and cold air moved across southern California and into the Southwest. As of Sunday evening, the low pressure center was located in southern Nevada, with a cold front trailing to the south across the Imperial Valley of southern California. Rain fell along the coastal regions of Southern California and in the vicinity of the Los Angeles Basin. Because cold air was being drawn southward along the western flank of this storm system, thunderstorms were a distinct possibility. The cold air was also causing the snow levels to drop to 3500 feet in the mountains surrounding the Los Angeles Basin. As much as 7 inches of snow accumulation was forecast for the San Bernardino Mountains. To the north and east of the low, heavy snow fell across central and northern portions of Nevada and Utah, where a variety of winter storm and heavy snow warnings were in effect. Some locations near Tonopah, NV had between 10 to 12 inches by late evening.
This system was associated with a significant temperature contrast across the West. Cold conditions were found to the north of this system. Afternoon high temperatures across the northern Rockies, northern portions of the Great Basin and the Pacific Northwest ranged from 10 to 20 degrees below the average highs for this time of year. Oakland (Downtown), CA had a record low temperature of 36 degrees on Sunday morning. A broad area of warm air was situated to the south and east of this system. Unseasonably warm conditions were found from the Southwest eastward to the Gulf Coast region, as afternoon high temperatures were at least 25 degrees above the long-term average high temperatures for the third week of January. Record high temperatures for the date were set at San Angelo (81 degrees),
This storm system is forecast to continue eastward on Monday, reaching the Four Corners (Arizona, New Mexico, Colorado and Utah) by dawn. Heavy snow should fall across the mountains of Utah, Wyoming, southern Idaho and western Colorado on Monday.
A RECAP -- The severe thunderstorms that rolled through the South on Thursday night and early Friday morning spawned approximately 70 tornadoes in addition to strong, damaging thunderstorm winds and large hail. Especially hard hit were counties in central Arkansas near Little Rock and in middle Tennessee near Clarksville, where a tornado inflicted major damage to the historic district around the county courthouse before dawn on Friday morning. At least 9 tornado-related fatalities were reported. As of Saturday morning, 102 tornadoes had been reported across the nation during the month of January, nearly twice the previous record number of January tornadoes.
TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 20 degrees below zero (Fahrenheit) at West Yellowstone, MT, while Sunday's highest temperature was 86 degrees at Tucson, AZ and Carlsbad, NM.
ALASKAN WEATHER -- Following a week of relatively clear skies and cold conditions associated with high pressure, much of interior Alaska experienced cloudy skies and warmer air from the Pacific on Sunday afternoon as several low pressure systems dominated the state's weather. The clouds extended to Seward Peninsula and to northwest Alaska in association with a low pressure system that had moved across the Kuskokwim Mountains of southwest Alaska. Strong winds were found circulating around the western and southwestern regions of this low pressure system. Winds gusted to 51 mph at Cold Bay, to 47 mph at Saint Paul and to 44 mph at Dutch Harbor. Snow fell near Fairbanks in the interior and at King Salmon along the Alaska Peninsula. Another low pressure system over the Panhandle spread clouds across the Panhandle and southeast Alaska. Snow fell over Juneau, Ketchikan and Petersburg, while rain was reported at Sitka and Skagway. A third storm system situated to the south of Shemya was responsible for cloudy skies across the western Aleutian Islands.
Of note: A record 3.07 inches of liquid equivalent precipitation, to include snow and ice pellets, fell at Cold Bay during the 24 hours ending on Friday evening. On Saturday morning the temperature at McGrath reached 39 degrees, a record high temperature for the date.
The lowest overnight temperature in Alaska as of Sunday was 23 degrees below zero at Northway, and the midafternoon highest statewide temperature was 43 degrees at Annette.
HAWAIIAN WEATHER -- A wind shear line, representing a region where the near-surface winds vary in speed or direction, moved across the islands on Sunday. This shear line was the southern end of a cold front that extended southward from midlatitudes and is along a weak region or trough of low pressure. Clouds, rainshowers and gusty winds were found over the islands, with especially heavy showers expected to linger over the windward slopes of Maui and the Big Island. As the shear line passed over Kauai on Friday, flash flood watches were issued for the heavy rains produced by slow moving thunderstorms. After the shear line has passed late Sunday, skies were expected to clear and winds from the northeast should increase in speed, reaching between 20 and 35 mph. These winds, called northeast trade winds in the subtropical latitudes, were being generated along the southern flank of high pressure cell located approximately 1500 miles to the northeast of Oahu. This high pressure system is expected to move slowly to the east, with a slight weakening of the trade winds during the early part of the week. Gale warnings were in effect for all channels between islands for winds between 39 and 54 mph. Small craft advisories were also posted for coastal waters and a high surf advisory remained in effect for the east shores of the islands as the strong winds from the east continued to generate ocean swells and surf with heights between 6 and 10 feet.
AN INVITE -- If you witness some interesting weather phenomena or would like to share some weather-related experience with others in the Online Weather Project, we cordially invite your contributions. Please email these to the address appearing below. Some of these may appear in the section titled "Reports from the Field"
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.