DATASTREME DAILY SUMMARY

Monday 8 October 2001


00Z Weather Systems


Today is the Federal Holiday, Columbus Day, and also Thanksgiving Day in Canada.

WEATHER OVER THE WEEKEND -- A large portion of the country experienced the first cold weather of the autumn over the weekend as cold air from the Prairie Provinces spread southward and eastward. By the end of the weekend, a storm system was poised to bring snow to the Pacific Northwest and the northern Rockies.

Cold air invaded the nation's midsection on Friday, extending from the Rockies eastward to the lower Great Lakes and from the Canadian border southward to north Texas. This cold air accompanied a large high pressure cell that was centered over the Big Horn Mountains of north central Wyoming as of Friday morning and western Kansas by evening. Record low temperatures were set on Friday morning in Montana at Butte (14 degrees) and Kalispell (19 degrees); in Idaho at Pocatello (21 degrees) and in the Columbia Basin of Oregon at Meacham (19 degrees) and at Pendleton (32 degrees) and of Washington State at Grand Coulee Dam (31 degrees) and at Chief Joseph Dam near Bridgeport (30 degrees). High temperatures across the Plains and Midwest ranged from 10 to 20 degrees below the average highs for the first week of October. Record low high temperatures were either tied or set on Friday in Colorado at Trinidad (45 degrees), Colorado Springs (47 degrees) and La Junta (48 degrees), in Kansas at Goodland (50 degrees) and in Illinois at Lincoln (49 degrees).

The leading edge of the cold air was a cold front that stretched from the eastern Great Lakes to the Texas Panhandle on Friday morning. By Friday evening northern and eastern portions of the front remained over the eastern Lakes, while the western sections of the cold front had pushed south to the Texas Gulf Coast. In the warm air ahead of the advancing cold front high temperatures on Friday were up to 15 degrees above the average across the Northeast.

Some active weather also accompanied this vigorous cold front. Thunderstorms generated strong winds that damaged property and downed trees across south central Kentucky and central Mississippi on Friday afternoon, as well in southern Texas late Friday night. Heavy rains in Texas established new daily precipitation records on Friday at Victoria (2.04 inches) and at Lufkin (0.80 inches).

By Saturday morning the large cold high pressure system had moved southward into Oklahoma. Another high pressure center with cold air was also situated over the Chimney of northern Idaho. On Saturday morning, record low temperatures were either tied or set at in Montana at West Yellowstone (8 degrees); in Wyoming at Laramie (18 degrees) and Rawlins (20 degrees); in North Dakota at Fargo and Grand Forks (both 19 degrees); in South Dakota at Aberdeen (20 degrees); in Kansas at Dodge City (30 degrees), Garden City (30 degrees) and Liberal (33 degrees); in Texas at Amarillo (34 degrees), Lubbock (34 degrees) and Wichita Falls (40 degrees); in Oklahoma at McAlester (36 degrees) and Oklahoma City (37 degrees). Record lows were also set on Saturday evening at were also set at Green Bay, WI (23 degrees) and at Bergstrom Airport in Austin, TX (48 degrees).

The cold front had moved across the Appalachians, and stretched southward from a low pressure center near Montreal in Quebec to western portions of the Florida Panhandle, then westward across the Gulf of Mexico to the lower Rio Grande Valley of South Texas.

The high pressure cell moved eastward into the Mississippi Valley by Saturday evening, with one center located over Arkansas and a second center over southeastern Minnesota. Northern portions of the cold front had moved off the Atlantic Coast. Even with relatively cloud-free skies in many locations, daytime temperatures did not rebound rapidly as cold air continued to move southward and eastward. On Saturday afternoon the high temperatures across the center of the country, to include essentially the entire Mississippi and Ohio Valleys, the western Great Lakes and the western Gulf Coast were below average, with the largest departures ranging between 10 to 15 degrees below the average highs. Low maximum temperatures were either tied or established in Texas at Houston's Intercontinental Airport (65 degrees), Lufkin (68 degrees) and Bryan/College Station (70 degrees). Highs in the northern Rockies and Intermountain West were slightly above the seasonal averages. To the south of the cold front, Melbourne, FL experienced a record high temperature of 92 degrees.

By Sunday morning the coldest air was found near the center of the high pressure ridge located over central Indiana. The cold air had moved eastward and southward, with the cold front moving southward across the Florida Peninsula. Record low temperatures were reported across the Midwest in Minnesota at International Falls (18 degrees) and Duluth (24 degrees); in Wisconsin at Rhinelander (19 degrees), Green Bay (21 degrees), Madison (23 degrees), and La Crosse (26 degrees); in Iowa at Dubuque (25 degrees); in Illinois at Rockford (26 degrees) and Chicago's O'Hare (29 degrees); in Ohio Mansfield (31 degrees) and in Kentucky at Jackson (33 degrees). Other record lows on Sunday morning were set in Longview, TX (25 degrees), Hot Springs, AR (37 degrees), Bluefield, WV (32 degrees) and at BWI Airport near Baltimore, MD (35 degrees).

Another feature of the weekend's invasion of the cold air was the development of lake-effect snow along the downwind shores of the Great Lakes. The flow of cold air across the relatively warm Lakes Superior and Michigan produced some of the first snow of the season in Michigan on Saturday morning. By Saturday afternoon, 7 inches had fallen in Carlshend and 4.2 inches at Marquette in the Upper Peninsula, as well as a trace at Grand Rapids in the lower Peninsula. The snowfall at Marquette and Grand Rapids set records for the date. Since the ground was relatively warm, little of the slushy snow remained on the ground for long. As the cold air moved toward the east, lake-effect rain and snow also developed across the eastern Lakes late Saturday and into Sunday. Locales downwind of Lake Ontario in Upstate New York especially near Oswego reported rain, lightning, snow, and graupel, a form of soft hail, all indicative of the convection associated with cold air heated from below as a consequence of passage over relatively warm water.

The high pressure center and the accompanying core of the cold air moved eastward on Sunday. Much of the nation to the east of the Mississippi River, along with a portion of the southern Plains experienced unseasonably chill conditions, with afternoon highs between 10 to 15 degrees below the average highs for the date.

A cold front made landfall in the Pacific Northwest on Saturday and moved eastward across the Plains during the second half of the weekend. Following unseasonably cold conditions at the end of last week, portions of the central Rockies and western Plains had high temperatures on Sunday that were at least 10 degrees above the long-term average.

Rainshowers and thunderstorms moved across portions of the Southwest on Sunday morning in association with a cold pool of air in the mid to upper troposphere.

WEATHER FOR THE START OF THE NEW WEEK -- The following highlights of the national weather have been extracted from the surface weather map for late Sunday night.

A large ridge of high pressure extended from the northern Lakes southward to the Southeast, with a center located over West Virginia. With clockwise circulation around the northern flank of the high, some light lake-effect precipitation was found over and downwind of the Lakes, especially over the Mohawk and Champlain Valleys of Upstate New York. Light precipitation was also detected across portions of Maine. The southern extent of the cold air was the cold front that lay across south Florida. Rainshowers and thunderstorms were found along the front.

The high is expected to drift slowly eastward on Monday. The cold air coupled with the cloud-free skies, the low humidity and the weak winds near the center of the high should cause overnight temperatures to fall rapidly as the result of strong radiative heat loss from the surface. As a result, a variety of frost and freeze advisories or warnings were found across much of the region extending southward from Lower Michigan to northern Georgia and eastward to southern New England.

A weak low pressure system was located over the western Plains, the Black Hills of South Dakota and the Rockies of Wyoming. This low had a warm front that extended eastward across the Plains into Iowa. Some light and widely scattered precipitation was found across the Plains and the northern Rockies.

This low pressure system is expected to move eastward across the Plains. Precipitation associated with the warm front is expected to spread eastward into the Upper Mississippi Valley, with as much as 0.3 inches possibly falling through Monday evening.

A front associated with a storm system in the Gulf of Alaska was located several hundred miles off the Washington and Oregon Coasts. Some widely scattered precipitation was falling across portions of the Pacific Northwest ahead of this system. This front is expected to move onshore by Monday morning, pushing eastward across the Montana Rockies by evening. Widespread precipitation should increase and continue across the Northwest on Monday. Between 0.2 and 0.5 inches should fall in the 24 hours ending on Monday evening, particularly along the western or upwind slopes of the mountain ranges. Snow advisories have been issued for the Olympics and the Cascades in Washington as between 1 to 3 inches of snow could fall at elevations above 4500 feet by Monday morning, with as much as an additional 3 inches possible by evening. A winter storm watch was posted for Monday night and Tuesday morning for the Uinta and Wasatch Mountains in Utah and southeastern Idaho. As much as a foot of snow is anticipated at elevations above 8000 feet.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 12 degrees at Sparta, WI, while Sunday's highest temperature was 97 degrees at Death Valley, CA.

ALASKAN WEATHER -- Clouds covered much of Alaska as the result of several storm systems either located over or near the state late Sunday afternoon. One storm system was located over the eastern Gulf of Alaska to the southwest of the southern Panhandle. This low pressure system, with a central pressure of 979 mb, had an occluded front that trailed southward paralleling the British Columbia coast, before becoming a cold front west of Oregon. Another storm system was located over the western Aleutian Islands. A third storm system was located over northwest Alaska. The low pressure center was found near Kotzebue Sound, with a stationary front that extended eastward along the Brooks Range, and a nearly stationary front that curved southwestward across the Seward Peninsula and then out over the northern Bering Sea. Windy conditions were found in the North and over the Panhandle, to include Shishmaref with gusts to 38 mph and Ketchikan with gusts to 37 mph. Rain fell at Bethel, Ketchikan and Petersburg, while snow was reported at Barrow, Healy and McGrath. Annette Island had a 24 hour rainfall total of 1.24 inches by Sunday afternoon.

The lowest overnight temperature in Alaska as of Sunday was 14 degrees at Barrow and the midafternoon highest statewide temperature was 54 degrees at Skagway.

HAWAIIAN WEATHER -- An elongated ridge of high pressure located approximately 600 miles to the north of Hawaii produced a sufficiently tight pressure gradient across the islands, resulting in strong trade winds within the range of 15 to 30 mph. Clouds and accompanying showers were found across the Big Island and along the windward portions of the other islands. These clouds and precipitation should dissipate by late Monday. As a result of the strong trade winds, small craft advisories were posted for all state waters and high surf advisories were in effect for all east-facing shores.

EYE ON THE TROPICS -- In the tropical North Atlantic, a tropical depression intensified to Tropical Storm Iris late Friday afternoon and then became a hurricane on Saturday afternoon. At least three fatalities attributed to Iris were reported in the Dominican Republic on Saturday. As of late Sunday night Hurricane Iris had maximum sustained surface winds of 90 mph and was situated 460 miles east of Belize City, Belize. Movement to the west was at 20 mph.

Another tropical depression formed in the Atlantic on Saturday morning (51 W) and then became Tropical Storm Jerry, the tenth named tropical system of the season on Sunday morning. The position of Tropical Storm Jerry as of late Sunday night was 40 miles east of St. Vincent in the Windward Islands and movement was to the west-northwest at 14 mph. Maximum sustained surface winds were 50 mph.

NEW WORLD WEATHER -- Since today is the Federally observed Columbus Day, check the Monday optional Supplemental Information for a discussion of the weather hazards that confronted Christopher Columbus on his voyages to the New World.


HISTORICAL WEATHER EVENTS - 8 October

From the files of the Aviation Weather Center, Kansas City, MO and Intellicast


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URL Address: datastreme/learn/m_sum.html
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.