DATASTREME DAILY SUMMARY

Friday, 5 October 2001


00Z Weather Systems


The following highlights of the national weather have been extracted from the surface weather map for Thursday night:

COLD AIR POURS INTO THE NATION -- Cold air has spread southward from Canada behind a series of cold fronts. High pressure associated with this cold air was located across the southern Prairie Provinces. High temperatures on Thursday across the western Plains and the northern Rockies ranged from 10 to 20 degrees below the average highs for early October as a result of the cold air advection behind the fronts.

The first cold front trailed southwestward from a low pressure center over the lower St. Lawrence Valley across the eastern Great Lakes before becoming a stationary front over the Ohio and mid-Mississippi Valleys. This stationary front, marking the southern advance of the colder air, continued across the Plains to the Texas and Oklahoma Panhandles, then curved to the northwest, traveling across the central Rockies to southern Idaho.

A second cold front associated with a low pressure center near Hudson Bay curved southwestward from the western Great Lakes across the upper Mississippi Valley into the northern Plains. Temperatures below this second front were slightly lower than in the region between the first and second fronts.

Cold air is expected to move southward across the Plains as high pressure moves southward along the eastern slopes of the Rockies. By Friday evening, the high is expected to be located over western Kansas, with a cold front having pushed southward into central Texas. With cold air over the region, coupled with clear skies and weakening winds, temperatures are expected to fall to the upper 20s across the northern Plains. As a result, freeze advisories were in effect for the western Dakotas and for portions of Wyoming and the Nebraska Panhandle. Farther west in the Columbia Basin, freeze warnings were posted for south central Washington State and north central Oregon. On Thursday morning, a record low temperature was established at the Grand Coulee Dam, WA at 34 degrees.

SEVERE WEATHER ACROSS THE PLAINS -- The section of the nearly stationary cold front across the central Plains was the focus for thunderstorm activity. Thunderstorms continued along and to the north of the first front across portions of Kansas and Missouri into Thursday night. During the late afternoon and early evening, some of the thunderstorms became severe. Thunderstorm winds damaged property in west central Missouri near Kansas City, while in Oklahoma and Kansas winds associated with thunderstorms reached gusts of 60 mph. Large hail also fell across portions of western Missouri and southern Kansas. Some of the largest hail reached diameters of 2.50 inches near Wichita in south central Kansas. Farther south, more thunderstorms had developed along a trough line across west Texas. Large hail fell from thunderstorms near San Angelo.

Severe thunderstorms continued to move from northeastern Oklahoma into southwestern Missouri as of early Friday morning. In southeast Kansas, radar-estimated rainfall from the thunderstorms was on the order of 5 inches by local midnight, with as much as two more inches possible. As a result, flash flood warnings were placed in effect.

The nearly stationary front is expected to remain across the central Plains through Friday morning before pushing southward as a cold front later during the day. More than 2 inches of rain were expected over Kansas and Missouri during the 24 hours ending on Friday evening. A slight risk of severe thunderstorms continues through early Friday morning across the Plains, extending from northern Oklahoma to west central Illinois. On Friday, as the front moves south, a region extending from southern Texas northeastward to southwestern Ohio is expected to be under a slight risk for severe thunderstorms.

WARM WEATHER FOUND OVER THE NORTHEAST -- High pressure located over the Southeast and an advancing cold front from the Midwest produced a southwesterly wind flow along the East Coast. With southwesterly winds resulting in warm-air advection, high temperatures across New England and portions of the Middle Atlantic States were on the order of 15 degrees above the seasonal average highs. Record high temperatures were either tied or set in Maine at Orono (79 degrees), Bangor (78 degrees), Houlton (78 degrees), Caribou (77 degrees) and Eastport (73 degrees).

SNOW IN THE ROCKIES -- Snow fell across the Rockies of Wyoming and northern Colorado on Thursday as a result of cold air coupled with upslope flow. The high pressure system moving southward from the eastern slopes of the Canadian Rockies provided the necessary cold air. An easterly wind flow moving "upslope" from the Plains toward the Rockies provided the moisture and the necessary lifting mechanism for snow formation. Most of the snowfall was light, with little accumulation because of the relatively warm ground.

TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 22 degrees at Dixie and Elk City, ID and Ukiah, OR. Thursday's highest temperature was 107 degrees at Death Valley, CA.

ALASKAN WEATHER -- A strong storm system that has moved slowly northward across the Bering Sea continued to spread clouds, rain and wind across the Alaska Peninsula and much of southwest Alaska. An occluded front extended eastward from the low pressure center to the vicinity of St. Lawrence Island, where a warm front continued across Norton Sound into interior Alaska, while a cold front stretched southeastward across the Yukon-Kuskokwim Delta and the Alaska Peninsula out into the Gulf of Alaska and the eastern North Pacific Ocean. A trough line was also found across the western Alaska Peninsula. The tight pressure gradient surrounding the storm system generated strong winds, such as the east winds that gusted to as high as 50 mph at Iliamna. Rain had fallen earlier on Thursday at Nome, Kaltag, Cape Romanzof, Dillingham, Kodiak and Whittier. On the North Slope, Barrow reported snow with an inch on the ground. High pressure was found across western Canada.

The lowest overnight temperature in Alaska on Thursday morning was 17 degrees at Deadhorse, while the mid-afternoon highest statewide temperature was 66 degrees at Sleetmute.

HAWAIIAN WEATHER -- The typical trade winds were returning across the islands as a subtropical ridge of high pressure moves to its usual position to the northeast of the Aloha State. Clouds and showers remained in the vicinity of the islands late Thursday afternoon. However, skies were expected to become relatively clear on Friday, except for the clouds associated with the usual trade showers on the windward slopes of the islands. With continued strengthening of the high, the trades have speeds ranging between 15 to 30 mph by Friday afternoon.

EYE ON THE TROPICS -- In the tropical North Atlantic near the Windward Islands, a low pressure region called a tropical wave and associated area of clouds and precipitation developed into the eleventh tropical depression of the hurricane season. As of late Thursday night, Tropical Depression 11 was situated 75 miles west-northwest of St. Vincent, with forward movement to the west-northwest at 18 mph. Maximum sustained surface winds were 35 mph. Continued strengthening is expected to what would be known as Tropical Storm Iris.

In the eastern North Pacific, Tropical Storm Lorena weakened and was downgraded to tropical depression status on Thursday. By late Thursday night, Lorena had made landfall along the Mexican coast.


HISTORICAL WEATHER EVENTS - 5 October

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

6 October

7 October


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