DATASTREME DAILY SUMMARY

Monday, 4 December 2000


00Z Weather Systems


WEATHER OVER THE WEEKEND -- A storm system that spread snow across the northern Plains and the Upper Mississippi Valley last Thursday night traveled to the Southeastern States over the weekend, accompanied by wintry weather. On Friday morning the low pressure center was located over central Missouri and by Friday evening the low was situated near Memphis, TN. The track of the system curved toward the east on Saturday, moving from central Alabama on Saturday morning to off the South Carolina coast by Sunday morning. The system was accompanied by snow that fell across the Ohio and Tennessee Valleys into the Carolinas and northern Georgia as sufficiently cold air followed behind the storm. By Sunday evening, some upland locations along the southern Appalachians had received as much as 7 inches of snow. As much as 14 inches of snow fell in the Piedmont of North Carolina to the north of Raleigh. Jackson, KY reported a record 1.5 inches of snow on Saturday, followed by 2.3 inches on Sunday, which was another record snowfall total.

Unseasonably cool air moved across much of the eastern portion of the country as high pressure that was located over the Prairie Provinces last Friday morning spread southeastward. By Saturday morning the high was centered over the Upper Mississippi Valley and by Sunday morning, the high had become elongated, stretching from western New York State to the middle Mississippi Valley. On Sunday afternoon record low maximum temperatures were set at Charleston, SC as the Custom House had a high of 43 degrees, while the Airport registered a 41 degree high.

A storm system moved onshore into the Pacific Northwest on Saturday morning, then moved eastward across the northern Rockies by late Saturday. Most of the precipitation initially associated with this system dissipated across the Northwest. Farther south, high pressure produced several high temperature records in California, with the Museum station in Oakland reaching a record high of 67 degrees on Saturday, while Simi Valley set a record high of 86 degrees on Sunday afternoon.

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.

Except for a storm system along the Carolina Coast, much of the nation experienced cool but relatively tranquil weather conditions on Sunday night. An intensifying low pressure center was situated approximately 200 miles off the Outer Banks of North Carolina. A tight pressure gradient to the west of the storm system produced strong winds over much of eastern North Carolina. Gale warnings were in effect for the Middle Atlantic coast from Cape Charles, VA to Little River Inlet, SC, except for a portion of the North Carolina coast from Currituck Beach Light to Ocracoke Inlet, where storm warnings were posted in anticipation of winds greater than 55 mph. The winds also piled the water onshore necessitating a coastal flood watch for the southern Pamlico Sound and the Outer Banks. In addition to the strong winds, precipitation in the form of coastal rain and inland snow was also found across the region, where a winter weather advisory had been in effect during Sunday evening. This low is expected to continue moving toward the northeast, with a diminishing of the winds and a dissipation of the precipitation on Monday morning.

The unseasonably chilly air continued to spread across the Southeast behind the cold front that trailed the storm system. High pressure located over the Ohio and Tennessee Valleys should continue to maintain this cool air over the region. A wind-chill advisory was posted for central Florida for Sunday night as brisk northerly winds coupled with low nighttime temperatures are expected to cause wind-chill equivalent temperatures to fall into the mid to upper 20s -- in a region where many residents are relatively unprepared.

Two other areas of relatively light precipitation were reported on Sunday night. A weak trough of low pressure off the Texas Gulf Coast was responsible for some light rain across south Texas. Earlier, this precipitation had produced ice pellets and freezing rain in the Texas Hill Country. Midland in the Permian Basin had a record snowfall of 0.5 inches. The precipitation is expected to linger along the lower Rio Grande Valley into Monday. Another weak trough of low pressure moving eastward across the eastern Dakotas produced some very light snow across the Upper Mississippi Valley into the western Great Lakes.

A cold front that stretched across the Canadian Prairie Provinces on Sunday night was poised to move southward across the Plains on Monday. This cold front which trailed from a low pressure system over Hudson Bay was the leading edge of arctic air centered near Great Bear Lake in northwestern Canada. As the cold front travels southward and eastward across the Upper Midwest on Monday, lake effect snow should begin to fall across the western Great Lakes. Several inches of lake-effect snow are expected across the eastern half of Michigan's Upper Peninsula, as well as the northern portion of Lower Michigan as cold northwesterly winds move across the relatively warm waters of Lakes Superior and Michigan. Along the western end of the front, upslope easterly winds could also produce some light snow across the Montana Rockies on Monday.

High pressure across much of the western portion of the country has meant that scattered areas of dense fog have begun forming in the valleys of California, Oregon, Washington, Idaho and western Montana. Weak winds and relatively clear skies in association with the high pressure helped produce nighttime cooling to the dewpoint, resulting in the fog.

UPPER AIR -- The dominant feature on both the 500 and 300 mb charts for 00Z Monday was a height trough across the northern Plains, reflecting the pool of cold air to the north of the Canadian border. A strong jet stream was located over the central Rockies, as indicated by winds reaching 110 knots on the 300 mb surface.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 9 degrees below zero at Saranac Lake, NY, while Sunday's highest temperature was 86 degrees at Simi Valley, CA.

ALASKAN WEATHER -- Arctic high pressure with a center over the Chuckchi Sea has continued maintaining a cold air mass over much of Alaska on Sunday. The air mass was modified slightly as temperatures have increased over the weekend. Warm air remained over the Aleutians, the southern Bering Sea, south central Alaska and the Panhandle. This region was south of a stationary front that stretched along the southern coast. Some precipitation was found along the frontal zone, with snow reported in the Anchorage Bowl, while light rain was found at Kodiak, on the Kenai Peninsula, over Prince William Sound, and over the northern Panhandle. The front was an extension of an occluded front that was associated with a storm system over the Bering Sea to the north of the central Aleutians. A weaker low was found over Bristol Bay. During the morning, strong easterly winds with gusts ranging between 45 and 50 mph were reported along the front at King Salmon, Kodiak, Homer and Illiama. Both Barrow and Deadhorse along the Arctic coast reported wind-chill equivalent temperatures of 61 degrees below zero. Light snow was reported across the Seward Peninsula.

The lowest overnight temperature in Alaska as of Sunday was 49 degrees below zero at Umiat, and the midafternoon highest statewide temperature was 43 degrees at Ketchikan and Metlakatla.

HAWAIIAN WEATHER -- A cold front approaching the Aloha State from the northwest on Sunday afternoon contributed to a weakening of the ridge of high pressure to the north of the islands. As a result, the prevailing trade winds have slackened, along with a turning from the east or northeast to a more southeasterly direction. Since the atmosphere is fairly stable, relatively cloud-free skies and few showers have been found across the islands. The cold front is expected to stall and weaken before reaching the islands, while a ridge builds to the north of the islands causing a return of the trade winds and trade showers on Wednesday.

WINTER AWARENESS -- Mississippi and South Carolina will observe Winter Weather Awareness Week during the upcoming week of 4-8 December 2000. Residents of these states should review the winter weather safety rules issued by their local National Weather Service Offices.

Special thanks are extended to Linda Kremkau of the Office of Meteorology, National Weather Service for her help in obtaining information concerning the schedule of individual state Winter Awareness Weeks.

HURRICANE SEASON REVIEW -- The official 2000 North Atlantic hurricane season ended last Thursday, 30 November 2000 . As a quick review of this year's statistics consult Monday's optional Supplemental Information.


HISTORICAL WEATHER EVENTS - 4 December

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, 2000, The American Meteorological Society.