WEATHER OVER THE WEEKEND -- Much of the nation experienced a rather cool and relatively quiet Thanksgiving Day to start the long holiday weekend. The cold air was associated with high pressure that dominated much of the country. Expansion of this large cell of high pressure eastward across the northern tier of states caused the winds to weaken across the Great Lakes, signaling a termination of the lake effect snows. Earlier in the Thanksgiving week, Buffalo, NY on the eastern shores of Lake Erie had been effectively shutdown as 25 inches of lake-effect snow fell in a 24 hour time span. The cold high continued eastward into New England by the beginning of the weekend. Under the clear skies and weak winds associated with the high pressure, daily record low temperatures were set Friday morning in Upstate New York at Massena (8 degrees below zero), Albany (zero degrees). The low at Massena also tied the monthly record low for November. Friday afternoon's high in Worchester, MA was only 24 degrees, a record low high for the date. On Saturday morning record low temperatures were set at Concord, NH (5 degrees), Portland, ME (9 degrees) and Windsor Locks, CT (12 degrees)
The only region of the country that experienced widespread precipitation on Thanksgiving Day was across the Southern Plains and lower Mississippi Valley in association with a low pressure system that was located along the western Gulf Coast. This system had moved eastward along the US-Mexican border on Wednesday, then redeveloped along the Gulf Coast by Thursday. On Thursday daily record rainfall amounts of 4.19 inches were established at Texarkana, AR and 0.66 inches at Waco, TX. By Friday morning the low pressure system was beginning to move northeastward reaching the lower Mississippi Valley by evening. During the morning hours, high winds downed trees and power lines in east Texas. Later on Friday afternoon and evening, winds caused damage across southern Mississippi and central Alabama. Record rainfall totals fell on Friday at Little Rock, AR (2.83 inches) and at Monroe, LA (2.12 inches). The low pressure system, which had become occluded as of Saturday morning, was centered near the Bootheel of southern Missouri. A large area of precipitation fell across the Southeast, including a record 2.58 inches at Wilmington, NC. Thunderstorm activity occurred in the warm sector to the south and east of the warm and cold fronts. On Saturday morning some minor damage was sustained near Palm Beach, FL from an unconfirmed tornado. The primary low pressure center continued to move north-northeastward across the mid-Mississippi Valley, reaching southern Lake Michigan by Sunday morning. A secondary low that had formed at the point of occlusion moved from South Carolina on Saturday night to Tidewater Virginia by Sunday morning. The precipitation associated with this occluded storm system spread northeastward across the Middle Atlantic States. The counterclockwise circulation around the storm system brought warm air and rain into the interior locations that had received snow earlier last week. However, freezing rain and ice pellets in the colder air across portions of New England and Upstate New York caused driving difficulties on Sunday.
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.
The storm system that had produced rain across the Southeast and Middle Atlantic States over the weekend continued to affect the weather across the northeast quadrant of the country on Sunday night as an occluding storm system. The primary low pressure center remained over Lake Huron with an occluded front stretching eastward to a secondary low pressure system over New York's Long Island. This low pressure center was located near the point of occlusion where a warm front extended eastward in the north Atlantic, while a cold front trailed southward off the Eastern Seaboard. A large area of precipitation continued to be associated with this occluded storm system. Rain was found across southern Lower Michigan, Lake Erie, the Ohio Valley, Upstate New York and much of northern New England. Snow was falling across northern Maine, along with some freezing rain.
This storm system is expected to move slowly toward the east-northeast on Monday. The primary low pressure center is forecasted to reach southern Ontario near Toronto by daybreak, while the secondary low would be over the Gulf of Maine. By evening, the primary low is anticipated to be located in Quebec and the secondary low over the Canadian Maritimes. A winter weather advisory remained in effect for the northern counties of Maine, as snow turning to a mixture of ice pellets (sleet) and freezing rain was expected. Between 1 to 2 inches of additional snow accumulation could fall before the transition. During the 24 hours ending on Monday evening between 0.25 and 0.50 inches of precipitation associated with this system is expected across northern New England. Most of the precipitation across New England should fall as rain. A gale warning was posted for the New England Coast from Plymouth, MA to Eastport, ME.
The cold front that was associated with the storm system in the Northeast continued southward across South Florida on Sunday night. A weak low pressure center was found along the cold front over Florida. Rainshowers and embedded thunderstorms associated with the low and cold front were found just off the Florida Coast and over the Florida Keys.
A weak trough of low pressure was moving across the Dakotas on Sunday night, producing some clouds and light snow showers across the northern Plains. This weak system was expected to move into Upper Mississippi Valley on Monday, reaching the Arrowhead of Minnesota by evening.
A cold front was approaching the Washington State coastline on Sunday night. This front was associated with a low pressure system that had moved eastward across northern British Columbia. A large area of precipitation ahead of this front had spread across Washington, western Oregon and northwestern California. Much of the precipitation was in the form of rain, except for snow over higher elevations of the Cascades and eastern Washington State. As much as 2 inches of rain fell across portions of western Washington on Sunday afternoon, resulting in a flash flood watch for the Skokomish River.
The cold front should continue to move eastward into northern Idaho as the low pressure system redevelops to the east of the Canadian Rockies in Alberta by Monday morning. By evening the low should be located over Saskatchewan, while the trailing cold front progresses eastward across Montana and Wyoming. Snow advisories were in effect for the Olympics and the Cascades of Washington and Oregon, where as much as 7 inches of snow could fall at the higher elevations north of Mount Hood. Between 0.25 and 0.50 inches is expected by Monday evening over much of the Pacific Northwest, with the largest amounts falling along the crest of the Cascades.
Elsewhere, high pressure across the Intermountain West produced relatively tranquil weather for the region. The Southeast also experienced relatively tranquil weather on Sunday night.
UPPER AIR -- Both the 500 mb and 300 mb charts for 00Z Monday contain a closed cyclonic (counterclockwise) circulation regime over the Great Lakes. The vertical stacking of the centers of the upper level height troughs above the primary surface low pressure center is reflective of an occluding storm system. A strong upper tropospheric jet stream, as indicated by winds exceeding 120 knots on the 300 mb surface along the Eastern Seaboard, was providing support for the secondary low pressure system at the surface. Along the West Coast, an onshore, westerly jet stream at 300 mb was contributing to the clouds across the Pacific Northwest.
TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 2 degrees above zero at Aberdeen, SD, while Sunday's highest temperature was 87 degrees at Opalocka, FL.
ALASKAN WEATHER -- Several low pressure systems located to the south of Alaska spread windy weather, clouds and precipitation across southern Alaska on Sunday afternoon. One low pressure center was located over the Gulf of Alaska south of Cordova. Rain fell across the Panhandle and southeast Alaska, while snow fell across south central Alaska and parts of the Yukon-Kuskokwim Delta. Snow also fell in the vicinity of Kotzebue. Another complex low pressure system with multiple centers was situated over the central Aleutians. Several lows were also located across the northern Pacific Ocean south of the Aleutians. A weak occluded front stretched eastward across the eastern portion of the island chain. A large high pressure system located over central Siberia spread a cold arctic air mass across the northern two thirds of Alaska. Cold air advection occurred on northerly winds. Anaktuvuk, Deadhorse, Point Hope and Shishmaref had wind-chill equivalent temperature readings as low as 47 degrees below zero. The southern boundary of this arctic air mass was a front that stretched from near Dillingham eastward to the Alcan border, passing north of the Anchorage Bowl. Northerly winds also produced clouds across the North Slope and northwest Alaska. Partly cloudy skies were found across the interior.
The lowest overnight temperature in Alaska as of Sunday was 24 degrees below zero at Tanana, and the midafternoon highest statewide temperature was 45 degrees at Annette, Hydaburg and Metlakatla.
HAWAIIAN WEATHER -- An elongated ridge of high pressure located to the north and northeast of Hawaii maintained trade wind weather across the islands on Sunday afternoon. Some showers passed across the windward and mountain areas of the islands and the trade winds were from the northeast. A weak cold front situated approximately 300 miles to the north-northwest of Kauai was moving slowly toward the east-southeast causing an anticipated weakening of the winds across the islands on Monday. Some clouds and showers are also expected across the northern islands as the front approaches. An increase in the speed of the trades should occur by Tuesday as the next high pressure fills in behind the front. High surf advisories were in effect for the northwest facing shores of the islands.
SPACE WEATHER -- Over the weekend several major solar eruptions produced flares that were observed emanating from the sun. These flares were expected to send large pulses of electrically charged particles outward into space. These solar particles moving outward on the solar wind could reach the earth in 50 hours. Once in the earth's magnetic field, these particles could produce more impressive aurora borealis (or northern lights) that would extend farther southward across the nation. The increased solar activity could also adversely affect satellite communications and the power grids across Canada and the northern states. The Space Environment Center of the National Oceanic and Atmospheric Administration monitors the solar activity and produces various current material regarding solar activity on its Space Now Page (http://www.sec.noaa.gov/SWN/index.html).
HOLD ON TO YOUR HATS -- The National Weather Service alerts the public to these windy conditions with special advisories, watches and warnings as described in Monday's 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, 2000, The American Meteorological Society.