WEATHER OVER THE WEEKEND -- Some of the coldest air of the season spread across the northern tier of states over the weekend. On Friday morning high pressure across the Northeast sent the temperature at Massena, NY to a record low of a 17 degrees below zero. However, the leading edge of a more impressive arctic air mass moved southward into Montana and the Dakotas early Saturday morning. By Sunday morning, the cold air had spread southward and eastward across the Plains and the Upper Mississippi Valley. Shortly after midnight on Sunday morning, the temperature at Rapid City, SD fell to zero, marking the first time in a record setting 705 days that the temperature had reached zero. Miles City, MT had a record low temperature on Sunday morning of 21 degrees below zero. The high temperature at Glasgow, MT was 9 degrees below zero, a record low high for the date, which followed a record low temperature during the morning of 24 degrees below zero.
Elsewhere, the Alberta Clipper that moved across the Great Lakes on Thursday moved across the Northeast on Friday. Light snow fell in the cold air along the north side of the storm. At Bridgeport, CT, 0.5 inches of snow fell on Friday, tying the record snowfall for the date.
The southern end of the cold front that trailed the Alberta Clipper system stalled over the Florida Peninsula. Heavy rains fell across South Florida along the stationary front. On Sunday, Miami, FL received a record 5.06 inches of rain.
WEATHER FOR STARTING THE NEW WEEK -- The following highlights of the national weather have been extracted from the surface weather map for late Sunday night.
The arctic air mass continued to wedge its way farther south and east across the nation's midsection. This air mass was associated with an elongated ridge of high pressure that extended from the Northwest Territory of Canada to north central Montana. By mid-evening, temperatures across the plains of Montana east of the Divide had fallen to the teens below zero and before midnight, the temperature at Cut Bank fell to a record setting 24 degrees below zero, while Great Falls set a record of 22 degrees below zero. The leading edge of the arctic air mass was a cold front that stretched southwestward from Quebec across the Great Lakes and mid-Mississippi Valley to the Red River Valley of north Texas, where it curved westward and then finally northwestward across the Texas Panhandle into Colorado. The front became a stationary front along the Continental Divide, stretching northwestward from Colorado to northern Idaho. A weak low pressure system was located along the front across western Colorado. Temperature contrasts across the cold front were impressive, with a mid-evening temperature of 32 degrees in Oklahoma City, OK, which experienced northerly winds on the north side of the front, while 200 miles to the south the temperature was 62 degrees in Dallas-Ft. Worth, TX on southerly winds.
The cold air is expected to continue spreading southeastward across the western Plains on Monday. Wind chill advisories were in effect across southwest Kansas as wind-chill equivalent temperatures could fall to 35 degrees below zero. By evening, the cold front is forecast to reach the Texas Gulf Coast.
Despite a lack of an organized surface low pressure system, a large precipitation shield spread eastward across the Plains into the Mississippi Valley on Sunday night. Snow was falling from the Colorado Front Range to eastern Iowa. Snow was falling at a rate of about one inch per hour across portions of Nebraska and Iowa late Sunday night. Farther south, freezing rain and drizzle were falling across southeastern Kansas and southern Missouri, where air temperatures were in the teens and low twenties. Consequently, freezing rain advisories were in effect for southeast Kansas and southwest Missouri. On Sunday evening heavy snow was falling across the mountains of western and southwestern Colorado in association with the low pressure system located on the western slopes of the Colorado Rockies. Thundersnow was reported near Montrose. Snowfall rates reaching two inches per hour were expected. In the northwesterly winds to the west of the low, lake-effect snow fell on the lee shores of Utah's Great Salt Lake, especially in the Salt Lake City metropolitan area. As much as 12 inches were anticipated, along with thundersnow.
By Monday morning, a low pressure system is expected to form along a kink in the cold front over southwest Missouri and begin moving northeastward across the mid-Mississippi Valley. The position of the low by daybreak is forecast to be over southeast Missouri, and by evening the low is anticipated to be in east central Indiana. With cold air across the Plains to the north and humid air across the Gulf Coast, along with upper level support (see below), this storm system has most of the necessary ingredients to help produce a major winter storm. As a consequence of the current snowfall, coupled with the snow anticipated from the new storm system, a variety of advisories, watches and warnings covering the winter storm have been issued for a wide area, stretching from western Colorado eastward to the Plains and then northeastward along the forecast storm track to lower Michigan. The greatest snow is expected within 100 to 150 miles to the northwest of the storm track. Therefore, as much as a foot of snow could fall across northern Illinois, to include the Chicago metropolitan area.
A stationary front ran in a north-south direction along the Eastern Seaboard on Sunday evening. Some rainshowers were detected over southern New England, the Middle Atlantic coast and off the Outer Banks of North Carolina. Farther south, rainshowers and some embedded thunderstorms continued across south Florida and adjoining waters of the Atlantic. This rain was associated with the trough of low pressure that lingered from earlier in the day. The rain is expected to move off the coast by sunrise on Monday.
A storm system with a trailing cold front was approaching the Washington and Oregon coast on Sunday night. Precipitation is expected to spread across the Pacific Northwest late Monday.
UPPER AIR -- The dominant feature on both the 500 and 300 mb charts for 00Z Monday was the height trough that was beginning to develop across the Rockies and the Intermountain West. This trough was a reflection of the cold air that was found in the lower to mid troposphere. The trough caused the winds to become more southwesterly across the Plains. A jet core, representing a pocket of strong winds with speeds to 130 knots, was detected on the 300 mb constant pressure surface over the Texas and Oklahoma Panhandles. This jet core was positioned favorably for the development of a surface cyclone, since the winds passing through the jet core were producing sufficient upper level divergence that would compensate the low level convergence in the low pressure center.
TEMPERATURE EXTREMES IN THE COTERMINOUS U.S. -- The lowest temperature on Sunday was 35 degrees below zero at Flag Island, MN while Sunday's highest temperature was 85 degrees at Ocala and Brooksville, FL.
ALASKAN WEATHER -- A large high pressure system located over the central Arctic Ocean continued to dominate the weather across much of Alaska on Sunday afternoon. While most of the state was cloudy, breaks in the overcast were reported across interior and western Alaska. Strong east to northeast winds were found across northern Alaska, as the result of a tight pressure gradient produced between this high pressure system and several low pressure centers to the south. One weak low pressure system was situated in the central Bering Sea near St. Matthew Island. A second low pressure system was situated near Adak Island. Winds gusted to 50 mph across the North Slope, producing wind-chill equivalent temperatures to as low as 55 degrees below zero at Barrow, Gambell, Point Hope and Wainwright. Snow fell at St. Paul Island and at Nome. A weak trough of low pressure situated near Kodiak brought rain and snow to southern Alaska. Snow was reported at Valdez and Yakutat, while rain fell across southeast Alaska and the Panhandle, to include Homer, Seward, Cordova and Yakutat. Another storm system located in the eastern Pacific to the west of the Queen Charlotte Islands should move southeastward and is not expected to affect the Panhandle.
The lowest overnight temperature in the state as of Sunday was 20 degrees below zero at Anaktuvuk Pass. Sunday's midafternoon highest temperature was 43 degrees at Chignik.
HAWAIIAN WEATHER -- An approaching cold front has caused the trade winds to switch to weak southerly winds across the islands on Sunday afternoon. At that time, the front was approximately 380 miles northwest of Kauai. This front is expected to weaken to a wind shear line as it passes Kauai by Monday night. Some showers are also expected. Once the shear line passes across the islands, the winds are expected to return to the more typical trade wind direction, with the northeast winds increasing to between 15 and 30 mph by Tuesday. The buoy moored to the west of Kauai indicated an increase in ocean swell. This swell could produce 10 foot surf along the northwest facing shores by late Monday.
THE FULL MOON -- The moon reached its full moon phase early this morning at 0903 Z (4:03 AM EST, 3:03 AM CST, etc.). This December full moon is also called the "Moon Before Yule".
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.