THE CLEAN-UP -- The storm system that left a band of snow from the Upper Midwest to the Middle Atlantic during the first half of the week continued to move eastward out to sea on Wednesday. Some light snow continued across the Northeast on Wednesday morning on the western side of the low as the storm moved out to sea. As much as a foot of snow buried Washington, DC and surrounding suburbs. By later in the day, bright sunshine was helping melt the snow.
A BACKDOOR WARM FRONT -- A variety of precipitation, to include snow, ice pellets and freezing rain, was falling over northern and eastern Maine on Wednesday night. This precipitation was associated with warm air advection along a warm front that was moving to the west across the Canadian Maritimes toward Maine. The warm front extended from a storm system over the North Atlantic northwestward across New Brunswick. Mild Atlantic air circulated around the north and northwest side of the low.
This warm front is expected to continue to move slowly toward the west, accompanied by the wintry mix of frozen and freezing precipitation. Winter weather advisories for snow, ice pellets (sleet) and freezing rain were in effect for Wednesday night and Thursday.
COOL WEATHER -- A large high pressure system located over northwestern Ontario to the west of Hudson Bay continued to pump cold air southward into the eastern half of the United States on northerly winds.. Afternoon high temperatures across much of the nation east of the Mississippi were cooler than average, with locations in the Ohio Valley having highs that were 20 degrees below the climatological average highs for the date.
The ridge of high pressure should continue to remain fairly stationary, with cool weather extending southward. Because of the weak northerly winds, coupled with clear skies freeze warnings were posted for a large section of South Carolina.
SNOW MOVES ACROSS THE PLAINS -- An area of snow moved southeastward from the western Dakotas into the Upper Mississippi Valley on Wednesday. By late evening, the precipitation had stretched from South Dakota into northwest Iowa. As much as 18 inches of snow fell at Sturgis in South Dakota's Black Hills. This snow was associated with a disturbance at jet stream levels, with little apparent features seen on the surface weather maps..
This region of snow was expected to remain over the Upper Mississippi Valley into Thursday morning. Little significant snow accumulation was anticipated.
A SOUTHWEST STORM -- A trough of low pressure with several low pressure centers was located over the southern and central Rockies late Wednesday night. A warm front extended southeastward across Texas toward the Mississippi Delta. Some light rain fell across Arkansas to the north of the warm front.
The trough is expected to develop and one of the low pressure centers should move southeastward toward the Hill Country of south central Texas by Thursday morning. A slight risk of severe thunderstorms could develop across Texas in the warm sector of the storm system during Thursday.
A NEW PACIFIC STORM -- The next storm system was located approximately 200 miles west of Cape Mendocino, CA on Wednesday night. Rain was expected to spread eastward and southward across coastal sections of southern Oregon and northern California. Snow was expected at higher elevations. Snow advisories were posted for northern California for as much as 7 inches of snow at elevations above 2000 feet.
YESTERDAY'S TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Wednesday was 18 degrees below zero at Saranac Lake, NY. Wednesday's high was 91 degrees at Laredo, TX.
ALASKAN WEATHER -- A large storm system moving northeastward across the North Pacific passed to the south of Cold Bay in the Alaska Peninsula on Wednesday afternoon. Clouds associated with this system were found over southeast Alaska. Rain was reported at Cordova and Juneau, while Yakutat had mixed rain and snow. A nearby stationary front stretched from the eastern interior to the coastline before turning westward. Associated clouds stretched from the Yukon Valley to the coast and then to the Kuskokwim Valley. Snow fell over the Anchorage Bowl, Prince William Sound and the Kenai Peninsula. The stationary front extended westward along the coast, with additional clouds covering the Alaska Peninsula, the Aleutians, and the Pribilofs. Snow fell over Saint Paul, Dutch Harbor and Cold Bay.
Strong winds were also associated with this storm system. Northerly winds circulating around the north and west side of the low were found across southwest Alaska, with Dutch Harbor having a peak gust of 60 mph, Cold Bay with a gust to 51 mph, St. Paul gusting to 37 mph and Cape Romanzof with gusts to 33 mph. Both Dutch Harbor and Cold Bay reported blowing snow.
To the northwest, a large region of weak high pressure centered over Far Eastern Russia was responsible for maintaining relatively cloud-free skies across the much of northern and western Alaska.
On Wednesday morning the minimum temperature at Barrow was a record tying low of 43 degrees below zero at McGrath, the minimum of 36 degrees below zero tied the record low.
The state's lowest overnight temperature on Wednesday morning was 54 degrees below zero at Umiat Airport. The midafternoon state highest temperature was 46 degrees at Klawok.
HAWAIIAN WEATHER -- The high pressure cell to the northeast of Hawaii continued to produce relatively pleasant weather across the islands on Wednesday. Some scattered clouds and precipitation crossed the islands. Easterly trade winds ranged between 10 to 25 mph. Little change in the position of the high is expected through Friday. High surf advisories continued for the north shores of the islands.
THE CHINOOK WINDS -- For more information describing the various sets of lines on a Stüve Diagram and how you can make graphical determinations from a Stüve Diagram, you may consult the optional material in Thursday's electronic 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, 1999, The American Meteorological Society.