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STORMY WEATHER CONTINUES ACROSS THE WEST -- A pattern persists where frequent storms move eastward across the North Pacific and pound the West Coast. As of Wednesday night, one low pressure system was located in the Wyoming Rockies, a day removed from the eastern Pacific. Another storm system following on the heels of several recent predecessors was situated several hundred miles off the Washington State coast. An occluded front curved southeastward from the low pressure center to the Oregon Coast, where a warm front extended eastward across the Great Basin, while a cold front continued to curve to the south and then southwestward across northern California, before trailing out to sea near San Francisco Bay.
A widespread region of precipitation associated with these two storm systems had spread from western Washington State south to the Los Angeles Basin, and from the immediate coast eastward to the mountains of western Wyoming. Heavy rain was found over low elevation and coastal locales, especially over southwestern Oregon and northwestern California. Flood watches and warnings continued for several rivers in western Washington State and Oregon. Heavy snow fell across the Sierras of northern and central California. Winter storm warnings have been effect for much of Wednesday for some of the mountains of northern California, as more than a foot additional snow is expected. Strong winds helped create blizzard conditions above 5500 feet. As a result, high wind warnings were issued for parts of Oregon. Additional winter storm warnings and snow advisories have been posted for the mountains of eastern Washington, Oregon, Utah, western Wyoming and Colorado.
In addition to the widespread, heavy precipitation, onshore winds along the coast continued to remain strong. Southwest winds between 39 and 54 mph are expected, necessitating gale warnings along the Oregon Coast, from Cape Shoalwater, WA to Florence, OR. Farther south, heavy surf advisories were posted for the California coast between and Point St. George and Point Arena. Inland, wind advisories and warnings were posted across Southern California and Nevada for winds that were expected to reach 70 mph. Winds near Guadalupe Pass in west Texas could gust to 80 mph. Because the strong winds increased the airborne inhalable particulate matter to unhealthy levels, a health advisory was issued for Nevada's Las Vegas Valley.
Forecasts indicate that the storm lurking along the coast may continue across the Rockies and redevelop into a potentially intense storm that could affect the Plains and Midwest by the early weekend.
ARCTIC AIR LURKS ACROSS THE NORTH -- A pool of arctic air moved slowly south across the Canadian Prairie Provinces into the Dakotas and northern Minnesota. This arctic air mass was associated with a large region of high pressure located to the northeast of the Manitoba lakes region. The southern edge of the air mass was a frontal zone that paralleled the US-Canadian border, stretching westward from the Maritime Provinces, across the northern Great Lakes, the upper Mississippi Valley, the Plains states before turning northwest along the eastern slopes of the Montana and Canadian Rockies. Because of the slow movement of the cold front, a portion was classified as a stationary front. As of Wednesday evening, temperatures were below zero across North Dakota. A band of light snow and freezing rain was found to the north of the front from eastern Minnesota to central Wisconsin.
FREEZING PRECIPITATION ACROSS THE MID-MISSISSIPPI VALLEY -- A band of precipitation that included freezing rain was found across the mid Mississippi Valley from southern Iowa into central Illinois. This precipitation was found to the north of a stationary front that stretched from Tidewater Virginia westward across the Ohio and Mississippi Valleys to a weak low pressure center that was situated over southern Kansas on Wednesday night. Near-surface air temperatures to the north of the front were in the low to mid 30s across the Mississippi Valley. Precipitation formed in the warm, humid air that moved northward over the front. Freezing rain and drizzle was found in those regions were the rain fell into the shallow subfreezing pool of air.
This region of precipitation is expected to move eastward along the front. Some thunderstorms could form to the south of the front and move across the Ohio Valley.
WARM WEATHER ACROSS THE SOUTHERN TIER -- Unseasonably warm conditions were found across the country to the south of the above-mentioned stationary front. Afternoon high temperatures were nearly 20 degrees above the long-term average high temperatures for this time of year over an area that stretched from the Carolinas to the southern Rockies. On Wednesday afternoon, record high temperatures were set across Texas at San Angelo with 85 degrees, at Abilene (82 degrees) and at Midland (79 degrees). The 59 degrees in Delta, UT tied the daily record high temperature. In the Southeast, record high temperatures for the date were tied or set at Florence, SC (75 degrees) and Asheville, NC (66 degrees). A wind flow around the western flank of high pressure centered over south Florida brought warm, humid air from off the Gulf of Mexico into the Southern States.
Widespread dense fog is also expected by early Thursday morning as nighttime cooling of the air to saturation should result. As a result of the more organized onshore flow of humid Gulf air, the regions where the dense fog could seriously restrict visibility extend farther inland to Arkansas.
TEMPERATURE EXTREMES IN THE CONTINENTAL U.S. -- Wednesday morning's lowest temperature was 6 degrees below zero at Roseau, MN, while the Wednesday afternoon highest temperature was 88 degrees at McAllen and Kingsville, TX.
ALASKAN WEATHER -- High pressure, centered along the Arctic Circle, continued to dominate the weather across interior Alaska on Wednesday, providing the region with relatively cloud-free skies and cold temperatures. Many locations had temperatures colder than 40 degrees below zero. On Wednesday morning, Anaktuvuk reported a wind-chill equivalent temperature of 75 degrees below zero. Some areas, to include the Anchorage Bowl, also experienced fog and haze. Mostly clear skies were also prevalent across the Alaska Peninsula, the North Gulf Coast and Southeast Alaska. A low system in the Central Bering Sea spread clouds from the western Aleutian Islands across the Pribilof Islands, Saint Lawrence Island to the coast of the Yukon-Kuskokwim Delta. Strong winds associated with this storm system were recorded over southwest Alaska. Cape Romanzof had winds gusting to 58 mph, while Dutch Harbor had gusts to 36 mph. Saint Paul Island had rain, snow, fog and wind gusts to 35 mph. Along the Arctic Coast, winds from the west caused blowing and drifting snow near Prudhoe Bay.
The lowest temperature in Alaska on Wednesday morning was 58 degrees below zero at Arctic Village and Chandalar Lake. The highest statewide temperature as of Wednesday afternoon was 39 degrees at Dutch Harbor.
HAWAIIAN WEATHER -- Prevailing winds began to turn and come from a typical northeasterly "trade wind" direction across the islands on Wednesday ahead of a trough of low pressure. This trough, associated with a cold front, had passed over French Frigate Shoals on Wednesday afternoon and was expected to stall over Kauai and Oahu on Thursday night. As a result, increased clouds and showers were expected. Behind the trough, a high pressure system is anticipated to move eastward and intensify. Consequently, the trade winds should intensify starting on Thursday afternoon, strengthening sufficiently to require small craft advisories.
High wind warnings were posted for the Mauna Kea and Mauna Loa Summits on the Big Island late on Tuesday night. High surf advisories continued for the north and west shores of the islands, as high surf built to between 15 and 20 feet during Wednesday afternoon.
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.