STORMY WEATHER ACROSS THE NORTHWEST -- Precipitation fell across western Washington and Oregon as a warm front approached within 200 miles of the Washington coast. This warm front was associated with a major storm system that was along the British Columbia coast north of Vancouver Island. The relatively tight packing of the isobars across Vancouver Island and Washington's Olympic Peninsula indicates an intensification of the pressure gradient, accompanied by increased winds. Southerly winds are expected to increase to 30 mph by morning, with gusts reaching 50 mph along the coastal headlands of Washington and Oregon. Gale warnings remained in effect through Thursday night for the coastal waters of Oregon and Washington from Cape Blanco, OR to Cape Shoalwater, WA and for the Strait of Juan de Fuca.
By Friday morning, the cold front that trailed the storm system should have made landfall and reached the Cascades in Washington and Oregon. The cold front is forecast to cross the northern Rockies of northwest Montana by evening. Following passage of the cold front, winds over coastal regions should shift to the west and then weaken. A heavy surf advisory was posted for Friday night along the Washington coast as storm generated swell between 15 to 18 feet is expected from the storm system.
As much as an inch of rain is forecast to fall on Friday along the coasts of Oregon and Washington. Inland the colder air following the cold front should cause the snow levels to drop to 4000 feet in the Cascades by Friday evening, with an anticipated 3 inches of snow. In the Sierras of northern and central California, snow levels are forecast to descend to 7000 feet as the cold front passes on Friday night.
INDIAN SUMMER ACROSS THE MIDWEST -- A large high pressure cell over the Ohio Valley was responsible for a pleasant, warm October day across the Midwest and northern Plains with sunny skies, which according to tradition, would be considered "Indian Summer" as most locations have sustained a hard freeze. The southerly winds on the west limb of the high pressure system helped transport warm air northward. While the sunlight is not as intense as during high summer because of lower sun angles, the nearly clear skies across the region meant that much of the available sunshine would heat the ground and the near surface air. As a result, afternoon high temperatures across the northern Plains into the Upper Mississippi Valley ranged between 20 and 25 degrees above the climatological average highs for mid October. Record high temperatures were either tied or exceeded in South Dakota at Mitchell (88 degrees), Huron (87 degrees), Brookings (84 degrees) and Watertown (82 degrees); in Minnesota at the Redwood Falls (86 degrees), St. Cloud (85 degrees), Alexandria (85 degrees), and Twin Cities (84 degrees); in Iowa at Waterloo (83 degrees) and Mason City (81 degrees); and in Wisconsin La Crosse (82 degrees) and Eau Claire (81 degrees).
The high pressure system in the Ohio Valley is forecast to move eastward, reaching central Virginia in the Middle Atlantic States by Friday morning and near Hampton Roads at the mouth of Chesapeake Bay by evening. As this high drifts eastward, the next cold front should follow across the Midwest.
A DRY FRONT -- A cold front was moving southeastward across the Plains and upper Mississippi Valley in nearly uneventful fashion. The front trailed southwestward from a low pressure system that had reached the western shores of Hudson Bay. Stretching from the Arrowhead of northeastern Minnesota across the Plains to southeast Wyoming, this front was the leading edge of a slightly cooler and drier air mass. The 10 PM CDT temperature at the Twin Cities in southeastern Minnesota was 72 degrees with strong south-southwest winds, while 200 miles to the northwest the temperature was 57 degrees at Fargo, ND, with light northwest winds. Because of the lack of significant moisture, little precipitation accompanied this front. However, satellite imagery indicated some clouds behind the front across the western Plains.
With the eastward movement of the low pressure system across Hudson Bay, the cold front is expected to continue its southeastward travels, crossing northern Wisconsin by morning and reaching the southern portion of the Badger State by evening. Slightly cooler conditions are anticipated behind the front, with little precipitation.
WET WEATHER OVER THE SOUTHWEST -- Rainshowers and thunderstorms were found across southern Arizona and New Mexico on Thursday night. Between 1 to 4 inches of rain fell near Tucson, necessitating the issuance of a small stream flood warning for that region in southern Arizona. This precipitation was associated with a low pressure system located over the lower Colorado River Valley that drew tropical moisture northward from Mexico.
On Friday, the precipitation area is expected to move eastward toward west Texas, leaving residual showers across New Mexico. Forecast precipitation amounts for the 24 hours commencing Friday morning range from 0.25 inches in southeast Arizona to nearly an inch in the Rio Grande Valley near Del Rio, TX.
TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 15 degrees at Fraser, CO. Thursday's highest temperature was 96 degrees at Death Valley, CA.
ALASKAN WEATHER -- Three storm systems affected the weather across southern Alaska on Thursday afternoon. One storm system located along the British Columbia coast near the Queen Charlotte Islands contributed to precipitation across the southern Panhandle, to include Juneau and Sitka. A second low pressure system was located over the Gulf of Alaska southeast of the Kenai Peninsula, with an associated trough that extended northward across the Anchorage Bowl into eastern interior Alaska. A third storm system was an intense low pressure system that was situated just to the south of the central Aleutians. Rain was reported at Cold Bay in advance of the approaching system. High pressure was found across interior Alaska north and west of the Alaska Range, where skies ranged from partly to mostly cloudy. As a result, afternoon temperatures across interior Alaska remained in the teens and 20s. Onshore flow from the Arctic contributed to snow at Barrow and Deadhorse.
The lowest overnight temperature in Alaska on Thursday morning was 4 degrees below zero at Bettles, while the mid-afternoon highest statewide temperature was 49 degrees at Juneau.
HAWAIIAN WEATHER -- With humid air approaching the windward side of the Big Island, at least four inches of rain fell over Hilo between Wednesday afternoon and Thursday morning. Trade winds had weakened early on Thursday, resulting in fairly warm conditions. However, by Thursday evening the subtropical high pressure system north of the 50th State meant a strengthening of the trade winds and relatively dry conditions across the islands through most of the weekend. High surf generated by a storm system is expected to reach the northwest facing shores of the islands by Sunday.
EYE ON THE TROPICS -- Hurricane Michael raced northward across the western Atlantic on Thursday at speeds reaching 50 mph and made landfall in Newfoundland during the evening. Heavy rains and hurricane force winds battered Newfoundland. At the time of the final hurricane advisory issued by the Tropical Prediction Center, Hurricane Michael continued to have sustained near-surface winds of 85 mph as it was located 90 miles north-northwest of Sagona Island in interior Newfoundland. Movement of this system, that had lost its tropical characteristics and assumed those of an extratropical system, was at 46 mph to the north-northeast.
On Thursday afternoon the eighteenth tropical depression of the Atlantic hurricane season formed in the western Atlantic south of Bermuda. By late Thursday night, Tropical Depression 18 had 35 mph surface winds and was located 440 miles east-southeast of Bermuda moving to the north-northeast at 13 mph.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
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Prepared by Edward J. Hopkins, Ph.D.
© Copyright, 2000, The American Meteorological Society.