WELCOME TO WEEK ONE OF ONLINE WEATHER - The Daily Weather Summary file will describe the current weather pattern across the U.S. Additional Supplemental Information Files will provide optional background material.
ICY CONDITIONS MOVE INTO THE NORTHEAST -- The widespread precipitation shield associated with the storm system that had plagued the Gulf Coast over this past weekend continued to move to the northeast on Monday. A variety of precipitation -- rain, freezing rain, ice pellets and snow -- was reported across the Appalachians and the Piedmont on Monday morning as the precipitation moved north over the cold air trapped along the eastern slopes of the Appalachians.
By late Monday night, the precipitation area stretched from the coast of the Carolinas north to the eastern Great Lakes. A nearly stationary warm front extended northward along the Atlantic Seaboard from a low pressure cell located over the western Florida Panhandle. This front separated the warm humid air to the south and east of the front from the colder air over the Appalachians and then westward into the interior of the content.
As the rain moved farther northeast overnight, a change to freezing rain is anticipated over portions of northern Pennsylvania, into Upstate New York and interior sections of New England. The freezing rain episode would result from the rain falling through a shallow layer of cold air trapped in interior valleys. Accumulation of ice upon items such as tree branches and power lines is expected. The Hudson and Mohawk Valleys in New York State could experience major icing conditions. A variety of winter weather advisories and watches were posted for the region. Closer to the coast the moderating effects of the Atlantic Ocean maintained sufficiently warm above freezing conditions at the surface, permitting most of the precipitation to fall as rain with little freezing rain. Well to the north, over snow it may fall in the cold air over the Adirondaks of Upstate New York and the mountains of northern New England.
In addition, the precipitation, coupled with the snow melt and ice jams could cause flooding across the Catskills of southern New York State and the Berkshires of Massachusetts.
Farther south, the heavy precipitation from the same storm system was reported across the Southeast, where flooding posed a threat on rivers in Mississippi and the Carolinas. Record rains fell for a second consecutive day across portions of the Florida Peninsula. Daytona Beach reported a record 0.37 inch of rain on Monday, following Sunday's record.
DENSE FOG ACROSS THE UPPER MIDWEST -- A large area of the Upper Midwest, extending across most of Wisconsin and neighboring portions of northern Illinois, northeast Iowa and southeastern Minnesota was blanketed by thick fog on Monday. This fog reducing visibilities to between one eighth and one quarter of a mile persisted for much of the daylight hours on Monday. This type of fog is called an "advective fog" by meteorologists. Warm, humid tropical air was brought northward through the Mississippi Valley by southerly winds to the east of a cold front found in the eastern Plains. Such a horizontal transport process by large scale air motion is called "advection". As the warm air passes over the extensive snow cover that extends across the Upper Midwest, the air near the surface is cooled to saturation by contact with the snow.
In addition to the fog, some areas especially across a region from Minnesota to northern Michigan, may also experience freezing drizzle as near surface temperatures fall below the freezing point.
CONTINUED STORMY WEATHER OVER THE NORTHWEST -- Another storm in the present series of Pacific storm systems to batter the Northwest was located off the British Columbia coast late Monday night. This present system was affecting the weather across the Pacific Northwest. A warm front associated with this system was expected to move onto the Washington Coast on early Tuesday. An extensive band of precipitation ahead of this approaching warm front was already onshore. Because of the heavy rains associated with a nearly persistent onshore winds, flood watches and warnings were in effect for many rivers of western Washington State and Oregon.
Following frontal passage, strong winds from the southwest are anticipated. As a result, gale warnings for winds between 39 and 54 mph were posted for the Pacific Coast for Cape Flattery, WA to Cape Blanco, OR and along portions of Puget Sound. A high wind watch was in effect for coastal areas of Washington and Oregon.
A variety of winter storm warnings and snow advisories have been issued for the Washington Cascades, the Blue Mountains of northeast Oregon and the mountains of northern Idaho for as much as two feet of new snow in some locations on the windward side of the Cascades. Elsewhere, six inches of snow were expected.
WINDY CONDITIONS ACROSS THE WEST --Farther south, a large high pressure system with a center over the Great Basin was dominating the weather across the Southwest. The clockwise circulation of winds around this high pressure cell was producing some windy conditions in well-separated locations.
On the southwest flank of the high, east winds flowing from the Great Basin westward to the coast of Southern California were developing a downslope and offshore wind regime which is often called a Santa Ana. The present situation does not have the strong Santa Anas that can cause major damage. Wind advisories have been posted for the mountains and mountain passes of southern California because northeast winds are expected to reach speeds of 40 mph.
To the north of the high pressure system, the winds move from west to east across the northern Rockies. A intensifying pressure gradient over the northern Rockies increased the westerly winds cross the mountains. High wind watch was in effect for the northern mountains of Wyoming near Cody and the Big Horns , for wind gusts reaching 60 to 70 mph. A high wind warning was in effect for the Upper Yellowstone Valley of Montana for gusts to 75 mph.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature in the lower 48 states on Monday was 13 degrees below zero at Glens Falls, NY and the highest temperature for Monday was 82 degrees at McAllen, TX.
ALASKAN WEATHER -- An arctic air mass remained entrenched over northern Alaska on Monday. This cold air mass was associated with an elongated high pressure system that extended from Siberia across the Bering Sea into western Alaska. Little precipitation was detected across the region dominated by the dry arctic air. To the south and east, several low pressure systems were responsible for most of the state's precipitation along the southern coast of the state. One storm system was located in the northern Gulf of Alaska south of Prince William Sound with accompanying fronts that extended along the north Gulf coast from the Alaska Peninsula and into southeast Alaska. Another storm system was located near British Columbia's Queen Charlotte Islands. On Monday more than five inches of snow fell at Valdez in a seven hour interval. A winter storm warning for heavy snow was posted for the inner channels of southeast Alaska and the east Gulf Coast, with snow advisories for other portions of the southeast. Strong winds, produced by the strong pressure gradient between the high pressure system in northwest Alaska and the low pressure systems in the Gulf of Alaska, contributed to dangerous wind-chill conditions across many portions of the state. Wind-chill warnings were issued for the coast of the Yukon Delta, Kotzebue Sound, the Tanana, upper Yukon and upper Kobuk valleys as well as the passes in the Brooks Range, since wind-chill equivalent temperatures ranged between 80 and 90 degrees below zero.
On Sunday, Kodiak had a minimum temperature of 4 degrees below zero, a new record low for the date and Nome tied a record low temperature with a reading of 40 degrees below zero. On Monday, McGrath reported a record tying low temperature of 61 degrees below zero.
The lowest temperature in Alaska on Monday morning was 61 degrees below zero at McGrath, and the mid afternoon highest statewide temperature was 36 degrees at Shemya.
HAWAIIAN WEATHER -- Several upper level pools of cold air passing close to the islands continued to produce showers and isolated thunderstorms primarily over Kauai and the Big Island on Monday morning. The especially heavy rainfall on the windward side of the Big Island has prompted the continuation of urban and small stream advisories to remained in effect for these portions of the Big Island. By later on Monday afternoon, conditions improved across the islands. Easterly trade winds were maintained at speeds between 15 to 30 mph as a high pressure system remained relatively stationary over the eastern Pacific near the California coast. An increase in the speed of the trade winds are expected by midweek as a new high pressure system is forecast to move to the north of the island and continues to intensify. As of Monday afternoon, small craft advisories continued for all state waters and high surf advisories for north facing shores of the islands.
On Sunday, the afternoon high temperature at Hilo reached only 71 degrees, tying the coldest high temperature for the date at that location.
WHAT TIME IS IT? -- For additional Z-time explanation, call up Tuesday'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, 1999, The American Meteorological Society.