Today is the traditional observance of George Washington's Birthday. As a farmer, Washington was a weather observer who maintained a weather diary for his plantation, Mount Vernon on the banks of the Potomac River south of Alexandria, VA. The last weather entry in his diary was made on 13 December 1799, the day before he died.
STORMS MOVE ACROSS THE SOUTHWEST --The storm system that produced wet weather along the central California coast on Sunday moved inland and by Monday night the low pressure center was located over southern Idaho. A cold front extended southward from this low across Utah and Arizona. Strong thunderstorms that briefly produced severe weather conditions were found along the cold front, extending from near Tucson, AZ northward to southern Utah. While strong thunderstorm winds caused some damage in Phoenix late Monday afternoon, little precipitation (0.01 inch) fell at the airport. Winds gusted to 63 mph at St. George, UT.
Rain associated with this storm system continued across southern California through much of Monday. By late afternoon as rain continued to fall, Lindbergh Field in San Diego, CA had received 1.06 inches of rain, surpassing the previous daily rainfall record for the date. Other daily rainfall records across southern California included UCLA in Los Angeles (2.18 inches) and Pasadena (1.95 inches). These heavy rains produced flash floods in the Los Angeles Basin. Automobiles were literally floating on Los Angeles freeways as a result of the high water collecting below underpasses. Several locations in the mountains surrounding the Los Angeles Basin, to include the San Gabriel Mountains received heavy snow, with total liquid precipitation accumulations exceeding 6 inches. One spotter in the San Bernardino Mountains reported 18 inches of snow, with 6.5 inches of snow falling in less than 6 hours Monday afternoon . Along the central California coast, landslides due to the heavy rain caused a washout, cutting State Highway 1 near Big Sur.
The area of precipitation associated with this storm system should move eastward across the Great Basin toward the Rockies. Snow advisories were continued for the elevations above 6500 feet on the Mogollon Rim of Arizona for as much as 6 inches of snow. Snow and blowing snow advisories were posted for the mountains of eastern Utah and western Colorado for snow accumulations to as much as 8 inches, coupled with winds gusting to 30 mph.
By Tuesday morning some of the effects of this system are expected to reappear along to the east of the Rockies. While a slight risk of severe thunderstorms remained during the overnight hours for portions of eastern Arizona, the risk of severe weather increases during the 24 hours commencing early Tuesday morning ahead of a cold front in an area that extends across the high Plains from the Hill Country of central Texas northward to southern Nebraska.
THE NEXT ROUND IS IN THE NORTHWEST -- Some low elevation rain and mountain snow spread into across Washington State on Monday night ahead of the next storm system that was off the coast. This potent storm system was located off the coast of British Columbia's Vancouver Island with a cold front that trailed southward across the eastern Pacific Ocean. Strong winds were associated with this system.
Strong winds and precipitation associated with the storm system are expected along the Pacific coast during Tuesday as the storm approaches. By evening the cold front is expected to have moved inland across western Washington and Oregon. In anticipation of the strong southerly winds in advance of this storm, gale warnings for winds between 39 and 54 mph were posted for a large portion of the Pacific Coast, extending from Cape Shoalwater, WA to Point Piedras Blancas, CA. A high wind warning was issued for the southern Oregon coastal communications as the headlands were expecting gusts to exceed 55 mph. Widespread rain and mountain snow were anticipated to spread southward across California to as far south as the central coast and inland to the Sierras and the Cascades by Tuesday evening. Winter storm watches were posted for the Sierras of California and Nevada through Wednesday for snow and high winds.
MILD WEATHER ACROSS THE PLAINS -- A broad flow of southerly and southwesterly winds developed across the Plains on Monday, transporting warm air northward, resulting in unseasonably warm weather across the central and northern Plains. The southerly winds were on the western flank of a large high pressure system that was drifting eastward across the Middle Atlantic States during the day. Many areas experienced afternoon high temperatures that ranged between 20 and 30 degrees above the long-term climatological average high temperatures for the date. Record high temperatures were either tied or set on Monday at Dodge City, KS (79 degrees), in South Dakota at Mitchell (71 degrees), Huron (70 degrees), Brookings (63 degrees) and Watertown (58 degrees), in North Dakota at Devils Lake (52 degrees) and Grand Forks (49 degrees), at International Falls, MN (50 degrees) and at Marquette, MI (46 degrees).
How high the temperatures reached on Monday in part depended upon the amount of snow cover. As of early Monday morning, little or no snow cover was reported across south Dakota and in the Red River Valley of eastern North Dakota and western Minnesota. Consequently, temperatures across these areas warmed considerably, in part as a result of warm air advection, as well as from stronger February sunshine. Locations across Iowa, Minnesota and Wisconsin that had as much as a foot of snow had a slower start in the warming. In addition, afternoon clouds moved across some of these areas. The effects of the warm-air advection could be seen readily as of late Monday night as temperatures remained in the 30s across Minnesota and northern Wisconsin as southerly winds continued across the Upper Mississippi Valley. These temperatures were at least 10 degrees higher than 24 hours previously as westerly winds were relatively weak.
A QUIET DAY IN THE EAST -- Except for some lingering snowshowers across northern New England, much of the East experienced relatively quiet weather on Presidents Day as a result of the sprawling high pressure system that drifted eastward across the region. With another day of dry weather, the floodwaters in the rivers of the Upper Ohio River basin were beginning to recede after the heavy rains of last Friday. By Monday night the center of this high pressure system was centered over the Del-Mar-Va Peninsula. Another day of tranquil weather with higher temperatures is expected on Tuesday as the center of the high moves off the coast.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature in the lower 48 states on Monday was 9 degrees below zero at Saranac Lake, NY. Monday's highest temperature was 86 degrees at Cotulla, TX.
ALASKAN WEATHER -- A weakening low pressure system moved across the Alaska Peninsula and entered the North Pacific as of Monday night. A weak trough of low pressure associated with this system extended northeastward to near Prince William Sound. A stationary front remained across interior Alaska separating arctic air to the north from unseasonably mild air to the south. Cloudy skies were found across much of the state. Rain fell at Sitka, while snow was reported during the afternoon at Deadhorse, Kotzebue, Nome and Eagle.
On Monday morning, the lowest temperature in the state was 35 degrees below zero at Point Lay. The midafternoon high across the state on Monday was 43 degrees at Port Alexander, Elemendorf AFB, Hydaburg and Metlakatla.
HAWAIIAN WEATHER -- A high pressure system was passing to the north of Hawaii on Monday night, resulting in gusty northeast trade winds across the islands. This high is expected to stall to the northeast of the islands, maintaining the trade winds with speeds ranging from 15 to 30 mph through midweek. Few organized showers are expected other than the usual trade showers on the windward slopes of the islands, while the leeward sides remain dry and cloud-free. On Monday morning the high surf advisories were canceled as the ocean swells diminished to below critical levels.
ESTIMATING WARM AIR AND COLD AIR ADVECTION -- For details describing how you can use a surface weather map to determine regions of warm or cold air advection, consult 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, 2000, The American Meteorological Society.