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.
The following discussion is based upon the major weather features appearing on Wednesday night's surface weather maps:
STORMY WEATHER DEVELOPS ACROSS THE SOUTH -- A cold front separating a large arctic high pressure system located across the Plains to the north from relatively warm Gulf air to the south was the focal point for stormy weather across the South on Wednesday. As of late evening, the cold front stretched from the Carolinas westward across the Gulf Coast states to a low pressure center over northwest Louisiana and then to west Texas.
The type of weather depended upon where one was with respect to the front. Thunderstorms developed along and to the south of the cold front in the warm and humid air. Some of these thunderstorms produced large hail and strong winds on Wednesday afternoon and evening from northeastern Oklahoma through northern Arkansas, southern Missouri, western Tennessee and northern Alabama. Hail that ranged from dime size (0.75 inches in diameter) to golfball size (1.75 inches) was reported. In Tennessee the accumulation of hail was several inches deep. Thunderstorm winds downed trees and power lines. Doppler radar indicated a possible tornado near Birmingham, AL on Wednesday evening.
In the cold air to the north of the front, freezing rain fell across southwestern Missouri. Thunder was heard with the freezing rain near Springfield and Joplin. Farther north, the precipitation fell as snow.
The low pressure system is forecast to begin intensifying as it moves eastward across the Gulf Coast states on Thursday. By sunrise, the low should be located over northern Alabama and by evening the low should be found off the Carolina coast. Most of the precipitation associated with this system is expected to located to the north and east of the low pressure center, spreading across the southern Appalachians toward the Middle Atlantic states during the afternoon. Snow is expected to fall in the cold air first near the Ohio Valley and then into the Middle Atlantic States. Freezing rain and ice pellets (sleet) is anticipated across a region closer to the storm system, extending from Missouri across Kentucky, Tennessee, and the mountains of western North Carolina. As a result, a winter storm warning was issued for a large portion of central and eastern Kentucky, while winter weather advisories were in effect for southeastern Missouri, southern Illinois, southern Indiana, southern Ohio, much of West Virginia and portions of Virginia and North Carolina. Winter storm watches were posted for northern Virginia, much of Maryland, Delaware and southern New Jersey. Three to six inches of snow are possible across portions of the Middle Atlantic states.
THE ARCTIC AIR MOVES EASTWARD -- An arctic air mass accompanying a large high pressure system moved eastward from the Dakotas into the Great Lakes states on Wednesday. Record low temperatures were set on Wednesday morning at Marquette, MI (18 degrees below zero) and in South Dakota at Huron (20 degrees below zero) and Sisseton (19 degrees below zero). Interestingly, the record low temperature at Huron comes exactly one year after a record high temperature of 70 degrees had been set. The arctic air mass, coupled with an extensive snow cover, helped produce this year's record low. Afternoon high temperatures in an area extending from the Upper Mississippi Valley into the central Plains were on the order of 15 to 20 degrees below the average high temperatures for the date.
A reasonably tight pressure gradient between the high pressure across the Great Lakes and a low pressure system over Labrador has produced strong northwesterly winds across New England. The combination of subzero air temperatures and high winds have produced dangerous wind-chill conditions. A wind chill warning was in effect across Maine for wind-chill equivalent temperatures to fall into the danger category, as low as 55 degrees below zero. With winds possibly reaching between 39 to 54 mph, a gale warning was in effect for marine interests along the New England coast from Watch Hill, RI to Eastport, ME.
The twin centers of the arctic high pressure system were located over Lakes Michigan and Erie on Wednesday night. By Thursday morning a high pressure center is forecast to be situated over the Hudson Valley of New York State and by evening, the high should be located to the south of Nova Scotia.
LIGHT SNOW ACROSS THE UPPER MIDWEST -- Clouds and light snow spread eastward across Iowa into Illinois and southern Wisconsin, just to the west of the high pressure center. These clouds and snow were associated with overrunning, where warm air is carried over a cold dome of air, causing the development of clouds and precipitation. The warm air was located to the west of a warm front that had developed across the western Plains, stretching from a series of weak low pressure centers over Saskatchewan and the Dakotas southward to west Texas. One of the low pressure systems is expected to move eastward across Manitoba and western Ontario on Thursday. A cold front trailing from the low is expected to sweep rapidly across the northern Plains, developing an occluding storm system over the Manitoba Lakes and the Upper Mississippi Valley by morning. This occluding system is forecast to reach the Great Lakes by evening. Light snow is expected across the Upper Midwest in association with this system.
WARM WEATHER CONTINUES ACROSS THE SOUTHEAST -- Relatively warm and humid air was found south of the cold front that stretched across the Gulf Coast States. Afternoon high temperatures across the Southeast ranged from 10 to 15 degrees above the long-term average highs for the third week in February. Downtown Charleston, SC reached a record high temperature of 80 degrees.
THE NEXT PACIFIC STORM -- The next storm in the current series of Pacific storms to batter the West Coast was situated off the Oregon coast on Wednesday night. An occluded front stretched southeastward from the low pressure center across southern Oregon and northern California before becoming a cold front over the central valley of California. Low elevation rain and mountain snow were falling across portions of northern California, Oregon and Washington State. During the afternoon small hail fell in central Oregon, accumulating to a one inch depth. Strong thunderstorms were detected by radar off the northern California coast near Cape Mendocino on Wednesday night.
The storm system is expected to move inland on Thursday. Precipitation associated with this system is expected to continue over the Pacific Northwest, extending southward along the Sierras in California. Between 0.25 and 0.50 inches of liquid equivalent precipitation is anticipated across northern California during the 24 hours ending on Thursday evening. Snow advisories were in effect through Thursday morning for the mountains of northern California and the northern Sierras, where between 4 to 6 inches of snow are likely, while a winter storm watch was posted to be effective through Thursday night for the southern Sierras for as much as a foot of new snow.
TEMPERATURE EXTREMES IN THE CONTINENTAL U.S. -- Wednesday morning's lowest temperature was 39 degrees below zero at Embarrass, MN, while the Wednesday afternoon highest temperature was 86 degrees at McAllen, TX.
ALASKAN WEATHER -- The large high pressure system located over the Yukon Territory continued to dominate the weather across much of Alaska on Wednesday afternoon. A strong storm system to the east of the Kamchatka Peninsula was accompanied by a front that stretched across the central Aleutians. Extensive cloud cover was found across western Alaska. The tight pressure gradient between the high in eastern Alaska and this storm system contributed to strong winds across western Alaska. Winds gusted to 52 mph at Cape Romanzof and to 40 mph at Hooper Bay, Cold Bay and Whittier. A relatively weak storm system positioned off the southern tip of the Panhandle spread clouds across the extreme southeastern corner of the state. Only a few locations across the state reported light precipitation on Wednesday afternoon. Nome, Nabesna and Elmendorf AFB had snow, Yakutat had rain and Juneau had a mixture of rain and snow.
The lowest temperature in Alaska on Wednesday morning was 24 degrees below zero at Nuiqsut and the highest statewide temperature as of Wednesday afternoon was 45 degrees at Klawok.
HAWAIIAN WEATHER --Winds across the Aloha State have weakened to the point where local sea and land breezes developed across the islands on Wednesday afternoon. A ridge of high pressure was situated sufficiently close to the islands to produce weak southerly winds across Kauai, southeasterly winds over the central island, while easterly winds remained over the Big Island. Except for some showers over Kauai and Oahu, skies remained relatively cloud-free across the islands. The ridge should remain relatively close to the islands through Thursday before a trough of low pressure passes to the north of Hawaii. Because of surf with heights ranging between 6 to 10 feet, high surf advisories continued for the northwest facing shores of the islands.
SEASONS -- For a detailed description of meteorological seasons, see Thursday'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.