THE ACTIVITY SHIFTS SOUTH -- A storm system with a low pressure center that was situated over the northern Great Lakes on Tuesday night continued moving toward the east on Wednesday. During the day, a secondary low pressure system developed along the cold front that extended southward across the eastern Lakes and the Ohio Valley in an "occlusion process" typical of the life-cycle of many mid latitude storm systems. By late Wednesday night, the primary low pressure system was located to the northeast of Georgian Bay and was expected to ultimately dissipate. A nearly dissipated occluded front extended from this low center to a secondary low pressure center over south central Pennsylvania. This secondary low was becoming the dominant system, with a warm front extending eastward into the Atlantic off the New Jersey coast. A cold front extended southwestward from the new low pressure center to the Gulf Coast near the Mississippi Delta.
Light snow continued across portions of the Upper Peninsula and northern Lower Michigan in association with this primary low pressure center. Some of the snow was lake-enhanced as northwesterly winds continued to cross the open Lakes Superior and Michigan as part of the counterclockwise circulation around the western flank of the low. A widespread area of rain was also found across portions of New England. However, the main weather action had shifted southward as a broad area of rain and imbedded thunderstorms was found across the Southeast on Wednesday night. The precipitation was associated with the nearly stationary cold front and stretched from the Virginias southwestward across the Carolinas, east Tennessee, Georgia and Alabama. Additional thunderstorms were detected by radar and satellite imagery over the Gulf of Mexico south of Apalachicola, FL.
The area of precipitation is expected to move slowly eastward along with the front across the Piedmont on Thursday morning. Farther north, the precipitation should expand across the Middle Atlantic states.
A WINTER STORM ORGANIZES -- A potentially major winter storm system that could affect the central portion of the nation near the end of this week with significant snow was beginning to organize in the Colorado Rockies. As of late Wednesday night a weak low pressure system was located to the lee of the Rockies over eastern Colorado. A region of precipitation was found along a stationary front over the western Dakotas and the Nebraska Panhandle, while widely scattered areas of snow were detected across the Rockies of Colorado and Wyoming. On Thursday this storm system is anticipated to organize and move eastward across the Plains, accompanied by the precipitation shield that was located over the western Dakotas. Snow is expected on the cold, north side of the low pressure center, with sizable accumulations falling across Kansas and Nebraska. To the south of the system, rain and thunderstorms should fall across Oklahoma. In the transition region closer to the low, ice pellets (sleet) and freezing rain may affect the Plains.
STORMY WEATHER PERSISTS ALONG THE WEST COAST -- One of the many storm systems in the parade of Pacific storms to slam into the West Coast moved inland early Wednesday and dissipated. This storm system was accompanied by strong winds and heavy precipitation. The winds contributed to the high surf that reached heights of at least 30 feet along the Oregon coast, and surf to 15 feet along the southern California coast. By late Wednesday evening the high winds and heavy surf had subsided before the next system approached. Most of the heavy precipitation had diminished in intensity, but not before heavy rains had fallen at low elevations while heavy snow, with accumulations of more than a foot, fell across the Sierras and the Cascades.
The next storm is expected to reach the Pacific Northwest later on Thursday. As of late Wednesday evening, this storm system was approximately 800 miles to the west of the northern California coast. Some of the precipitation in advance of this system was beginning to fall across the coastal locations. By Thursday morning, a more extensive region of precipitation should be found along the coast from central California northward. A variety of winter storm watches and warnings were issued for the higher terrain of the Sierras and the Cascades, as at least a foot of snow was expected for later on Thursday.
Gale warnings continued along the Oregon coast. Ocean swells with up to 22 foot heights were measured by moored offshore buoys. These swells, associated with some of the next storms, necessitated the continuation of heavy surf advisories for the coast from Cape Mendocino, CA to the Oregon border.
YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- The lowest temperature on Wednesday was 13 degrees below zero at Roseau, MN. Wednesday's high was 82 degrees at McAllen, TX and Thermal, CA.
ALASKAN WEATHER -- A weakening storm system located in the Bering Sea north of Saint Paul Island on Wednesday afternoon continued to maintain clouds over much of the Bering Sea. Areas affected included St. Lawrence Island, the Pribilofs, the eastern Aleutians and the western Alaska Peninsula. Saint Paul reported snow, while Cape Romanzof had reports of blowing snow. Another storm system located over the northeastern Gulf of Alaska near Prince William Sound brought clouds and fog to coastal regions of the state from the southeast to south central Alaska, with an additional cloud band that extended over portions of interior Alaska from the Copper River Basin and the lower Tanana Valley to northwest Alaska. Light snow was reported over the Anchorage Bowl, Whittier and Valdez, while rain fell at Yakutat. In the interior, snow was also reported at Northway and Delta Junction. Partly cloud skies were found elsewhere in the state.
The lowest overnight minimum temperature in Alaska on Wednesday morning was 24 degrees below zero at Nuiqsut and the midafternoon high was 46 degrees at Hydaburg.
HAWAIIAN WEATHER -- The fair weather pattern that was found across the islands on Wednesday should continue through most of Thursday. A ridge of high pressure to the east-northeast of Hawaii was moving away from the islands. This high had been responsible for the weak trade winds with isolated trade showers. A shear line representing the remnants of a midlatitude cold front should reach Kauai by Thursday night, and the other islands on Friday. As of Wednesday afternoon the shear line was approximately 150 miles northwest of Kauai. Clouds, showers and a change in wind direction are expected to accompany the passage of the shear line. High surf advisories were continued for the north, west and south shores of the islands.
MONITORING THE SEASONAL MOTIONS OF THE SUN -- We are rapidly approaching the Spring Equinox (on Saturday, 20 March 1999), where we all experienced 12 hours of sunlight (plus a few minutes - see Thursday's optional Supplemental Information file), the length of daytime is increasing by several minutes from one day to the next. For Washington, DC, this increase is about 3 minutes more possible sunshine each day. This effect is accentuated the higher the latitude. On the first day of winter, 21 December, International Falls, MN on the Canadian border had only 8 hours and 17 minutes of possible sunlight compared to Key West, FL at 10 hours and 37 minutes. (Barrow, AK had NO sunlight, being north of the Arctic Circle.) By the summer solstice on 21 June, residents in International Falls should bask in a lengthy 16 hours and 9 minutes of possible sunshine, while Key West would have 13 hours and 40 minutes of possible sunshine (Barrow conceivably could have 24 hours of sunshine, barring no clouds). A portfolio of sunrise photos shows the beginning of the path of midlatitude sun over year.
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.