AN INTENSE STORM MOVES ALONG THE EAST COAST -- The storm system that produced the severe weather across the Gulf Coast on Tuesday night moved eastward on Wednesday. By late Wednesday night, this storm system consisted of a deep low pressure system that was located over southern Pennsylvania with a cold front that extended southward along the Atlantic coastline to southern Florida. A large region of precipitation, to include imbedded thunderstorms, surrounded the low pressure system, stretching from northern New England westward to eastern Ohio and southward to Virginia.
The cold front, representing the leading edge of a cold air mass, was especially active in that it was the mechanism that contributed to the development of the severe thunderstorms. These thunderstorms developed in the warm, humid Gulf air to the east of the advancing cold front. After producing at least one tornado in Texas, the thunderstorms continued through the overnight hours, causing wind damage across Alabama, Georgia and the Florida Panhandle. The storms caused a fatality north of Montgomery, AL when a tree smashed into a trailer home were a man was sleeping. A tornado damaged approximately 55 home in the Florida Panhandle. During the daylight hours of Wednesday, thunderstorms associated with the cold front moved eastward, accompanied by strong thunderstorm winds and large hail. Thunderstorm winds, that reached in excess of 60 mph across North Carolina, caused damage in North Carolina, Virginia, Maryland and Pennsylvania. Sixteen people were injured as strong winds damaged a construction site at Petersburg, VA. Near the southern extremity of the cold front, an unconfirmed tornado was reported by the public near Miami on Wednesday.
The temperature contrast across the cold front was impressive, leading to summer-like temperatures near 70 degrees across coastal North Carolina, while in the western part of the state, temperatures were in the 30s. As a result, in the cold air following the cold front, at least 4 inches of snow fell across the western North Carolina mountains. As of late Wednesday night, rain continued to fall across the Middle Atlantic and New England states to the east of the front. To the west, snow continued to fall. Thundersnow-- were thunder is heard during a snowstorm -- was reported at various locations, such as at Johnstown, PA. A burst of heavy snow accompanied the thunder and indicated vigorous vertical motions and turbulence. Winter storm warnings were in effect from western New York to western Virginia.
Because of the deep central low pressure, with a central pressure of approximately 983 mb, a strong pressure gradient had formed around the storm system, as indicated by the tight packing of the isobars on the surface weather analyses of Wednesday night. This pressure gradient generated strong non-thunderstorm winds, especially over the open waters of the Atlantic. Storm warnings for winds in excess of 54 mph were in effect along the coast from Eastport, ME to Watch Hill, RI, while gale warnings for winds between 39 and 54 mph were continued southward to Surf City, NC.
The low pressure system should continue moving toward the lower St. Lawrence Valley of southeast Canada on Thursday.
WINDY CONDITIONS ACROSS THE PACIFIC NORTHWEST --A major storm system that had a central pressure of approximately 960 mb on Tuesday night passed over Vancouver Island on Wednesday morning. Because of the strong pressure gradient surrounding this storm system, high winds of "hurricane-force" speeds were generated. A peak wind of 105 mph was recorded on Tuesday night at Cannon Beach along the Oregon coast approximately 20 miles south of the mouth of the Columbia. Other stations along the coast had peak gusts over 85 mph. Wind damage was reported in the Portland, OR area. A buoy moored 12 miles off the coast at Newport, OR recorded seas to 46 feet, and wind gusts to 67 mph. Tens of thousands of customers were without electric power and ferry service across Puget Sound was interrupted. In Washington, a man was killed when a tree fell on the car that he was driving. Farther south, as the associated cold front passed over the Sierras, high winds were reported at Reno, NV, where a 87 mph gust was recorded.
As of late Wednesday night the storm system had moved inland, with a portion of the system moving across the Rockies. One low pressure center, located in southern Alberta represented the remnants of the original low pressure system that had undergone an occlusion process. Several other low pressure centers had developed along the accompanying cold front. On low was located to the east of the Continental Divide in southern Montana and another low was located along the cold front in Nevada.
The storm generated ocean swells that propagated southward along the coast. High seas caused flooding of Raymond, WA. As 18 to 20 foot seas were reported to continue along the California coast on Wednesday, a heavy surf advisory remained in effect through Thursday morning for the coast from Point St. George south to Point Piedras Blancas. Small craft advisories for hazardous seas remained in effect for the Washington, Oregon and northern California coasts.
In addition to the high winds, the storm also produced heavy snow in the mountains of the Northwest. Accumulations of at least 8 inches of new snow were reported in eastern Washington State. By late Wednesday night, lingering precipitation was found across the Pacific Northwest, with rain and snow along the windward slopes of the Cascades and Olympics, as a result of the continued onshore flow.
On Wednesday morning, the low pressure system should move eastward into the western Plains. A region of snow is expected to move eastward across the Dakotas. Scattered areas of snow are also forecast to be found across the Rockies and the Great Basin.
Record high temperatures were either tied or set at Delta and Zion National Park in Utah, and at Nogales, Safford and Douglas in Arizona.
YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- The lowest temperature on Wednesday was 2 degrees below zero at Devils Lake, ND. Wednesday's high was 91 degrees at Thermal, CA.
ALASKAN WEATHER -- A large ridge of high pressure continued to expand eastward and intensify over northern Alaska on Wednesday. The high pressure center was located over the upper Yukon Valley. As a result, a large portion of the state was relatively cloud-free. A trough of low pressure was anchored along the eastern Gulf coast. However, the clouds and precipitation over the Panhandle began to dissipate. Low clouds were reported over Kodiak Island and Alaska Peninsula. Light snowshowers were reported at Kodiak. The storm system that had dominated the western Bering Sea began to weaken as high pressure of the North Pacific began expanding northward. However, rain and snow continued to fall over the western Aleutians. Snow was reported over the eastern Aleutians and the Pribilofs.
With a strengthening of the high pressure system over the interior, the pressure gradient between this high and the Gulf low pressure system intensified, leading to windy conditions along the Gulf coast. Winds gusts reached 50 mph at Whittier. With wind gusts increasing to 35 mph at Seward, a wind advisory was issued.
On Wednesday morning the state lowest temperature was 40 degrees below zero at Chandalar Lake, while the midafternoon state high was 48 degrees at Annette.
HAWAIIAN WEATHER -- Light easterly trade winds were found across the islands on Wednesday afternoon as a result of the weak ridge of high pressure located to the north of Hawaii. This situation is expected to continue through Friday. With light winds, the local afternoon sea breeze should dominate, with an increase in afternoon clouds and showers over the interior of the islands due to heating.
PRESSURE ALTIMETERS -- For information on pressure altimeters and their readings, see Thursday's optional Supplemental Information.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
Return
to Online Weather Homepage
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 1999, The American Meteorological Society.