ONLINE DAILY WEATHER SUMMARY

Friday, 5 March 1999


WINTRY WEATHER MOVES THROUGH THE NORTHEAST -- The storm system that brought strong winds, heavy precipitation and thunderstorms to the Northeast on Wednesday night was centered over eastern Quebec and the lower St. Lawrence Valley on Thursday night. Widely scattered snow continued across New England and Upstate New York, accompanied by brisk northwesterly winds.

Earlier on Thursday a large widespread area of snow fell across the eastern Great Lakes into the Appalachians, partly due to the intense counterclockwise circulation around the storm system that carried moisture from the Atlantic around the north and west sides of the storm and partly from the lake-enhanced snow associated with northwesterly wind across the lakes. Some locations across the Northeast experienced blizzard and whiteout conditions as strong winds to as high as 40 mph along with the heavy snow reduced visibility in the blowing snow. More than 18 inches of new snow had fallen across the high terrain of West Virginia, central Pennsylvania and western New York State. As of late Thursday afternoon, Rochester, NY had received 24.3 inches of snow, the second highest 24 hour snowfall in station history. At times, snow fell at a rate of 2 to 3 inches per hour.

As the storm system continues to move toward the northeast on Friday morning, the pressure gradient should relax and the strong northwesterly winds of Thursday should weaken. A winter weather advisory continued into Friday for portions of New York State's Mohawk Valley for several inches of additional snow.

UNSETTLED WEATHER IN THE MIDWEST -- Light snow moved eastward from the northern Plains into the Upper Midwest on Thursday night along an east-west running stationary front that extended from the western Great Lakes westward to the northern Rockies. Accumulations of up to inch or so are possible.

Farther to the southwest, a warm front ran from a low pressure area in northern Kansas eastward into the mid-Mississippi Valley. A broad southerly wind flow south of this warm front is expected to create "overrunning" on Friday. The air in the southerly wind flow would be carried up and over cooler air near the surface, producing widespread precipitation to the north of the front. On Friday the low in the Plains is expected to intensify, resulting in several inches of snow to fall from the Mississippi Valley eastward into the lower Great Lakes.

To the south of the warm front, the southerly flow of warm moist Gulf air could also increase the possibility of severe weather. A slight risk of strong to severe thunderstorms exists on Friday for the lower and mid-Mississippi Valley. An intensifying pressure gradient over the western Plains necessitated issuing a wind advisory for north Texas, where southerly winds could reach speeds of 30 mph.

MOUNTAIN SNOWS -- Snow fell across the central Rockies on Thursday in association with a trough of low pressure located in Colorado. Additional snow was expected to continue from the Colorado and Wyoming Rockies to the Wasatch Front in Utah, where snow advisories were posted.

A CHILLY START ACROSS THE SOUTHEAST -- A large region of high pressure centered over east Tennessee on Thursday night dominated the weather across the Southeast. With the ingredients for radiational cooling -- clear skies, low atmospheric humidity and weak winds under high pressure -- overnight low temperatures across the Southeast could fall to the upper 20s. As a result, freeze advisories were posted for much of South Carolina and east central Georgia.

A RESPITE IN THE NORTHWEST -- After nearly a week of being battered by storms, the Pacific Northwest experienced quieter and drier weather as high pressure moved into the region. As of late Thursday night, the high pressure ridge extended westward from the Oregon Coast. Some widely scattered rain and snow lingered along the mountains along the northern flanks of the ridge as onshore winds continued to interact with the mountain barriers in western Washington State and Oregon. This high pressure ridge is expected to build eastward into interior sections of the Northwest on Friday morning. Light upslope rain and snow may be found over the northern Cascades.

A frost advisory was posted for California's Sacramento and San Joaquin Valleys as high pressure develops across the region and the cool, dry air mass will permit temperatures to fall into the mid 30s. Freeze warnings were also posted for Mendocino County in Northern California.

YESTERDAY'S TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Thursday was 9 degrees below zero at Ironwood, MI and Eagle River, WI, while the day's high was 86 degrees at Laredo, TX.

ALASKAN WEATHER -- A sprawling ridge of high pressure centered over the Yukon Valley brought relatively cloud-free skies and unseasonably cold weather to much of the Alaska mainland on Thursday. A storm system over the Gulf of Alaska off the coast of the Panhandle brought low clouds to the Panhandle and eastern Gulf Coast, while snowshowers were confined to coastal sections of the Panhandle. Another storm system in the western Bering Sea spread clouds and precipitation across the Aleutians. Shemya had snow for much of Thursday, while Adak had pre-dawn rain and snow, with winds gusting to 41 mph.

Strong northerly and northwesterly winds developed as a result of the pressure gradient between the high pressure over interior Alaska and the Gulf low pressure system. At some locations, winds increased as they were channeled through mountain passes. Valdez had gusts to 62 mph, Whittier reported gusts to 46 mph and Kodiak experienced 36 mph gusts. Wind advisories were posted for both Seward and Valdez. The strong winds helped produce some large temperature rises across south central Alaska on Thursday morning. A shift in wind direction coupled to a 30 mph increase in wind speed in the region between Wasilla and Willow destroyed the strong temperature inversion, mixing warm air downward into the cold surface layer and causing the temperature to rise 15 degrees within 2 hours. These off-shore winds also cleared the clouds from along the north Gulf Coast.

The statewide overnight lowest temperature as of Thursday morning was 38 degrees below zero at Fort Yukon. The midafternoon highest temperature was 43 degrees at Klawock.

HAWAIIAN WEATHER-- A ridge of high pressure located to the northeast of Hawaii brought pleasant weather with relatively cloud-free skies to the islands. This ridge is expected to weaken and move slightly to the southwest, resulting in a slight weakening of the wind speeds to less than 20 mph and a turning of the winds to a easterly or southeasterly direction. With weakening of the trade winds, the locally driven sea breeze circulation regime should become more dominant, with light afternoon rain showers especially over the interior sections of the islands. This pleasant weather should continue through the weekend. High surf advisories were in effect for the north and west shores of the islands.


HISTORICAL WEATHER EVENTS - 5 March

From the files of the Aviation Weather Center, Kansas City, MO and Intellicast

6 March

7 March


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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 1999, The American Meteorological Society.