DRY WEATHER HELPS WILDFIRES CONTINUE ACROSS FLORIDA --- A large ridge of high pressure remained over the Gulf of Mexico on Monday. The lack of significant precipitation for months has helped produce drought conditions across the Southeast, with portions of Alabama, Georgia and Florida especially hard hit. The clear skies, high temperatures, low humidity and northwest winds have exacerbated the situation, increasing the wildfire potential. Major wildfires continued to burn across the Everglades of south Florida on Monday. More than 100,000 acres across the state have been burned as of late Monday. Haze from the fires has caused problems, including the closing of the portion of I-75 known as Alligator Alley for a second day.
The dry conditions with dewpoints in the 30s and 40s have helped produce some large diurnal temperature fluctuations. Daytime temperatures rise rapidly from a chilly start. As a result of clear skies, low dewpoints and weak winds, the overnight minimum temperature on Monday morning at Tallahassee broke a daily low temperature record of 35 degrees, while Orlando had a record-tying 46 degrees.
THUNDERSTORMS MOVE ACROSS THE OHIO VALLEY -- Showers and thunderstorms formed along a front that extended from Tidewater Virginia westward to the southern Plains. This front separated a cool air mass situated over the Great Lakes from warmer air over the Gulf Coast. Several waves of low pressure formed along this front. One large area of precipitation was found across the upper Ohio Valley from eastern Ohio into southwestern Pennsylvania. Additional precipitation was found across West Virginia and Kentucky. Thunderstorms erupted across Middle Tennessee late Monday night near one of the waves of low pressure along the front. Some of these thunderstorms became severe when they produced large hail while they moved through the Nashville, TN metropolitan area. Some hail was reported to be baseball-sized.
A low pressure center is expected to move eastward, reaching the Blue Ridge of northern Virginia by Tuesday morning. The precipitation shield associated with this system should extend across coastal regions of the Middle Atlantic states.
LIGHT PRECIPITATION ACROSS THE NORTHERN PLAINS -- An area of rainshowers was found across the western Dakotas, eastern Montana and northern Wyoming. This precipitation was associated with a nearly stationary front and weak lows that formed along the front over the western Plains. By Tuesday morning, the area of precipitation is expected to move to the eastward into Minnesota and northern Iowa. Thunderstorms could develop over eastern Nebraska and Kansas, and extend across northern Missouri.
SHOWERS CONTINUE ACROSS THE NORTHWEST -- Widely scattered rain and rainshowers continued to be found across the Pacific Northwest. A cold front that trailed from a low pressure system in the Gulf of Alaska was positioned along the immediate coastline of Washington, Oregon and northern California. Rain across the Snake Valley was associated with a weak trough of low pressure located in southwestern Idaho.
The cold front is expected to sweep inland, having reached the Rockies of northwest Montana by Tuesday morning. A region of low elevation rain and mountain snow is forecast to extend from the Canadian border southward to Utah's Great Salt Lake and include the northern Rockies and much of the Intermountain region.
HOT WEATHER CONTINUES ACROSS THE SOUTHWEST -- Record high temperatures were set once again in southern California as the afternoon high at Pasadena reached 92 degrees and 78 degrees at Mount Wilson.
UPPER AIR -- Both the 500 and 300 mb charts for 00Z Tuesday had a ridge of high heights across the western half of the country, and a trough of lower heights across the East, with a trough line extending from the Great Lakes toward the Atlantic Coast.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature in the lower 48 states on Monday was 18 degrees at Gallup, NM and Monday's highest temperature was 104 degrees at Thermal, CA and Lake Havasu City, AZ.
ALASKAN WEATHER -- A large low pressure system moved into the northern Gulf of Alaska just to the south of Kodiak Island on Monday. A southerly onshore flow from the Gulf of Alaska provided the moisture for rain across portions of the Panhandle, Prince William Sound and the Kenai Peninsula. To the west, in the cooler northerly flow, snow fell across the Aleutians and the Alaska Peninsula. Locally strong winds blew through Portage Pass, with gusts reaching 63 mph on Monday morning.
An elongated trough of low pressure developed from the low in the Gulf northward into the central interior of the state. As a result, the ridge of high pressure that had been located over the central interior split, with one cell remaining over western Canada and the other cell over eastern Russia. However, the clear skies associated with remnants of the ridge permitted sufficient sunshine to produce unseasonably warm weather across the central and eastern portions of interior Alaska for another day. At McGrath, a record high temperature of 59 degrees was set on Monday.
A ridge of high pressure situated over the Arctic Ocean helped generate a large pressure gradient across northern and northwest Alaska. Strong northerly winds with gusts to as much as 45 mph brought cold air southward into the Chuckchi Sea coast and through the Bering Strait. Wind-chill equivalent temperatures across the region fell to 54 degrees below zero and blowing snow was also reported at places such as Tin City and on St. Lawrence Island. Snow was reported along the Arctic Coast, to include Deadhorse and Prudhoe Bay. An east-west oriented stationary front separated the cold air on the North Slope from warm air to the south.
The record high temperature of 68 degrees set on Sunday at Fairbanks was not only a daily record, but it was the warmest day ever for so early in the spring season.
The lowest overnight temperature in the state on Monday was 9 degrees below zero at Point Hope, while the warmest temperature across the state by midafternoon was 66 degrees at Eielson AFB.
On Monday morning, Shishaldin Volcano erupted, producing an ash and steam plume that quickly rose to an altitude of between 40,000 and 60,000 feet within an hour before drifting south on northerly upper air winds over the Pacific Ocean. This volcano is located on Unimak Island to the west of Cold Bay. A volcanic ash warning is in effect for Unimak Island and aviation alerts have been posted for high flying aircraft in the vicinity of the Aleutians. While the island has been shrouded in clouds, the National Weather Service Forecast Office in Anchorage has posted several impressive satellite images of the eruption at http://www.alaska.net/~nwsfoanc/volcano.html.
HAWAIIAN WEATHER --A ridge of high pressure strengthened to the north of Hawaii on Monday causing an increase in the speed of the trade winds across the islands. Earlier in the day a band of showers passed across the islands. Starting late Tuesday the high pressure cell is expected to push southward toward the islands, causing the winds to slacken as the pressure gradient weakens. Drier weather should also ensue.
WATCHES AND WARNINGS -- For a description of the terminology used in the official statements issued by the National Weather Service to inform the public of high non-thunderstorm winds, please read the Tuesday 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, 1999, The American Meteorological Society.