WEATHER OVER THE WEEKEND --A major storm system moved eastward across the Midwest on Friday morning, accompanied by heavy rain on the north side of the system and thunderstorms on the south. Grand Rapids, MI received 1.44 inches of rain by mid-day Friday, setting a daily precipitation record for the date. By Friday evening the low and accompanying cold front reached the Middle Atlantic coast. As the system moved eastward across the Ohio Valley and into the Middle Atlantic states, thunderstorms produced large hail and high winds from Ohio and West Virginia into Pennsylvania, Maryland and Virginia. Two and one half inch diameter hail was reported at Winchester, VA, while trees were stripped of their leaves in a suburb near Dulles Airport in northern Virginia. Hail did damage to windshields of vehicles. Tornadoes were reported in southwestern West Virginia and at Lynchburg, VA. Additional thunderstorms farther south along the cold front produced large hail across northern Alabama.
High pressure moved in behind the storm system from the Prairie Provinces on Friday. As a result, much of the Great Lakes and the Northeast had relatively cloud-free, pleasant and tranquil weather over much of the weekend. By Sunday this high pressure system had become entrenched over the Lake Michigan.
Heavy snow continued to fall over the central Rockies. As of Friday morning, more than 2 feet of new snow had fallen at Lander, WY. By the end of the storm, 51.7 inches of snow fell, setting a new record total snowfall for a single storm. The 28.6 inches set a 24 hour snowfall record and the 69.4 inches for the month was a monthly record. Other mountainous locations across Wyoming and Colorado also received on the order of 3 feet of snow. However, at lower elevations, such as at Denver, CO, only 8 inches fell. On Sunday, 8 inches of snow fell at Cheyenne, WY. In addition to the heavy snow, strong winds were also a problem across the West. The winds produced blizzard conditions across Wyoming. On Friday morning Brigham City Airport, approximately 40 miles north of Salt Lake City, UT, reported a peak wind gust of 113 mph, setting a new state wind record for a Utah valley or low-elevation location that is below 5000 feet. These winds caused considerable tree damage and turned over 11 tractor trailers.
On Saturday morning thunderstorms accompanied by hail and strong winds developed again along the cold front and moved eastward from the southern Plains into the Southeast from Oklahoma and Arkansas eastward through Alabama and Georgia to South Carolina. Heavy rain across Oklahoma and Arkansas. By late afternoon, the cold front had become stationary, stretching from Carolinas westward to west Texas. Thunderstorms moved across northern portions of drought-stricken Florida on Sunday, accompanied by large hail. Thunderstorms with hail and damaging winds moved across eastern Colorado and into western Kansas on Sunday afternoon.
Elsewhere on Friday afternoon, Houston (Intercontinental), TX had a record-tying high temperature of 91 degrees.
WEATHER FOR STARTING THE NEW WEEK -- Severe thunderstorms with damaging winds, large hail and heavy rains were found across Oklahoma and Arkansas on Sunday night. These thunderstorms were moving eastward along a warm front that extended to the east of a low pressure system located over the Texas Panhandle. This warm front paralleled the Red River Valley across southern Oklahoma, then crossed northern Louisiana and southern Mississippi before merging with a cold front that continued eastward over Florida. The precipitation associated with these thunderstorms was "overrunning precipitation", a result of the warm, humid Gulf air that was transported northward and carried upward along the sloping warm front. More than five inches of rain were reported from northeastern Oklahoma. The heavy rain that fell across Oklahoma, Kansas and Missouri created flash floods on many streams and rivers. As a result, a variety of flash flood watches and warnings continued in effect for portions of Oklahoma, Kansas, Missouri, and Arkansas. Widespread rain was also found across the Plains, from the western Dakotas south to western Kansas, associated with a trough line that extended northwestward from the Panhandle low center to a weak low pressure area over northern Wyoming.
To the southwest, severe thunderstorms exploded late Sunday night along the Rio Grande and northward into the Hill Country of central Texas. These thunderstorms developed along a frontal boundary known as a "dry line" which stretched southwestward from the low pressure center in the Panhandle to the Big Bend region. This boundary in air density was between the dry air over West Texas with low dewpoints and the more humid air with high dewpoints over central Texas.
The low pressure system and the accompanying warm front are expected to move northward across Oklahoma by Monday morning. The dry line should move eastward across central Texas as a cold front. Showers and thunderstorms are expected to continue across the lower Mississippi Valley, in the warm sector of the storm, while overrunning precipitation should expand northward across the Plains states. A slight risk of severe thunderstorms is expected over Texas and Oklahoma through Monday morning. This risk area should move eastward into the lower Mississippi Valley during much of Monday. Light snow is expected across portions of southern Wyoming, the Wasatch Front of Utah and northern Colorado.
A large ridge of high pressure stretched from one high pressure center over northern Indiana to another high off Hampton Roads, VA. Relatively quiet weather across the Great Lakes and the Northeast was associated with this high pressure. By Monday morning the high pressure cell should have moved off the Carolina coast.
A cold front that entered the Pacific Northwest trailing a low moving across British Columbia produced a noticeable drop in temperatures on Sunday. This cold front stretched from the Idaho Panhandle southwestward to northern California by Sunday evening. Widely scattered precipitation accompanied this front, primarily over eastern Washington and Oregon, along with portions of the Idaho Panhandle. This front is expected to continue to move eastward across the Montana Rockies by Monday morning. Light rain and rainshowers were forecast to expand across the Northwest, encompassing an area from northern California through central Oregon, eastern Washington and northern Idaho.
UPPER AIR -- The 500 and 300 mb charts for 00Z Monday both contained a large closed cyclonic (counterclockwise) circulation around a large pool of cold air over the central Rockies of Colorado and Wyoming. This upper level feature, appearing as a trough of lower heights, is associated with the surface storm system over the Rockies. Winds at 300 mb exceeded 80 knots, especially around the southern extremity of the trough in the West. The jet streak of strong winds maintained the nearby surface low by causing upper level divergence which compensates the low level convergence into a surface low pressure cell.
TEMPERATURE EXTREMES IN THE COTERMINOUS U.S. -- The lowest temperature on Sunday was 16 degrees at Saranac Lake, NY while Sunday's highest temperature was 97 degrees at Lajitas, TX.
ALASKAN WEATHER -- A low pressure system located in the northern Gulf of Alaska south of Cordova spread clouds and light precipitation across the Panhandle, southeast Alaska and the north Gulf coast. Strong winds were found across southern Alaska, with Seward experiencing gusts to 41 mph, Whittier and Iliamna having gusts to 40 mph and Kodiak gusts to 39 mph. An elongated trough of low pressure extended across northern portions of the state. Clouds were also reported across portions of the North Slope, northwest Alaska, the Seward Peninsula and the Yukon-Kuskokwim Delta. Snow fell at Prudhoe Bay and McGrath.
A ridge of high pressure located in the North Pacific Ocean south of Dutch Harbor extended northward, bringing relatively clear skies to the eastern Aleutians, portions of the Alaska Peninsula, Bristol Bay and Kodiak Island.
The lowest overnight temperature in the state as of Sunday was 15 degrees below zero at Ugnu-Kaparuk. Sunday's midafternoon highest temperature was 52 degrees at Cordova.
As of early Friday morning, Juneau had received 6.10 inches of precipitation for the month of April, setting a new monthly precipitation record. Juneau has had only three days this April when precipitation has not fallen.
HAWAIIAN WEATHER --Cold air associated with an upper level low moved westward toward the islands. As a result of the cold air aloft producing unstable atmospheric conditions, heavy showers were expected across the Big Island late Sunday. Increased clouds and showers could also reach the other islands. This upper low should remain nearly stationary to the east of the islands through Monday. A surface ridge of high pressure located north of the islands should maintain trade winds with speeds that should remain between 10 and 20 mph.
BECOMING AWARE -- As April comes to a close, most states have conducted their Severe/Hazardous Weather Awareness Weeks in anticipation of upcoming spring and summer severe weather events. During this week 26 April-2 May, no states have scheduled Severe Weather Awareness Weeks. However, Wyoming will schedule a Severe Weather Awareness Week. Later in May, Texas during the week of 21-27 May and Hawaii during the week of 31 May-4 June will conduct their Hurricane Awareness weeks. If you live in any of these states, you should take time to become familiar with the various public affairs announcements issued by your local National Weather Service Office. In upcoming weeks, other states will observe Severe Weather Awareness weeks.
HURRICANE SEASON REVIEW -- The official 1999 hurricane seasons will be starting soon in both the eastern North Pacific and North Atlantic. As a quick review of last year's statistics consult Monday'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.