The following highlights of the national weather have been extracted from the surface weather map for Tuesday night:
UNSETTLED WEATHER ACROSS THE NATION'S MIDSECTION -- A large area of precipitation was spreading northward from the western Gulf coast across the Plains into the mid-Mississippi Valley. This precipitation was to the east (ahead) of an elongated trough of low pressure that had one center located along the U.S.-Canadian border in northwestern Minnesota and another center over southeastern Colorado. Most of the precipitation was falling as rain, with some light snow detected across Nebraska. Relatively heavy rains had fallen in rainshowers and embedded thunderstorms across Texas. Austin (Bergstrom Airport) received 0.47 inches, a daily record. Some of the thunderstorms along the Texas Gulf coast had the potential of becoming tornadic during the early hours of Wednesday morning.
Southerly winds to the east of this elongated storm system carried relatively warm and humid Gulf air northward. High temperatures across the Upper Mississippi Valley and Great Lakes were between 15 to 20 degrees above the average highs for the date. Marquette, MI had a record-tying high temperature of 41 degrees.
The northern low pressure system is expected to move northeastward across western Ontario on Wednesday. Some precipitation should fall along the cold front that is forecast to trail southwestward across the Plains from this low pressure center. Some of this precipitation could fall as snow. The southern low pressure center that was located over southeast Colorado is expected to move toward the east-northeast, reaching southwestern Missouri by Wednesday evening. A fairly large amount of precipitation is anticipated to accompany this storm system. Between 0.5 and 2.5 inches of rain are expected to fall during the 24 hours ending Wednesday evening from the Gulf Coast near Houston, TX and Lake Charles, LA northward across the Mississippi Valley to the Ohio Valley. As a result of the recent rains and the anticipated additional rains, a flash flood watch was posted for the lower Mississippi Valley, to include portions of Louisiana, Arkansas and Mississippi. East Texas, southern Oklahoma, most of Louisiana and Arkansas and extreme southern Missouri are expected to experience a slight risk of severe thunderstorm activity on Wednesday.
WINTRY WEATHER CONTINUES ACROSS THE SOUTHWEST -- A cold pool of air continued to dominate the weather across the Southwest and the Great Basin, where high temperatures on Tuesday were 10 to 15 degrees below the long-term average. Widely scattered snow continued to fall across the higher terrain. Flagstaff in northern Arizona had received between 4 to 6 inches of snow by late Tuesday morning. Precipitation is expected to continue to fall through Wednesday morning across Arizona and New Mexico. A variety of winter storm warnings and snow advisories were posted for the Mogollon Rim and the White Mountains of southeastern Arizona where 3 to 6 inches of snow are anticipated and across a large portion of New Mexico, where as much as 10 inches in the southwest mountains near Silver City.
Farther west, the cold air has necessitated a frost advisory for portions of the central and southern San Joaquin Valley in California.
ANOTHER STORM APPROACHES THE NORTHWEST -- A storm system moving southward from the Gulf of Alaska should approach the Washington State coast on Wednesday evening. Prefrontal precipitation is expected to spread inland ahead of this storm system. As a result, winter storm watches have been issued for Wednesday night through Thursday that cover northeastern Washington, northern Idaho and northwest Montana. As much as 8 to 12 inches of snow are expected in the Idaho mountains, while 6 to 10 inches could fall in the Montana mountains.
Gale warnings were in effect for coastal waters from Cape Shoalwater, WA to Florence, OR.
UPPER AIR -- Both the 500 and 300 mb charts for 00Z Wednesday contained an amplified height trough over the Intermountain West. This trough reflects the cold pool of air in the West that extends upward through the troposphere. A relatively strong jet stream is found on the 300 mb chart. This jet, with winds exceeding 110 knots, traveled southward along the West Coast, curved eastward around the southern extremity of the trough across southern Arizona before curving to the northeast across the Rockies and into the Plains. The winds become westerly across the eastern US.
YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Tuesday morning's lowest temperature was 21 degrees below zero at Bondurant, WY, while the highest temperature on Tuesday was 86 degrees at Fort Myers, FL.
ALASKAN WEATHER -- The ridge of high pressure that had dominated the weather across the state was drifting eastward from eastern Alaska into northwest Canada. A strong storm system brought strong winds and snow to southwestern Alaska. The storm consisted of a low pressure center located at the eastern end of Bristol Bay, along a stationary front that extended westward along the Aleutians and eastward across south central Alaska to northern British Columbia. The central pressure was 984 mb. Westerly winds gusted to 63 mph at Dutch Harbor and to 48 mph at Sand Point. Snow was also reported over the Kenai Peninsula and around Prince William Sound, while both rain and snow were found across the Panhandle.
The state's lowest overnight temperature on Tuesday morning was 27 degrees below zero at Fort Yukon. The highest temperature by mid afternoon of Tuesday was 43 degrees at Hydaburg and Metlakatla.
HAWAIIAN WEATHER -- Strong and gusty trade winds continued across the islands on Tuesday as the result of a strong 1033 mb high pressure system located well to the northeast of Hawaii. This high is expected to remain nearly stationary, weakening by Friday with a corresponding weakening of the strong trade winds. An upper tropospheric trough moving westward is expected to pass to the south of the islands and spread clouds and some locally heavy showers over the islands beginning on Wednesday evening. Winds had begun to increase at the summits of Mauna Kea and Mauna Loa, the volcanic peaks on the Big Island. Since the trough is a cold-core system, snow and ice pellets could fall on these peaks on Wednesday. As a result, a winter storm watch has been posted for the summits of the Big Island. With strong trade winds, a gale warning was issued for the Alenuihaha Channel, while high surf advisories were continued for the east-facing shores of the islands. Small craft advisories also remained for all state waters.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast