The following highlights of the national weather have been extracted from the surface weather map for Tuesday night:
SEVERE WEATHER ACROSS THE PLAINS -- Numerous active thunderstorms developed along and to the east of a cold front that stretched across the Plains from northwest Minnesota to southeastern New Mexico. A weak area of low pressure had formed along the front. This front served as a boundary between warm air to the east from cooler air to the west. In the southerly flow to the east of the storm system, afternoon high temperatures ranged from 10 to 15 degrees above the average highs for the date across portions of the Plains and the upper Mississippi Valley. To the west of the front, high temperatures from the Black Hills of South Dakota westward across the Rockies and Great Basin were as much as 10 degrees below the average highs.
Some of these thunderstorms became severe, spawning tornadoes, generating high winds and producing large hail. As many as 22 tornado reports were filed with the Storm Prediction Center from both Oklahoma and Nebraska, commencing during the mid-afternoon and continuing into the evening. In Oklahoma, most of the 11 tornado reports were from Elk City in western Oklahoma eastward to Oklahoma City, roughly paralleling I-40, while in Nebraska the tornadoes were near Columbus in the east central portion of the Cornhusker State. While many of the tornadoes were short-lived and causing essentially no damage, several homes were damaged or destroyed in Cordell in west central Oklahoma and in Silver Creek near Columbus, NE. In addition to the tornadoes, straight-line thunderstorm winds also produced damage in Oklahoma, Nebraska and southwestern Missouri. Some of these winds had gusts measured to 80 mph in Nebraska. The thunderstorms also produced large hail that fell across western Oklahoma, central Kansas, east central Nebraska, southeastern South Dakota and western Iowa. The largest hailstones were approximately 2.50 inches in diameter, reported near Hays in western Kansas. The thunderstorms also produced some heavy rains in some locations. Oklahoma City, OK and Aberdeen, SD both received record rainfall totals for the date, with 2.35 inches and 1.59 inches, respectively.
The low pressure center that formed along the front is expected to move northeastward reaching central Minnesota by Wednesday morning and the northern shore of Lake Superior by evening. During that time, the cold front is expected to move eastward across the Plains to the Mississippi Valley. A moderate risk of severe thunderstorms continued through Tuesday night for portions of Oklahoma and Nebraska, while a slight risk of severe weather covered much of the Plains ahead of the storm system, stretching from the Red River Valley of north Texas to southwest Minnesota. A slight risk of severe thunderstorms remains for Wednesday across the South Central states, extending from the Edwards Plateau of southern Texas northeastward to the Ozarks of northern Arkansas and southwestern Missouri. Between 0.5 and 2.0 inches of rain could fall during the 24 hours ending on Wednesday evening over a large portion of the nation's midsection, extending from north Texas northward to the Arrowhead of northeast Minnesota. As a result of the recent rains and the expected additional rain, a flash flood watch was in effect for southwest Missouri and southeast Kansas.
ONE MORE CHILLY START IN THE EAST -- The cold air mass that accompanied a large high pressure cell finally reached the Eastern Seaboard by Tuesday evening. At that time the center of the high was located over the Atlantic Ocean off the Del-Mar Va Peninsula. However, one more morning of record low temperatures was found across the East while this high pressure system was centered over the Eastern Seaboard on Tuesday morning. Record low temperatures either tied or set in New York State at Albany and Binghamton (both 27 degrees); in Pennsylvania at Allentown (26 degrees), Reading (28 degrees), Harrisburg and Pittsburgh (both 30 degrees); in Connecticut at Windsor Locks (28 degrees); in Maryland at BWI Airport near Baltimore (28 degrees); in Virginia at Dulles Airport near Washington, DC (26 degrees) and at Lynchburg (29 degrees); in West Virginia at Elkins (23 degrees); in Delaware at Wilmington (31 degrees) and in North Carolina at Greensboro (33 degrees).
The high pressure system should continue to drift slowly toward the east, resulting in more southwesterly winds flowing across the East. As a result, overnight low temperatures should not fall as much as they had on Tuesday morning. In addition to affecting a smaller region, the air mass had undergone modification as it moved eastward. One of the signs that the cold air mass had undergone airmass modification was the fact that afternoon high temperatures along the immediate Eastern Seaboard on Tuesday were only about 5 to 10 degrees below average, as compared with larger departures earlier in the week.
CONTINUED WINDY WEATHER ACROSS FLORIDA -- Easterly winds on the southern flank of the high pressure system off the Middle Atlantic Coast remained relatively strong across Florida through late Tuesday. Since these winds were expected to continue into Wednesday a wind advisory was posted for the East Coast of Florida and a heavy surf advisory was continued for marine interests along the coast from Ocean Reef in south Florida to Altamaha Sound in Georgia. In addition to the winds, rainshowers and thunderstorms continued across the Florida Keys.
ANOTHER CHILLY START IN THE WEST -- High pressure located over the Chimney of northern Idaho was producing clear skies and light winds across much of the Northwest, conditions that are nearly ideal for rapid overnight cooling. As a result, freeze warnings were posted for the Klamath Basin of southern Oregon and northern California, the Snake Valley of southern Idaho, the Gunnison Basin of western Colorado, and a portion of the Salt Lake Basin in Utah.
A cold front associated with a storm over the Gulf of Alaska should reach the Pacific Northwest and move onshore during the late afternoon. As much as one inch of rain could fall over the Olympic Peninsula of Washington State by Wednesday evening in association with this approaching frontal system.
YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US --Tuesday morning's lowest temperature was 14 degrees at Chemult, OR, while the highest temperature on Tuesday was 92 degrees at Harlingen and McAllen, TX.
ALASKAN WEATHER -- A strong storm system along the northern Gulf of Alaska coast brought clouds, rain and strong winds to the southern part of Alaska. This storm consisted of a low pressure center situated near the Kenai Peninsula with an associated front that curved eastward across south central and southeast Alaska before turning southeastward across the Yukon and British Columbia. A tight pressure gradient developed across the Bering Sea and western Alaska as a result of the pressure differences between a strong high pressure system located over eastern Siberia and the storm over the northern Gulf. This tight gradient produced strong northwesterly winds across northern and northwest Alaska, along with cold-air advection. As a result, winter-like temperatures were found across northern Alaska, together with snow. During the afternoon rain was reported at Iliamna, Kodiak, Whittier, Valdez and at several locations in the Panhandle, while snow was falling at Galena, Kaltag, McGrath and Bethel. Strong northerly winds with gusts to over 45 mph combined with relatively low air temperatures produced wind-chill equivalent temperatures that were near 30 degrees below zero at Kivalina and other locations in northwest Alaska. An afternoon air temperature of 4 degrees below zero at Wainwright was the lowest temperature reported in the state so far this season.
The state's lowest overnight temperature on Tuesday morning was 2 degrees below zero at Barrow. The highest temperature by mid afternoon of Tuesday was 54 degrees at Ketchikan.
HAWAIIAN WEATHER -- The trade winds continued at speeds between 15 to 25 mph across the islands on Tuesday as a result of the subtropical high pressure cell located to the north of the islands. Nighttime trade showers on the windward slopes of the islands were found along with the relatively pleasant weather elsewhere across the Aloha State. The trades are expected to decrease in intensity by Thursday as the high moves toward the northeast away from the islands.
High surf advisories were in effect for the east shores of the islands, while small craft advisories were continued for all state waters.
EYE ON THE TROPICS -- Remnants of former Hurricane Iris could be found nearing the Gulf of Tehuantepec along the Pacific coast of extreme southern Mexico on Tuesday night, after crossing Belize and Guatemala earlier in the day. As Hurricane Iris moved inland it generated heavy rains, high winds and a storm surge. At least 11 people were killed when a boat was capsized at Big Creek Port in Belize. Some of the passengers on this boat were from Richmond, VA. Approximately 900 people were left homeless as several towns were heavily damaged in the wake of Iris. By daylight Iris was downgraded to a tropical depression as winds weakened to less than 39 mph during its travel over the rough terrain, away from the warm ocean waters.
MONITORING THE DROUGHT -- Read the optional Wednesday Supplemental Information concerning assessing drought conditions.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast