The following discussion is based upon the major weather features appearing on Monday night's surface weather maps:
SLOW-MOVING STORM IN THE MIDWEST -- A large cloud and precipitation shield covered a large portion of the nation's midsection on Monday evening due to a slow-moving storm. The storm, which formed over northern Texas on Sunday evening, had slowed as it moved northeastward across the mid-Mississippi Valley. As of early evening, the storm's low-pressure center was located over southeastern Missouri. A nearly stationary warm front extended eastward from the low pressure center across the Ohio Valley to the Appalachians and the Middle Atlantic States, while a cold front trailed southward along the lower Mississippi Valley to the central Gulf Coast and out over the Gulf of Mexico.
The cloud and precipitation shield formed the familiar comma-shaped appearance characteristic of midlatitude storms. Relatively steady rain fell across sections of the Midwest to the north of the storm's center and warm front, covering a region that stretched from northern Ohio westward to the Missouri Valley separating Iowa and Nebraska. To the west of the storm's center, snow was falling across eastern Kansas in the colder air. A line of showers was found across the Southeast, paralleling the cold front, from Tennessee southward across Mississippi and Alabama.
Between one and two inches of rain had fallen across sections of the mid-Mississippi Valley on Monday according to radar estimates, with the largest amounts found across sections of south central and eastern Missouri. Ottumwa, IA received 1.53 inches of rain on Monday, which set a daily maximum precipitation record for the date. As of Monday evening, a section of the Illinois River had risen above flood stage, while the Mississippi River near the confluence with the Illinois was a foot below flood stage. Flood warnings had been posted along the Illinois and Mississippi Rivers along with several tributaries.
To the west of the storm, snow fell in the colder air across Kansas and Nebraska. As of Monday evening, between four and twelve inches of snow had fallen across sections of northern Kansas. The weight of the accumulated snow caused power lines to break.
Since the storm has been cut-off from the main upper tropospheric westerly wind flow, the surface low-pressure system could take a slow meandering path. On Tuesday, the storm's low-pressure center was forecast to reach the St. Louis metropolitan area. Ultimately, the pressure center should reach northeastern Missouri by Wednesday evening, a northward displacement of approximately 300 miles in two days. While the storm's center moves slowly northward, the storm should undergo the usual occlusion process associated with midlatitude storms. The nearly stationary warm front should remain across the Ohio Valley, while the cold front sweeps eastward across the Southeast, eventually overtaking the warm front. An occluded front would develop where the cold front overtook and merged with the warm front.
Significant rainfall was forecast to continue across the mid-Mississippi Valley in association with this storm. Rainfall forecasts for the 24 hours ending early Tuesday evening indicate totals approaching 1.75 inches across sections of northeastern Missouri, southeastern Iowa and western Illinois. Flood watches were continued across this region through Tuesday afternoon. Although thunderstorm activity could occur across the lower Ohio Valley on Tuesday, no severe thunderstorms were anticipated.
Winter weather advisories were continued through midmorning on Tuesday across northeastern Kansas and northwest Missouri, including the Kansas City metropolitan area. Several inches of snow were expected. However, since temperatures were above freezing, most of the accumulation should be on grassy surfaces.
STORMY WEATHER CONTINUES ACROSS THE NORTHWEST -- The other area of unsettled weather across the nation on Monday was found across the Pacific Northwest. Clouds, precipitation and windy weather conditions continued across western sections of Washington and Oregon as of mid-evening, due to a series of weather systems moving across the region.
A low pressure system moving across Vancouver Island and into British Columbia during the early morning hours of Monday was accompanied by a warm front that moved into western Washington before dawn, while a cold front stalled along the coast. By late afternoon, this front came onshore and dissipated, as another low pressure system and accompanying front approached the coast. By evening, this new frontal boundary was located approximately 300 miles of the Washington coast.
Between four and five inches of rain fell across Washington's Olympic Peninsula and along the coast as of late afternoon. Quillayute reported a record 3.31 inches of rain on Monday, while the Seattle Weather Forecast Office received 0.84 inches, which also set a daily maximum precipitation record.
In addition to the locally heavy rain, strong southerly winds also accompanied the approach of the fronts. Several stations across Washington and Oregon had sustained winds to 45 mph, with gusts exceeding 70 mph. A wind gust reached 95 mph late Monday evening near Waldport along the central Oregon coast. Some non-thunderstorm wind damage was reported.
The low-pressure system and accompanying front were forecast to reach the coasts of British Columbia, Washington and Oregon during the predawn hours of Tuesday. By late afternoon, the low-pressure center would have crossed the southern Canadian Rockies, while the cold front would have moved into the interior Northwest after passing over the Cascades.
A broad area of precipitation, in the form of low elevation rain and mountain snow, should follow the cold frontal passage. Unlike weather systems in the Midwest and East that have most of the showery precipitation ahead of the cold front, much of the precipitation associated with fronts moving into the Pacific Northwest is often found behind the frontal passage. The onshore flow of humid air from the eastern Pacific would cause precipitation that would be enhanced by the orographic lifting over the Olympics, the Coastal Ranges and the Cascades. Cooler air moving in behind the system could also become destabilized. Some isolated thunderstorms are also possible. Between two and three inches of liquid-equivalent precipitation were forecast to fall across the coastal sections of Washington and Oregon during the 24 hours ending late Tuesday afternoon.
Although snow levels were high on Monday evening due to warm air brought in to the Northwest on southerly winds, these snow levels should drop with passage of the cold front and the arrival of cold air on Tuesday afternoon. Winter weather advisories were posted for the Oregon Cascades, effective for most of Tuesday. Between six and ten inches of snow were expected above 2000 feet, while up to a foot of snow could fall around Mount Hood and nearby Mount St. Helens in southern Washington. Farther south, a winter weather advisory was in effect for the Sierras of California from Tuesday afternoon through early Wednesday morning as two to four inches of snow could fall above 4500 feet elevation near Lassen Peak National Park following the cold front passage.
Strong winds were also expected along the coast with the approach of the cold front. Gale warnings were in effect for coastal waters from Cape Flattery, WA southward to Cape Mendocino. Inland, high wind warnings and wind advisories were in effect across the Northwest.
QUIET WEATHER CONDITIONS -- While the Midwest and the Pacific Northwest experienced unsettled weather, other sections of the nation had uncharacteristically quiet weather for mid-November. A large area of high pressure located over the central Rockies and the Great Basin helped maintain the tranquil weather and relatively cloud-free skies across the Southwest and the Rockies. A ridge of high pressure extended eastward across the upper Mississippi Valley and over the western Great Lakes north of the storm located over the mid-Mississippi Valley. Skies across the northern Plains and the upper Mississippi Valley ranged from clear to partly cloudy.
Freeze warnings were in effect across the southern Plains, running from south central Kansas southward to the Edwards Plateau of south central Texas.
UPPER AIR -- Both the 500 and 300-mb charts for 00Z Tuesday had a cutoff flow situation across the nation's midsection associated with the slow-moving surface low-pressure system located over the mid-Mississippi Valley. Nearly circular and closed patterns of height contours surrounding a height trough were found on these two upper-air charts, centered over southwestern Missouri and eastern Kansas. The height trough was associated with a column of cold air that extended up through the entire troposphere from the surface low-pressure center. A counterclockwise wind circulation was found at the two pressure levels. Winds on the 300-mb level were in excess of 100 knots around the southern side of this height trough. This trough and its circulation were cutoff from the flow of westerly winds that were moving across central Canada. Therefore, the storm system was slow moving due to the absence of steering winds.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Monday was 6 degrees below zero at Greeley, CO and Laramie, WY, while Monday's highest temperature was 84 degrees at Miami (Kendall-Tamiami), FL.
ALASKAN WEATHER -- A ridge of high pressure stretched across northern Alaska from a high-pressure center over Far East Russia to a weaker high pressure center over northwestern Canada. A lobe of this ridge also extended southeastward across the Bering Sea toward the eastern Aleutians. Due to high pressure, partly cloudy skies were found across many areas of western and northern Alaska. The high-pressure ridge was also accompanied by a cold arctic air mass. Afternoon temperatures across interior Alaska remained near 30 degrees below zero. Cloudy skies and snow were found along the Arctic and Beaufort Sea coasts due to a weak trough of low pressure located along the state's northern coastline. Skies were also cloudy across southeastern and eastern sections of the state due to a large complex low-pressure area located over the northern Gulf of Alaska. This low-pressure area had multiple low-pressure centers, with one center situated south of Prince William Sound and another center along the coast of the southeast Panhandle south of Sitka. Snow fell in the Fairbanks area in east central Alaska southward to Juneau in the Panhandle, while rain fell at Ketchikan in the southern Panhandle. A tight pressure gradient between the high-pressure ridge over the Bering Sea and the area of low pressure over the northern Gulf produced strong northerly winds across southwestern and south central sections of the state. Cold Bay had gusts to 40 mph, while Whittier had gusts to 55 mph. Farther west, a frontal system associated with a storm near Russia's Kamchatka Peninsula was bringing clouds and rain to the western and central Aleutians.
A wind chill advisory was posted for the Susitna Valley north of Talkeetna in south central Alaska through late Tuesday morning as winds between 15 to 30 mph along with ambient air temperatures to 15 degrees below zero could send wind chill temperatures down to near 45 degrees below zero.
The state's lowest temperature on Monday morning was 44 degrees below zero at Huslia. The highest temperature across Alaska as of midafternoon on Monday was 43 degrees at Shemya and Annette.
HAWAIIAN WEATHER -- Scattered to broken low clouds, along with scattered to numerous showers were traveling to the west-southwest across the Aloha State on Monday evening, carried along by strong east-northeast trade winds. The clouds and showers were the result of unstable atmospheric conditions caused by an upper tropospheric pool of cold air. The lower troposphere was also relatively humid. The strong trade winds were caused by a tight pressure gradient across the island between a large high pressure cell centered over the North Pacific well to the north-northwest of the islands and a trough of low pressure near the equator. The prevailing winds and the numerous rainshowers were causing relatively wet conditions on the windward slopes of the islands. Since the winds were strong, some of the showers were crossing over to the leeward sides of the smaller islands. With cold air aloft, some of the precipitation fell as snow on Monday atop the Mauna Kea summit on the Big Island. The trade winds were expected to increase in strength on Tuesday as the high was forecast to strengthen as it passes north of the state.
With strong trade winds, high wind-driven waves were responsible for a continuation of the high surf advisory for the north and east facing coasts of the islands though early Wednesday evening. In addition, a small craft advisory due to strong winds and high seas that cover all state waters should continue through Wednesday.
PUERTO RICO/US VIRGIN ISLANDS WEATHER -- Although rainshowers decreased across eastern Puerto Rico, Culebra, Vieques and the Virgin Islands late Monday night, cloudy skies remained across the islands and surrounding waters. Some light showers and several isolated thunderstorms continued to move onshore from the southwest across southwestern Puerto Rico. More showers were detected over the waters of the Caribbean to the south of the islands and over the Atlantic to the north. The showers and thunderstorms earlier in the evening resulted in several rivers reaching flood stage across central interior Puerto Rico. The showers and thunderstorms were associated with a weak trough of low pressure located across the region. Aloft, a large pool of cold air in the upper troposphere located north of the islands helped destabilize the regional atmosphere, resulting in the convective precipitation. While surface winds across the islands were light and variable, southerly winds extending up through much of the troposphere helped provide a feed of abundant equatorial water vapor that produced the heavy rainfall totals. Following a relatively quiet early morning, more rainshower and thunderstorm activity was forecast for Tuesday afternoon and evening.
EYE ON THE TROPICS -- No organized tropical cyclones were detected across either the North Atlantic or the eastern North Pacific basins on Monday evening; no cyclone development was anticipated through Wednesday.
REPORT FROM THE FIELD --Joe Joyner, LIT Leader from Virginia Beach, VA, reported on the nor'easter that blasted southeastern Virginia and northeastern North Carolina at the end of last week. This storm contained remnants of the former Hurricane Ida. Joe said that some areas near where he lives had precipitation totals that exceeded 10 inches of rain in a 24-hour span. Schools, colleges, universities military installations, federal agencies, and many businesses were closed for all or a portion of Thursday and Friday. Apparently, the storm caused flooding that was comparable to the flooding seen in the area from Hurricane Isabel in September 2003. He also forwarded portions of articles from the Virginian-Pilot, the local newspaper, that showed a large 570-ft container barge that ran aground along a nearby beach due to the strong onshore winds.
The National Weather Service is mandated by Federal law to monitor, predict and provide necessary information to the public on impending destructive weather or hydrologic events. These events can be grouped into local convective or severe weather, tropical, marine, winter storm and other non-precipitation events. Public statements issued for various winter storm events were previously described in the Week 10 Tuesday Concept for the Day. These statements conform to a specific wording that the National Weather Service uses to alert the public to various hazardous events. In general, the following terms are used:
Most of the watches for the country, to include all severe local storms, are currently issued by the Storm Prediction Center in Norman, OK. Watches for tropical weather events are issued from the National Hurricane Center near Miami, FL. However, warnings for specific local weather events are issued by the local Weather Service Offices when hazardous weather events are occurring in their area of responsibility.
For a description of the terminology used in the official statements issued by the National Weather Service to inform the public of severe local storms, please read the Tuesday optional Supplemental Information .
To be submitted on the lines for Tuesday on the Study Guide, Week 11 Chapter Progress Response Form, under section B. Daily Summary.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast