A STORM DEVELOPS IN THE NORTHERN PLAINS -- Several weak low pressure centers that traveled across the Rockies were developing into a storm system that would affect the Midwest by Wednesday. A weak low pressure system and trailing cold front were moving eastward across the high Plains of southern Saskatchewan and eastern Montana on Monday night. The storm system had come onshore along the Pacific Northwest coast late Sunday and had moved eastward across the Cascades and northern Rockies. Widely scattered precipitation associated with this low pressure system was found across the western Dakotas, Montana. and Idaho. Some of the precipitation fell as rain, while snow fell at higher elevations.
Farther south, another weak low pressure center was situated over the high Plains of Colorado. Some mountain snow had fallen in association with this sytem over Colorado and Wyoming, while rain was detected across western Nebraska. Snow advisories remained in effect for the north central mountains in Colorado through Monday night, as 5 inches of new snow could fall at elevations above 10,000 feet and winds could gust to more than 40 mph.
The northern storm system appears to be the system that is expected to move eastward across the Plains on Tuesday. The low pressure center is forecast to reach the Missouri Valley near Bismarck, ND by morning and south central Minnesota by evening. Winter weather advisories remained in effect through Tuesday morning for portions of southeastern South Dakota, northeastern Nebraska, southwestern Minnesota and northwestern Iowa. Freezing rain and ice pellets (sleet) changing to snow are forecast. As much as 4 inches of new snow is anticipated. A high wind watch was in effect through early Tuesday morning for western South Dakota, to include the Black Hills and the Badlands, for northwest winds with speeds between 30 to 45 mph, along with gusts to over 44 mph.
ANOTHER STORM ON THE HORIZON -- A developing storm system approximately 1000 miles to the west of the northern California coast is expected to approach the Pacific Northwest coast by Tuesday evening. Coastal precipitation and increased winds should announce the approach of this next storm system, which should have become relatively intense with a central pressure less than 980 mb. Gale warnings were posted for the Washington State coast from Cape Flattery to Cape Shoalwater. A winter storm watch was posted for northern California, effective for Tuesday night and Wednesday, as high winds reaching 60 mph and heavy snow, with accumulations of greater than 12 inches are anticipated, especially at the higher elevations of the coastal mountains and the northern Sierras.
High surf, with 8 to 10 foot breakers, was expected to continue along the central California coast into Tuesday. The surf was produced by the northwest ocean swells that propagated from a strong storm over the North Pacific Ocean at the end of last week.
BLUSTERY WEATHER LINGERS OVER NEW ENGLAND -- Some scattered light snow continued to fall across northern Maine in the wake of the storm system that had traversed the Gulf, South Central, Middle Atlantic and New England States over the Thanksgiving weekend. The storm system was located over the Maritimes late Monday night, with a trough line extending westward from the low center across New England and the St. Lawrence Valley of Quebec.
While the low continues to pull away from New England toward the northeast on Tuesday, light snow is still expected across the region on Tuesday.
PLEASANT WEATHER ACROSS THE SOUTHEAST -- A large high pressure cell centered over the eastern Gulf Coast contributed a relatively tranquil weather regime. Afternoon high temperatures were relatively close to the daily average high temperatures. This pattern should continue through Tuesday.
UPPER AIR -- Both the 500 and 300 mb charts for 00Z Tuesday depict a relatively zonal flow regime in the mid and upper troposphere. The observed winds and the height contours show that the flow is primarily from west to east, with few north-south excursions. A wind maximum of 100 knot winds at the 300 mb level over Colorado reflect the developing storm system over the Rockies. The current lack of a large north-south excursions, which are typical of a meridional circulation pattern, indicates a momentary pattern of rapidly moving surface weather systems with few large swings in the temperature across a large portion of the country.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Monday was 5 degrees at Butte, MT, while Monday's highest temperature was 80 degrees at Monrovia and Hemet, CA.
ALASKAN WEATHER -- A storm system located to the south of the Alaska Peninsula was responsible for unsettled weather across the eastern Aleutians and southern Alaska. Rain fell across the Panhandle and at Kodiak, while snow fell at Valdez, Cordova and Bethel. Farther west, a developing storm system was located southwest of Shemya in the western Aleutians. Weak low pressure was also noted over interior Alaska, contributing to light snow across western Alaska, to include Tanana, McGrath and Bettles.
High pressure over eastern Siberia maintained a large arctic air mass over northern Alaska. The southern edge of this cold air was an arctic front that remained relatively stationary from near Dillingham in southwest Alaska to the Yukon Territory in the east, passing near the Anchorage Bowl. Strong northeast winds, coupled with low temperatures, helped drive wind-chill equivalent temperatures down to 50 degrees below zero at Kivalina, Barrow, Point Hope and Shishmaref. Snow was reported at Deadhorse.
The state's lowest temperature on Monday morning was 17 degrees below zero at Arctic Village. The highest temperature across Alaska as of midafternoon on Monday was 45 degrees at Metlakatla.
HAWAIIAN WEATHER -- Except for some showers that were detected by radar east of Kauai, most of the islands were relatively free of precipitation and clouds on Monday afternoon. A shear line, a remnant of a cold front was dissipating to the north of Kauai. Trade winds also strengthened during the afternoon as a result of a subtropical high pressure cell moving eastward across the North Pacific to the north of the 50th State. These strong trade winds, with speeds reaching 20 to 25 mph, should continue through Wednesday. Because of the strong winds, small craft advisories were in effect for state waters.
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, Part B, Applications, Week 11 Chapter Progress Response Form, under section B. Daily Summary.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast