The following highlights of the national weather have been extracted from the surface weather map for Thursday night:
UNSETTLED WEATHER MOVES ACROSS NORTHEAST -- Scattered areas of snow were moving eastward across Upstate New York and northern New England on Thursday evening. Some thunderstorm activity was detected over the offshore waters of southern New England. By late evening, some locations in Maine had received nearly two inches of snow. This precipitation was associated with two weather systems. One system was a relatively compact low-pressure system that had developed off the North Carolina coast early Thursday and traveled northward along the coast, passing east of the New England coast during the evening. Winds circulating around the northern and western sides of this low were bringing humid air in from off the North Atlantic. The other weather system was a weak low-pressure center and accompanying cold front that was moving eastward across southern Canada. By evening, the low-pressure center was located over Ontario's St. Lawrence Valley with a cold front trailing across sections of Upstate New York.
The offshore low-pressure system was forecast to deepen on Friday as it travels northeastward over the North Atlantic waters past Nova Scotia. Wrap-around precipitation circulating around the southwestern quadrant of the low on northerly winds should continue producing scattered areas of rain along the southern New England coast, while snow across the higher terrain of New York State and northern New England. Nearly one quarter of an inch of liquid-equivalent precipitation was anticipated.
QUIET BUT COOL -- An elongated ridge of high pressure stretching from Lake Ontario southward to the lower Mississippi Valley was responsible for tranquil weather and relatively cloud-free skies across a large section of the Midwest and Southeast on Thursday. Some clouds were associated with a cold front that moved southward across the central and eastern Great Lakes. However, no significant precipitation accompanied this front that reached northern Ohio before dissipating during the late evening. Temperatures across much of the nation east of the Mississippi River during the late evening were lower than what they had been 24 hours earlier, with the largest temperature departures occurring over the western Lakes and the Ohio Valley, where Thursday's temperatures were 10 to 15 Fahrenheit degrees lower.
The high-pressure ridge was expected to drift eastward on Friday. By evening, the ridge axis should lie along the Eastern Seaboard. Because of the clear skies and weak winds in combination with cool and dry air mass, early morning temperatures were expected to fall to the low 30s across the interior Southeast. Therefore, freeze warnings and frost advisories were posted through early Friday morning for sections of the Southeast, stretching from west Tennessee eastward to the Piedmont of North Carolina, along with the Tennessee Valley across northern sections of Alabama and Mississippi.
WARM WESTERN WEATHER EXPANDS EASTWARD -- The dome of unseasonably warm air that has been located over the Southwest earlier in the week has spread eastward across the Rockies and out on to the Plains on Thursday. Afternoon high temperatures ranged from 10 to 20 Fahrenheit degrees above the long-term average highs of early November across the Plains, the Rockies and the Intermountain West. Nearly three dozen stations across nine Western states reported high temperatures on Thursday that either tied or broke previous daily high temperature records. In addition to setting daily record high temperatures, monthly high temperatures were reached at Sidney, NE (81 degrees) and Salt Lake City, UT (75 degrees).
The warm air was expected to spread eastward across the Plains and the Mississippi Valley on Friday and Saturday. A broad south to southwest flow of winds across the region should result in warm air advection across the Plains and the Midwest. The warm front located over the western Dakotas was expected to move northeastward, signaling the advance of the warm air.
STORMY WEATHER HITS PACIFIC NORTHWEST -- Widespread clouds and several large bands of moderate to heavy precipitation had moved onshore along the Washington and Oregon coasts during the evening hours of Thursday. While most of the precipitation was falling as rain, some snow was detected across the higher terrain of the Cascades. Several isolated thunderstorms were detected along the Washington coast and over the offshore waters, indicative of unstable atmospheric conditions. These clouds and precipitation were along and ahead of a strong cold front that was approaching the coast during the late afternoon. Eventually, this front came onshore during the early evening. By late evening the precipitation had spread inland as far as the northern Panhandle of Idaho.
Strong winds also were accompanying the front, with south winds along the coast in advance of the front, but shifting to southwesterly in direction over offshore waters following frontal passage. Winds along the Oregon coast gusted to 91 mph at Garibaldi and 89 mph at Sea Lion Caves on Thursday afternoon.
Northern sections of the cold front were forecast to travel quickly eastward reaching the northern Rockies before dawn on Friday morning and the Plains of North Dakota by evening. Southern sections of the cold front would move southeastward before stalling over northern sections of California and Nevada.
An onshore flow of humid air from the Pacific should result in significant amounts of orographically enhanced precipitation along the western slopes of the Olympics, the Cascades and the Coastal Ranges. Liquid-equivalent precipitation totals ranging between one and three inches were forecast for these mountains during the 24 hours ending late Friday afternoon. Nearly one inch of precipitation could also fall along the western slopes of the northern Rockies in the Idaho Panhandle. Passage of the cold front would bring in sufficiently cold air on west and northwest winds that snow levels should drop along the Washington Cascades and Olympics from 5500 to 3000 feet on Friday. Therefore, a winter weather advisory was in effect through late Friday evening for the Cascades and the Olympics as up to 11 inches of snow could fall. Farther south, the winter weather advisory was to run through early Sunday morning in the Oregon Cascades, since six to ten inches of snow were anticipated.
The winds circulating around the deep storm in the Gulf of Alaska were generating giant ocean swell that was propagating southeastward across the eastern North Pacific. High surf warnings and advisories were to be in effect along the Washington, Oregon and northern California coasts from midmorning Friday through late Saturday after noon. The giant ocean swell would reach the coast and could produce waves and breakers with heights to 28 feet. Hazardous sea warnings were also posted for the coastal waters southern Oregon and northern California running through Sunday afternoon due to the winds and high seas.
The eastward movement of the cold front would result in strong winds through many of the valleys of the Northwest. Several wind advisories were issued for the Columbia River Basin in Washington and Oregon. Winds associated with the front could gust to 50 mph. A high wind warning was posted through Friday evening along northwestern Montana's Rocky Mountain Front near Glacier National Park. Westerly winds with sustained speeds reaching 45 mph could have gusts to 75 mph through some of the mountain passes following frontal passage.
UPPER AIR -- The 500 and 300-mb charts for 00Z Friday showed that the wave pattern in the mid and upper tropospheric flow pattern had progressed eastward from 24 hours earlier. A height trough associated with cold air over the East was located over the eastern Lakes and the Northeast. A large height ridge had moved eastward out onto the Plains, reflecting the warm air spreading across the region from the Intermountain West. A deep height trough was moving onshore along the West Coast, associated with the cold air behind the powerful cold front that came onshore into the Pacific Northwest. The wind flow was to the north around the ridge over the Plains and southward around the eastern trough.
TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 11 degrees at Daniel, WY and Farson, WY. Thursday's highest temperature was 93 degrees at Mesa, AZ.
ALASKAN WEATHER -- A powerful storm located over the northern Gulf of Alaska dominated the weather across much of Alaska on Thursday afternoon. The storm's center, which was located approximately 400 miles south of Prince William Sound, had a minimum central pressure of 946 mb. An occluded front associated with this storm curved southeastward and then southward along the Alaskan coast and sections of the Panhandle. Since the central pressure was relatively low, a tight pressure gradient surrounded the storm's center, resulting in strong winds across much of the state. Strong southeasterly winds were found across the Panhandle and southeast Alaska, where winds ranged between 25 and 40 mph at Ketchikan and Gustavus, while strong northeasterly winds were reported as far north as Barrow. Southwestern Alaska and the eastern Aleutians experienced strong northwest to west winds, with winds gusting to 70 mph at Cold Bay and 58 mph at Dutch Harbor. A weak trough of low pressure was located over western Alaska, primarily over the Seward Peninsula. Clouds were found across southern and western sections of the state. Snow fell across the North Slope and the northwestern coast, while snow and rain were found across the Aleutians. Much of the Panhandle and coastal sections of south central Alaska experienced steady rain.
The lowest overnight temperature in Alaska on Thursday morning was 15 degrees below zero at Anaktuvuk Pass, while the mid-afternoon highest statewide temperature was 54 degrees at Middleton Island.
HAWAIIAN WEATHER -- Moderate easterly trade winds returned to the Aloha State on Thursday afternoon as a ridge of high pressure moved eastward across the North Pacific north of the Hawaiian Islands. Some low clouds and showers continued to move westward across the state and surrounding waters during the late afternoon, in part due to the remnants of a cold front that had dissipated east of the Big Island. These light to moderate showers were affecting the windward sides of the islands, while the leeward sides remained relatively dry. High level cirrus type clouds remained across the western islands of the state due to a pool of cold air in the mid and upper troposphere located approximately 1150 miles west of Kauai. The high-pressure ridge was to pass north of the islands on Friday and Saturday, maintaining the moderate to fresh trade winds through much of the weekend. Another band of low clouds and showers located approximately 200 miles northeast of the Big Island should move across the state late Friday night. However, the air mass across the region was relatively stable, meaning shower activity should remain relatively light.
PUERTO RICO/US VIRGIN ISLANDS WEATHER -- Skies were partly cloudy across Puerto Rico, Culebra, Vieques and the Virgin Islands late Thursday night. Isolated to scattered rainshowers were detected moving westward over the coastal Atlantic and Caribbean waters by radar. A few of these light showers were passing across northern sections of Puerto Rico. A weak low-pressure trough had passed across the region during the morning hours resulting in increased northeasterly winds, followed by a weakening in speed as the winds turned to a more southeasterly direction following passage of the trough axis. With a weak pressure gradient across the region during the late evening, surface winds were light and generally from the southeast. Widely scattered rainshowers should continue into Friday morning across area waters. By afternoon, the typical buildup of clouds, showers and thunderstorms should occur over the islands due to daytime heating. Over the weekend, a frontal boundary was expected to pass across the region, producing increased shower activity and winds.
EYE ON THE TROPICS -- During the early morning hours, Tropical Storm Ida intensified to become the third hurricane of the 2009 North Atlantic hurricane season over the southwestern Caribbean offshore of Nicaragua. As a minimal category-1 hurricane (on the Saffir-Simpson Scale), Hurricane Ida made landfall along the coast 75 miles north of Bluefields, Nicaragua. By early afternoon, Ida weakened to a tropical storm as it moved inland across high terrain. As of early evening, Tropical Storm Ida weakened sufficiently and was downgraded to a tropical depression as maximum sustained winds surrounding the depression's center weakened to 35 mph. At that time, the center of Tropical Depression Ida was located approximately 40 miles west-southwest of Puerto Cabezas, Nicaragua, as it traveled to the north-northwest of 5 mph. The current forecast has Ida continuing to weaken on Friday as it moves northward across northeastern Nicaragua and eastern Honduras. However, it could intensify again after the tropical depression emerges over the northwestern Caribbean Sea early Saturday. Although Ida had weakened to a depression, the flood threat continued, as rainfall accumulations of five to seven inches were possible over coastal sections and between 15 and 20 inches over the elevated terrain in Honduras and Nicaragua. Flash floods and mudslides were possible. A tropical storm watch was in effect for the northeast coast of Honduras.
Although no organized tropical cyclones were found across the eastern North Pacific on Thursday evening, the National Hurricane Center continued to monitor an area of low pressure located approximately 270 miles south of the border between Mexico and Guatemala. This rainshowers and thunderstorms in this low-pressure area had diminished slightly, but forecasters gave this system a medium chance of becoming a tropical cyclone before Saturday night as this low would drift to the north or northeast.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast