The following highlights of the national weather have been extracted from the surface weather map for Wednesday night:
COASTAL STORM CONTINUES TO AFFECT THE NORTHEAST -- A powerful storm moving northward along the coast of New England was continuing to produce a wintry mix of precipitation types across the Northeast into late Wednesday evening, stretching from Pennsylvania northward to Maine and from the Atlantic Coast westward to the eastern Great Lakes. Light rain and drizzle continued along the New England coast and across eastern Maine. However, the rain had turned to snow across sections of western Maine, New Hampshire and Vermont along with western Massachusetts and Connecticut. Light snow was falling across sections of northern New Jersey and southeastern New York State. Farther inland, moderate to heavy snow was reported across Upstate New York.
The storm responsible for the continued precipitation across New England had organized off the coast of the Carolinas by late Monday night and then traveled northward along the Middle Atlantic Coast on Tuesday, reaching the southern New England coast by evening. On Wednesday, the storm slowed as it moved along the coast of Massachusetts, New Hampshire and Maine. While traveling northward, the storm went through a portion of the occlusion process in which a secondary low pressure center had formed. This new low then became the storm's primary low pressure center. By early Wednesday evening the storm's center was located off the coast of Downeast Maine. A nearly stationary warm front extended toward the northeast into the Canadian Maritimes, while a cold front curved out to the southeast across the open waters of the North Atlantic.
The storm was responsible for considerable amounts of precipitation due to the onshore flow of humid air on the northern side of the storm. Orographic lifting of the air across the higher terrain in the interior sections of the Northeast also enhanced the precipitation totals. As of midevening, storm-total rainfall accumulations exceeded five inches in Massachusetts and three inches in New York State, Connecticut, Rhode Island, New Hampshire and Maine. In addition, the storm had produced up to 20 inches of snow in Upstate New York, 19 inches in Vermont, 13 inches in New Hampshire and 11 inches in Maine.
Strong winds had accompanied the storm due to the tight pressure gradient that surrounded the storm's low pressure center. Northeasterly winds continued to gust to between 25 and 30 mph along the Maine coast as of late Wednesday evening. On Tuesday night, the observatory on top of Mount Washington in New Hampshire reported a wind gust to 85 mph.
The storm was forecast to move slowly and somewhat erratically toward the northwest across New England on Thursday before becoming stationary over northern New England on Friday. The precipitation shield associated with this storm would remain large on Thursday and contain a variety of precipitation types. Rain was expected to continue to the east and northeast of the storm as warm humid air would be brought into eastern Maine and adjacent areas of eastern Canada from the western North Atlantic. Sections of New Brunswick could receive over one and a half inches of rain during the 24 hours ending Thursday evening. Because of the possibility of continued heavy rain, a flood watch was continued for coastal sections of eastern Maine.
On the cold side of the storm, snow was expected to continue to the north and west of the storm's center, extending across the higher terrain of New Hampshire, Vermont, western Massachusetts and Connecticut. . Between six to twelve inches of additional snow were expected across sections of western New York State. Some light snow was also possible along the Appalachians to as far south as West Virginia. Ice pellets and freezing rain could form in the transition zone between the rain and the snow. Some locations across New England could have ice accumulations of ranging from one tenth to one quarter inches due to freezing rain. By Friday the areal coverage of the precipitation should begin to shrink.
As of late Wednesday evening winter storm warnings and winter weather advisories were in effect across interior sections of the Northeast, extending from northern Pennsylvania north to northern Maine. While some of the warnings and advisories would be allowed to expire during the early morning hours of Thursday, several would continue through at least Thursday afternoon across western sections of New York State.
STORMY WEATHER CONTINUES ALONG THE WEST COAST -- Light to moderate rain continued to fall on Wednesday evening across West Coast States running from northern California's San Francisco Bay area northward to Washington's Olympic Peninsula and eastward into the Panhandle of northern Idaho. This precipitation was accompanying a cold front that had come onto the Washington and Oregon coasts during the early afternoon. By late afternoon northern sections of the front had reached the Cascades, while to the south, sections of the front remained of along the northern California coast. This front was beginning to dissipate as it continued to travel eastward.
A southwesterly flow in the lower troposphere was carrying abundant quantities of water vapor from the subtropical North Pacific. Orographic lifting along the Olympics, the Cascades and the Coast Ranges was also enhancing the precipitation totals. The rainfall across western sections of Washington and Oregon was substantial, as some locations received between two and three inches of rain by late afternoon. Farther to the south, several locations in northern California received as much as one inch of rain.
A new storm had developed on Wednesday afternoon over the eastern North Pacific behind the section of the cold front off the California coast. By midafternoon the storm's low pressure center was located approximately 600 miles to the west of the northern California coast. This new storm was forecast to travel to the northeast toward the Oregon and Washington coasts. While the storm's low pressure center would remain off the Pacific Northwest coast on Thursday, the system's cold front would reach the northern California coast by early morning and proceed to move inland during the day. By evening northern sections of the front would have moved into the interior Northwest and the Great Basin of Nevada after crossing the Cascades and the Sierras. Eventually the storm's low pressure center was projected to travel across British Columbia's Vancouver Island early Friday morning. By that time the cold front would have traveled farther to the east across the Intermountain West.
The approach of the next cold front would produce widespread precipitation across areas from California northward to Washington. The orientation of the plume of humid air would bring copious quantities of precipitation to northern California. Over eight and a half inches of liquid-equivalent precipitation were expected to fall across the region to the north of the San Francisco Bay area during the 24 hours ending late Thursday afternoon. Farther to the north, nearly two inches of precipitation were forecast for the Oregon and Washington coasts, with the largest totals over the Olympic Peninsula.
Isolated thunderstorms could develop along the West Coast on Thursday. Several of these thunderstorm cells along the California coast could become severe during the afternoon and early evening as they would generate strong thunderstorm wind gusts. A Sections of coastal California from near the San Francisco Bay area near San Jose southward to the Los Angeles metropolitan area were considered to be under a marginal risk of severe thunderstorms.
Significant snowfall could fall across the higher terrain of the Sierras in California beginning Thursday evening and continuing into Friday afternoon. Some locations could receive two to feet of snow by late Friday. Winter storm warnings and blizzard warnings were issued for the Sierras. Strong winds accompanying the snow would reduce visibility to near whiteout conditions in some locations.
The approach of the next storm would produce strong winds across the West. A windstorm of major proportions could occur from Thursday evening into Friday across the Pacific Northwest. Southerly winds could gust to between 60 and 65 mph in many locations. Storm and gale warnings were in effect along most of the coastal waters extending from the Olympic Peninsula in Washington south to the Channel Islands in southern California. The storm-force winds could produce high surf and coastal flooding along the Washington Coast. Numerous high wind warnings and wind advisories were posted across interior sections of Washington, Oregon, Idaho, California and Nevada.
TEMPERATURE EXTREMES IN THE CONTINENTAL U.S. -- Wednesday morning's lowest temperature was 2 degrees above zero at Alamosa, CO. The Wednesday afternoon highest temperature was 82 degrees at Yuma, AZ.
ALASKAN WEATHER -- Weather stations across mainland Alaska reported sky conditions ranging from partly cloudy to mostly cloudy and overcast on Wednesday afternoon. Many areas had fog, including the Anchorage Bowl in south central Alaska. Satellite imagery revealed numerous clusters of low clouds across the 49th State. The clouds were associated with a broad area of low pressure that covered most of southern sections of Alaska along with the Gulf of Alaska. Multiple separate low pressure centers were scattered across this large low pressure area. The strongest low pressure center was a storm that was moving northward along the southeastern Gulf of Alaska near Haida Gwaii (formerly known as the Queen Charlotte Islands), just to the south of Alaska's southeastern Panhandle. Two other low pressure centers were located over southwestern Alaska, with one along the northern coast of the Alaska Peninsula over Bristol Bay and the other near Kodiak Island over the northwestern Gulf of Alaska. A stationary front stretching from east to west across southern Alaska lay in a trough of low pressure. Rain was reported across the Panhandle. Scattered areas of snow were detected across interior Alaska and along the southwestern sections of the state around Bristol Bay.
The pressure gradient across the state between high pressure across the Arctic and low pressure across the Gulf of Alaska remained tight on Wednesday. This tight pressure gradient resulted in strong and gusty winds, especially across northern Alaska, where gusts reached 60 mph. In the interior and across southeastern Alaska, gusts of 50 mph were reported.
A dense fog advisory was to run through late Thursday morning for the area around Anchorage and along Turnagain Arm.The lowest temperature in Alaska on Wednesday morning was 32 degrees below zero at Deadhorse. The highest statewide temperature as of Wednesday afternoon was 53 degrees at Ketchikan.
HAWAIIAN WEATHER -- Stations across Kauai, Oahu and Molokai reported mostly cloudy skies on Wednesday afternoon, while those on Maui and the Big Island remained partly cloudy. Winds were beginning to gust from the northeast and north after lighter and more variable winds had been reported earlier. The increase in clouds and gusty northerly winds signaled the passage of a cold front across the Aloha State. By midafternoon the weak cold front had reached Molokai as it was proceeding toward the southeast along the island chain. This cold front was trailing from a powerful storm that was moving toward the north off the coast of British Columbia. Satellite imagery showed a band of numerous low clouds moving southward across Kauai and Oahu in association with the passage of the cold front. Farther to the south, few clouds were seen across the islands and surrounding waters. Radar detected a line of rainshowers moving to the south across the waters between Oahu and Molokai. As much as one inch of rain fell across Kauai earlier in the day with the passage of frontal showers.
The weakening cold front was forecast to continue traveling toward the southeast along the Hawaiian Islands on Thursday. Some clouds and showers accompanying the front should continue across Maui and the Big Island through early Friday before the front weakens and dissipates. Northeasterly trade winds were expected to return across the islands as high pressure located to the northwest of Kauai on Wednesday continues to travel eastward, passing to the north of the islands. With a return of the northeast trade winds, the shower activity would favor the windward sides of the islands.
Instrumented buoys moored off the coasts of the islands continued to detect large ocean swell moving toward the southeast. This swell was producing high surf along the coasts of the islands. The high surf warning was to continue through late Thursday afternoon for north- and west-facing coasts of Niihau, Kauai, Oahu and Molokai and for the north-facing shores of Maui. Because of the large swell and the strong trade winds, small craft advisories were to run through early Thursday evening for essentially all state waters.
PUERTO RICO AND US VIRGIN ISLANDS WEATHER -- Skies began to clear across Puerto Rico, Culebra, Vieques and the Virgin Islands on Wednesday evening, leaving partly cloudy skies at most locations by late night. Satellite images revealed several large clusters of low clouds moving westward across the region, carried along by easterly winds in the lower troposphere. In addition, several high clouds were traveling eastward across the region due to upper tropospheric westerly winds. Radar imagery detected scattered light to moderate rainshowers traveling toward the west across waters of the Atlantic and the Caribbean surrounding the islands. A few showers lingered into the late evening across the islands after scattered shower activity during the late afternoon. The late night surface winds across the islands were from the east-northeast to northeast with speeds between 10 to 20 mph.
The dry and stable air mass should continue to provide fair weather conditions across the islands on Thursday. However, atmospheric humidity levels were expected to increase by Friday, which would result in more clouds and showers.
Large ocean swell approaching the islands from the north-northeast were creating high surf, rip currents and coastal flooding along north-facing coasts of the islands. High surf and coastal flood warnings were to run through at least midday on Thursday for these north-facing coasts. Small craft advisories were to remain in effect through early Friday morning for hazardous seas resulting from a combination of large swell and increasingly strong easterly to southeast winds.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2014, The American Meteorological Society.