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Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
000 FXAK68 PAFC 191328 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 528 AM AKDT Fri Apr 19 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today through Sunday night)... The highest impact weather remains on Kodiak Island, where heavy rain has led to at least one landslide in Kodiak City. Since steady rain settled in Tuesday night, Kodiak Airport has recorded just over 6 inches of rainfall. The 5.82 inches recorded in the past two days (April 17-18) at Kodiak Airport is the highest two day total ever recorded in Spring (March through May) and the 10th highest two day total for any time of year. Kodiak climate records go back to September 1913. A Flood Advisory remains in effect for Kodiak City and surrounding areas, while a Flood Watch remains in effect for the remainder of the island. The overall pattern remains stable for now, with a strong blocking ridge centered over northwest Canada and extending westward across much of Mainland Alaska. A large vertically stacked low continues to spin south of the Alaska Peninsula and Kodiak Island, embedded within a high amplitude negatively tilted trough which extends well down into the Northeast Pacific. In between the trough and ridge is deep strong southeast flow, with an atmospheric river pointed right at Kodiak Island and the northwestern Gulf of Alaska. A stationary front is positioned over the southwestern Gulf just south of Kodiak Island. The latest in a series of upper level short-waves crossing the Gulf and Kodiak Island has exited to the Bering Sea. This has allowed rainfall rates on Kodiak to lighten up considerably. However, as one short-wave digs southeastward across the northeast Pacific, another is rotating northwestward toward Kodiak Island. As a result, rainfall rates will pick back up again through the morning hours, with the heaviest rain expected between 10am and 4pm. Rain will then lighten up significantly, or even temporally end as the short-wave passes by late this afternoon into the evening hours. At this point in time, there will be a fundamental change in what has been a stationary pattern. The upper level trough in the Pacific will continue to dog all the way toward the Northwest CONUS, cutting off the atmospheric river. At the same time, the upper level ridge will begin to retreat to the north and east, allowing winds to weaken at all levels of the atmosphere. Therefore, by Saturday a much weakened front will be positioned over the southern Gulf and Kodiak Island with much weaker upper level short-waves embedded in the flow across the Gulf. Kodiak Island will still see periods of rain tonight through Saturday night, but intensity will be light. Thus, the threat of flooding and landslides will diminish greatly as we head through the weekend. By Sunday, multiple short-waves along with the remnants of the current upper center will all morph into a newly formed upper low south of Kodiak Island. Precipitation will become more showery, with some breaks from the rain. Meanwhile, the upper level ridge will continue to produce warm and dry conditions over nearly all of Southcentral. The only exception is the southern Kenai Peninsula, which will remain along the northern periphery of the precipitation shield. Cloud cover has been extensive the past couple days. However, as the upper trough digs across the northeast Pacific and becomes more negatively tilted, flow between the trough and ridge will back toward the east. This will help clear out clouds for all except the Kenai Peninsula, bringing a return to sunny skies. Gusty winds will linger across the Kenai Peninsula and Turnagain Arm today before diminishing tonight through Saturday. The upper level ridge over Mainland Alaska will weaken on Sunday, allowing the upper low and trough over the Gulf to lift northward toward Southcentral. Models have been struggling with exactly what form the upper low and accompanying short-waves will take, but is generally looks like increasing clouds and a potential return of precipitation to Southcentral, especially for coastal areas. This will also lead to somewhat cooler temperatures. && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... As low pressure spinning south of the Alaska Peninsula moves southeastward, a shortwave rotating around the north side of the low will move westward across the Alaska Peninsula and eastern Bering Sea, bringing another round of precipitation to the Alaska Peninsula westward to Dutch Harbor through this afternoon. The short-wave and precipitation will dissipate as pushes westward into the central Bering. The pressure gradient and strong northerly flow that has persisted from the Pribilof Islands to the Eastern Aleutians will finally weaken as this short-wave moves through. Further north, localized blizzard conditions have been observed along the Kuskokwim delta coast (namely for Toksook Bay and vicinity) ahead of the aforementioned short-wave. However, snow is now pushing westward to Nunivak Island. Wind gusts and persistent snow/blowing snow along the coast will continue to diminish this morning, ending by late morning as the shortwave moves west of the region. Another short-wave rounding the north side of the Pacific low will track across Bristol Bay later today and into the eastern Bering Sea tonight. This will bring another round of precipitation along with gusty winds to Bristol Bay communities today. The Kuskokwim delta could also see a glancing blow before the short- wave exits across the Bering Sea and Pribilof Islands. Weaker short-waves embedded in the upper level flow will keep clouds and a chance of precipitation in the forecast for Bristol Bay and the Kuskokwim Delta as we head into the weekend, while the Kuskokwim Valley will remain dry. Attention will shift to the Aleutians as we continue through the weekend, with a shift in the large scale pattern. A deep upper level low will drop out of Russia into the western Bering today. It will then continue south toward the western Aleutians this weekend, ultimately phasing with a short-wave crossing the north Pacific and bringing a return to widespread precipitation and stronger winds for much of the Aleutian Islands and central Bering Sea. -DJ && .LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)... An upper level ridge is slowly losing its hold across Mainland Alaska. A Western Gulf of Alaska low weakens and slips across the Gulf to Haida Gwaii by Wednesday before dissipating. A well developed Aleutian low maintains some additional upper level support from both Siberia and and the Northern Pacific through midweek. A number of moderate shortwaves rotate through the pattern across the Aleutians and along the Western Coasts. Periods of rain spread across Southcentral Alaska through Wednesday from the Kenai Peninsula to the Canadian Border. The most active weather will be associated with the Aleutian/Bering low and its front on Monday. Heavy rains spread across the Central and Eastern Aleutians, with mixed rain and snow over the Bering with the low center. Gusty Southerly winds move with the front from the North Pacific, across the Pribilofs and St Matthew Island. Rain continues to spread into the Alaska Peninsula with the front through Tuesday, and into Southwest Alaska late Tuesday and Wednesday. Another round of locally heavy rains moves into Kodiak Island late Tuesday through Thursday. Gusty Southeasterly winds moves through the Barren Islands into Kamishak Bay Wednesday and Thursday. Kutz $$ .AVIATION... PANC...VFR conditions and light winds will persist. && $$
