616 FXAK69 PAFG 252126 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 126 PM AKDT Tue Jul 25 2017 .DISCUSSION... Models...Surface initialized well against the 25/18Z analysis. They are in good agreement out to around 84 hours before differences start showing up in the major features. The big difference being how they handle the upper level low that will move moving south over the west coast. Over the Arctic persistent westerly flow will continue, but by Friday afternoon models diverge on how the ridge builds north over the Beaufort Sea. Aloft...At 500 hpa...A 521 dam low high in the Siberian Arctic will persist with ridging building over the Beaufort Sea Friday and Saturday, so westerly to southwesterly flow will persist over the Arctic through the weekend. A 554 dam low over the Bering Strait will continue to dive to the southeast to be over King Salmon by Wednesday afternoon, and continues south into the Pacific. A 562 dam low over the northeast Pacific will move northeast into British Columbia by Wednesday evening. Ridging from a 597 dam high over the north Pacific will build north over the Chukchi Sea tonight, then rotate southeast Wednesday night with the axis extending from Amchitka Island to Nuiqsut by Thursday morning, then extending north along 150W. By Friday morning the ridge will rotate to lie over the Alaska Peninsula to Lake Iliamna to Anchorage to Demarcation Point and north over the Beaufort Sea. A 553 dam low over the Sea of Ohkotsk will move northeast into Siberia, then east of the Chukotsk peninsula by Thursday evening, then over St Lawrence Island by Friday evening at 558 dam with troughing extending from Unimak Island north to St Lawrence Island then over 170W. At 850 hpa...No significant change in temperatures into Wednesday, then a warming trend over the interior that will continue into the weekend. Surface...A broad area of low pressure with a 1010 mb low over the Upper Yukon Flats, 1010 mb low over Kotzebue Sound, and a 1012 mb low over the southwest mainland this afternoon. A cold front lies from Kotzebue to Russian Mission to Togiak this afternoon and will move southeast to lie from Sleetmute southeast over Kodiak island by Wednesday morning. The thermal trough which lies over the upper Yukon Flats will slide south to the Upper Tanana Valley and north slopes of the Alaska Range by Wednesday morning. A ridge is continuing to build over the eastern Bering Sea, Chukchi Sea, and Arctic Coast with a 1020 mb high over the Gulf of Anadyr, a 1020 mb high over the Chukchi Sea, and a 1018 mb high over MacKenzie Bay. By Thursday morning the ridging will lie from the eastern Bering Sea to the Bering Strait to Barrow and east with a 1021 mb high near St Matthew Island, a 1021 mb high over Barrow, and a 1020 mb high north of MacKenzie Bay. Wednesday night a cold front will move to the Bering Strait then stall over the area Thursday as it decays. The high over Barrow will move east to be just north of MacKenzie Bay Thursday morning at 1022 mb. As the high moves east the Thermal trough will slide a bit north to lie from Northway to Livengood, then southwest to McGrath. Arctic Coast and Brooks Range...A weather front moving through the area will be east of the area by Wednesday morning. Expect some clearing skies Wednesday from west to east across the area as mainly offshore flow develops with the high moving east. Temperatures will generally be in the mid 40s to mid 50s on the coast and 50s to lower 60s inland Wednesday, then rising Thursday with coastal areas rising into the 50s to lower 60s, and inland areas reaching into the 70s. The warmer temperatures will last into the weekend. Winds turning east to southeast at 5 to 20 mph for most areas the remainder of the week. West Coast and Western Interior...cloud to mostly cloudy conditions will continue over the coastal areas this week with periods of showers. There will be a little break Wednesday with some clearing before the next system moves to the eastern Bering Sea bringing another round of showers to the area. For the inland areas clearing early Thursday will last into Friday, then increased clouds and a chance of showers. Temperatures quite a bit warmer on Thursday after it clears out, then cooling back down a bit with the increased cloudiness. Winds northwest at 5 to 15 mph for most areas, with 20 to 30 mph winds on some of the outer Capes. As the next system moves to the Bering Strait Thursday, winds will snap around to southeast to south with 10 to 20 mph winds over the coast, and 15 to 30 mph winds on the Capes. Winds inland will generally be less than 10 mph. Heaviest rainfall has ended over the Upper Noatak and Upper Kobuk Basins and streams remain high so Advisory will continue into the evening then be reevaluated. Central and Eastern Interior...Isolated to scattered showers continue across the area through Wednesday afternoon then clearing. Rainfall amounts generally less than one tenth inch, some locations in the Alaska Range could see up to one quarter inch. Isolated thunderstorms south of Chicken this evening, then over most of the area on Wednesday. Clearing across the Central and Eastern Interior Thursday with warming temperatures that will last through the weekend. Central interior will see some increased clouds on Friday with a chance of showers as front pushes over the West Coast. Winds will generally be light, but they pick up to 10 to 20 mph along the AlCan Border north of Eagle and over the Upper Yukon Flats Wednesday night and Thursday. && Coastal Hazard Potential Days 3 and 4...None. && .Fire Weather...Pretty quiet with isolated to scattered showers through Wednesday evening, then a drying trend for all the interior areas. Isolated Thunderstorms over the eastern and southeastern interior Wednesday with the thermal trough over the area, then over the Upper Tanana valley along the north slopes of the Alaska Range to the Upper Kuskokwim and Middle Yukon south of Galena Thursday. High pressure building in will bring drier and warmer conditions to the Central and Eastern Interior, but no Red Flag conditions expected. && .Hydrology...Heaviest rainfall has ended over the Upper Noatak and Upper Kobuk Basins and streams remain high so Advisory will continue into the evening then be reevaluated. Significant rises in the middle Koyukuk River near Bettles with this last rain event, but everything remains well within banks, so no issues. && .AFG WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory for PKZ210-PKZ220-PKZ225. && $$ SDB JUL 17 |