162 FXAK69 PAFG 162318 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 318 PM AKDT Mon Oct 16 2017 .DISCUSSION... Models...Trending toward colder pattern next couple days. Initialized well against the 16/18Z surface analysis. Run to run solutions remain very good in the short term and midrange. Some significant discrepancies in the extended periods over the Aleutians that will need to be worked out over time. Models have handled the low dropping out of the high Arctic similarly with not much spread in location or strength. Temperature guidance is not very good, and in particular is not handling low temperatures well since many areas remain snow free on the ground. Will utilize a blend of the solutions for precipitation and will lean on continuity for temperatures but need to make some changes to match current trends. Aloft...At 500 hpa...Stacked low that has been over the Gulf of Anadyr the last few days continues to weaken and will eventually merge with the low dropping out of the Arctic. The low dropping out of the Arctic is 100 nm north of Banks Island at 495 dam and will move southwest to be over Point Barrow by Thursday morning at 496 dam, and over the Seward Peninsula by Friday afternoon at 500 dam. Ridging west of 160W in the Arctic and over the Chukchi Sea will continue to be pushed west as the low moves southwest and will be west of 180 by Tuesday evening. Weak ridging over the southwest mainland with a 525 dam center will continue to weaken and move east tonight and merge with ridging over the Gulf of Alaska. A shortwave associated with the Arctic low is moving over the Arctic Coast this afternoon and will continue to rotate around the low. A second shortwave will move to the coast on Tuesday afternoon, and a third on Wednesday morning. A 513 dam low over the central Aleutians will move rapidly east through Thursday then dissipate over the southeast Panhandle. At 850 hpa...Zero isotherm south of the state. The low over the Canadian Archipelago continues to spin colder air south and the -10 isotherm lies from Dawson YT to Anaktuvuk Pass to Cape Lisburne this afternoon, and will lie from Dawson YT to Bettles to Teller and west by Tuesday afternoon. By Wednesday morning it will lie from Chalkyitsik to Monday morning. By Tuesday morning it will lie almost entirely south of out forecast area. The -20 isotherm approaches the central and eastern Arctic Coast Wednesday. Surface...Weak high pressure over southwest mainland and eastern interior will weaken and pull back over the northeast Pacific and Yukon Territory. Weak high pressure over the western Brooks Range will pull back to the west. A weak trough over the Seward peninsula extends east over the upper Yukon Flats and will continue to expand as broad area of troughing develops between the 991 mb low near Banks Island, and the 975 mb low over the western Aleutians. The low near Banks Island will remain stationary through the evening, then move north Tuesday rotating west then south to be over Point Barrow by early Thursday morning. A rapidly developing low 500 nm north of Point Barrow will move to 150 nm north of Point Barrow by Tuesday morning at 998 mb and over the central Arctic Plain by Tuesday evening. High pressure west of 160W and over the Chukchi Sea will weaken and be pushed west as the low drops out of the Arctic to the coast. The low in the western Aleutians will move to 100 nm south of Cold Bay by Tuesday morning, and into the northeast Pacific tuesday night. The low over Banks Island will continue to move south after moving over the coast Thursday and will be over Kotzebue Sound by Thursday afternoon at 993 mb. Arctic Coast and Brooks Range...Could be very interesting Tuesday as the low sitting high in the Arctic moves to the Central Coast. Winds will increase from Point Barrow west and Winter Weatehr Advisories remain in place for zones 201 and 202. Conditions will be improving on the eastern Arctic Coast by morning. Snowfall amounts 2 to 4 inches but may be up to 6 inches depending on development of the low and how much moisture it will pick up. The open water factor, no sea ice within 500 nm of most of the Arctic Coast, will have unknown impact on the moisture values. Northwest winds 5 to 15 becoming north 10 to 30 mph with the strongest winds between Point Lay and Point Barrow. West Coast and Western Interior...Quiet period overall. Some Sprinkles or flurries with mostly cloudy conditions. Patchy fog along the rivers in the morning. Winds generally variable to 10 mph through Tuesday. Temperatures slightly cooler. Central and Eastern Interior...Cloudy with some flurries this evening, then some light snow developing early Tuesday morning with up to 2 inches of snow possible. Heaviest snow will be in the White Mountains and Upper Chena River Basin east of Two Rivers. Patchy fog. Generally light winds. Temperatures will continue the cooling trend with lows falling to around 20 and high around 30 in Fairbanks and vicinity. Coldest temperatures will be north of the Yukon River where lows will fall to zero to -10. Much cooler temperatures for the end of the week through the weekend across the area. && Extended forecast for days 4 to 7...Saturday through Monday models remain in good agreement. They are currently having issues with the potential of an extra tropical system being caught in the flow and moving rapidly over the Aleutians. && Coastal Hazard Potential Days 3 and 4...None. && .AFG WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory for AKZ201-AKZ202-AKZ204. Heavy Freezing Spray Warning for PKZ240-PKZ245-PKZ505-PKZ510. Small Craft Advisory for PKZ240-PKZ245. && $$ SDB OCT 17 |