Area Forecast Discussion
Issued by NWS Fairbanks, AK
Issued by NWS Fairbanks, AK
621 FXAK69 PAFG 192217 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 217 PM AKDT Thu Sep 19 2024 .DISCUSSION... .SYNOPSIS... There will be a few spotty showers possible this evening over the Mainland, with the main brunt of the showers remaining over the White Mountains. These will continue to taper off through the overnight hours with skies remaining mostly cloudy to overcast. Weak troughing remaining in place will help to develop a few showers again tomorrow. An arctic front will begin to dig southward going into this weekend with some colder air advection and the possibility of snow making it down into portions the valley floor of the Interior this weekend. There will also be more significant snowfall amounts expected for the northern slope of the Brooks Range beginning tomorrow and especially by Saturday through Sunday. Overall weak troughing to the north and another major shortwave trough moving into the Gulf of Alaska early next week will help to provide some instability for additional showers, and accumulating snow showers above 1000 ft, to continue through the mid part of next week with the colder temperatures still locked in place. && .DISCUSSION... Upper Levels and Analysis... The decaying low pressure system well to the southeast will continue to propagate eastward. There will be an Aleutian low undergoing cyclogenesis well to the south, which will track into the northeast corner of the Gulf. This will provide some wrap- around moisture, which will help for shower development over the Upper Tanana by later in the evening on Friday. Meanwhile, a weak arctic trough will begin to deepen over the North Shore and into the Interior this weekend. Another major shortwave trough with an associated strengthening low pressure center will move south and into the Gulf early next week, along with weak upper level troughing remaining over the Mainland through the mid part of next week. Forecast and Model Discussion... The weak instability in place over the Mainland, due to weak troughing, and the exiting low towards the southeast, will allow for some spotty showers to be possible through tomorrow. The low pressure moving into the northeast Gulf by tomorrow evening will increase the probability of showers by tomorrow evening and through Saturday morning over the Yukon-Tanana Uplands, with snow accumulations for the White Mtns. As the troughing over the North Shore deepens this weekend with an associated arctic front moving southward into the Interior and advecting in colder air from the north, it will bring about the possibility of snow occurring at lower levels this weekend. The NAM and GFS have been the more reliable model with resolving this features, and most of the blend has incorporated these models. The NBM has been the more heavily relied on for temperatures. Central and Eastern Interior... Spotty light rain showers will continue to be possible throughout the day tomorrow, and then the probability will begin to increase going into Saturday as the arctic front continues to dive south and advect in colder temperatures. Most of the snowfall will occur above 2000 ft through tomorrow, although these snow levels will continue to drop down around 1000 ft and possibly lower for some locations by Saturday. Depending on whether skies clear out and get cold enough for some locations Saturday night, there could even be light accumulations occurring for portions of the valley floor. West Coast and Western Interior... Light onshore winds out of the west will continue to keep some periodic light rain showers in place. The will eventually begin to mix with some snow showers over the NW Arctic and W Brooks Range by Friday and through early Saturday colder air begins to settle in, then there will be some drier air moving in with the north winds with weak high pressure building in behind the trough, which will help to limit the amount of shower activity and just keep skies mostly cloudy to overcast, with patchy fog possible. North Slope and Brooks Range... As the arctic trough continues to deepen this weekend, initial accumulating snow will be possible for the W Brooks Range by Friday of a few inches, by even more so going into the weekend, with 48 hours totals of being anywhere from 6 to 12 inches expected. At this time, it is going to be close on the timing and intensity of snowfall amounts to reach Winter Storm Warning criteria, and will continue to be analyzed as a result. Accumulations of a few inches or more will also be possible for the lower elevations, although likely remain more on the drier side over the W Arctic. Extended Forecast Days 4-7... For early to mid part of next week, the arctic troughing will remain in place, and there will also be a low pressure system to the south which will also help to increase the instability and keep the possibility of rain/snow showers in place over the Mainland, and especially for the eastern half of the Interior. The W Interior does look to be more on the drier side with the continuation of more prevailing northerly winds. Coastal Hazard Potential Days 3 and 4...None. && .HYDROLOGY... No concerns. && .AFG WATCHES/WARNINGS/ADVISORIES... AK...Winter Storm Watch for AKZ809. PK...None. && $$ Steward