Area Forecast Discussion
Issued by NWS Fairbanks, AK
Issued by NWS Fairbanks, AK
662 FXAK69 PAFG 180803 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 1203 AM AKDT Wed Sep 18 2024 .SYNOPSIS... A powerful occluded low is moving inland over Bristol Bay this morning. That low shifts east today and eventually clouds and shower chances increase over the Alaska Range and Southern Interior into Thursday night. An arctic trough will bring colder air and accumulating snow chances to the Brooks Range and Arctic beginning Thursday. The arctic trough will dig south this weekend bringing colder and and chances for snow even down into the Interior. && .DISCUSSION... Upper Levels and Analysis... A 530 dam low is moving east across the Bristol Bay region, in the form of a strong occluded low. The low center is currently analyzed around 991 mb near King Salmon. There is a weak shortwave trough over the NW Arctic, and another over the E Beaufort Sea. Weak flow dominates over N Mainland. The only notable gradient is over the AK Range where the south gradient is pushing gusts to 50 mph in the E Alaska Range, but this will wane quickly this morning. Forecast and Model Discussion... The low to our south will continue to shift east and weaken as it traverses the Gulf of Alaska. Weak shortwave trough energy aloft will move east across the Mainland and bring chances for rain showers over the Interior later today through Thursday. A stronger arctic trough is projected to dig south across the North Slope and into the Interior Thursday night into the weekend, which will bring snow chances to the Brooks Range and eventually into the higher elevations of the Interior. We favored a strong blend to NAM nest early for winds then the GFS thereafter, which introduces more chances for precip after Friday than the prior forecast had given the westward shift with the arctic trough. Central and Eastern Interior... Moisture will continue to move north today with increasing chances for light rainfall/showers by later this afternoon. On/off showers will prevail through Friday but will slowly be tapering off. The best chance for light rainfall accumulations will be tonight and Thursday for the S Interior and Alaska Range with light snowfall down to 2500 feet in the Alaska Range. Temps are on the downtrend for the late week as an arctic trough digs south and brings down cooler air along with chances for potential light snowfall down as low as 1000 feet by Sat morning for parts of the E Interior. West Coast and Western Interior... Light showers will move across the West Coast and Interior all the way into the late week as the flow turns westerly/onshore behind the deep low moving into the Gulf of AK. Light snow will be possible over the W Brooks Range for the later week as an arctic trough digs south, with light snowfall accumulations at elevation. This same trough will dry the remainder of the area out Friday and Saturday as the north winds kick in. Extended Forecast Days 4-7... An arctic trough digging over the Mainland will be the highlight beginning this weekend. The global numerical model guidance is strongly trending toward a solution of what the GFS has been showing for the past couple days, which is a stronger arctic trough crossing the Brooks Range and setting up over the Central and Eastern Interior Saturday through Tuesday of next week. The ECMWF has completely flipped from the past several days and now also supports this pattern evolution, which means it will be cooling with increasing chances for lower elevation snowfall over parts of the Interior this weekend. Large uncertainty at this juncture with any chances for snowfall, but it should be noted that there is a chance, possible even down to valley elevations. Coastal Hazard Potential Days 3 and 4...None. && .HYDROLOGY... Rainfall of 0.5 to 0.75 inches fell over the YK Delta and Lower Yukon Valley/Middle Kusko Valley the last 24 hours. Smaller stream and larger stem river rises are occurring, but will not be significant. Elsewhere, no concerns as rivers are running low due to fairly low snow levels. && .AFG WATCHES/WARNINGS/ADVISORIES... AK...None. PK...Small Craft Advisory for PKZ801. Small Craft Advisory for PKZ802-850-853. Small Craft Advisory for PKZ803-852. Small Craft Advisory for PKZ804. Small Craft Advisory for PKZ805. Small Craft Advisory for PKZ806. Small Craft Advisory for PKZ807. Small Craft Advisory for PKZ816-817-854-857. Small Craft Advisory for PKZ851. Small Craft Advisory for PKZ856. && $$ Ahsenmacher