textproduct: Fairbanks

SYNOPSIS

Snow showers persist today for the Central and Eastern Interior, dropping several inches of new snow in many locations. Expect snow showers to gradually weaken through the evening, with areas along the Alaska range and in the eastern Interior holding onto snow showers into tonight. A much colder and drier airmass behind this week's winter storm has already settled into Western Alaska and should overspread the rest of the state by tomorrow resulting in sub zero highs once again and lows in the -20 to -40 degree range.

Focus shifts to the next multi-day winter storm expected to impact the majority of the state Saturday through mid next week. Winter Storm Watches for blizzard conditions have already been issued from the Seward Peninsula to the North Slope and for all of the Brooks Range, including the Dalton Highway. Dangerous travel conditions likely for several days both on and off the road system for a majority of Northern Alaska. Heavy precipitation and strong winds begin as early as Friday evening in the Bering Strait, overspreading the West Coast and NW Arctic Coast on Saturday then expanding eastward Sunday. Watching the potential for mixed precipitation and temperatures near or above freezing in Coastal areas of Western Alaska south of Point Hope. While the finer details are still being worked out for this next event, confidence is increasing in widespread heavy snow and blizzard conditions for Northern and Western Alaska. There are growing concerns for anomalously high snowfall accumulations for the Arctic Coast based on latest forecast guidance. Continue checking back for the latest updates on this next impactful winter storm. Additional winter weather headlines may be needed for the Interior in the coming days as this entire systems pushes southward early next week.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Scattered snow showers continue this evening and tonight for the Eastern Interior. Additional accumulations of 1 to 3 inches possible.

- Wind Advisory is in effect for the Upper Tanana Valley tonight through late Friday morning for wind gusts up to 45 mph.

- Much colder temperatures Friday through the weekend with lows potentially below -30F Saturday and Sunday mornings.

West Coast and Western Interior...

- Much colder air tonight and Friday with double digit sub zero low temperatures.

- A series of Winter Storm Watches have been issued for the Seward Peninsula, Baldwin Peninsula, and Noatak Valley for potential blizzard conditions beginning late Friday night.

- A chance for a wintry mix is possible across the portions of the YK-Delta coast, Seward Peninsula, and St. Lawrence Island. Chances for the mixed precipitation will start late Friday, early Saturday morning.

- Significant snowfall accumulations expected this weekend north of the Seward Peninsula, including Kotzebue and surrounding areas.

North Slope and Brooks Range...

- Another significant multi-day winter storm to impact the Arctic Coast and North Slope from Saturday through at least Monday with widespread blizzard conditions and heavy snow. Wind gusts may reach 55-70 mph along the NW Arctic Coast and through the Brooks Range.

- Anomalously heavy snow accumulations expected for the North Slope and Arctic Coast

FORECAST ANALYSIS AND DISCUSSION

Winter storm warnings remain in effect across the Interior as convective snow showers persist through the Central and Eastern Interior through this evening. Upper troughing continues to deepen over Northern Alaska with the its axis and associated upper level boundary directly over Fairbanks and the Central Interior. The surface front will continue eastward into the Eastern Interior tonight, ushering a much colder airmass for the next several days. Today's set up is prime for convective snow showers capable of producing snowfall rates up to 1" per hour with very high snow to liquid ratios. Fairbanks 12z RAOB soundings indicated very steep lapse rates of 8.0C/km above an inversion 2400 ft agl. Lift along both the surface and upper level boundaries combined with a saturated dendritic growth zone and 25-35 kts of shear have resulted in heavy convective snow showers today. Cold air advection along and just behind the front may steepen lapse rates even more, adding additional instability for heavy snow showers. As of 1 PM, Fairbanks has picked up an additional 5 inches of snow since midnight with surrounding areas and those at higher elevations observing even more. PVA ahead of an upper level shortwave dropping south from the north slope should promote additional lift for continued snow shower activity into tonight with satellite and radar imagery confirming this threat. Will note that as cold air advection continues this evening, the entire column becomes colder than the dendritic growth zone, leading to snow grains rather than larger snow flakes. Snow showers later this evening and tonight will likely have much lower snow to liquid ratios due to the small snowflakes, slowing down the rate of accumulations, but still expect windy conditions and low visibility under any snow shower.

Looking over the West Coast, a ridge continues to build up over the Bering Sea setting up northerly flow aloft and further advecting the aforementioned arctic airmass into the state. Double digit sub zero low temperatures expected tonight for the west and those areas that clear out. The core of the arctic air shifts east into the weekend, becoming centered over the Eastern Interior. With 850mb temps as low as -25 to -30C, would not be surprised for typical cold valleys to reach -40F on Saturday morning and possibly Sunday morning.

Focus now shifts to a significant multi day winter storm expected to impact the majority of Western and Northern Alaska Friday evening through at least early next week. Mid and long range guidance has been consistent in showing a deep fetch of tropical moisture in the vicinity of Hawaii being advected northward around a North Pacific high and into the Arctic. With strong high pressure in place for several days, the atmospheric river of moisture will be aimed at the West and Northwest Coast Friday evening through Monday. ECMWF EFI has highlights a significant portion of the NW Arctic Coast and nearly all of the North Slope for the possibility of significant snowfall amounts well outside of climatology for this time of year. With how long this atmospheric river will be aimed a the state, would not be surprised to see record breaking daily snowfall amounts from Kotzebue northward and across much of the North Slope. In addition, with the building ridge, strong southwest flow advects a warmer airmass northward with highs near or above freezing in Coastal areas on the Seward Peninsula and points southward. These areas have a better chance at seeing a transition to freezing rain or rain at times Saturday and Sunday before colder air advects back in on the backside of this entire system.

Widespread blizzard conditions and high winds expected with this next system within the Bering Straight, Around Kotzebue and the NW Arctic Coast, through the majority of the Brooks Range and along the North Slope. Southerly winds along the coast may gust over 60-70 mph at times while southerly gap winds through the Brooks Range and along the Dalton Highway could exceed 50+ mph later this weekend and into early next week.

EXTENDED FORECAST DAYS 4-7

The multi day significant winter storm persists into the long term as the threat for widespread significant snowfall accumulations push into the interior. The strong ridge over the North Pacific, directing an intense atmospheric river into Alaska, slowly flattens out end of the weekend and into Monday as lower pressure traverses the Arctic Coast. As the ridge flattens and the entire axis shifts into Northwest Canada, strong moisture advection becomes aimed at the West Coast and Interior, shifting the impacts further south. This pattern supports widespread heavy snowfall accumulations throughout the interior as tropical moisture advects in from the west/southwest. Mid range guidance does show strong wind shear through the column, which may again lead to fracturing dendrites and lower snow to liquid ratios. With that said, even with SLRs closer to 10:1 or 12:1, the anomalously high amounts of QPF expected may still result in broken daily snowfall records.

Mid week and beyond, confidence is increasing in another extended stretch of arctic air for the majority of Northern Alaska. Longer range guidance has been consistent showing an arctic trough settling over the state by midweek, with 850mb temps in the -25 to -35C range through next weekend. Double digit sub zero temperatures likely each morning for the majority of the Interior and Northern Alaska in the extended range. Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Winter Storm Watch for AKZ801-814>818-820>823. Winter Storm Warning for AKZ834-838>847. Wind Advisory for AKZ836. PK...Brisk Wind Advisory for PKZ807. Brisk Wind Advisory for PKZ808-809-812-855. Brisk Wind Advisory for PKZ810-811-856>858. Brisk Wind Advisory for PKZ817-854.