textproduct: Fairbanks

SYNOPSIS

The multi-day winter storm continues to impact a good portion of Northern Alaska today with the heaviest snow now shifting into the interior. Winter weather hazards remain in effect through Tuesday, slowly ending from west to east as conditions improve on the backside of the system. The overall winter storm has been going according to forecast with many locations across Northern Alaska breaking daily precipitation records. Satellite and radar imagery today continue to show heavy snow bands throughout the interior with snowfall rates of 0.5 to 1 inch per hour at times and brief periods of visibility at or below a quarter mile. Widespread heavy snow begins to taper off across Western Alaska this evening with the back edge slowly pushing eastward tonight. Expect the area of heaviest snow to shift into the Central and Eastern Interior tonight through early Tuesday, where another 5 to 10 inches of additional snow may accumulate. By Tuesday afternoon, scattered snow showers remain in the eastern Interior and along the Alaska Range, while the main area of heavy snow lingers in the Eastern Brooks Range and Upper Tanana valley. Westerly winds increase along and behind the cold front sweeping across the state over the next 24 hours. Gusty westerly or northerly winds have already began across the far Western and Northwestern portions of the state and will shift eastward with the front. There will likely be a period Tuesday where gusty winds along and behind the front occur with leftover snow showers in the Central and Eastern Interior. This may lead to periods of blowing snow and brief white out conditions at times through the day, including the Fairbanks area.

Focus shifts to an extended period of well below normal temperatures for this time of year as a much colder and drier arctic airmass settles into the state, beginning Tuesday and persisting into the first week of March. Temperatures under clear skies will drop into the 20s and 30s below zero Tuesday morning for the western and northern portion of the region, then across all of the Interior by Wednesday morning. Typical colder valleys and wind sheltered areas may see daily morning lows nearing the -40F range over the next week. With the sun angle quickly rising into the first week of March, expect larger diurnal ranges in this pattern as afternoon highs reach the -0s to -10s.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Winter Storm Warnings and Advisories remain in effect through at least Tuesday. Expect an additional 6 to 12 inches of snow for the Fairbanks North Star Borough and Western Alaska Range through Tuesday.

- Gusty westerly winds through the Tanana Valley and Eastern Interior may lead to periods of blowing snow on Tuesday,particularly southeast of Delta Junction where winds could gust up to 40 mph. - Northerly gap winds through Alaska Range passes will strengthen Tuesday night/Wednesday morning with gusts up to 45 mph through Thursday morning.

- An extended period of well below normal temperatures arrives Wednesday with daily lows in the -30F to -45F range.

- Large amounts of snow on frozen rivers and streams is leading to areas of water overflowing the ice. Use caution while travel along or on frozen waterways.

West Coast and Western Interior...

- Improving conditions for the West Coast the this evening into tonight as heavy snow ends and shifts east. Blowing snow may persist along the Bering Straight, western Seward Peninsula and NW Coast.

- Periods of mixed precipitation continue within the YK Delta this afternoon before tapering off tonight.

- A extended period of well below normal temperatures for this time of year continues through the weekend with lows in the -15F to -35F range and highs remaining below zero.

North Slope and Brooks Range...

- Strong westerly winds with gusts up to 45 mph will swell along the coast east of Utqiagvik. Periods of blizzard conditions are possible along the Arctic Coast through Tuesday. Strong winds persist through Wednesday along the Coast east of Prudhoe Bay.

- Another round of snow and blizzard conditions expected for the Central and Eastern Brooks Range and North Slope tonight and Tuesday.

- An extended period of below normal temperatures expected this week with temperatures in the -20F to -45F range.

FORECAST ANALYSIS AND DISCUSSION

A record breaking multi-day winter storm continues to impact a large portion of Alaska today and tomorrow. A strong north pacific high remains in place south of the Aleutians, directing a deep plume of tropical moisture northward into the arctic and over the top of the ridge. Numerous shortwaves within the jet stream have brought renewed waves of precipitation into the state, resulting in many broken one day precipitation and snowfall records. The North Pacific ridge is showing signs of breaking down today as a polar low develops in the high arctic, slowly flattening the top of the ridge and directing the bulk of the moisture advection into the Interior. Over the next 24 hours, the top of the ridge continues to flatten, resulting in a 140 kt jet west-east jet streak over Southwest Alaska, placing much of the Central and Eastern Interior in an area of enhanced lift. 500mb Vort maps depict a mid level feature within the jet over the western interior while observations indicate a surface reflection underneath. These features traverse eastward across the Interior tonight and Tuesday within the left exit region of the upper jet. Forecast soundings indicate a deep and lowering dendritic growth zone during this period as cold air advection filters in from the north. This scenario is ideal for heavy snow with higher snow to liquid ratios and efficient dendrite production through at least mid morning on Tuesday. There is high confidence that the heaviest snow from this entire event is likely to occur this evening through early Tuesday morning for the Central and Eastern Interior in this pattern with an additional 6 to 12 inches of snow possible over the next 24 hours.

As the surface low passes by, winds shift to the west/northwest behind the cold front. Gusty northwest winds are already being observed across the West and Northwest Coast today resulting in areas of blowing snow. Due to such strong cold air advection behind the front, expect steep low level lapse rates tomorrow throughout the Interior with westerly wind gusts of 20-35 mph mixing down to the surface at times. Watching the Eastern Interior, Alaska Range, and Tanana Valley tonight into tomorrow as there will be an overlap with the gusty winds and snow showers, leading to periods of blowing snow and low visibility, and brief whiteout conditions. During the daylight hours tomorrow, as cold air continues to advect in, much of the atmospheric profile will be falling below the optimal dendritic snow growth temperatures, leading to a transition to tiny snow grains rather than larger dendrites seen today. This may lead to periods of even lower visibility than seen on Monday, especially when combined with gusty winds.

Quick note for the YK Delta, southwest flow continues to keep many locations in SW Alaska at or above freezing. Many locations in the YK Delta are reporting mixed precipitation today from the same system that is bringing heavy snow to areas further inland. Observations and surface plots already show colder air filtering in from the north as the main surface low tracks eastward. Expect a brief transition to snow later this evening then plummeting temperatures and drying conditions this evening into tonight.

A big pattern change is on the way for Northern Alaska as the parade of storms finally ends, replaced by a strong polar low and arctic airmass. A deepening sub 500mb upper low over Chukchi sea drops southeast into Alaska, becoming Centered over the Western Interior by Wednesday morning. This system essentially pushes the Pacific Ridge well to the southwest and cuts of moisture advection into the state. At the same time, a strong 1040mb+ polar high over Siberia nudges into Alaska, working with the polar low aloft to bring in a much colder arctic airmass. Temperatures at 850mb are expected to drop as low as -20C to -35C over state through possibly the first week of March. Confidence is increasing in daily low temperatures at or below -40F in Interior Valleys, beginning as soon as Wednesday morning. Due to the increasing sun angle, daily highs should rise into the -0s to -10s range.

EXTENDED FORECAST DAYS 4-7

The arctic airmass explained above continues to impact the state well into the long term period. Confidence is high that an extended period of dry and well below normal temperatures for this time of year will persist into the first week of March. By the start of the extended period on Thursday morning, the coldest upper-level air appears to be over the southern and eastern Interior as well as the eastern Brooks Range resulting in widespread morning low temperatures in the -30F to -40F range. Potential is there for interior valleys to make a run for -40F to -50F, however expect temperatures that low to be confined mainly to the coldest valleys. As mentioned above, there is enough daytime heating at this point in the year to bump high temperatures up into teens below zero during the day. Looking further into the long term, this cold and dry pattern is expected to continue. Lower resolution, long range guidance typically is not cold enough in these types of patterns, so expect low temperatures to be well below most model guidance for at least the next week or so.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Winter Weather Advisory for AKZ836-837-849. Winter Weather Advisory for AKZ851-852. Winter Storm Warning for AKZ812-825-826-830-831. Winter Weather Advisory for AKZ814>818. Winter Weather Advisory for AKZ820-821. Winter Storm Warning for AKZ822-823. Winter Storm Warning for AKZ824-828-829. Winter Storm Warning for AKZ804-805-808>810-832-834. Winter Weather Advisory for AKZ833-835. Winter Storm Warning for AKZ838>846. Winter Storm Warning for AKZ847. PK...Brisk Wind Advisory for PKZ801-811. Brisk Wind Advisory for PKZ802-814. Brisk Wind Advisory for PKZ803-815-852-857-860. Brisk Wind Advisory for PKZ804. Gale Warning for PKZ805>807-853-854-856. Gale Warning for PKZ808-809-855. Gale Warning for PKZ810. Brisk Wind Advisory for PKZ812. Brisk Wind Advisory for PKZ813-859. Gale Warning for PKZ816-817-850-861. Brisk Wind Advisory for PKZ858.