textproduct: Fairbanks

SYNOPSIS

Another significant winter storm is impacting Alaska over the next several days bringing high winds and widespread heavy snow accumulations to the state. Winter weather hazards are in effect through the rest of the today for the West Coast and Western Interior, then begin for the Central and Eastern Interior by this evening. An additional 4-8" of snow is expected in areas along southern facing slops throughout Western Alaska today, with blizzard conditions persisting for coastal areas within the YK Delta, Seward Peninsula and NW Arctic Coast. Heavy snow spreads eastward into the Interior tonight, reaching the Fairbanks area before midnight. Moderate, to at times heavy, snow persists through the morning and early afternoon hours with 4-6" of snow accumulations in Fairbanks by Wednesday evening. A secondary round of snow showers develops across Western Alaska Wednesday night then pushes eastward on Thursday into the Interior, potentially dropping another couple inches of snow in areas under heavier snow showers. Drier and much colder air sets up Thursday through the weekend, resulting in the return of lows in the -20F to potentially -40F degree range each morning.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Winter Storm Warnings and Advisories go into effect this evening through Thursday where widespread snowfall accumulations of 4 to 10 inches are expected. Highest amounts likely north and west of Fairbanks where isolated spots could see 10 to 15 inches by Thursday evening.

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

West Coast and Western Interior...

- Blizzard conditions persist along the West Coast with heavy snow spreading into the Western Interior tonight into Wednesday.

- Snowfall amounts range from 6 to 12 inches along the coast to up to 15 inches of snow in the Kobuk Valley.

- Much colder air arrives Thursday and Friday with double digit sub zero lows. Expect a warming trend into the weekend ahead of the next winter storm Saturday and Sunday.

North Slope and Brooks Range...

- Strong winds and light snow continue through tonight for the Western Brooks Range/Chukchi Sea Coast and blizzard conditions around Point Hope and potentially Point Lay.

- South winds increase with gusts to 50 mph in Anaktuvuk and Atigun Pass through Wednesday evening. This may result in areas of blowing snow to 1/2 mile.

- On the south side of the Brooks Range, light snow moves in tonight with 2 to 5 inches of snow expected in Coldfoot and along the Dalton Highway through Wednesday night.

FORECAST ANALYSIS AND DISCUSSION

A strong upper level low and associated surface reflection over Western Siberia are responsible for the current round of winter weather impacting the state of Alaska this week. Satellite imagery shows an impressive fetch of moisture ahead of these systems spanning from near the Philippines to the West Coast of Alaska. Observed and forecast soundings indicate strong unidirectional southwest flow and deep saturation through the column under an area of strong lift and upper level divergence. This atmospheric river type set up with a cold airmass at the surface is ideal for widespread heavy snow and strong winds through Western Alaska and the interior. Over the next 24 hours, the upper jet and best moisture advection shift eastward into the Interior, bringing widespread moderate to heavy snowfall further eastward as well. Forecast soundings continue to show deep saturation into the Interior, but wanted to focus on snow to liquid ratios (SLR) which have an impact on overall snow amounts. While there is deep saturation through both low and mid level dendritic growth zones, strong winds and shear through the column may fracture dendrites resulting smaller flakes and lower SLRs...similar to what happened over the weekend with the initial round of snow. Confidence is still high for widespread accumulating snow across the region, but will watch snowflake type as this event unfolds as finer, smaller flakes may lead to more compaction and lower snowfall amounts, despite not change in actual liquid amounts.

By Wednesday afternoon and evening, the Alaska range cuts off southwesterly moisture advection into the Interior. Flow becomes westerly over the state as the low over Siberia moves into NW Alaska and another mid to upper level waves moves in from the Bering. A front traverses west to east across the state Wednesday, marking the shift from to westerly winds. BUFKIT soundings show enhanced lift right along this front before dry air advects in behind it, so expect a brief periods of locally higher snowfall rates, low vis, and windy conditions as the front passes through, including Fairbanks. This wind shift looks to occur around 3PM for Fairbanks and earlier in the morning/afternoon for points west. Steep low level lapse rates right along and behind the front may result in a period of convective snow showers briefly before dry air shuts off precipitation. Any convective snow shower has the possibility of produces 1-2+ inch per hour rates, low visibility, and a brief period of strong winds. A brief period of dry conditions exists post front Wednesday evening before the next wave moves in from the west.

The next round of snow Wednesday night into Thursday should be more showery in nature; however could be intense at times. A westerly flow pattern sets up during this time period with strong cold air advection aloft steepening low and mid level lapse rates with a saturated DGZ close to the surface. These potentially convective snow showers will likely be low topped; however strong omega through a near surface DGZ should lead to more efficient dendrite production and higher snow to liquid ratios. Similar to the previous day, any convective snow shower may result in 1-2+ inch per hour rates, low visibility, and a brief period of strong winds. While the bulk of the accumulating snow occurs Wednesday, several inches of additional snow should occur Thursday in the Interior. Any location that gets numerous heavy snow showers or those in westerly upslope favored areas may receive higher snow amounts than forecast.

Conditions improve Thursday for the majority of the West Coast and Western Interior as ridging builds in overhead. Watching the Northwest Arctic Coast north of the Seward Peninsula for continued blowing snow Thursday as strong winds become northwesterly under the sting jet of the surface low. Areas not prone to high winds should expect benign conditions Thursday in the west. Much drier and colder air advects in from Siberia and the high Arctic plummeting temperatures into the double digits below zero Thursday and Friday. This same arctic airmass makes its way eastward into the Interior Friday into the weekend.

EXTENDED FORECAST DAYS 4-7

A much colder and drier airmass settles in over Alaska as strong ridging builds over the Bering Straight and troughing deepens over the eastern Interior and NW Canada. Latest guidance has strong agreement on 850mb temperatures as low as -30C Friday through Saturday before the ridge shifts east pushing the core of the arctic airmass into Canada. Skies clear from west to east on Friday, keeping the eastern half of the state relatively mild compared to those areas that clear out further west. Saturday morning is expected to be the coldest morning across Northern Alaska as the core of the cold airmass overlaps with clearing skies. Saturday morning has the best chance at lows below -30F, and potentially below -40F in typically cold valleys. The arctic airmass begins shifting eastward by Sunday, however Sunday morning may be another cold one for the Eastern Interior as lows make a run for -30F to -40F once again. A "warming" trend shifts across the rest of the interior toward the latter half of the weekend and into the beginning of next week as yet another winter storm impacts the state from the southwest. More details on this next system in the coming days as longer range guidance agrees on the overall evolution and set up.

Across the west, a significant warming trend is expected by Saturday as the ridge axis aloft shifts east, placing Western Alaska in a southwest flow pattern once again with strong warm air advection ahead of the next system. Temperatures rise near the freezing mark for coastal locations this weekend with another round of heavy precipitation for the majority of the West Coast. Additional winter weather headlines may be needed as confidence increases in the finer details of the next winter storm. Friday may be the one relatively benign day for all of Western Alaska as the parade of storms continue to impact the state.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Blizzard Warning for AKZ801-815-817. Winter Storm Warning for AKZ813-814-816-819-823-824. Winter Weather Advisory for AKZ809-818-826-828-829. Blizzard Warning for AKZ820>822-825-827. Winter Storm Warning for AKZ831. Winter Storm Warning for AKZ834-838-841>846. Winter Weather Advisory for AKZ839-840-847. PK...Brisk Wind Advisory for PKZ801. Brisk Wind Advisory for PKZ802-813-850-853. Brisk Wind Advisory for PKZ803>805-812-816-817-851-852-854-858. Gale Warning for PKZ807-808. Gale Warning for PKZ809>811-855>857. Brisk Wind Advisory for PKZ859.