textproduct: Fairbanks

SYNOPSIS

Unsettled weather will continue across Northern Alaska. Substantial snow is ongoing and will continue through tomorrow for the southern Alaska Range, especially near the Richardson Highway south of Trims Camp, for which a Winter Weather Advisory is currently in effect. Light, showery weather extending from the Lower Yukon Valley into the Central and Eastern Interior continues. These showers will be reinforced tomorrow by an incoming frontal system which will bring robust moisture, with signicant snow possible across parts of the West Coast and extending well inland. This system will also bring brisk easterly to northeasterly winds to the Bering Sea and adjacent coastal areas, which could result in blowing snow conditions in places where they can manage to combine with falling or recently fallen snow. Temperatures will drop considerably in Western Alaska with a cold airmass and northerly winds tomorrow before recovering somewhat, with a more significant drop on Tuesday next week. The Central and Eastern Interior will also see temperatures fall to a lesser extent in the latter case.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Rain and snow showers persist in the Interior with steadier snow moving into the southern AK Range through Saturday. * Snowfall totals will generally be less than 1 inch in the Interior and around 6 to 12 inches south of Trims Camp with up to 18 inches away from the road.

- High temperatures remain in the 30s and low 40s with low temps in the teens and 20s. Warmest temps are expected to reside in the Middle/Upper Tanana Valley.

- Another round of snow, potentially heavy again in the southern AK Range Sunday through Tuesday with significant accumulations possible. Lighter snow and rain possible in the Interior with minor accumulations possible.

West Coast and Western Interior... - Wind speeds along the Bering Strait with sustained winds around 15 to 25 mph continue this morning, but northeast winds increase tomorrow afternoon and continue to to increase through Saturday. * Northeast wind gusts in St. Lawrence Island by Saturday evening will be as high as 55 mph. Elsewhere along the coast, expect northeast wind gusts around 25 to 45 mph with the weakest being in Norton Sound.

- Steady snow moves into SW AK Saturday night and spreads north/east through Sunday. Blowing snow and low visibility below 1 mile at times is possible in the YK Delta on Sunday. * Snow accumulations from Sunday to Monday may be as high as 6 inches in portions of the Western Interior, especially in higher terrain.

- Similar temperatures are expected today compared to yesterday. A cooling trend arrives on Friday with highs in the teens and 20s from Shungnak to St. Lawrence Island. Highs in the low 30s from Nome to Hooper Bay and mid to upper 30s in the Interior. * Expect a continued cooling trend into Saturday with 20s to near 30 hanging on in the YK Delta, teens and low 20s north of there along the coast and upper 20s to mid 30s in the Interior.

- Wind chills as low as 20F to 30F are possible in the Bering Strait Region Saturday and Sunday as temperatures drop and winds increase.

North Slope and Brooks Range... - Areas of stratus and fog along the Arctic Coast will persist through Saturday morning but there will be breaks Saturday afternoon.

- Areas of snow move over the Central Brooks Range Friday night and continues through Saturday and into Sunday. * Snow totals around 3 to 7 inches are possible with the heaviest being around Coldfoot/Wiseman and the lightest being in Anaktuvuk/Atigun Pass.

- Light snow then moves to the North Slope with around 1 to 2 inches of snow from Umiat north and east.

- Temperatures remain chilly for the Brooks Range with highs around 0 along the Beaufort Sea Coast, single digits in Atigun/Anaktuvuk Pass, 10 to 20F near Point Hope and 20s to near 30 in the southern Brooks Range. * Low temperatures will be in the single digits and teens below zero from the Brooks Range northward with teens above zero in around Wiseman/Coldfoot.

FORECAST ANALYSIS AND DISCUSSION

A long stretch of active weather continues across Northern Alaska. A very cold ~508 dm Arctic trough is just beginning to shift southward into the North Slope, with 850 mb temperatures of around 22 C. A broad ridge extends across the eastern Gulf of Alaska, with a ~524 dm upper-level (500 mb) low over the YK Delta. The low is nearly vertically stacked with a very weak surface low; ahead of this surface low, any remaining snow in the area from yesterday has since moved north and east of the YK Delta, with some residual lights showers in parts of the southwestern Interior and Norton Sound areas. There are also a few light snow showers in the Eastern Interior, mostly in the higher terrain, although any accumulations will be minimal. With southerly flow at 500 mb and a surface gradient across the eastern Alaska Range of around 2-4 mb, there are some moderate gap winds (gusting as high as 30 to 40 mph) on the north side of Isabel Pass. These should weaken by later this morning as as the gradient decreases. Later today, a remnant shortwave from the upper low over the YK Delta will combine with another shortwave crossing the Alaska Range to yield snow showers across the northwestern Interior into the Brooks Range which will continue through Saturday night. Additional showers will form in the Central/Eastern Interior and may be convectively driven, with many forming off the higher terrain. These showers will likely continue through Saturday evening, and their precipitation type could be diurnally-driven in the valleys, with rain more likely during the afternoon/evening hours. On the south side of the Alaska Range, upsloping could lead to heavy snowfall, especially in the Eastern Alaska Range / near the Richardson Highway.

An extratropical cyclone (low) has just crossed the Aleutians into the southern Bering Sea and has a central pressure of around ~980 mb. As it moves northeastward today, it is expected to eventually attain a minimum central pressure of around ~965 mb by tonight into tomorrow. While the low-pressure center itself is relatively strong, the strongest winds are generally expected to be along the leading warm front and occluded front on the north side of the system. Here, east to northeast gale-force winds will begin to enter the northern Bering Sea by tomorrow morning. The highest winds will mostly remain offshore except over St. Lawrence Island, the western YK Delta, and the Bering Strait and Lisburne Peninsula (with winds being more northerly in these latter two cases). In addition to these strong winds, an extensive band of snow will begin to move inland; it will initially affect the YK Delta, then spread across the Norton Sound/Seward Peninsula area before overspreading the Western and Central Interior and southern North Slope. Compared to yesterday, the general model consensus has shifted from having most precipitation along a band either farther west or farther east to a broader area encompassing both solutions to an extent. In these areas, liquid-equivalent precipitation could range significantly, with lower totals around 0.2 inches on the margins to higher totals of ~0.7 inches near the center of the main band. In spite of some briefly warmer temperatures with the initial warm front, temperatures even in valleys locations in the Western Interior will remain fairly cool, with most precipitation falling as snow. Snow ratios could be high; models soundings indicate potential for saturated dendritic growth zones which could support ratios of 15:1 or higher at times. This will allow for many areas to potentially receive 6 inches or more of snow through Tuesday morning, especially between the Lower Yukon Valley and Bettles. The Dalton Highway Summits, White Mountains, and Yukon Uplands could also potentially see several inches of snow accumulation. There is high uncertainty on snow totals for the Middle and Upper Tanana Valleys given potential for downsloping, but the trend in model guidance has been more aggressively in favor of bringing numerous snow showers through the area with west to southwest flow, especially Sunday night into Monday morning, which if it panned out could permit multiple inches of snow to fall in the area.

While snow totals across much of the West Coast/St. Lawrence Island will likely be lower than inland, blowing snow will be possible where fresh or especially falling snow can combine with strong winds. Sunday, the ridging over the Gulf/North Pacific flattens out, allowing for generally zonal flow across the area at the 500 mb level. While this is normally not conducive to southerly gap flow through the mountains, the 700 and especially 850 mb upper low over Western Alaska will have a more southwesterly gradient, with a 6 to 8 mb surface pressure gradient across the mountains. This will permit breezy/gusty winds through the passes. Easterly winds will also pick up on the eastern Arctic Coast Sunday into Monday.

EXTENDED FORECAST DAYS 4-7

At the beginning of the extended time frame of Monday, cold troughing on the western North Slope will shift southward, with northerly flow on the west side of the low helping to pull very cold air across Western Alaska. This will lead to highs broadly falling below freezing. Even the Central and Eastern Interior will see highs dip by at least a few degrees into the mid or lower 30s. There is the potential for a second low in the Bering Sea around the middle of next week which could help push this cold air back out with another warm front and yet another push of precipitation across the Western and Central Interior.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Winter Weather Advisory for AKZ850. PK...Brisk Wind Advisory for PKZ806-807-817-854-856. Brisk Wind Advisory for PKZ810. Brisk Wind Advisory for PKZ811-857. Heavy Freezing Spray Warning for PKZ816. Small Craft Advisory for PKZ816. Brisk Wind Advisory for PKZ851.