textproduct: Fairbanks

SYNOPSIS

A strong coastal storm pushing into the Chukchi Sea will be the primary driver of inclement weather conditions for the next few days. Strong winds and onshore flow along the Bering and Chukchi coastlines will continue to produce high surf and coastal erosion through Friday afternoon. Meanwhile very heavy rainfall associated with an atmospheric river will take aim on the West Coast and western Brooks Range tonight and early Friday with the heavy rain threat slowly shifting east towards the Interior by the weekend.

KEY MESSAGES

Central and Eastern Interior... - Continued cool and damp conditions are expected across much of the Interior for the next few days. Highs will be a tad bit warmer Friday (generally 50's and lower 60's) before dropping back into the 50's over the weekend.

- A warm front associated with a storm in the Chukchi will continue to bring widespread precipitation to the Interior through this evening with rain tapering off by Friday morning.

- A second wave of precipitation will push into the region later Friday and continue into parts of Saturday as a cold front associated with the Chukchi low moves eastwards. This feature will also tap into an atmospheric river, so rainfall may be heavier in some locations. Additional rainfall amounts through the weekend could range from 0.50" to 1.50". - By early next week, another low is expected to move into the Bering Sea and bring additional chances for rain and gusty winds across the Central/Southern Interior, especially for the Alaska Range.

West Coast and Western Interior... - High Surf Advisories remain in effect through late Friday night along the coast from the Yukon Delta to Kivalina for water level rises around 2 to 5 feet above the normal highest high tide line.

- High Wind Warnings remain in effect through Friday afternoon for St. Lawrence Island and the Bering Strait for wind gusts up to 65 mph.

- Due to the influence of an Atmospheric River, storm total rainfall amounts through Saturday will be around 0.25" to 1.00" regionwide.

- Highest rainfall totals are expected to across the Southern Seward Peninsula, along the southern slopes of the Western Brooks Range, and throughout the Kobuk/Noatak/Wulik River Valleys where 1.50" to 2.50" is possible. Locally higher amounts nearing 2.75" to 3.50" are also possible across the higher terrain due to strong upslope flow.

- By early next week, a new low pressure system is expected to move into the Bering Sea Monday into Tuesday bringing yet another round of widespread rain and gusty winds to Western Alaska. No coastal major impacts are expected right now, but we will continue to monitor this system over the next few days.

North Slope and Brooks Range... - As a storm enters the Chukchi Sea, widespread rain and gusty winds will continue.

- Strong onshore flow will continue to impact the NW Arctic Coast where high surf and minor coastal erosion is expected.

- High Surf Advisories remain in effect for the NW Arctic Coast from Point Hope to Wainwright for water level rises around 3 to 5 feet above the normal highest high tide line. High Wind Warnings also remain in effect through Friday afternoon for Point Hope to Point Lay for wind gusts up to 65 mph.

- Storm total rainfall amounts through Saturday will range from 0.50" to 1.00" regionwide, with the highest rainfall totals in the Western Brooks Range around 1.50" to 2.50". Locally higher amounts nearing 2.75" to 3.50" is possible across the higher terrain due to strong upslope flow.

- By early next week, the Chukchi Sea low will continue to progress farther east into the Beaufort Sea with the potential for a coastal low-level jet to develop along portions of the Beaufort Sea coastline. This area will continue to be monitored for the potential of very strong winds Late Sunday and into monday.

SHORT TERM /THROUGH SUNDAY NIGHT/

A potent coastal storm continues to unfold along the west coast of ALaska as well as along the Northwest Arctic Coastline as a strengthening surface low slowly emerges from Russia's Chukchi Peninsula into the Chukchi Sea proper near Wrangel Island tonight. The upper atmospheric pattern remains unchanged with an associated upper trough over the Chukchi region while an anomalously strong Pacific ridge extends into the northern Gulf of Alaska. This setup lends high confidence to the eventual path of the surface low as models all agree on an eastward progression across the southern Beaufort over the next several days.

Sensible weather highlights for the rest of today and into tonight will still focus on strengthening southwest flow through the Bering Strait and into the southern Chukchi. This wind direction represents mostly onshore flow for west coast communities leading to much higher than normal water levels through tonight and into parts of Friday. Several High Surf advisories along with High wind Advisories and Warnings will remain in effect through Friday as a result.

Aside from the short term wind concerns, there is also a threat for very heavy rainfall. A warm frontal boundary that has advanced from the west coast through the Interior the past 24 hours has continued to prime the area with widespread moderate rainfall. Southwest flow aloft will tap into an atmospheric river which will focus a band of heavy rainfall from the Seward Peninsula through the western Brooks Range and up onto the western North Slope tonight and Friday. Storm total rainfall amounts will range from 0.50" to 1.00" regionwide with the highest rainfall amounts expected in the Southern Seward Peninsula, south slopes of the Western Brooks Range, and the Kobuk/Noatak/Wulik River Valleys. In these areas, rainfall amounts will range from 1.50" to 2.50" with locally higher amounts nearing 2.75" to 3.50" possible across the higher terrain due to strong upslope flow. Hydrologic concerns across this area will continue through the early weekend as runoff and saturated soils could play a role inn some localized flooding. Additional information on this is found below in the Hydrologic section.

This atmospheric river will shift eastwards towards the Central and Eastern Brooks Range as well as much of the Interior for Friday evening into Saturday. Additional moderate will fall in these areas as well as the weekend gets underway. In general, additional rainfall amounts of 0.10 to 0.50" can be expected in these areas as the cool damp conditions of the past several days continues. However, some drying could set in, especially for the Interior by late in the weekend.

Meanwhile the tail end of the weekend will not be as pleasant along the eastern Arctic coastline as the remnants of the original surface low over the Chukchi advances eastwards. While models are all in agreement that this system will result in additional precipitation across portions of the North Slope, there are disagreements on the intensity of the surface winds, especially near the coastline. While it is too early for any headlines, the potential for high winds from Utqiagvik to Kaktovik will exist Sunday into early Monday as a potential coastal low-level jet sets up near the coastline.

LONG TERM /MONDAY THROUGH THURSDAY/

Our extended period begins on Monday with an arctic low north over Alaska, and low pressure system moving north into the Bering Sea. As the Bering Sea low progresses north it will force a ridge east over Alaska by Tuesday morning. Tuesday evening through Wednesday morning, the Bering Sea low will strengthen as it begins to approach the West Coast. Wednesday morning the arctic low's flow will get wrapped into the Bering Sea low, which will deepen the cyclone, and strengthen it before it moves through Alaska on Wednesday afternoon. As the storm travels across Alaska throughout Wednesday it will travel northeast up the ridge leaving our area Thursday morning.

Model guidance has shown a greater confidence and alignment in the Bering Sea low's track, as well as the atmospheric river associated with these systems. Guidance shows the Bering Sea low progressing north through the Bering Sea, and then moving east towards Alaska. During this time, guidance has suggested that the atmospheric river, that previously was directly headed for our area, will now instead trend east and be caught within the pacific highs flow. Which as a result, directs the heaviest amounts of atmospheric moisture east away from our area. Although there is enough evidence to see a diminish in the moisture supply with this storm, the Bering Sea low still will likely hold a substantial amount of atmospheric moisture within its core as it tracks towards Alaska.

Due to the previous moisture that was supplied by the atmospheric river, this storm has the potential to produce a substantial amount of rainfall for majority of the Western Interior, and YK-Delta. There is a chance for the South/Central Western Interior receiving rainfall accumulations up to a total of 2 inches Wednesday through Thursday, with the West Coast seeing amounts anywhere between 0.5 to 1 inch. As this storm rides up the ridge over the eastern portion of Alaska, the cyclones circulation can shift to a more southerly trend. If this occurs, the remaining amount of moisture will likely be downsloped, and light to moderate rainfall accumulations would impact the Eastern Interior Wednesday through Thursday. However, there is general uncertainty in all of these rainfall totals, and will continue to be monitored through the week until higher model confidence is demonstrated.

Throughout the extended, wind gusts are expected with this upcoming storm. When the low approaches the Bering Sea Monday through Wednesday it will form a pressure gradient with the sustained ridge over Alaska. This pattern supports development of a 925 mb Jet, and as the northern low's arctic air gets wrapped into the Bering Sea low, chances for these winds to mix down to the surface increase. If this pattern persists, the YK-Delta, Southwestern Interior, West Coast, and Alaska range may experience another round of gusty winds Wednesday morning. Exact wind gust speeds still need to be monitored but at this current solution, models are suggesting the Yk-Delta, West Coast, and Southwestern Interior seeing gusts between 30 to 40 mph Tuesday through Thursday. If the Bering Sea low supports southerly flow on its approach to Alaska Tuesday through Wednesday, gusts could potentially reach warning criteria along the Alaska Range, specifically within Isabel and Windy pass. However, there is discrepancy on the low track through the Interior.

COASTAL HAZARD POTENTIAL

A strong low is quickly moving into the Chukchi Sea this afternoon bringing gusty southwesterly winds along the West Coast. These gale force winds and a long fetch of southwesterly flow will result in water rises of 2 to 5 feet above mean high water from Hooper Bay to Point Lay. The highest water levels will be from Golovin to Unalakleet. The areas of the biggest concerns will be Golovin due to it potentially reaching 5.5 feet which could begin to overtop the berm, and Kivalina due to heavy rain in the Wiluk River basin draining into the lagoons surrounding the community paired with an additional 2 to 4 feet of storm surge. We are not anticipating any significant impacts, but we are continuing to monitor the situation as it evolves.

Due to a roughly 48 hour prolonged period of strong southwesterly winds, there will be multiple high tide cycles that will be elevated. Waters are slowly rising today along the Norton Sound and the Yukon Delta Coastline, reaching their peak Thursday night before gradually returning to normal by late Friday night. For communities along the Kotzebue Sound and NW Arctic Coastline, waters will begin to rise early Thursday morning and peak Friday morning before gradually returning to normal Saturday morning.

FIRE WEATHER

A weak trough is moving through the Tanana Valley this afternoon and will eject southeast towards the AlCan Border. This trough could bring a quick round of isolated to scattered showers to the Upper Tanana Valley with the best chances from Tok to Delta Junction. Accompanying this rain will be gusty northwesterly winds up to 20 to 25 mph from Tok to Northway. Moving into the overnight hours these winds will begin to subside. As the trough moves east a ridge of high pressure will quickly move into the region. This will bring a brief warming and drying trend for the Upper Tanana Valley tomorrow morning. Temperatures will rise into the upper 60s and potentially 70 degrees. Minimum RHs will be around 35 to 40 percent, but increasing cloud cover in the afternoon will help to moderate these RHs.

Friday evening and into the overnight hours a cold front from a coastal storm will begin to move through the Tanana Valley bringing gusty winds, cooler temperatures, and wetting rains. The driest point in the Upper Tanana Valley will be Northway, but still should pick up 0.10" of rainfall as the front moves through the region. Looking ahead in the Upper Tanana the rest of the weekend looks to be mild but dry as weak ridging is over the region. Another system Monday to Wednesday could bring another round of wetting rains, but there is a lot of uncertainty with this storm.

HYDROLOGY

A strong low is moving into the Chukchi Sea late Thursday night and will be accompanied with an atmospheric river extending to the tropics. This atmospheric river will help to produce 72 hour rainfall totals of 0.5" to 2.5" for most of Northern Alaska. The wettest areas will be the Southern Seward Peninsula and the south slopes of the Western Brooks Range will be the wettest. Friday and into Saturday the front that brought the moderate to heavy rainfall will drape and stall across the northern slopes of the Alaska Range. This could help to produce 0.75" to 1.5" of rainfall in 24 hours from Denali Park to the White Mountains including the FNSB. This rainfall isn't looking likely that it will produce any flooding impacts, but could create rapid rises in the smaller tributaries.

In the Western Brooks Range and Northwestern Interior particularly the Kobuk, Noatak, and Wulik a hydrologic outlook has been issued. With the continued periods of heavy rainfall in the region the smaller streams will be more vulnerable to see bankfull conditions and rapid rises. No flooding in this region is expected.

Across most of Northern Alaska the mainstem rivers are rising due to multiple rounds of moderate to heavy precipitation, but with enough time in between rounds of precipitation the main stem rivers have stayed below action stage. However, on the smaller creeks and streams could see rapid rises and/or bankfull conditions. Recreators should be prepared for rapidly changing water conditions in the smaller tributaries.

AFG WATCHES/WARNINGS/ADVISORIES

AK...High Wind Warning until 4 PM AKDT Friday for AKZ801-820-821- 827. High Surf Advisory until 4 AM AKDT Saturday for AKZ801-802- 815>818. High Surf Advisory until 10 PM AKDT Friday for AKZ820>822-824- 825. MARINE...Small Craft Advisory until 1 PM AKDT Friday for PKZ801-850. Small Craft Advisory until 4 PM AKDT Friday for PKZ802-803-853. Small Craft Advisory until 6 PM AKDT Friday for PKZ804>810-816- 817-852-854>856. Gale Warning until 10 AM AKDT Friday for PKZ806. Gale Warning until 7 PM AKDT this evening for PKZ807. Gale Warning until 10 PM AKDT this evening for PKZ810-856. Gale Warning until 1 AM AKDT Friday for PKZ811. Small Craft Advisory until 4 AM AKDT Friday for PKZ811-857. Small Craft Advisory from 1 PM to 6 PM AKDT Friday for PKZ811- 812-851-857. Small Craft Advisory until 7 AM AKDT Friday for PKZ812-858. Gale Warning from 7 PM to 10 PM AKDT this evening for PKZ812. Small Craft Advisory from 10 PM this evening to 4 AM AKDT Friday for PKZ813. Small Craft Advisory from 7 PM this evening to 6 PM AKDT Friday for PKZ814. Small Craft Advisory from 4 PM to 6 PM AKDT Friday for PKZ815- 858. Small Craft Advisory until 10 AM AKDT Friday for PKZ851. Small Craft Advisory from 1 AM to 4 AM AKDT Friday for PKZ859. Small Craft Advisory from 10 PM this evening to 6 PM AKDT Friday for PKZ860.