textproduct: Fairbanks

SYNOPSIS

An occluded low near Bristol Bay is expected to remain stationary through the first portion of the weekend. Shortwave troughs associated with the low will move in from the south, then southeast. Southerly flow looks to continue, resulting in gusty winds for the passes through Friday morning. Thunderstorm potential is expected to increase Friday and continuing through the weekend, highest probabilities occurring Saturday.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Increase chance for thunderstorms beginning Friday with chances increasing to around 30% in the Central Interior by Saturday.

- Seasonably normal temperatures are expected to continue across the Interior through much of the week.

West Coast and Western Interior... - Showery conditions are expected along the Lower Yukon and Yukon Delta regions throughout the week. These showers will be mostly rain, especially nearer the Western Interior, but some periods of snow and light wintry mix are possible near St. Lawrence Island and the Bering Strait Coast.

- Increased thunderstorm potential around 15% for Friday through the weekend, primarily for the Middle Yukon Valley and Upper Kuskokwim Valley, with highest chances increasing to 30% on Saturday.

North Slope and Brooks Range.. - Gusty northeasterly winds will gradually increase, to around 25 and 35 mph, along the Arctic Coast over the next couple of days. Gradient will begin to lighten by Friday night.

- Diurnal showers along the southern portion of the Brooks Range are expected to continue through the week. Little to no precipitation is expected for the North Slope.

- Chilly temperatures persist with highs in the 20s and lows in the teens along the North Slope. A gradient of temperatures across the Brooks Range with highs in the 50s to near 60 along the southern slopes and low 40s for the northern slopes.

FORECAST ANALYSIS AND DISCUSSION

A stationary weak front is expected to develop near the Brooks Range and Yukon Flats from a shortwave moving up from the south through tonight. In its wake, tight gradients near the Alaska Range will result in continued wind gusts up to 55 mph through Isabel Pass. The gusty winds will taper off throughout the day, Friday, as the low over Bristol Bay quickly fills in.

In addition to the low weakening throughout the day, Friday, a shortwave will track eastward across the gulf of Alaska, reaching the southern portions of the Alaska Panhandle by Saturday morning. This track of the shortwave will be closely monitored as it has the potential to set up East to Southeast Flow, aloft, across the Central and Eastern portions of the Interior, favorable for scattered thunderstorms. Instability will begin to increase Friday, setting up a chance for isolated thunderstorms across the Central and Northern Interior during the afternoon. As the trough progresses further eastward in the Gulf and easterly flow set up across the Interior, this will transition winds aloft to southeasterly, with inverted shortwave troughs moving from southeast to northwest. A thermal trough is expected to develop for the aforementioned area, with modest vorticity advection aloft from the passing inverted trough aloft, resulting in scattered thunderstorms. Latest guidance shows the greatest potential to be along a line from the Upper Kuskokwim to around Bettles, spreading across the White Mountains and into portions of the Fortmile Country. Broad troughing will continue across the southern portions of the state into the mid weekend. In addition, models are hinting at an upper- level ridge strengthening over the Yukon Valley. Both of these will continue to support the chances for isolated showers and thunderstorms across the Interior through the start of next week.

FIRE WEATHER

The greatest area of concern this week is from Delta Junction south, where are increasing through the afternoon to 55 mph, continuing through the night, and weakening during the morning hours. Not much recovery is expected due to persistent downsloping winds. Min RHs are expected to be 20% on Friday for the Tanana Valley. While Red Flag conditions are possible, probabilities of occurrence are around 20% at this time. Friday is a drier day overall across the Interior with isolated rain showers and thunderstorms, though the coverage will be far less than Thursday. Saturday and Sunday continues the dry trend in terms of low min RHs (20 to 30% in the valleys), but thunderstorms will be isolated to scattered across the Interior and there is a chance that Saturday is the most active thunderstorm day in the Interior so far this year. Sunday looks to be another active thunderstorm day, but the threat does shift northeast from Fairbanks to the Kobuk Valley eastward to the Al-Can Border. Any thunderstorm can come with lightning, brief heavy rain, small hail and erratic wind gusts. To wrap it up, expect wetting rain north of the White Mountains today, a drier day on Friday, then active thunderstorm days this weekend with temperatures remaining relatively cool and RHs near critical values in the valleys.

HYDROLOGY

Yukon River: The breakup front on the Yukon has passed Russian Mission. As of 12AM AKDT Thursday, a sharp increase in water level was recorded near Pilot Station, indicating that a release is possible. Then, as of 11am AKDT Thursday, an ice jam 10 miles downstream of Russian Mission has been confirmed to be releasing, according to the River Water team. Further information is needed regarding the speed of release and There is another minor ice jam downstream from Holy Cross, with water levels remaining mostly steady. The most extensive flooding is occurring at Holy Cross and in the lowlands between Holy Cross and Anvik.

Flood warnings remain in effect for Russian Mission, Holy Cross, and Grayling. A Flood Advisory is in effect for Anvik. Extensive flooding of the lower portion of Holy Cross community was occurring Tuesday, including the Holy Cross runway. Water remains high on the Yukon upriver from the breakup front due to snowmelt and the Yuki Ice Jam release. As of noon Wednesday the River Watch Team reported that the river slows down around Anvik and that the backwater from the jam seems to have extended to Anvik.

As the ice jam releases, there will likely be a period of water level rises and dense ice runs at Russian Mission for at least 24 hours as the backwater flows past there. Downriver of the ice jam towards Marshall the ice is rotten and river levels are low.

Innoko: Reports from Shageluk indicate that the Innoko River has begun to backup due to high water in the area. Currently not expecting significant impacts.

Chena: The Chena River continues to respond to warmer temperatures with higher elevation snowmelt leading to rivers running higher than normal, but likely remaining below action stage.

Additional Information: Visit www.weather.gov/aprfc for the latest hydro information.

Please report observed flooding to local emergency services, law enforcement, or to the National Weather Service when you can do so safely..

EXTENDED FORECAST DAYS 4-7

Most likely temperatures remain similar to this week across the Interior and North Slope and the larger variance will lie within wind strength and precipitation early next week. Going into the next work week, a strong low looks to move into the Bering Sea near Bristol Bay. Diverging solutions in ensemble models can be simplified into two solutions. The first, at roughly 60% likelihood, shows the low become vertically stacked near Bristol Bay, with persistent southerly flow aloft. This would result in strong wind gusts for Isabel and Windy Pass, possible elevated fire weather concerns for Delta Junction, along with possible showers and thunderstorms outside of downsloping areas. The other solution, 40% likelihood, shows a progressive system, moving the trough into the northern gulf. This solution would result in additional thunderstorm chances for the interior, with less windy conditions in the passes.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Wind Advisory for AKZ849. Flood Watch for AKZ826-830. PK...Small Craft Advisory for PKZ801-850. Small Craft Advisory for PKZ812. Brisk Wind Advisory for PKZ814-815. Small Craft Advisory for PKZ858. Brisk Wind Advisory for PKZ860. Brisk Wind Advisory for PKZ861.