textproduct: Fairbanks

SYNOPSIS

Showery and stormy conditions expected for the weekend across the Interior. Areas of fog and low clouds impact the Chukchi Sea Coast and may last into Sunday. Low clouds remain draped across the North Slope. Monday and Tuesday easterly winds increase across the Northern Interior and North Slope. Tuesday and Wednesday sees another round of strong southerly winds through the Alaska Range Passes. Afternoon showers and the occasional isolated thunderstorm remain possible for most of the upcoming week, although less frequent than over the weekend.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Showery and stormy conditions expected across the Interior Saturday and Sunday. Isolated thunderstorms and scattered showers are expected across most of the Interior with the highest chances of thunderstorms (30%) along the Canadian border and southern Brooks Range. Isolated thunderstorms remain possible through next week.

- Gusty east/northeast winds return across the Interior late Monday through Tuesday with potential gusts between 20 and 30 mph for most areas. Stronger gusts up to 50 mph are possible along the Dalton Highway Summits.

- Southerly gap winds return to the Alaska Range passes Tuesday morning and continue into Wednesday. Gusts up to 60 mph are possible. Near Red Flag Conditions for Delta Junction are possible.

West Coast and Western Interior... - Showery conditions continue across the West Coast and Western Interior through the weekend. Isolated afternoon thunderstorms are possible in the Western Interior throughout the upcoming week. Chances are highest (15%) Saturday through Tuesday.

- Areas of dense fog have formed along the Chukchi Sea Coast, especially near Kotzebue due to onshore flow. Dense fog remains a threat through Sunday due to west/northwest winds.

- Gusty northeast winds return to the West Coast late Monday. The strongest winds are expected from St. Lawrence Island through the Bering Strait to the Lisburne Peninsula with gusts of 30 to 40 mph possible.

North Slope and Brooks Range.. - Intermittent periods of mixed precipitation, including the chance for freezing drizzle, for the Arctic Coast east of Point Barrow through Sunday morning. Little to no accumulation is expected.

- Slightly cooler than normal temperatures expected with highs in the upper 20s to mid 30s and lows in the upper teens to mid 20s along the North Slope. Highs in the low 40s for the northern Brooks Range. Highs in the 50s to low 60s for the southern Brooks Range.

- Easterly winds increase across the Arctic Coast Monday night with gusts up to 30 mph possible east of Point Barrow and up to 40 mph west of Wainwright.

- Low clouds and patches of fog continue across the North Slope.

FORECAST ANALYSIS AND DISCUSSION

For Saturday through Tuesday. At the start of the forecast period Saturday morning, the pattern is dominated by broad troughing across Northern Alaska centered on a weakening stacked low over the YK Delta. A weak area of high pressure continues to rest over the North Slope. A shortwave rotating around the low reaches the Gulf of Alaska and strengthens Saturday evening, thus becoming the dominant low in the pattern. This new low in the Gulf of Alaska deepens the trough and allows it to push further south and drag what remains of the YK Delta low with it to the southeast. As the low moves east it pulls areas of increased vorticity towards it from Canada which, along with a small amount of CAPE and increasing instability, will allow for a wave of showers and isolated thunderstorms to wash across the region Saturday afternoon. Thunderstorms are possible across the Interior, but most likely along the Alaska/Canada border north of the Alaska Highway and along the south slopes of the Brooks Range due to locally higher instability. These showers and storms will be wet, but dry air at the surface will need to be overcome before many locations, especially valleys will begin to see rain. Virga is therefore likely along with gusty outflow winds.

Sunday sees the developing low in the Gulf completely take over and continue its march southeast towards Vancouver Island. The weak high pressure over the North Slope expands and strengthens somewhat as the low moves farther away. Another low moves from the North Pacific towards the Bering Sea yet again, but will not reach the Eastern Bering Sea until Monday. As pressure increases to the northeast and these lows move showery/stormy conditions Sunday become more concentrated to the higher terrain of the Eastern Interior where northeasterly winds will push showers and storms to the southwest. Valleys will still have a large amount of dry air to overcome, but this presents a good chance for rain for the Upper Tanana Valley. Upslope flow into the northeastern slopes of the Alaska Range will enhance snow showers above the treeline. By Monday the Gulf low will have moved too far to the southeast to be the main driver of weather and the new Bering Sea low will take over. Showers and isolated thunderstorms therefore can stretch across the Interior once more bringing chances back to the Western Interior. Northeast to southwest storm motion is still expected once again keeping showers closer to the northeastern side of the Alaska Range.

By Tuesday the low in the Bering will have reached Bristol Bay and the pressure gradient across the region will reach a peak. Strong east to northeast winds are expected across the higher terrain of the Interior, especially near the Dalton Highway Summits. Strong southerly gap flow returns once more to the Alaska Range Tuesday morning. It is expected to peak Tuesday afternoon and continue into Wednesday.

FIRE WEATHER

Low pressure systems in the Bering Sea refuse to give high pressure a foothold over Alaska, staving off any particularly hot and dry weather for at least another week. Expect steady temperatures and relative humidities as a result. The weak ridge that exists over Canada will be eroded over the weekend by a mess of shortwaves wrapping around a main low situated over the YK Delta. This will result in generally unsettled weather for the Interior, including good chances for afternoon showers and thunderstorms Saturday and Sunday. Most areas in the Interior will have chances for isolated thunderstorms (~15%) as thermal troughs develop in the afternoon. There are slightly better chances for scattered thunderstorms (~30%) in the higher terrain along the AlCan border from Fortymile Country to the Eastern Brooks Range, and westward along the southern edge of the Brooks Range into the Kobuk Valley Saturday evening. Similar probabilities exist for the Yukon Flats and surrounding terrain on Sunday.

On Sunday, the main low follows a short wave into the Gulf of Alaska. The combination of deepening low pressure in the eastern Gulf and high pressure moving down from the north will strengthen northeasterly winds primarily in the higher terrain of the northeast Interior, but also slightly in the rest of the Interior.

Winds will strengthen more on Monday as new low approaches from the west along the Aleutians. The northeast to southwest gradient will produce easterly winds across Interior and Western regions by Monday afternoon. Areas of higher terrain in the Interior will see gusts up to 50 mph from Monday night through Tuesday afternoon. As the new low tracks closer to Bristol Bay on tuesday morning, southerly gap winds through the Alaska Range will strengthen, which when combined with lower relative humidities from downslope winds into the Tanana Valley, could result in near Red Flag Warning conditions around Delta Junction on Tuesday.

HYDROLOGY

Yukon River: The ice jam downriver from Holy Cross released Thursday evening. Water levels in Holy Cross fell several feet. Downriver at Russian Mission water levels started rising and minor flooding was observed during an overflight. Rising water levels and minor flooding were reported at Marshall on Friday. The Yukon River breakup front was likely along the stretch from Pilot Station to Mountain Village as of Friday afternoon. Reports were received of minor flooding at Marshall and moving ice at Mountain Village. As of Saturday morning there have been reports of ice moving near Emmonak, Nunam Iqua, and Kotlik.

The surge of water from the Holy Cross ice jam release will increase ice jam and flooding potential for Marshall, Pilot Station, St. Mary's, and Mountain Village. Flood Warnings remain in effect for those same communities as well as Russian Mission and Holy Cross. Flood Watches remain in effect for the rest of the Yukon River downstream of Russian Mission.

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

For late Tuesday through next Saturday. At the start of the extended forecast period late Tuesday, the pattern is yet again dominated by a low pressure system centered over Bristol Bay. This low brings strong east/northeast winds to the Northern Interior and strong southerly winds through the Alaska Range passes late Tuesday as well as another front of showers and isolated thunderstorms across the Interior. This low stalls and slowly weakens in place through Wednesday morning before moving once again. As the low slowly weakens southerly winds continue through the Alaska Range, but the easterly winds across the Northern Interior will have significantly weakened. Showers/storms become more isolated as well.

Unlike with previous lows this one does not linger for long near Bristol Bay and moves southeast into the Gulf of Alaska by Thursday and remains there through the end of the week. Broad troughing once again resumes over Northern Alaska with little more weather than afternoon showers and the occasional isolated thunderstorm expected.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Flood Watch for AKZ825-826. PK...None.