textproduct: Fairbanks

SYNOPSIS

A low pressure system over the Bering Sea will continue to bring additional rainfall to most of the West Coast through Friday. As the low moves to the northeast starting this afternoon, showers are likely for the North Slope, moving east through the weekend. Isolated to scattered thunderstorm chances are expected this afternoon for the Eastern Interior, North Slope, and Dalton Highway Summits, with the Yukon Flats likely seeing the highest concentration of storms. Chances for thunderstorms are expected to move east, primarily over the Al-Can Border, by Friday afternoon and eventually move out of the region by the weekend. The northeast- moving low will influence a brief cooling trend going into the weekend for most of Northern Alaska.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Warm and dry conditions expected to continue across the Interior today with highs in the upper 70s, followed by a slight and brief cooling trend before highs warm back to the mid to upper 70s by the end of the weekend.

- Isolated to scattered thunderstorms possible across the Eastern Interior this afternoon through the evening, with chances moving east predominantly over the Al-Can Border by Friday afternoon.

- Showers are expected over the Central Interior today and Friday with the heaviest amounts expected on the Southern Slopes of the Central Brooks Range.

West Coast and Western Interior...

- Widespread showers continuing across the West Coast and Western Interior with additional totals between 0.15" and 0.5" through tonight.

- Heavier rainfall amounts, up to 1", possible along south-facing slopes along the western Brooks Range, Nulato Hills, and southern Seward Peninsula.

- Slight warming trend possible over the Western Interior by the start of the weekend ahead of another low likely moving into the Bering Sea Saturday bringing more rain showers and cooler temperatures across the region.

North Slope and Brooks Range..

- Above seasonable normal temperatures will continue across the North Slope Thursday, The Arctic Plains is under a Heat Advisory and will be in the mid 70s and even near 80 today. The Arctic Coastline will be in the upper 50s to low 60s. A cooling trend is likely to begin by the start of the weekend.

- Rain showers expected to continue across the western Brooks Range through today. Isolated thunderstorm chances return this afternoon across the Arctic Plains and Eastern Brooks Range.

- An additional 0.1" to 0.5" of rain is expected over the Western Brooks Range through Utqiagvik on Friday.

FORECAST ANALYSIS AND DISCUSSION

A 550 decameter low pressure system over the Bering Sea is expected to continue bringing rain to most of the West Coast through early Saturday morning. Additional rainfall totals of around 0.15" to 0.5" are likely for the Western Interior and Southern Slopes of the Western Brooks Range as southwest flow brings moisture to the region. Higher terrain, including the Southern Slopes of the Western Brooks Range and Nulato Hills could see up to 1". Occasional scattered showers are likely for portions of the Interior including higher terrain. A Heat Advisory is still in effect through Thursday night for the Arctic Plains as high temperatures are expected to exceed 75 degrees. Isolated thunderstorm chances pick up Thursday afternoon through evening over the North Slope, Dalton Highway Summits, and Fortymile Country with scattered chances likely for the Yukon Flats. By Friday morning, ridging to the east is likely to weaken as the aforementioned low begins to move northeast, with isolated thunderstorm chances lingering along parts of the Al-Can Border near Fortymile Country. Moisture is likely to migrate north of the Brooks Range and bring rain to parts of the Western and Eastern Arctic Plains as well as most coastal communities, shifting east throughout the weekend. Additionally, temperatures across Northern Alaska are expected to cool slightly going into the weekend.

Models are indicating the potential for a second low to move into the Bering Sea from Siberia by early Saturday morning. Latest GFS guidance is estimating for the low to be about 558 decameters and travel south through the Bering Sea towards the Aleutian Islands. Up to 0.5" of additional rainfall is likely for coastal communities on the YK Delta and Norton Sound, with inland locations on the West Coast likely seeing less than 0.1" through Sunday morning. Drier conditions are expected for most of Northern Alaska by early next week as widespread ridging sets up once again.

FIRE WEATHER

A low that has been lingering over the West Coast begins to move Thursday to the northeast. This will shift the previously static pattern in 3 notable ways.

The first is that as the low moves to the northeast it suppresses a ridge of high pressure over the Eastern Interior that has been keeping temperatures warmer. Temperatures fall slightly Friday and further Saturday with Saturday highs across much of the Interior in the 60s to low 70s. Minimum RHs recover with this cooling trend as well, rising above 40 for most of the Interior. The exception remains the Upper Tanana Valley where temperatures in the mid 70s and minimum RHs in the mid to low 30s are expected.

The second is that thunderstorm potential increases as the ridge is suppressed and instability increases over the Northeastern Interior. Isolated thunderstorms are possible across much of the Eastern Interior and Brooks Range Thursday with scattered thunderstorms expected over the Yukon Flats and nearby elevated terrain. Friday sees the greatest potential move east with isolated thunderstorms expected along the Canadian border north of the Alaska Highway.

The third is that as the low pushes into the Western and Central Brooks Range it wrings out much of its remaining moisture causing the area of heaviest rain to move into the Western Interior and southwestern Brooks Range Thursday and then across the Brooks Range and North Slope Friday. Much of the remaining rain is expected to fall Thursday with totals in the 0.25 to 0.5 inches across much of the Western Interior expected with south facing slopes seeing between 0.5 to 2 inches. Friday totals will be lesser with between 0.25 and 0.5 inches for much of the Central and Eastern Brooks Range and between 0.1 and 0.3 inches for much of the North Slope. Near the center of the surface low greater totals are expected Friday with between 0.2 and 0.5 inches possible from Point Barrow to Howard Pass as the low moves across the North Slope.

HYDROLOGY

The heavy rainfall expected over the southern portions of the western Brooks Range have resulted in accumulations equivalent to a 2 to 5 year return interval. While flooding is not expected at this time, there will be significant rises in smaller streams and rivers and a slow to moderate rise on the Kobuk River.

EXTENDED FORECAST DAYS 4-7

As low pressure exits the area by late Sunday into Monday, models begin to depict a ridge building over Northern Alaska. There is uncertainty regarding the strength of this ridge and its exact orientation. Isolated thunderstorm chances are likely to stay low for the beginning half of the week. As the week continues, the GFS depicts ridging in the northwest to connect with a ridge in the southeast. As a result, high temperatures in the Interior could see a slight warming trend throughout the week.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Heat Advisory for AKZ806-808. PK...None.