textproduct: Fairbanks

SYNOPSIS

A cold, wet, and windy start to the week will give way to a brief break Tuesday before renewed rain and wind returns from the West on Wednesday. The Chukchi Sea low will move further southeast across the Interior on Monday bringing continued rain to the southeastern Interior, gusty winds, and accumulating wet snow in the Alaska Range. Showers will decrease Tuesday as the low pulls away and high pressure builds across the Interior, while cooler and showery conditions continue to linger across the North Slope. By Wednesday, a strengthening low pressure system in the Bering Sea will bring renewed widespread rain and increasing winds to the West Coast.

KEY MESSAGES

Central and Eastern Interior...

- Wet snow in the Alaska Range today. Snow levels will fall to around 2,000-2,500 feet with 3 to 7 inches possible along the Richardson Highway near Isabel Pass and locally higher amounts at higher elevations.

- Cool, wet, and windy weather continues through today. Showers will affect much of the Interior today, with gusty west to northwest winds, especially in exposed areas and higher terrain. Heaviest precipitation coverage is expected to shift further southeast today into the Upper Tanana Valley with totals ranging from 0.10-0.50 inches. Strongest winds expected through the Tanana Valley with gusts up to 35 mph possible.

- Cool conditions continue through today with highs generally in the 40s and 50s and overnight lows in the mid 30s to low 40s. Clearing overnight tonight will allow for some valleys to fall near freezing temperatures on Tuesday morning. Temperatures are expected to warm through Wednesday with highs in the mid to upper 50s across most of the Interior, with locally lower temperatures in the southeast temperatures where cloud cover and showers are expected to linger.

West Coast and Western Interior...

- Gusty winds are expected to be the most noticeable impact along the West Coast. West to northwest winds will increase today with gusts peaking around 20-30 mph along the northern Seward Peninsula coasts into the Kotzebue Sound. Winds will then dramatically increase with the arrival of the next system in the Bering with wind gusts ranging 25-45 mph possible along the Bering Sea Coast. Greatest gusts are expected to be along St Lawrence Island as the main system is expected to remain in the western Bering Sea.

- Any lingering showers along the Chukchi Sea Coast will gradually decrease throughout the day before widespread precipitation returns Wednesday. Rainfall totals are expected to be around 0.10-0.50 inches of rain with the highest impacts expected along the southern Seward Peninsula, Norton Sound Coast, and YK Delta. Rainfall is expected to be especially heavy across St Lawrence Island with locally higher totals up to an inch possible.

- Temperatures are expected to remain relatively steady with highs near 50 before cooling to the mid 40s Wednesday as the next system begins to impact the area. Overnight lows are generally expected to be in mid to upper 30s.

North Slope and Brooks Range...

- Cool and unsettled weather remains through midweek. Scattered to numerous showers are expected to continue beneath the lingering upper level trough. Rainfall will generally be 0.10-0.50 inches through Monday with the highest totals expected further west. Snow levels around 1-2,000 feet will support snow in the Brooks Range, with total accumulations of a trace to 2 inches expected.

- Westerly winds increase Monday with gusts of 30 to 40 mph possible along the Arctic Coast west of Deadhorse and gusts of 15 to 25 mph possible along the coast east of Deadhorse.

- Highs are expected to be the warmest today, gradually trending cooler through midweek with temperatures in the upper 40s to low 50s today dropping to the upper 30s to mid 40s by Wednesday. Overnight lows will generally be in the mid 30s with some areas in the western Arctic Plains falling below freezing into the upper 20s Tuesday night. Areas across the Brooks Range are expected to remain colder with lows in the low 20s.

- Expect showers through much of the week as additional disturbances continue to circulate around the lingering low pressure in the Arctic.

SHORT TERM

Today through Wednesday Night. The current pattern is dominated by a broad upper trough over northern Alaska, with a cold core low moving southeast from the Chukchi Sea across the Interior. This system will keep conditions cool, wet, and windy today as the low continues to move southeast over the region. Precipitation will shift farther southeast today, with the best coverage across areas of higher terrain where orographic lift adds to the the large-scale ascent. Cold air aloft will keep snow levels fairly low, generally around 1,500-2,500 feet, so areas of higher terrain may be of concern for accumulating snowfall. West to northwest winds will increase behind the low as pressure rises over western Alaska, with the strongest gusts along the Northwest Coast and higher terrain across the Interior. As the low moves farther southeast towards the panhandle this evening, the main area of precipitation will shift along with it and become less organized, but the larger trough will remain, keeping chances for continued scattered showers.

The Alaska Range deserves particular attention today as the combination of cooling aloft, persistent precipitation, and terrain lift allows snow levels to fall to around 1,500-2,500 feet. This is low enough for accumulating snow along the higher portions of the Richardson Highway in Isabel Pass, where 4 to 8 inches are expected with locally higher amounts above pass level. Precipitation will initially be wet, but continued cold advection and evaporative cooling should allow the snow level to fall throughout the day rather than rise much with daytime heating. Northerly to northwest flow into the range will also maintain orographic lift even as the main surface low shifts east, helping snow persist over the higher terrain throughout the day.

The upper low over the panhandle will continue to weaken and move farther south on Tuesday allowing the pressure gradient and precipitation coverage to ease across much of northern Alaska. The remaining trough will still support scattered showers, especially across the Brooks Range and North Slope, but the central and eastern Interior should see a noticeable decrease in precipitation as subsidence increases behind the departing system. Higher pressure building in from the North Pacific should bring more breaks in the clouds and allow temperatures to begin to recover. How much warming occurs will depend on how quickly cloud cover breaks with some areas warming into the 50s, while lingering clouds and showers will keep other areas cooler. The developing ridge will also weaken the winds across the Interior, however some gusts will linger near the West Coast and exposed ridges in higher terrain. By Tuesday night, attention will shift west as the next disturbance strengthens over the western Bering Sea. Increasing height falls and moisture transport ahead of that system should start rebuilding the cloud and wind fields along the West Coast, bringing an end to the brief improvement in conditions.

The western Bering system becomes the main feature on Wednesday as the low strengthens and its associated frontal zone moves toward western Alaska. Increasing moisture transport ahead of the low should bring a return of more widespread rain to the West Coast and western Interior, while tightening pressure gradients bring stronger coastal winds. The central and eastern Interior should remain relatively quiet as the front remains west, but precipitation and wind impacts could spread farther east if the Bering Sea low deepens more quickly or tracks farther east than currently expected. A majority of the impacts will fall mainly in the extended period which will be covered in the extended forecast section.

LONG TERM

Thursday through next Monday. The upper level pattern mid to late week across Northern Alaska will be dominated by an H5 ridge in the Gulf of Alaska extending north into Alaska and Northwest Canada, with a broad H5 low and associated trough out over the Bering Sea and Western Alaska. Up across the North Slope and High Arctic, an H5 low centered over the Beaufort Sea Thursday will track east as upper level ridging from Siberia and the Chukchi Sea shift east. With this setup, southwesterly flow will help to push temperatures warmer later in the week while allowing for several fronts to work into Western Alaska with widespread rain and gusty winds. The first front will be ejected from a triple point low in the Bering Sea late Wednesday into Thursday into Western Alaska, with rain and winds shifting across the Interior Thursday into Friday.

This system will be tapping into atmospheric river moisture from as far south as 20-30N, supporting moderate to heavy rain across Western Alaska. The biggest difference amongst GFS/ECMWF ensembles continued to be how far east this precipitation will get, with the ECMWF favoring a more easterly track versus the GFS more westerly track. Overall rainfall amounts Wednesday through Friday have come into increasing agreement with the latest guidance, showing around 0.5 to 1.5 inches across the Central/Western Interior, Brooks Range, and Western Alaska. Locally higher totals around 1.5 to 2.5 inches will be possible across the West Coast, with highest totals expected out at St. Lawrence Island given their closer proximity to the main fetch of moisture. Driest conditions are expected across the Arctic Coast/Plains and in the Upper Tanana Valley where southerly downsloping flow will keep conditions drier. With colder antecedent conditions out ahead of this large plume of moisture lifting north towards the Brooks Range, expect a rain/snow mix in this corridor with moderate snow accumulations possible across highest elevations. Winds out of ahead of this first front will pick up late Wednesday into Wednesday night, peaking on Thursday, with strongest wind gusts across the West Coast around 30 to 50 mph. Limited coastal impacts are expected with these winds however, given the bulk of the strongest winds are expected to be offshore.

Following that first round of widespread precipitation late Wednesday into Thursday and Friday, persistent low pressure in the Bering Sea will continue to send additional shortwaves and surface lows into Southcentral and Western Alaska. This pattern will keep precipitation chances around through the weekend into early next week, as temperatures hold seasonable for early September. During this timeframe, the overall trend shows the bulk of ensemble guidance allowing for that broad area of low pressure in the Bering Sea to shift east, with the main caveat being just how quickly the ridge in the Gulf of Alaska will weaken and shift east.

COASTAL HAZARD POTENTIAL

A strong area of low pressure in the Western Bering Sea will eject a front into Western Alaska late Wednesday into Thursday with widespread moderate to heavy rain and gusty winds. While wind gusts are expected to peak around 30 to 50 mph along the West Coast, limited coastal impacts are expected at this time given the bulk of strongest winds will be offshore. The only exception to this will be around Hooper Bay where more southerly flow is expected.

FIRE WEATHER

Fire weather concerns remain low this week across the Interior. As a low tracks southeast into the Gulf of Alaska later today into tonight, scattered to widespread rain showers and high elevation snow will continue across the Southern Interior and Alaska Range. Additional rainfall totals through tonight will be around 0.10-0.50" in this corridor, locally higher around Delta Junction and the Alaska Range closer to 0.50-1.00". West to northwest winds will increase later today across the Interior, with gusts peaking around 25-35 mph, strongest in the Middle/Upper Tanana Valley and across higher elevations, before subsiding Tuesday morning. Conditions will trend drier Tuesday and Wednesday as isolated showers persist, with attention turning to late Thursday into Friday as another round of widespread rain lifts northeast from the Bering Sea. Southwest flow will lead to cooler temperatures early in the week trending warmer, which with drier air, will lead to minimum RHs Wednesday and Thursday dropping to around 35-45% for driest locations out ahead of the next round of widespread rain. Winds will be breezy on Wednesday with gusts to around 20 to 30 mph, with gap winds through Alaska Range passes picking up Thursday into Friday out of the south with gusts of around 30 to 45 mph.

HYDROLOGY

As as low pressure system tracks southeast towards the Gulf of Alaska today into tonight, rain and high elevation snow will continue across the Southern Interior and Alaska Range. Additional rainfall totals through tonight will be around 0.10-0.50" in this corridor, locally higher around Delta Junctionand the Alaska Range closer to 0.50-1.00". Another low is expected to bring more rain to the West Coast and Western Interior Wednesday into Thursday, with rain building across the Interior Thursday into Friday. Overall rainfall amounts Wednesday through Friday have come into increasing agreement with the latest guidance, showing around 0.5 to 1.5 inches across the Central/Western Interior, Brooks Range, and Western Alaska. Locally higher totals around 1.5 to 2.5 inches will be possible across the West Coast.

AFG WATCHES/WARNINGS/ADVISORIES

AK...Winter Weather Advisory until 4 AM AKDT Tuesday for AKZ849-850. MARINE...Small Craft Advisory from 1 PM to 4 PM AKDT this afternoon for PKZ811. Small Craft Advisory from 1 PM this afternoon to 4 AM AKDT Tuesday for PKZ812. Small Craft Advisory from 10 AM this morning to 10 PM AKDT this evening for PKZ857. Small Craft Advisory from 10 AM this morning to 4 AM AKDT Tuesday for PKZ858.