Area Forecast Discussion

SYNOPSIS

Precipitation has already spread across to the eastern North Slope & the eastern Brooks Range of Alaska and will continue shifting southeast this afternoon into tonight and Monday. This front brings a band of steady precipitation that lasts roughly 12-15 hours at any one location and an unseasonably cold airmass that allows for accumulating snow potential north of the Arctic Circle. Snow chances are greatest along the northern slopes of the Brooks Range, especially at elevations above roughly 1000 ft where temperatures quickly cool below freezing during the snowfall. This includes a stretch of the Dalton Highway between Atigun Pass and Sagwon where locally up to 6 inches of snow is possible, which will likely to result in hazardous travel. Saturated upslope flow continues as deeper moisture/snowfall depart, which may result in a period of snow showers and pockets of freezing drizzle lasting through tonight. This front brings breezy winds, scattered rain showers, and a few isolated thunderstorms to the remainder of northern Alaska through Monday. Drier conditions and a warming trend return ahead of the next cold front that tracks across the state as we go into Wednesday and Thursday. Behind the second front, conditions look to trend warmer and drier heading into next weekend as a ridge of high pressure builds-in from the west with some light isolated showers primarily confined to the coast where they will be experiencing onshore flow.

KEY MESSAGES

Central and Eastern Interior...

- Mostly clear skies into this afternoon have allowed temperatures to warm into the 60s to low 70s.

- A cold front continues to track southeastward across the Interior into Monday. A few isolated afternoon thunderstorms are possible ahead of the front with scattered showers, wind gusts to around 20 to 30 mph, and cooler temperatures expected heading into Monday. Winds will peak this afternoon and evening ahead of the front.

- Rainfall totals into Monday are expected to remain light overall, with amounts greater than 0.10" most likely nearer to the Brooks Range and Alaska Range. A few afternoon thunderstorms can't be ruled out, especially across the southeast Interior on Monday.

- A brief warming and drying period sets in for Tuesday and Wednesday as highs return to the 60s to low 70s ahead of another cold front moving southeastward across the Interior late Wednesday into Thursday with isolated rain showers and breezy winds.

- Following the secondary midweek front, warmer and drier conditions are expected to return heading into next weekend, as highs return to the 70s to low 80s.

West Coast and Western Interior...

- Temperatures have trended cooler today as a cold front tracks southeastward from the Chukchi Sea across western Alaska through tonight with scattered rain showers and breezy northwest winds.

- Rainfall totals through tonight are expected to remain light, overall, with highest totals along the northwest Arctic Coast and and Kobuk Valley where around 0.10-0.30" of rain is expected.

- Warmer and drier conditions return for Monday and Tuesday ahead of another cold front moving into northwest Alaska Wednesday into Thursday with scattered rain showers and breezy winds.

- Following the midweek/secondary front, warmer and drier conditions are expected to return heading into next weekend with isolated showers along the coast. Highs will return to 60s/70s for most with locally cooler conditions along the coast.

North Slope and Brooks Range...

- Temperatures have trended much cooler today as a cold front tracks southeastward from the Chukchi Sea across far northern Alaska through tonight and Monday morning with scattered to widespread rain/snow showers and breezy northwest winds.

- The heaviest of the snow accumulations associated with a cold front moving southeastward through the region will last into tonight across northern slopes of the Brooks Range(>1000 ft elevation). Around 3-6" of snow is expected for Atigun Pass north to Toolik and Ice Cut Hill with around 1-3" for Anaktuvuk Pass. Any snow totals farther north will be around a trace to 1".

- Rainfall/snow water equivalent totals through Monday will be around 0.20-0.40" region-wide, locally higher up to 0.75" across higher elevations of the southern Arctic Plains and in the Brooks Range.

- Dry conditions return from west to east into Monday as initially cooler temperatures see a warming trend through midweek. A secondary cold front remains on track to move-in Wednesday into Thursday with scattered showers and gusty winds.

- Following the secondary midweek front, warmer and drier conditions are expected to return heading into next weekend, with isolated showers along the coast. Highs will return to 60s/70s for most with locally cooler conditions along the coast.

SHORT TERM FORECAST DISCUSSION

Through Tuesday Night.

Upslope flow north of the Brooks Range has been working to slow the front's progression and cool the thermal profile below freezing resulting in a transition to snow as the day has progressed today. For the around the Dalton Highway, the precipitation transitioned over to snow around noon today local time. Potentially, heavy snowfall rates persist for around 6-hours after the transition allowing for up to 4-6" of heavy, wet snow, with lighter snow filing in behind the heaviest rates. The primary factors introducing uncertainty in accumulating snow are the warm and sunny conditions yesterday raising ground temperatures, the timing of the rain/snow transition, and ultimately how much of the QPF falls as rain vs snow. Even though there is uncertainty, the heavy snowfall rates and surface temperatures falling below freezing will overwhelm warm and wet antecedent conditions and result in hazardous travel conditions along the Dalton Highway north of Atigun Pass. Deep moisture shifts eastward Sunday evening with model soundings showing a loss of saturation in the DGZ. Models continue to show light QPF through tonight within an upslope flow regime that is most likely to fall as snow with pockets of freezing drizzle that could result in a light glaze on top of the fresh snowfall.

Farther south, the front is bringing scattered rain showers across the northwestern interior today with most places south of the Kobuk Valley receiving less than 0.10" of rain. There's also potential for a few isolated thunderstorms this afternoon along and ahead of the front across the northeastern interior. The thunderstorm potential continues Monday afternoon as the frontal boundary slows across the southeastern interior. With the front reaching the Fairbanks area Monday morning, the storm chances should stay east of town on Monday. Then there will be a general drying trend Monday night into Tuesday ahead of the next Arctic trough that digs southward toward the northwest Arctic coast Tuesday afternoon. Early signals point to a warmer system that should limit the winter weather threat with the bulk of precipitation expected across the North Slope. In between fronts, conditions will trend warmer and drier overall.

Coastal Hazard Potential Days 1 and 2...

A cold front has been moving southeastward from the Chukchi Sea, today. The Kotzebue Sound and Chukchi Sea Coast has been experiencing gusty northwesterly winds today following the front's passage to the east. Gusts today have been between 25 and 35 mph, and water levels are expected to rise to 0.5 to 1.5 feet above the normal high tide line late today, peaking overnight, and diminishing rapidly Monday morning. Residents along the coast should remain mindful of minor water level rises and take action to protect property on the beach.

LONG TERM FORECAST DISCUSSION

Wednesday through next Sunday. At the start of the extended forecast period, the overall pattern is dominated by 3 main features: a very large upper level low near the North Pole, a building ridge in the Bering Sea, and a low in the Gulf of Alaska connected by a trough to the North Pole low. A front moving around the North Pole low approaches the Western Arctic Coast Wednesday into Thursday. The ridge in the Bering simultaneously attempts to push east into the Western Interior. The ridge is expected to keep the front slightly farther north, but a period of gusty winds and rain is expected to sweep across the Northern Interior and North Slope Wednesday into Thursday.

After the front passes, there is a larger divergence in the potential forecast. A stronger frontal passage or one that stalls would restrict the ridge in its push into the Interior, keeping conditions relatively cooler and more showery than they otherwise would be. A weaker front or stronger ridge would enhance warming and drying on the back end of the front leading to a more seasonable end of the week. Currently the warmer and drier solution looks more likely. However, yet another low rotates around the North Pole low and towards the West Coast Friday into the weekend. Developing higher pressure over the Interior may keep it in the Bering Sea through the weekend. The forecast for this feature is currently too uncertain to accurately suggest any potential impacts.

Coastal Hazard Potential Days 3 and 4...None

FIRE WEATHER

This afternoon, an arctic trough and the associated cold front is spanning roughly from the southeastern Seward Peninsula to the Central/Eastern Brooks Range around Atigun Pass, bringing cooler air in behind it. Temperatures in the Central and Eastern Interior have had a chance to reach around 70F before the cold front arrival later in the afternoon. Winds are gusty along with the front, generally westerly ahead of the front in the Interior, but turning more northerly behind the front closer to the West Coast as well as through the Alaska Range. Winds will gust up to 25 mph for much of northern Alaska through this afternoon. Rainfall amounts associated with this front should be relatively light, generally less than a tenth of a n inch except on the North Slope and in the Brooks Range where between a quarter and half an inch in total is expected. There is potential for a few isolated thunderstorms to develop ahead of the front in the Eastern Interior.

For the start of next week, a cooler airmass will continue to linger over Northern Alaska. Monday will be the coldest day for most areas of the Interior. Max temperatures will likely be 10 to 15 degrees cooler than normal, peaking in the low 60s or 50s. Conditions should remain moderate, but follow a gradual warming trend through the rest of week, until a ridge provides the chance for temperatures above 70 again for the latter half of the week.

Another weaker trough looks like it will come in from the northwest again on Wednesday. Although the exact impacts from this trough are a bite more uncertain, it looks like the Interior will receive another round of light precipitation, with a less significant drop in temperatures.

AFG WATCHES / WARNINGS / ADVISORIES

AK...Winter Weather Advisory for AKZ809. PK...Small Craft Advisory for PKZ806-854. Small Craft Advisory for PKZ807-808-816-817-856. Small Craft Advisory for PKZ809. Small Craft Advisory for PKZ810-855. Small Craft Advisory for PKZ850. Small Craft Advisory for PKZ851. Small Craft Advisory for PKZ853.