textproduct: Fairbanks

SYNOPSIS

Sunny skies have spread across most of northern Alaska ahead of an Arctic front that represents the primary forecast challenge. Southerly winds ahead of the front are gusty near and north of the Brooks Range, which is allowing temperatures to warm well into the 60s. In fact, several North Slope sites are warmer than interior locations, but that changes quickly tonight into Sunday as an Arctic front tracks southeastwards. This front brings a band of steady precipitation that lasts roughly 12 hours at any one location and a seasonably cold air mass that allows for accumulating snow potential. 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 likely to result in hazardous travel. Saturated upslope flow continues as deeper moisture/snowfall depart, which may result in a period of freezing drizzle lasting through Sunday night. This front brings breezy winds, scattered rain showers, and a few thunderstorm 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 on Wednesday and Thursday.

KEY MESSAGES

Central and Eastern Interior...

- Mostly clear skies and light winds continue into Sunday afternoon with highs in the 60s-70s and lows mainly in the 40s tonight. A few valleys over the eastern interior may drop into the 30s.

- A cold front tracks southeast across the Interior late Sunday into Monday. A few afternoon thunderstorms are possible ahead of the front with scattered showers, breezy winds, and cooler temperatures in the 50s-60s along and behind the front.

- Rainfall totals later Sunday into Monday are expected to remain light overall, with amounts greater than 0.10" most likely near the Brooks Range and across the southeast interior. 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 the next cold front expected to track southeast across the Interior late Wednesday into Thursday with scattered rain showers and breezy winds.

West Coast and Western Interior...

- A weak low moving across southwest Alaska brings light rain showers for the Yukon Delta and far southwest Interior as dry conditions prevail elsewhere today. Areas of low stratus and fog will continue across western Alaska today, particularly in the Kobuk Valley and along portions of the West Coast.

- Temperatures warm into the 60s for most this afternoon then trend cooler for Sunday behind a cold front tracking southeast from the Chukchi Sea tonight into Sunday that brings scattered rain showers and gusty north winds.

- Rainfall totals tonight through Sunday night are expected to remain generally below 0.10" except across the Kobuk Valley and Lisburne Peninsula where localized totals above 0.25" are possible.

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

North Slope and Brooks Range...

- Following a cool morning today in the 30s/40s, highs will climb into the 50s/60s for most with low 70s around Deadhorse and the Arctic Plains due to warm southerly winds.

- Southerly winds increase today ahead of a cold front moving in from the Chukchi Sea. Strongest winds today are expected along the Northwest Arctic Coast with gusts up to 45 mph. North to northwest w ind gusts up to 40 mph shift eastward along the Brooks Range and Eastern Arctic Coast Sunday into Sunday night behind the front.

- This cold front brings a 12-18 hour period of steady precipitation as it shifts east tonight into Sunday. This begins as rain then transitions to snow as much colder air builds behind the front.

- The heaviest snow accumulations will be Sunday morning through Sunday evening 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 up to a around a T-1".

- Rainfall/snow water equivalent totals through Monday will be around 0.10-0.25" regionwide, locally higher up to 0.75" at the highest elevations across the southern Arctic Plains and in the Brooks Range.

- Dry conditions return from west to east Sunday 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.

SHORT TERM FORECAST DISCUSSION

Tonight through Tuesday.

A weak circulation/upper level low is tracking southeast towards Kodiak Island this afternoon resulting in a narrow corridor of scattered rain showers. The remainder of northern Alaska is mostly sunny with many locations warming into the 60s early this afternoon. Clear skies prevail for most locations ahead of the primary feature of interest, which is an Arctic front dropping south across the area this evening through Monday. Current satellite imagery shows the frontal boundary tracking southeast across the Chukchi Sea this afternoon and the latest CAMs guidance reaches the northwest Arctic Slope around 8 PM this evening. Precip types stay mostly rain through about 8 AM Sunday morning when the front should be positioned roughly between Kaktovik and Wales. In addition to precipitation chances, this front results in a sharp wind shift from gusty south-southwest winds approaching 45 mph Saturday afternoon/evening then becoming northwesterly up to 35-40 mph behind the front.

Upslope flow north of the Brooks Range seems to slow the fronts progress and cool the thermal profile below freezing resulting in a transition to snow through the morning hours on Sunday. For the Dalton Highway, this means a rain to snow transition around 18Z/10AM local time. Potentially heavy snowfall rates persist for about 6 hours after the transition allowing for up to 6" of heavy, wet snow. The primary factors introducing uncertainty is accumulating snow are the current warm and sunny conditions raising soil temps, 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 east Sunday evening with model soundings showing a loss of saturation in the DGZ. Models continue to show light QPF through Sunday night within an upslope flow regime that is most likely to fall as freezing drizzle that could result in a light glaze on top of the fresh snowfall.

Farther south, the front brings scattered rain showers across the northwest interior on Sunday with most places south of the Kobuk Valley receiving less than 0.1" of rain. There's also potential for a few thunderstorms Sunday afternoon along and ahead of the front across the northeast interior. The thunderstorm potential continues Monday afternoon as the frontal boundary slows across the southeast interior. With the front reaching Fairbanks Monday morning, the storm chances should stay east of town on Monday. Then there's a general drying trend Monday night into Tuesday ahead of the next Arctic trough that digs south toward the northwest Arctic coast Tuesday afternoon. Early signals point to a warmer system that should limit the winter weather threat.

Coastal Hazard Potential Days 1 and 2...

A cold front moving southeast from the Chukchi Sea Saturday night into Sunday brings gusty north to northwesterly winds across the Kotzebue Sound tonight into Sunday. Water levels are expected to rise as high as 1 foot above the normal high tide line across the Kotzebue Sound.

LONG TERM FORECAST DISCUSSION

Tuesday afternoon through Saturday.

At the start of the extended forecast period, upper level ridging continues to build over the Bering Sea with an Arctic trough to the north and a low in the Gulf of Alaska. Besides scattered showers and isolated thunderstorms possible over southeastern Alaska and the Alaska Range, fairly quiet weather persists over the state. A more notable change in the pattern occurs when the Arctic trough starts to dig farther south and pushes a front southeast over the North Slope early Wednesday morning. This front is expected to bring another round of rain/snow showers, potentially accumulating snow, and gusty winds along the Arctic Coast and Brooks Range Wednesday through Thursday. There's still a bit of uncertainty regarding how far south this front reaches, but will be highly dependent on the ridge over the Bering Sea. If this ridge keeps its strength and moves in tandem with the Arctic trough, it should keep the front farther north over Brooks Range. If the ridge weakens or takes a bit longer to move inland, the Arctic trough may be able to dip farther south past the Brooks Range and into the Northern Interior, bringing cooler temperatures and more widespread showers. However, current model guidance is leaning more towards the first solution, with the Interior and West Coast experiencing minimal effects from the Arctic front. Current guidance is hinting at mainly a few isolated to scattered rain showers possible through midweek. Exact rainfall and snowfall totals also remain uncertain for now as it will depend on timing and placement of the front. A faster moving front will produce lighter accumulations while a slower moving front may allow for lingering rain/snow showers to dump higher accumulations. Either way, current guidance hints at this front being weaker and drier compared the current system in the short term.

Thursday into Friday, the Arctic trough moves off into the northern Yukon territory as broad scale ridging rebuilds out west, bringing warmer and drier conditions to much of the state once again. A few late season thunderstorms are possible with this pattern, but conditions will be a bit more unfavorable given that the ridging is building in from the west rather than the east. Overall, fairly pleasant summer-like weather should prevail going into next weekend.

Coastal Hazard Potential Days 3 and 4...None

FIRE WEATHER

The Interior will see a slight increase in favorable fire weather conditions ahead of an approaching Arctic cold front. Light winds and temperatures warming to around 70F ahead of the frontal boundary resulting in another drying day with RH values as low as 30% across the southeast interior valleys. Behind the front, a substantially cooler and drier air mass spreads across the interior with highs mainly in the 50s to around 60F Sunday and Monday. The front itself brings scattered showers and isolated afternoon thunderstorms across the eastern interior, but the spatial extent of wetting rains seems limited to near the Brooks Range on Sunday and across the Fortymile area on Monday with spottier showers elsewhere. Despite the cooler temperatures, min RH values dropping to around 30% seem likely across interior valleys behind the front on Monday and Tuesday. Additionally, the front brings a brief period of gusty winds immediately behind the passage with

HYDROLOGY

With the recent widespread rainfall across the interior, rivers and their tributaries are near or past their crest as of Saturday afternoon. While no flooding is expected, remain mindful of the higher water levels.

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. PK...Small Craft Advisory for PKZ806. Small Craft Advisory for PKZ807-856. Small Craft Advisory for PKZ808-855. Small Craft Advisory for PKZ809. Small Craft Advisory for PKZ810. Small Craft Advisory for PKZ811. Small Craft Advisory for PKZ812-813. Small Craft Advisory for PKZ816-817-851. Small Craft Advisory for PKZ854. Small Craft Advisory for PKZ857. Small Craft Advisory for PKZ858. Brisk Wind Advisory for PKZ859.