textproduct: Fairbanks

SYNOPSIS

Multiple fronts passing over Northern Alaska will continue to support a mix of rain/snow showers, with the first front lifting north over the Central/Eastern Interior today into tonight. Colder air building in out of the west behind this front will support cooling temperatures and lowering snow levels, with light snow accumulations above 2000 to 2500 feet and flurries across lower elevations.

A series of Arctic fronts working southeast from the Chukchi Sea into Northwest Alaska and the North Slope/Brooks Range will support several rounds of light rain/snow today into tonight, culminating with a stronger front Tuesday into Wednesday. This stronger front will support steadier, more widespread rain/snow chances with peak wind gusts of 30 to 45 mph across the North Slope, strongest along the Arctic Coast.

A strong low tapping into tropical moisture remains on track to move into the Eastern Bering Sea mid to late week, with ensemble guidance pointing to the low moving onshore around the Bristol Bay to Y-K Delta region by the weekend. This setup with favor heaviest precipitation and strongest winds across Southwest and Southcentral Alaska, with strong southerly gap winds through the Alaska Range passes. Stay tuned for updates.

KEY MESSAGES

Central and Eastern Interior...

- Light rain and high elevation snow showers will continue to lift north today into tonight. Best accumulating snow chances will remain confined above 2000 to 2500 feet, with flurries possible across lower elevations where temperatures allow.

- With warmer temperatures around the Upper Tanana Valley and Fortymile Country today coupled with marginal instability, there will be around a 5-10% chance of afternoon/evening thunderstorms in this region.

- Conditions will trend cooler and drier on Tuesday, as lingering rain/snow showers dissipate. With these cooler temperatures, snow flurries will be possible across lower elevations, particularly during the overnight and morning hours.

- Highs today in the 40s/50s will see a cooling trend for most on Tuesday to the upper 30s to mid 40s, while warmest conditions will be confined along the Alcan Border and Upper Tanana Valley region, where highs will remain around 50F.

- Overnight lows this morning in the 30s to low 40s will also trend cooler for tonight and Tuesday night, dropping to the mid to upper 20s to low 30s. Coldest spots could drop to the upper teens and lows 20s by midweek.

- Under the increasing influence of high pressure Wednesday into Thursday, drier and sunnier conditions will prevail, as afternoon highs begin to gradually trend warmer. Overnight lows however look to remain cool given increasingly clear skies.

West Coast and Western Interior...

- Predominantly dry conditions will continue across the Western Interior and St. Lawrence Island today, while an Arctic front working southeast into the West Coast will work to support isolated to scattered rain and high elevation snow showers.

- A secondary Arctic front building into Northwest Alaska tonight into Tuesday/Wednesday will support continued rain/high elevation snow showers along the West Coast, with isolated showers expanding east to include the Western Interior.

- Under the increasing influence of high pressure building in out of the west Tuesday into Wednesday, temperatures will see a warming trend through midweek.

- Highs will be in the 30s/40s through Wednesday, warming to the 40s/50s on Thursday. Overnight lows in the 20s/30s will persist, locally warmer along the West Coast in the low 40s.

- Increasing confidence supports a strong low moving into the Bering Sea mid to late week, with lower confidence on the exact track, timing, and associated impacts. Stay tuned.

North Slope and Brooks Range...

- A series of Arctic fronts working southeast from the Chukchi Sea into Northwest Alaska and the North Slope/Brooks Range will support several rounds of light rain/snow today into tonight, culminating with a stronger front Tuesday into Wednesday.

- This stronger front will support steadier, more widespread rain/snow chances, with peak wind gusts of 30 to 45 mph across the Arctic Coast. Falling snow and gusty winds could lead to significant reductions in visibility at times.

- Additional snow accumulations through Wednesday will remain light across much of the Arctic Coast/Plains, with totals up around 1 to 3 inches in the Brooks Range and Southern Arctic Plains at or below pass level, locally higher above pass level.

SHORT TERM

Today through Wednesday Night. Early morning satellite imagery shows a series of fronts tracking over Northern Alaska: one lifting northeast across the Central/Eastern Interior north to the Arctic Coast, and another moving southeast into Northwest Alaska from the Chukchi Sea. These fronts will continue to be the main drivers of our rain/snow showers, with precipitation amounts expected to remain light overall. With the first front, low pressure in the Gulf of Alaska will continue to eject moisture northward, leading to rain and high elevation snow showers lifting north over the Alaska Range into the Central/Eastern Interior. CAMS remain in reasonable agreement here, showing the bulk of activity lifting northeast today into tonight, before becoming increasingly isolated on Tuesday. Evident of the moisture working over the Alaska Range, mesonet station HEAA2 in Healy has recorded 0.80 inches of rain over the past 24 hours. While conditions are trending cooler and drier on Tuesday in the Interior, snow flurries will be possible across lower elevations, particularly during the overnight and morning hours. Additional precipitation totals through Tuesday will be around a T-0.25 inches for most, with locally higher totals in the Alaska Range, especially south of Delta over Isabel Pass. Here is where we could see amounts closer to 0.25-1.00 inch. Accumulating snow amounts will remain confined generally above 2000 feet and remain light overall, with locally higher totals above pass level in the Alaska Range. With warmer temperatures around the Upper Tanana Valley and Fortymile Country today coupled with marginal instability, there will be around a 5-10% chance of afternoon/evening thunderstorms in this region.

Looking north and west, a broad 490 dam H5 low centered over the High Arctic up around 85N will continue to eject a series of Arctic fronts southeast from the Chukchi Sea into Northwest Alaska, supporting rain/snow showers. Best chances will remain confined to the North Slope, Brooks Range, West Coast, and Northwest Interior. A more organized front is expected to work southeast Tuesday into Wednesday with more widespread rain/snow chances and stronger winds. Winds out of the WSW will begin ramping up Monday night into Tuesday morning, peaking throughout the daytime hours on Tuesday with gusts up to around 30 to 45 mph. The stronger wind corridor for this event will be focused from St. Lawrence Island northeast across the Seward Peninsula to the Kotzebue Sound region and North Slope, with strongest winds expected along the Arctic Coast. Given the increased organization and dynamic forcing along this front, precipitation could be moderate to heavy at times, which coupled with gusty winds, could lead to significant reductions in visibility with snow. Winds will ramp down west to east Tuesday into Tuesday night, with lingering breezy winds at Kaktovik.

Behind that departing Arctic front Tuesday into Wednesday, ensembles remain in good agreement on bringing in a transitory H5 ridge of high pressure in from the Bering Sea into Northern Alaska. This will lead to warmer and drier conditions building in midweek, with overnight lows staying cooler especially where clearer skies remain more prevalent. Looking even farther west out towards Japan and Siberia, we are keeping a close eye on Typhoon Dujuan which is near Japan, in addition to a strengthening H5 low moving east from Siberia towards the Bering Sea. These two features will begin to interact with one another Tuesday into Wednesday, with the main H5 low moving off of Siberia and into the Bering Sea while at the surface level, remnants of the now rapidly weakening Typhoon Dujuan favor a more easterly track over the North Pacific south of the Aleutians. What the main H5 low in the Bering Sea will incorporate however, is tropical moisture from this system. This is reflected well in the latest Integrated Vapor Transport (IVT) guidance, showing the low in the Bering Sea strengthening as it enters a colder airmass, while wrapping in that tropical moisture.

While models remain in good agreement here through Wednesday, they differ on how the strong the H5 ridge will be out ahead of it. The latest ECMWF guidance points to a stronger ridge and a more northerly track of the low, while the GFS guidance differs with a weaker ridge and more southerly track. Nonetheless, those across the West Coast should begin to plan ahead for potential impacts from this storm, with those details to come into focus over the coming days. As of now, the strongest winds and heaviest precipitation looks to remain focused across Southwest Alaska south of the Seward Peninsula, with gusty winds also expected through the Alaska Range passes. See more about this storm in the Long Term and Coastal Hazard Potential sections below.

LONG TERM

Thursday through next Monday. To start the extended forecast, a northwest oriented H5 ridge will be in place over the Alaska mainland, with a broad H5 trough over the High Arctic along with an H5 trough over the Bering Sea. While conditions will be trending warmer and drier across Northern Alaska later in the week, attention remains focused farther west in the Bering, where a strong low tapping into tropical moisture is expected to move towards Western Alaska. The latest ensemble and deterministic guidance has come into slightly better agreement on the track and strength, showing the surface low strengthening to around 960-970 mb, sending heavy rain and gale force winds into Southwest Alaska.

While there is increasing confidence on strong southerly gap winds through the Alaska Range passes and strong E/SE winds south of the Seward Peninsula to the Y-K Delta and out at St. Lawrence Island, increased uncertainty surrounds just how much of the heavy rain will be able to lift north. That aforementioned ridge will attempt to act as a cap on top of this low, forcing the bulk of moisture to stay south and allow for drier conditions to prevail farther north. This is the main split amongst models, with the ECMWF model suite favoring the ridge shifting east while the GFS model suite keeps the ridge in place longer. This main difference is leading to vastly different rainfall/QPF forecasts, with the GFS hardly showing much rain across the Yukon Delta and Seward Peninsula, while the ECMWF favors rainfall closer to 0.25 to 0.75 inches.

In contrast, the wind field remains in reasonable agreement amongst models, favoring the strongest E/SE winds south of the Seward Peninsula and stronger southerly winds through the Alaska Range passes. The latest NBM 24 hour maximum wind gusts Thursday into Friday for these corridors is 40 to 50 mph along the West Coast, and 50 to 70 mph through the Alaska Range passes. Overall, how exactly fast the low in the High Arctic shifts east will determine the setup for this low, with a faster track favoring a more northerly push, while a slower track favors a more southerly track.

All in all, the current setup favors primarily low-end impacts across our CWA, with criteria for high surf and winds not being met along the West Coast, while better chances for a Wind Advisory/High Wind Warning will be for the Alaska Range passes. There will be changes to this forecast as we track the latest as see how this system phases with the ridge of high pressure out ahead of it, but for the time being, it is not looking overly impactful. Elsewhere across Northern Alaska, warmer and drier conditions look to prevail through the extended timeframe, with just how much moisture lifts north from that low in the Bering Sea being the main determining factor for how much rain we end up seeing.

COASTAL HAZARD POTENTIAL

As moisture from remnants of Typhoon Dujuan lift northeast into a strengthening low in the Bering Sea, strong winds and heavy rain are expected to build into Southwest Alaska Thursday into Friday. From the Yukon Delta north to the Seward Peninsula is where we are expecting the strongest winds, with gusts to around 30 to 50 mph out of the E/SE. North of the Seward Peninsula, we are still looking at breezy winds out of the E/SE, but with gusts peaking around 25 to 40 mph. This predominant offshore direction remains unfavorable for high water impacts along our forecast area of the West Coast. However, we will continue to monitor this system as details on the track and strength become clearer, and make any necessary changes to this forecast.

FIRE WEATHER

As a front lifts north over the Alaska Range today into Tuesday, isolated to scattered rain and high elevation snow showers will continue to push north into the Upper Tanana Valley and Fortymile region. Highest CWRs will remain focused northwest of a line from Dot Lake to Eagle, with only very light rain expected southeast of there. With sufficient daytime heating and marginal afternoon instability today, look for a 5-10% chance of thunderstorms this afternoon and evening across the Upper Tanana and Fortymile region. MinRHs will remain lowest today along the Alaska Highway near the Alcan Border, dropping to around 45-50%.

For Tuesday, colder temperatures will build in overnight, supporting the potential for flurries across lowest elevations. Accumulating snow potential looks to remain above 2500 to 3500 feet in the Alaska Range, and across highest elevations of the Fortymile. Dry conditions are expected back on Wednesday.

Temperatures cool over the next few days, with highs in the low 50s on Monday dropping into the low to mid 40s by Wednesday. Lows will also see a cooling trend towards midweek as lows regionwide drop into the 20s, locally colder in the teens. MinRHs stay in the 50-60% range and winds remain light and variable through Wednesday. High pressure building in starting Thursday will lead to MinRHs dropping to around 35-40% as conditions remain dry.

HYDROLOGY

Following moderate to heavy rain earlier this month, rivers across Northern Alaska have crested and are expected to gradually recede over the coming days. The Chena River in particular has dropped back below minor flood stage, although it still remains at or near bankfull. Use caution if on or near waterways given high flows and potential debris in the water.

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. MARINE...Small Craft Advisory from 4 AM to 6 AM AKDT Tuesday for PKZ857.