textproduct: Fairbanks

KEY MESSAGES

- Temperatures warm into the mid 60s/low 70s Wednesday and Thursday as a ridge builds into the Central and Eastern Interior. The warmest temperatures are expected in the Yukon Flats and Upper Tanana Valley, and the latter will see another couple of days of near- critical fire weather conditions.

- An isolated thunderstorm or two cannot be ruled out in Fortymile Country Wednesday and Thursday. Chances for isolated thunderstorms are more likely as the ridge breaks down on Friday in the Eastern Interior.

-A Bering Sea low will bring wetting rains into the Central Interior west of Fairbanks on Friday into Saturday. A low in the Northeast Gulf of Alaska could bring wetting rains into the Southeastern Interior Friday evning through Sunday morning, but forecast certainty is low at this time.

West Coast and Western Interior... -There is no dry spell in sight for the Northwest Interior, especially over higher terrain along the Middle Koyukuk, a region where between 2 and 4 inches have already fallen this week. An additional 1-2 inches could fall somewhere in the Northwest Interior by Saturday afternoon, but forecast confidence is low.

-Another Bering Sea low is set to arrive on Friday. There is still low model uncertainty in its track, but models are in agreement that it will be weak.Expect northerly/northwesterly wind gusts of up to 40 mph and precipitation totals between 0.5 inches and 1 inch, especially over higher terrain.

North Slope and Brooks Range... -A front moves across the North Slope/Brooks Range on Wednesday, bringing 0.1-0.25 inches of rain over the North Slope and 0.25-0.5 inches in the Brooks Range. There is also a chance for an isolated thunderstorm or two over the Southeastern Brooks Range Wednesday afternoon.

-Southerly flow over the Brooks Range will warm temperatures Thursday and Friday with high warming into the upper 40s/upper 50s on the coast and mid 60s inland by Friday afternoon. As southerly flow dies down on Friday afternoon, there is another chance for afternoon thunderstorms in the Southeastern Brooks Range.

-There is a chance of light snowfall (<1 inch) over the Western and Central Brooks Range Saturday morning/afternoon as a weak trough brings instability and colder air from the northeast.

SHORT TERM /THROUGH SATURDAY NIGHT/

Weak ridging is starting to build into the Central and Eastern Interior Wednesday morning, while an upper level low sits over the Alaska Peninsula. The low will move into and across the Gulf of Alaska, staying out of our CWA for now, but is a source of significant forecast uncertainty later on. Ridging will provide a slight warm-up for the Central and Eastern Interior (widespread highs in the mid 60s/low 70s) and respite from the showery conditions for Wednesday and Thursday. Chances for a lightning strike or two remain in the Upper Tanana Valley, Fortymile Country, and Eastern Brooks Range if energy from the low in the Gulf moves over the area around peak heating. Additionally, a weak trough and associated front swing across the North Slope Wednesday, bringing another round of rain to the region. Precipitation will range from just over 0.1 to around 0.25 inches on the North Slope, and up to 0.5 inches over the Northern Brooks Range. Energy stemming from both areas of lower pressure continues to bring shower activity to the Western Interior. The Middle Koyukuk, which has already reported 2-4 inches of rainfall in the past 72 hours in some places, will see another 0.5 inches.

Thursday looks to be the driest day of the week in Northern Alaska. Ridging keeps widespread showers out of the Central and Eastern Interior (with the exception of isolated thunderstorms in the Upper Tanana Valley and Fortymile Country, similar to Wednesday). The North Slope will see a lull in between vort maxes, keeping showers isolated and light as well. The Western Interior can't seem to catch a break from the showers since shortwaves from a new Bering Sea low pressure system start to move over the region just after the ones from the previous low leave.

The aforementioned Bering Sea low moves into the region on Friday. Both the GFS and Euro ensembles have weakened the system compared to 24 hours ago since they both are now projecting the upper level low will not close off, preventing the surface low from strengthening. The West Coast and Western Interior will see precipitation totals between 0.25 and 0.75 inches, with isolated totals up to 1.25 inches over terrain. Ensemble members haven't quite converged on a track for this system yet, so there is uncertainty in where those higher totals will fall. This low may potentially close off as it moves southeast on Saturday, bringing down more troughing into the Northwest Interior behind it. Though the troughing is relatively weak, it does bring colder air into Northwest Alaska. If combined with sufficient moisture, the colder temps could support light snowfall (<1 inch) in the Western/Central Brooks Range Saturday morning/afternoon.

The upper level low that has been moving across the Gulf all week makes it into the northeastern Gulf by Friday/Saturday. This system could bring a return to wetting rains for the Upper Tanana Valley, but the pattern is incredibly finicky. Models are in agreement that the low will make landfall around Yakutat and move northeast through the Yukon. This would bring moist, southeasterly flow into the Upper Tanana Valley. However, minor differences in how features develop and interact with the current environment could determine if the Upper Tanana sees over an inch of precipitation, or non-wettting rain, and when this potential precipitation occurs. If the low is able to stall vaguely north/northeast of the St. Elias Mountains due a more persistent ridge to the east, the Upper Tanana could see precipitation totals between 0.25 and 0.5 inches. Another solution that would favor higher precipitation totals would be if the low moving over the Bering on Friday is able to phase with this low, keeping semi-persistent southeasterly flow into the valley for up to a couple of days. If the ridge is weaker, southeasterly flow will be much more brief, which could keep totals closer to 0.25 inches. Even if a decent plume of moisture is able to make it into the Upper Tanana Valley, there is a decent dry layer at the surface, which would greatly inhibit the amount of precipitation that would be able to make it to the surface. As if the pattern wasn't complicated enough, there is a lack of model consensus as to when this low moves onshore, with about 24 hours of spread ranging from Friday afternoon to Saturday afternoon. A later solution would be more likely to phase with the low from the Bering, while an earlier solution would be more likely to be stalled by the ridge. There is more certainty in chances for isolated thunderstorms in Fortymile Country, the White Mountains, the Yukon Flats, and the Southeastern Brooks Range as the ridge moves east into the Yukon, especially if ridge breakdown occurs in the afternoon hours.

LONG TERM /SUNDAY THROUGH TUESDAY/

Early next week a very active and wet pattern will begin to set up for Northern Alaska. There is however a mix bag on uncertainty with the upcoming pattern. Ensemble guidance is showing a strong ridge axis in the Bering Sea being squished and moved to the southeast towards the Gulf of Alaska as an Arctic trough moves east into the Bering from the Kamchatka Peninsula. This squished ridge axis will set up southwesterly flow into the Bering Sea and then into mainland Alaska. In the Central Pacific there will be a decaying tropical cyclone. This system will potentially help to provide the moisture for the southwesterly flow. This cyclone is where the uncertainty begins for much of next week.

The aforementioned cyclone will begin to rotate around the North Pacific High towards the Aleutian Islands. As it moves closer to the Island chain, a strong arctic low will begin to rotate through the Bering Sea towards Western Alaska. This arctic low could potentially tap into the tropical moisture and begin to advect it towards Western Alaska. While some ensemble members are showing this as a possibility, some aren't which is creating large model spreads of the forecasted rainfall. At Nome for instance there is nearly a 2 inch spread of qpf between the 25th and 75th percentile within the ECMWF ensemble Sunday night and through Monday. This uncertainty will continue to carry eastward towards the Eastern Interior as the arctic low continues to moves east. While there wont be as much rainfall as compared to the coastline, there is still a spread of 0.25" to 0.5" of rainfall.

While there remains a lot of uncertainty regarding rainfall amounts, it looks to be a cooler and wetter start to the work week across all of Northern Alaska.

Coastal Hazard Potential... A very weak Bering Sea storm will bring higher waters to the Southern Seward Peninsula Friday morning during high tide. This storm could bring an additional 1 to 2 feet of water above the mean high water mark. This could create some minor beach erosion, but no flooding is expected with this system.

FIRE WEATHER

Cooler weather and isolated to scattered rain showers will keep fire weather concerns minimal across the Western and Central Interior. Temperatures will be in the 50s/60s across the region with the bulk of wetting rains in the Koyukuk Valley. Across the Eastern Interior however some slightly warmer and drier weather will make a brief return as weak ridging is building into the region. Daytime highs in the Tanana Valley and Yukon Flats will be in the upper 60s with the Upper Tanana Valley in the low 70s. Conditions will remain dry across the Upper Tanana Valley as weak downslope flow continues Wednesday. We will see minimum RHs near 30% with the driest being Dot Lake to the AlCan Border. If temperatures begin to climb today to around 73/74 instead of 70/71 than we could see RH values begin to approach that critical threshold of 25%. These warmer temperatures would have the best chance to occur before 4PM, as we are expecting increasing cloud cover to begin moving into the region after 4PM.

An isolated thunderstorm will be possible Wednesday and Thursday afternoon in the Fortymile Country near Chicken as a weak upper-level energy is moving through the weak ridge. These are not expected to move into the valleys, but if any mature thunderstorm does develop we could see gusty outflow winds in the area up to 30 mph. Friday, thunderstorm chances will extend across much of the Eastern Interior from the Upper Tanana Valley north to the Brooks Range. While temperatures will be roughly the same as Wednesday, extensive cloud cover will help to minimum RH values above 40%.

In the Upper Tanana Valley we could see wetting rains arrive this weekend as a low in the Northeastern Gulf of Alaska could bring southeast flow through the valley. These wetting rains require conditions to align as features aloft are interacting with each other later this week. If we are able to see wetting rains into the valley the most likely amounts would be 0.1" to 0.5", but again these rains are highly uncertain. We will continue to monitor of the next couple of days to see conditions aloft begin to shake up.

HYDROLOGY

The moderate to heavy rainfall in the Koyukuk and Middle Yukon Valleys have received over the past 48 hours has led to marginal increases of river levels. Smaller creeks and streams could still see bankfull conditions over the next couple of days, but no flooding is currently expected.

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. MARINE...None.