textproduct: Fairbanks

KEY MESSAGES

Central and Eastern Interior...

- Ridging will continue to provide for a few breaks in the clouds Thursday & Friday along with seasonably mild conditions with highs in the upper 60's and low 70's.

- There will be slight chances for a few isolated showers or thunderstorms the next couple of days as disturbances track north from a storm system in the northern Gulf. Chances for thunder will be best in the Fortymile region.

- Best chances for wetting rain for the eastern Interior will likely be Friday into Saturday as a storm from the Bering tracks south of the area, drawing moisture in from the east.

West Coast and Western Interior...

- A frontal boundary will approach the west coast late Thursday bringing additional rain to the region. This rain will overspread much of the west and could last into early Saturday, especially for the western Interior.

- A low pressure system from the Bering will reach the Yukon Delta by Friday helping to enhance overall rainfall totals. The heaviest rain will likely fall from the Yukon Delta to the northwest Interior.

- Overall rainfall totals of 0.5 inches to around 1 inch will be possible. However there is the potential for even higher totals, especially near the higher terrain of the Middle Koyukuk where heavy rainfall has already fallen this week.

- Stronger northerly flow will develop by Friday afternoon through the Bering Strait and across the northern Bering with winds gusting to around 40 mph and seas increasing to between 4 and 5 feet.

North Slope and Brooks Range...

- A disturbance will track across the western North Slope Thursday bringing some scattered light showers. Southerly flow with this feature will allow for warmer temps through Friday with afternoon highs in the upper 40's and 50's.

- A slight chance for thunderstorms is possible for portions of the southeastern Brooks Range Friday afternoon. Only isolated activity is expected.

- 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. Elsewhere scattered rain showers are expected as the system tracks east across the North Slope.

SYNOPSIS

Generally unsettled weather conditions look to continue for the next several days as several systems track into the region. However the central and eastern Interior will see a brief break from showery conditions the rest of today and into Thursday as temps also bump up a few degrees. Elsewhere more rain is expected to settle into western Alaska late Thursday and carry into the early weekend. There will be the potential for some additional heavy rain across parts of the western Interior and Brooks Range as well. Meanwhile temps will briefly climb the next few day across the North Slope despite a few passing showers. But this trend will be short lived as the early weekend will bring steadier precipitation and even some early season snowfall to parts of the central Brooks Range.

SHORT TERM /THROUGH SATURDAY NIGHT/

Showers have finally tapered off across the Central and Eastern Interior as a weak ridge has drifted over the region. With breaks in the clouds, temps will warm back to seasonal norms and should remain there for the next few days. Meanwhile a couple of upper lows dominate the western half of the state as broad troughing extends westwards into Siberia. An upper low near the western Brooks Range will continue to track northwards, resulting in southerly flow and slightly warmer temperatures the next couple of days across the North Slope as well.

Looking ahead, a fairly strong shortwave trough will drop out of eastern Siberia into the northern Bering by Friday. Initially this will push a frontal system towards the west coast with a band of steady precipitation arriving late Thursday and progressing eastwards into Friday and Saturday. As this occurs, a surface low will approach the YK Delta Friday afternoon. Successive model runs continue to weaken this cyclone with current progs showing the low at around 1000 mb and the approaching surface high over eastern Siberia at around 1016 mb. While this is still a respectable gradient, we have tapered down the expected north wind speeds through the Bering Strait and into the northern Bering for Friday. It now looks like 30 to 40 mph gusts will be the norm with 3 to 4 foot seas corresponding.

The primary concern with the approaching western trough continues to be total rainfall potential. Portions of the northwest Interior have seen as much as 2 to 4 inches of rainfall in the past several days. Certainly any additional heavy precipitation will result in increasing hydrologic concerns for the region. Current models continue to indicate a fairly wide range of outcomes with regards to upcoming rainfall in the region. The ECMWF is on the lower side of the spectrum with the NAM being the most aggressive while the GFS lies somewhere in the middle. Based on previous forecast trends, we have gone with a general GFS/EC blend which has resulted in higher QPF values from our last forecast package. Current thinking for storm total precipitation Thursday evening through Saturday is .25" to .50" closer to the coast with inland areas totaling between .50" and .75". However with a steady southwest fetch and additional orographic forcing, the area surrounding the higher terrain of the Middle Koyukuk could be in the precipitation bulls-eye with 1.00" of additional rainfall or more.

Elsewhere as this system tracks east across the state, precipitation should be less impactful. Across the central Brooks Range there will likely be a change over to snow for Saturday with anywhere from a dusting to around 2 inches of accumulation depending on elevation. At the same time showers will progress into the Central and eventually Eastern Interior for Friday and Saturday. Thunder may also pop up across the Central and Eastern Interior heading into the weekend as a low in the northeastern Gulf could send energy and moisture that way.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Models are in decent agreement at the beginning of the extended with a strong Arctic low up near the North Pole and weak ridging building over the Bering. Unlike majority of the ridges seen so far this season, models are not showing this to stick around for a prolonged amount of time. Sunday night into Monday, there is good agreement for a well defined shortwave to move east out of Siberia. This will be the forcing mechanism that may shift the ridging over Eastern Alaska, eventually setting up a broad area of westerly flow across the state by Tuesday afternoon. The aggressive ridge breakdown seen in the models will be monitored over the next several runs to see when the westerly flow sets up across the state.

By mid to late next week, attention turns to the remnants of Hurricane Lala. High pressure will have already been building up over the North Pacific, which will help drive this system further north toward the Aleutians. Models are hinting at the potential for another shortwave to move east out of Siberia around Wednesday, which will play a major role in determining how the remnants of Lala impact the state.

The GFS deterministic shows the most aggressive solution by having the Siberia low move east much slower than other models. This would allow the shortwave to phase with the remnants of Lala and develop into a defined system as it moves NE across the Bering. Ensembles and other deterministic models are showing a more benign solution with the shortwave moving east out of Siberia quicker, which won't allow for the phasing, and block the remnants from moving farther north toward the Aleutians. While both of these will still bring an increase in winds and widespread precipitation, the intensity and potential impacts differ greatly. With this in mind, this will continue to be monitored over the next several models runs to see how this plays out.

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

Recent heavy rainfall and cooler conditions have helped eliminate most fire weather concerns across the western half of Alaska as well as portions of the Central Interior. However, dry conditions continue to persist across portions of the Eastern Interior. This trend likely continues into Thursday as weak upper ridging remains in place.

Some weak upper energy is expected to track north into the Interior as a system tracks across the northern Gulf Thursday. This could well initiate an isolated thunderstorm or two across the region, but it appears as if the Fortymile country will be best positioned for this to occur. Meanwhile some breaks in the clouds will allow for additional warming during the afternoon hours with readings back into the 70's across the upper Tanana Valley. This could correspond with min RH values again dropping into the upper 30's and lower 40's. While these values do not represent critical thresholds, the presence of extremely dry fuels and increased diurnal wind speeds still need to be monitored. By Friday and Saturday, the low in the Gulf heads into the southern Yukon, which is a favorable position for wrap- around flow to drive additional moisture into the Eastern Interior. As such an increase in chances for wetting rainfall will exist for Friday and Saturday across the region.

HYDROLOGY

Despite moderate to heavy rainfall the past few days across the Koyukuk and Middle Yukon Valleys, water levels remain on the lower side. There have likely been some responses along smaller creaks and streams, but no flooding has been reported. Looking ahead, this area is in for another round of significant precipitation, especially Friday into Saturday. Current thinking is an additional .50" to 1.00" of rain could fall. While some response is expected, flooding along the main stem rivers is not expected.

AFG WATCHES/WARNINGS/ADVISORIES

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