textproduct: Fairbanks

SYNOPSIS

Generally cooler than normal temperatures prevail with areas of precipitation mainly confined to the West Coast and AlCan border today and tonight. Rain chances shift west across the eastern interior on Thursday then increase across the interior on Friday and Saturday as a frontal system drops southeast across the state. A few thunderstorms are possible across the southeast interior this afternoon then spread westward and become more likely each day through Friday. On Friday, thunderstorm potential should be focused along an east-west oriented frontal boundary roughly between Grayling and Nikolai and higher terrain farther north.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Scattered showers will continue the next few days across the Eastern Interior, especially in the Upper Tanana Valley and in the Fortymile Country.

- Isolated thunderstorms will expand further north and west throughout the Interior Thursday and Friday.

- Below normal temps generally in the 60's will continue into the weekend.

West Coast and Western Interior... - Rain and gusty northerly winds will continue to spread southward across the West Coast as a low pressure system moves into the Bering Sea.

- Chilly temperatures will continue in the 40's/50's near the coast with lower 60s over the western Interior.

- Isolated thunderstorms are possible over the higher terrain of the Western Interior Friday afternoon.

North Slope and Brooks Range.. - Rain and snow will occur across the western Brooks Range and western North Slope through Thursday. A Winter Weather Advisory is in effect for a wintry mix of freezing drizzle and light snow into Thursday morning from Utqiagvik to Point Hope.

- An arctic cold front moving over the northwest Arctic coast will result in below normal temperatures through Friday. Drier and milder conditions develop this weekend.

- Northerly winds increase across the Brooks Range Thursday, with potential gusts between 20 and 30 mph through the passes. This is expected to last through the start of the weekend.

FORECAST ANALYSIS AND DISCUSSION

Longwave troughing prevails through Thursday night before shifting southeastward ahead of a building ridge as we move into the extended period this weekend. The primary weather-makers during this forecast period are a closed low over the panhandle and an Arctic trough dropping south across the Chukchi Sea. A weak inverted ridge ahead of the Arctic trough keeps the central interior mostly dry through Thursday with shower and thunderstorm chances increasing toward the end of the week.

The panhandle low focuses precipitation chances across the eastern interior. The primary vorticity maxima tracks north from near Juneau across Canada's Northwest Territories. However, a series of shortwaves embedded within southeasterly flow ahead of the closed low focus rain chances. The first shortwave is currently along the AlCan border and shifts westward along the Alaska Range on Thursday. This disturbance focuses thunderstorm potential with a few thunderstorms over the southeast interior today, isolated storms along the Alaska Range on Thursday, then perhaps an area of scattered storms over the western interior on Friday. A secondary shortwave approaches the eastern interior on Thursday and focuses more stratiform rain chances along the AlCan Thursday night before diminishing on Friday. This disturbance may result in a few isolated thunderstorm chances over the central interior by Friday afternoon.

The Arctic trough over the Chukchi Sea this afternoon shifts south and closes off over the Kamchatka Peninsula tonight then southeast over Bristol Bay by Saturday morning. This system interacts with Thursday's Alaska Range disturbance to focus scattered thunderstorms over the southwest interior on Friday. Farther north, a cold front is stalled across the western Arctic Coast with temperatures near to below freezing and a rain/snow mix behind the front through tonight. Model soundings reveal deep saturation this afternoon that supports mainly snowfall, but a dry slot descends overnight leading to potential for the loss of cloud ice nuclei and more of a freezing drizzle scenario that tapers off Thursday morning. Despite decreasing precip changes, the front moves little until the upper level trough axis shifts southeastward across the North Slope on Friday then into the interior by Saturday.

FIRE WEATHER

July is upon us but we remain in a generally un-summerlike pattern. A series of low pressure systems are rotating around Alaska, keeping fire weather conditions moderate for the near future. Temperatures will range from the high 60s to low 70s, except in the eastern Interior where cloudier and rainier weather will keep things a little cooler. Relative humidity will bottom out in the 30-40% range. Winds should remain mostly unremarkable. Northerly winds build in from the east into the Yukon Flats on Thursday and will be slightly stronger for the entire Interior on Friday and Saturday, but only up to about 10 mph. The best chances for wetting rain will be in the Eastern Interior along the Alcan Border through the end of the week, with one front dissipating today and another building in Thursday into Friday. Otherwise, chances for precipitation will be limited to light showers and a few isolated thunderstorms. Isolated thunderstorm coverage will expand from the Southeast Interior and Brooks Range on Wednesday to include more of the Central/Western Interior and Interior Norton Sound for Thursday and Friday. The lack of wetting precipitation beyond the Eastern Interior means that although we aren't seeing particularly high fuel indices in the rest of the Interior, fuels will be getting steadily drier through the rest of the week. Looking ahead, warmer and drier conditions are favored to build in over the weekend into early next week, with areal coverage of highs in the 70s to near 80 expanding over much of Northern Alaska with afternoon minimum RHs dropping to around 25-35%.

EXTENDED FORECAST DAYS 4-7

The extended period will begin with a Siberian ridge moving eastward towards Alaska pushing out the longwave trough towards Canada. On Monday, it will orient itself over the West Coast of Alaska before weakening on Tuesday, when a Bering Sea low approaches the Southwest Alaska coast forcing the ridge over the Brooks Range. At the same time, the Bering Sea low will shift into Southern Alaska, supporting showers and thunderstorms in the Central Interior into the end of the extended period. This supports increased confidence in precipitation occurring in these areas throughout this period, with heavy rain not being a concern. Model guidance supports temperatures trending near or above normal as the Siberian ridge brings warmer air to Alaska throughout the extended period. Winds are likely to remain calm throughout Northern Alaska during this period with the main weather events being light showers and increased temperatures throughout the period.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Winter Weather Advisory for AKZ801>803. PK...Small Craft Advisory for PKZ806.