textproduct: Fairbanks

SYNOPSIS

Remnants of this past weekend's arctic front are slowly exiting the Fortymile and upper Tanana valley and into the Canadian Yukon this afternoon. Cloudy skies with a few lingering showers, or even a thunderstorm, remain possible this evening. Meanwhile a couple of weak shortwave troughs will move through the North Slope...Brooks Range and Seward Peninsula Wednesday into Thursday. Gusty west- southwest winds will occur, especially across the Lisburne Peninsula. Freezing levels are projected to increase to above 5000 feet ASL on Wednesday. Precipitation might begin as a wintry mix before quickly changing over to rain over Atigun Pass. The eastern Brooks Range should block most of that precipitation from the eastern Interior on Thursday though isolated showers near the Canadian border will be possible. The big story into this weekend is a strong high pressure ridge that will build over northern Alaska. Skies will primarily stay clear with a warming and drying trend. Widespread high temperatures in the 70s, and even 80s will develop throughout the Interior.

KEY WEATHER MESSAGES

Central and Eastern Interior... -Lingering chances of isolated showers for the Fortymile and upper Tanana valley through this evening, with drier weather developing the remainder of the week.

-Temperatures through this weekend will warm into the 70s and low 80s as a ridge of high pressure builds over the area.

West Coast and Western Interior... -Areas of light rain fog along the West Coast Wednesday and Thursday. Drier and warmer for areas farther into the Interior.

-Gusty west winds 15 to 25 mph Kotzebue Sound into the northwest Interior for Wednesday.

North Slope and Brooks Range..

-A storm system will spread rain across the North Slope and Brooks Range Wednesday into Thursday. Gusty west-southwest winds will occur.

-Drier and warmer weather is expected by Friday.

SHORT TERM FORECAST DISCUSSION

through Friday Clouds, isolated showers and thunderstorms over the Fortymile and upper Tanana valley will diminish this evening as a weakening front moves east into the Yukon.

A ridge developing over the Bering Sea will begin to move east over the Interior the next several days. As the associated high pressure builds overhead, the ridge will deflect shortwave troughs trying to advance out of the Chukchi Sea into the North Slope. Bands of rain will move across the the Lisburne Peninsula northward tonight, and then through the rest of the North Slope and the Brooks Range on Wednesday into Thursday. Most of the associated moisture will be blocked by the Brooks Range, though some light rain is possible near the Canadian border on Thursday. This is a warmer system than last weekend's arctic trough with model soundings showing freezing levels rising to above 5000 feet ASL. Atigun Pass might begin as a wintry mix before quickly changing over to rain with this system.

Friday the building high pressure ridge will be the dominant feature over northern Alaska. Skies should stay mostly clear with a drying trend. 850mb temps will increase into the 10-14C range by Friday over much of the Interior.

FIRE WEATHER

Skies have cleared behind a cold front which came through the Interior earlier this week. The exception is in the southeast Interior where the front lingers, resulting in cloudier weather in the Upper Tanana Valley and over Fortymile Country. Even where there are few clouds, the cooler air mass is keeping fire weather conditions moderate. Temperatures in the Interior should remain below 70F Tuesday and in the low 60s where there are clouds. The air mass is dry, but the cooler temps should lead to moderate relative humidity as well, between 30 to 40 percent at a minimum. Isolated thunderstorms may develop over the higher terrain surrounding the upper Tanana Valley Tuesday and Wednesday afternoon.

A ridge of high pressure will begin to assert itself over Alaska over the next few days. However, as it tries to do so, another arctic trough will come in from the northwest on Tuesday night to resupply the Interior with cool air. As a result, moderate temperatures and RHs will persist through Thursday. Winds will increase slightly along with the passage of the trough on Wednesday. Winds will be westerly in the Interior, with gusts in the teens for the valleys and stronger for higher elevations.

The ridge becomes more dominant starting Friday, leading to temperatures peaking in the mid 70s on Friday, and reaching the upper 70s and 80s in the Interior by the weekend. Minimum relative humidity will likely be in the 35 to 25% range in the Interior. This ridge looks to remain the key weather feature through the first few days of August. The ridge will shift east through the weekend, bringing the area of hottest temperatures along with it. The Yukon Flats should have the best chances to see temperatures above 80F on Sunday. The ridge should suppress thunderstorm development through the weekend. Light southerly chinooking across the Alaska Range Sunday as the ridge axis shifts to the east and a low drops south across the eastern Bering Sea.

LONG TERM FORECAST DISCUSSION

Saturday through Tuesday A high pressure ridge will remain in place over northern Alaska into Sunday. 850mb temperatures remain in the 10-14C range especially over the Central and Eastern Interior, so continued warm and dry conditions. Upstream a broad longwave trough will extend from the North Pole to about 35N, south of the Aleutians. In the middle will be a boundary separating cooler/wetter weather from the warmer and drier weather. All three 12z extended models show this transition region setting up over the Western Interior. The GFS appears to be the outlier in spreading a moist, southwest flow into the Eastern Interior by Monday. Both the Canadian and ECMWF ensembles are weaker with the energy bumping into this ridge and preferred. They keep the trough axis over the West Coast limiting clouds and rain.

The models then seem to realign restrengthening the high pressure ridge over northern Alaska while spinning up a low over Bristol Bay by next Tuesday. This would result in more warm and dry weather over northern Alaska except for the Yukon Delta and southwest Interior. If this ridge remains this persistent, we could begin to push heat advisory criteria by the middle of next week for the Central and Eastern Interior, and perhaps up into the Arctic Plains.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. PK...Small Craft Advisory for PKZ806-807-856. Small Craft Advisory for PKZ810. Small Craft Advisory for PKZ811-812-858. Small Craft Advisory for PKZ854. Small Craft Advisory for PKZ857.