textproduct: Fairbanks

SYNOPSIS

A picturesque low in the Bering Sea is rapidly strengthening and will occlude on Sunday as a front works its way northeast. This front will bring rain, snow and east winds up to 45 mph to the West Coast. The precipitation should be mostly light as the front weakens. There may be some blowing snow in St. Lawrence Island but temperatures across the coast will be in the 30s to near 40, so it is not of great concern. This front moves towards the Interior on Monday but will fizzle out before it gets there. Otherwise, the Interior will be mild and mostly dry with southerly AK Range gap winds increasing in the afternoon. Mild and dry weather continues into Monday before rain/snow showers return on Tuesday with a shortwave trough moving northward from the Gulf. The North Slope and Brooks Range will have temperatures near to slightly above normal with little to no precipitation expected until Monday night and Tuesday. This precip could come as light accumulating snow in the Brooks Range, especially towards Atigun Pass.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Persistent chinook flow keeps highs near to above average, in the 50s to near 60 across the interior valleys.

- Southerly gap winds gradually increase Sunday afternoon with gusts up to 50 mph possible through Monday then decrease on Tuesday.

- A front provides rain and snow showers on Tuesday. A few of these may come with graupel which could result in the first couple of lightning strikes of the year. The highest chance (<5%) is in the Alaska Range Tuesday afternoon.

West Coast and Western Interior... - A strong low in the Bering Sea brings easterly wind gusts around 35 to 45 mph and a mix of rain and wet snow for the West Coast this morning through tonight. Blowing snow is not of great concern. * Snow accumulations up to 3 inches possible in St. Lawrence Island.

- Easterly winds up to 45 mph bring potential for an ice shove (ivu) across Maknik Lagoon today or tonight.

- Rain and snow showers persist through the week. High temperatures range from the 40s and low 50s in the Interior to mid and upper 30s along the coast.

North Slope and Brooks Range.. - East winds increase tonight along the Chukchi Sea Coast with gusts up to 35 mph persisting through Tuesday night.

- A cool front brings snow chances from west to east as early as Monday nigh and especially Tuesday through Wednesday with accumulations possible for Atigun Pass.

- High temperatures in the southern Brooks Range rise into the 40s to near 50. The northern Brooks Range will range from the mid 20s to mid 30s. The Arctic Coast will be in the low to mid 20s with Point Hope being in the upper 30s to near 40.

FORECAST ANALYSIS AND DISCUSSION

The overall pattern won't be changing much over the next week. An upper low will remain over the Bering Sea with an upper high over western Canada. At 500mb, there is a strengthening 498 decameter low north of Adak, a shortwave trough extending from eastern Siberia to the Gulf of Alaska, and a 564 decameter high in the eastern Pacific extending northward towards the AlCan Border. The main feature in this pattern is the low in the Bering which will bring a front to the West Coast beginning this morning. This front is becoming occluded but will still provide active weather to the West Coast. Then, there is a second front that is coming from an energetic shortwave pivoting around the Bering low that lifts across northern Alaska Tuesday/Wednesday.

The occluding frontal system weakens as it moves into our area and is moving into a seasonably warm air mass suggesting lesser impacts. However, the combination of 6+ hours of steady cold rain or perhaps very wet snow and easterly winds gusting up to 45 mph confirm that it will be lousy weather as the front moves across the YK Delta, Seward Peninsula, and St. Lawrence Island. Fortunately, there is no great concern for blowing snow since due to the wet snow and warm temperatures. The potential for an ice shove (ivu) continues to be monitored across Maknik Lagoon. The southwest cape up to Powooilak Camp is also exposed, but sea ice is farther offshore and may not be able to reach the coast before winds weaken.

The next front brings mainly rain chances to many of the same locations Monday and Monday night before shifting northeast across the remainder of northern Alaska Tuesday through Wednesday. The upper level disturbance is energetic and negatively tilted implying strong dynamic forcing that could support convective showers with charge separation for the first lightning strikes of the season. Even if thunderstorms don't materialize, graupel is definitely possible with the stronger cells Tuesday afternoon/evening. Farther south across the Alaska Range, southerly gaps winds and high elevation snow are looking more likely. Snow levels appear to be 2500-3000 ft suggesting the Parks/Richardson highways won't be impacted, but heavy wet snow and strong winds may overload the existing snow pack resulting in some avalanche potential.

EXTENDED FORECAST DAYS 4-7

The extended forecast continues to feature troughing across the Bering and ridging across western Canada resulting in southerly flow over most of the state. The two most noteworthy features appear to be the frontal boundary lifting across the Brooks Range Tuesday night into Wednesday and the second is a low pressure system tracking north near the YK Delta Wednesday night and Thursday. EFI guidance is highlighting potential for unseasonable QPF and snowfall across portions of the Brooks Range and North Slope with the frontal boundary Tuesday night/Wednesday. EFI guidance indicates a similar combination of unseasonable QPF/snowfall potential across the YK Delta and St. Lawrence Island Wednesday night through Thursday night. Elsewhere, southerly winds across the Central Interior/West Coast and gusty winds through the Alaska Range passes remain possible, especially Thursday/Friday when the WPC is highlighting potential for high winds.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. PK...Brisk Wind Advisory for PKZ801-802-817-853. Brisk Wind Advisory for PKZ803-805-806-852. Small Craft Advisory for PKZ816. Brisk Wind Advisory for PKZ850. Gale Warning for PKZ851. Gale Warning for PKZ854.