textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

There is very little change to the overall forecast this afternoon. Our resident Gulf low will finally meander east and into Southeast Alaska tomorrow afternoon. Areas of fog remain across Southcentral this evening into tonight, though less widespread from yesterday. Into the overnight hours chances are high that fog redevelops and lingers through the morning hours on Monday. Colder temperatures and the retreating low will maintain gap winds through Passage Canal, Resurrection Bay, and Valdez Narrows into Valdez Arm.

The next front moves into the western Gulf later tomorrow with increasing easterly winds into Kodiak Island Monday night. Current thinking is that these winds will expand in coverage across the Gulf, with small craft winds covering much of the Gulf by Tuesday morning. The strongest winds will be through the Barren Islands and into Kamishak Bay, with easterly gusts as high as 35 knots.

Southcentral will remain largely dry Monday into Tuesday and the increasingly drier air mass should help erode more of the fog tomorrow and Tuesday. The front over the western Gulf will push into the northern Gulf coast on Wednesday with precipitation chances returning to coastal mountains and Prince William Sound.

BL

LONG TERM FORECAST (Days 4 through 7/Thursday through Sunday)

All attention in the long term should be paid to a likely atmospheric river event that could span from the Eastern Aleutians to as far east as the Cook Inlet region Friday and heading into the weekend.

Diving into the knowns and unknowns, the upper level pattern looks to become increasingly more amplified Friday morning as a deep, longwave trough takes shape over the Bering, Aleutians, and North Pacific with textbook difluent flow downstream over the western Gulf and interior Southwest Alaska. An anomalously strong 500 mb ridge over Southcentral Alaska, Gulf, and North Pacific becomes anchored over the weekend, forcing the storm track to become more north to south, which would track lows from the North Pacific to the Eastern Bering and northward up the western Alaska coastline.

Model agreement has decreased since yesterday, but guidance shows the semblance of a shortwave trough amid the mean upper flow rotating over the North Pacific as the longwave tries to take a negative tilt. This combination of forcing develops a surface low somewhere across the North Pacific and sends it northward towards the Aleutians and so on. However, location and timing of the low is poor as of the latest runs of the global models.

Along with being a wet system with periods of heavy precipitation, the possibility of strong winds are certainly there depending on the strength of the surface low and its associated front, though this parameter is of lower confidence. There is also a question of how much warm air advection the system may bring into Southwest Alaska, in which case rain and mixed p-types would likely make for hazardous conditions considering its current snow/ice cover.

Please stay tuned over the coming days as the forecast comes more into focus.

-AM

AVIATION

PANC...Fog and low stratus will prevail over the terminal through Monday morning. Like yesterday, there may be a period of VFR ceilings and visibilities this afternoon into early evening as breaks in the fog develop. However, fog, along with LIFR conditions are likely to return this evening and persist through the overnight hours as flow remains both weak aloft and at the surface. An inversion near the surface will also help low-level moisture to be locked in at the surface further aiding to the ingredients for fog development. A developing northeasterly flow aloft early morning Monday may help to erode and push the fog bank west away from the terminal by mid-morning Monday. There is still some model uncertainty regarding this solution. Nonetheless, it is possible that the rather stubborn fog bank diminishes earlier on Monday than we have seen the past two days.