textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

A shortwave trough is currently moving through Anchorage and the Mat-Su Valleys this morning, bringing areas of light rain and mountain snow. These will taper off through the morning, spreading into the Copper Valley and eastern Sound through Wednesday morning. This shortwave will also usher in some of the coldest air of the season, with 850 mb temperatures dropping to around -2C by Wednesday morning.

For Wednesday and Thursday an upper low and shortwave trough currently moving off of far eastern Russia will move over Kodiak Island early Wednesday morning before moving slightly north into the Gulf coast by Wednesday afternoon. This will help pull another shortwave trough and even colder airmass currently over the Chukchi Sea over Southcentral by Thursday. All of these features will combine to bring lift and a colder airmass to the region. For Wednesday, there are some discrepancies on where the surface low will develop, with high-res models pushing the low into the eastern Sound quicker with the upper level trough further to the east. This solution would yield drier conditions for Anchorage and the Mat Valley while leading to steady precipitation over the eastern Sound and Copper Valley. The alternative is a slower shortwave and the low lingering south of the Kenai Peninsula a little longer before then moving into the Sound. This solution would yield steady precipitation in the form of valley rain and upper elevation snow for Anchorage and the Mat Valley. All areas will likely receive precip Wednesday and Thursday, it's just a matter of where these features track for who will get the heavier precipitation. It does still look like the higher elevations of the Anchorage and Eagle River Hillsides will get snow Wednesday and/or Thursday, with more significant (2-4" possible) if the slower and farther west storm track ends up verifying. These areas would be Glenn Alps and South Fork Eagle River.

LONG TERM FORECAST (Days 4 through 7: Friday through Monday)

An active weather pattern continues as we make our way into October. An upper level trough over Interior begins to move out of the region. This was responsible for the colder than average temperatures for Southwest, Southcentral, and the Alaska Peninsula. The departure of the low will bring a slight warming trend through the weekend.

There are signs of slight ridging over Southcentral for Friday, which will be the best chance to see some sun. This will be short lived since a Gulf low is expected to bring rain and wind for the weekend. Looking at integrated vapor transport from the GFS, the values are low. Which means that the system is not transporting a lot of moisture from the tropics. Meaning, the low is not expected to generate a notable amount of precipitation. Using the GEFS member spread, the pressure gradient is nothing note worthy. No significant winds are expected at this time.

Another low from Kamchatka comes into the Bering Sea, then tracks over the Aleutian Chain through the weekend. There is growing model agreement of the low reaching peak maturity before going tracking through the Bering. Meaning minimal impacts, just like the other Bering lows that have gone through this week. There is low confidence of where the system goes after the weekend. Half of the members from the GEFS have the centers of the low track into the Gulf, crossing over the Alaska Peninsula. Other members have centers scattered around the Bering.

AVIATION

PANC...VFR conditions are expected initially, though brief MVFR ceilings will be possible through 16Z with passing showers. Light rain becomes more persistent after 16Z, with ceilings lowering to around 3500ft and periods of MVFR ceilings near 2500ft possible through 20Z. Ceilings then improve to around 5000ft after 20Z as precipitation diminished. Winds remain light through the taf period, shifting from southerly to northwesterly Tuesday afternoon.

-LM