textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages:

- Flood Warning remains in effect for the Petersville area through 5PM this afternoon.

- Flood Warning remains in effect for the Yentna River including Lake Creek through 1PM Friday.

Discussion:

No major changes with this forecast package as things look mostly on track. The pattern remains fairly stagnant, with scattered, intermittent light showers moving from south to north across the Cook Inlet region and into the Matanuska Valley. The driver of this precipitation is a stalled, decaying front draped from the northern Susitna Valley southward to Kodiak Island, which is essentially the remnants of our atmospheric river that once again hit the Susitna Valley hard with flooding this week. Flood Warnings remain in place for Petersville through 5PM this afternoon and another for the Yentna River and Lake Creek through 1PM Friday. The good news for Southcentral is that the region will trend warmer and drier through the rest of the week and into the weekend as high pressure builds in, which should help alleviate flooding concerns.

At 500 mb, a negatively tilted trough anchored by a closed low over the Norton Sound will begin to lift out of the region by Friday morning. Meanwhile, the mean flow over Southcentral will shift to a southwesterly one, and as the drier and warmer trend continues through Friday afternoon, weak waves embedded within the flow will likely help touch off a few showers across the Copper River Basin. There is currently a low to medium (30-40% chance) of an isolated storm or two as well, though confidence as of now is on the lower end. The model consensus right now looks marginal for storms, and even the usual aggressive NAM does not seem all that excited as of now, but definitely something to monitor - mainly because temperatures heading into Friday and Saturday afternoon will be in the mid to upper 70s to near 80 degrees with generally low (30-40%) relative humidity values. All said, the message is that we could be approaching red flag criteria this weekend for the Copper Basin. With the addition of low end chances of thunderstorms, fire weather concerns remain lower than average, but certainly non-zero for this weekend for the Copper Basin.

-AM

LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)

By the end of the weekend, troughs of low pressure will be moving through the South/Southeastern Bering Sea, moving over the Aleutians in the area. There is a divide between model solutions on where the lows will drop through precisely, and if it would bring gusty winds and/or rain to the Alaska Peninsula Sunday. That being said, the strength of these lows are not impressive, lending to the idea of weaker winds and rainfall totals anyway. Through Tuesday, as the troughs move through, a col may develop over the southern/central Bering Sea, leading to a mixed pattern of showers and confused winds and waves.

Over the Southern Mainland of Alaska, weak areas of high and low pressure are expected to develop through the late weekend and early next week. The resulting weather will be diurnally- driven showers this weekend into next week. This pattern supports more of a scattered shower regime as opposed to widespread stratiform. The challenge will be to gauge instability each afternoon to determine whether or not lightning will be a threat with any robust showers that form. Right now, it looks like the Copper River Basin, along the Talkeetna Mountains, and along the Western Alaska Range feature the most instability through the long-term period.

-CL

AVIATION

PANC...Southerly flow continues aloft with light southerly to southeast winds at the surface. Expect VFR conditions this afternoon transitioning to MVFR by this evening and overnight as a few showers move over the terminal. By the end of the TAF period, Thursday morning, showers will taper off. However, ceilings will continue to remain MVFR due to low-level moisture lingering.