Winter snow expected to make its presence felt this weekend

WASILLA — With scant snowfall across the most of the Mat-Su so far this winter, elements aligned Thursday evening to bring much of the state its first good taste. A major winter storm began its eastward track across Alaska Thursday afternoon with blizzard warnings on the Baldwin Peninsula.

The National Weather Service (NWS) officials issued a Winter Storm Warning for Mat-Su Wednesday afternoon. As of Thursday, the NWS was predicting 6 to 10 inches of snow for the area including Palmer, Wasilla, Sutton and Chickaloon through Friday morning. That amount was expected to be as much as 10-14 inches in the higher elevations along the Talkeetna and Chugach mountains. For areas from Houston to Cantwell and points east of Parks Highway, the same 6 to 10 inches was anticipated. The northern two-thirds of the state--with the exception of the north slope, were also facing the same scenario with winter storm and blizzard advisories posted.

The first expected significant storm for the borough resulted from a cold front providing good lift of moist, southwesterly winds from a low-pressure trough stemming the Gulf of Alaska and up Cook inlet. As of Thursday afternoon, only light snow had been reported across the region. Precipitation was anticipated to pick up at press deadline Thursday evening. Depending on winds, the NWS said a broad offshore flow along the north Gulf Coast could increase snow totals.

NWS officials said areas of South-Central south of Anchorage were expecting rain as temperatures rose above freezing. However, because of surface temperatures have been below that, rain was freezing on road surfaces. Whiteout conditions were reported near Kotzebue and surrounding areas.

By this morning, a short blast of reinforcing cold air was expected to flow in as the storm moved east. That colder air will be short-lived but will bring clearing skies starting this afternoon and into the New Year's Day weekend as temperatures in the Valley flirt with the freezing mark. So far this winter, persistent arctic highs have kept most storms stranded out in the Gulf affecting the state's panhandle region. NWS officials said the short-term weather pattern for at least the next week is expected to remain favorable for any strong storms moving up from the Pacific to affect South-Central.

Outdoor activities

According to Hatcher Pass Avalanche Center (HPAC) data, the recent snowfall may give winter outdoor enthusiasts a false sense of security. HPAC reports the avalanche hazard remained considerable above 3,500 feet and moderate at lower levels throughout the pass as of Thursday mainly due to persistent slabs. As of Thursday afternoon, approximately 16-24 inches of snow were on the ground in the uplands.

According to HPAC, the existing snowpack is very weak and discontinuous making for a complex avalanche situation. This is because there are areas completely devoid of an avalanche hazard, mixed with areas where triggering an avalanche are likely. Data revealed a very weak, sensitive snowpack. There is a possibility, and in some areas likely probability to trigger remote avalanches.

HPAC personnel stress those accessing Hatcher Pass should not take the considerable hazard warning lightly. More people end up in avalanche trouble when the danger level is considerable than any other rating. HPAC states because snowpack is so thin and low and mid elevations-- under 2,500 feet (low) and under 3,500 feet (mid), individuals may be lured into climbing into higher elevations where avalanche hazard levels are much higher.

According to HPAC, the fact that the area went from a non-existent snow winter to what it termed "full-on, scary avalanche conditions in a shallow snowpack" only complicated matters. It stated avalanches were remotely triggered just before Christmas. A snowboarder triggered a 25-foot wide, 60-foot hard slab slide on a 38-degree incline at the 3,800-foot mark of Marmot Ridge.

The most recent information from HPAC stated the area has tracks in steep terrain where avalanches were not triggered. This does not mean that these areas are safe. It may only take a person to migrate a short distance from an existing track to find the avalanche problem. Anywhere stiff, firm snow exists, there is a high likelihood of triggering an avalanche, according to officials.

Hatcher's mid- and lower-elevation snowpack is very shallow with exposed bushes and rocks. In many areas the snowpack is only a few inches deep. Pockets of stiff slab are present, but highly discontinuous, limiting the size of possible avalanches. Those in the area are encouraged to avoid areas withterrain traps, cliffs, and exposed hazards such as rocks. Even a small avalanche carrying you into this type of terrain can be very dangerous, state officials.

For the most part, HPAC stated, current areas of concern resides in specific locations at the upper elevations near ridgelines where previous wind loaded snow built stiff hard slabsup to two-feet thick. However, at mid-elevation, in specific areas where winds previously wind-loaded leeward features, it will also be possible to trigger persistent slabs. Avalanches will be stubborn to very sensitive—remote triggers possible to trigger. The distribution of the problem is highly variable. Their behavior will be difficult to predict. Avoid steep—30 degrees or greater—large, open slopes, terrain traps andrun-outs with rocks where triggering an avalanche could have higher consequences.

Expect to hearwhumpfingand in some cases produce shooting cracks in even the most benign, low angle terrain. Whumpfing is the sound made when the fracture of a lower snow layer causes an upper layer to fall or collapse, making a "whumpfing" sound. Avalanche experts warn such sounds are an obvious sign of instability.

"Whumph” has actually been adopted as a technical avalanche term to describe the sound of a collapsing snowpack when you cross the snow...this is the sound of nature screaming in your ear that the snowpack is very unstable. Most snowpacks collapse onto a “persistent” weak layer such as faceted snow, depth hoar or surface hoar, although occasionally whumphing occurs on very wet snowpack as well," states the National Avalanche Center.

Avalanche experts advise those hearing the sound when outdoors to heed caution and offer the following advice. Proceed with extreme caution or tuck tail and find a safer area to play. The best advice is stay on lower angle terrain--25 degrees or less and out of the run-out of steeper slopes where the snow quality for riding is actually quite good, but the avalanche danger is lesser.

Experts suggest those interested in avalanches to poke around in safe terrain. That will provide you with a thin, weak snowpack to study, an opportunity to test slabs over weak snow, and a chance to experience whumpfing and cracking.

For the latest Hatcher pass Data, visit the HPAC website at http://alaskasnow.org/forecasts-observations/hatcher-pass/#observations.