Tropical Tidbits from the Tundra

Redoubt restless - Snowy February?

By: Levi32, 5:27 PM GMT on December 18, 2008

There's lots of excitement in southcentral Alaska today. After dumping several inches of snow on the Kenai Peninsula yesterday, a slow-moving low pressure system is beginning to move off towards the east. Scattered snow showers remain north of Clam Gulch and reaching into the Anchorage Bowl. These showers will gradually diminish by tomorrow afternoon. Strong winds and single-digit temperatures on the back side of the low will generate nasty wind chills tonight and tomorrow throughout the area.

Down in Homer and Anchor Point some places are still experiencing blizzard conditions with 3-5 inches of new snow so far today. You may ask how is that possible if I see nothing on the radar loop? That's because the part of the peninsula south of Anchor Point is experiencing their version of lake-effect snow, similar to the Great Lakes region in the lower 48. In the SW quadrant of a storm such as this one that brings in an arctic airmass behind it, strong winds blow over the waters of Cook Inlet. These waters are much warmer than the air flowing over them, and so the atmosphere becomes unstable because warmer air near the ocean surface wants to rise. Shallow storm cells form over the water as a result, and are undetectable by radar because they are too low. Despite being shallow, these snow showers can get very intense and can drop several feet of snow at times if the low to the northeast sits in the same spot for a while. People along the coastline of Kachemak Bay get this the worst because the winds funnel right up the bay and stay over water longer than if they were just crossing the inlet.

The current snowfall will begin to taper off in about 12 hours as the 500mb vort max, currently over Bristol Bay, moves to our east and the flow aloft becomes dry out of the northwest, as opposed to the current moist flow out of the southwest.

As for the longer term, the developing pattern with a waning La Nina and cold over the eastern United States is going to set up a trough over Alaska for the next 10-15 days, which will flatten any ridge which tries to nudge it out of the way. This will set up 2 primary storm tracks: 1) Straight from the south out of the eastern Pacific and up into the gulf. 2) Riding the Aleutian chain from the west and southwest and skimming under or over the southern Alaskan coasts and into the gulf or southern interior. This will mean lots of snow during these systems and cold arctic air behind each one as they pass, spaced 2-3 days apart. Overall it's looking like February will be a very wintry month!

We shall see what happens!

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Volcano Information:

Mount Redoubt's unrest continues to intensify today. Seismographs and reports from the Alaska Volcano Observatory show increased action under the mountain. According to AVO no eruption has yet occured, despite several very intense episodes of seismic activity this morning. Current watch level is still at ORANGE. More information can be obtained from the AVO website.

Current Seismograph near the summit of Redoubt:

Current Ash trajectory forecasts (valid 10:00pm AKST tonight):

Current Redoubt Webcam:

Current Redoubt Webcam from across Cook Inlet:

Major snow event for the southern coasts

By: Levi32, 6:34 PM GMT on December 08, 2008

A significant snow event is shaping up for the southern and southeastern coastal regions of Alaska. Beginning today, a deep low pressure system south of Kodiak Island will spread an occluded front northward toward the SE panhandle, stretching all the way west to Bristol Bay. This would normally be a rain event for the gulf coast and panhandle with a deep-layer southerly flow, but an arctic high anchored over western Canada and interior Alaska has kept a firm dome of frigid air locked in place, which has been inching southward. The warm air associated with low to the south is going to hit a brick wall as soon as it reaches the coast, and temperatures even on the immediate coastline won't exceed the freezing mark by much during the course of the storm. The warm air will be forced up over the arctic airmass causing heavy overrunning snow. This is one of the best setups for record snow in southeast Alaska. The NWS has winter storm warnings out for Yacutat and the northern panhandle calling for up to 2-3 feet of snow in most areas of the upper panhandle and eastern gulf coast, and localized amounts of over 4 feet are possible in mountainous areas. Strong wind out of the SE will cause blowing snow and low visibility. People should stay safely inside and listen to the warnings posted by the NWS.

The affect of this storm further west isn't quite as obvious yet. The GFS takes the low center east of Kodiak and up into Prince William Sound, a good setup for snow in the Anchorage Bowl and the rest of southcentral. The jetstream will continue to deepen the low until it gets north of Kodiak Island, taking it below 960mb, so it's a good bet that this storm will deliver enough moisture to drop at least a few inches of snow in most areas of southcentral. Initial precipitation may start as rain near the Homer/Seldovia area, as temperatures are still in the upper 30s there, but the arctic air creeping southward will pull temperatures down below freezing by tonight, turning any precipitation into snow. Rain/snow will be periodic and sparse through tonight as the mountains will block most of it for now. The real deal will come once the low moves into Prince William Sound and across the Kenai Peninsula, moving north of Anchorage. This will bring all the cold air in and the wrap-around moisture on the west side of the low will bring snow. Right now it's still a bit too early to be calling amounts, but I think a solid 4-8 inch event is shaping up for the Kenai Peninsula and Anchorage Bowl. Some nasty winds out of the NW could spice things up and lower visibilities in blowing snow over the western Kenai Peninsula on Monday into early Tuesday. 20-30 mph winds with higher gusts are expected. By Thursday the low will have weakened significantly and moved off to the north. Lingering snow showers over the inlet will slowly taper off by the weekend.

We shall see what happens!

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Webcam overlooking Homer and Kachemak Bay:

Webcam mounted on Peterson Bay weather station looking across toward Homer:

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Tropical Tidbits from the Tundra

About Levi32

Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.

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