textproduct: Fairbanks

SYNOPSIS

An arctic airmass has settled into all of Northern Alaska today and will in place for nearly a week. Despite the increasing sun angle this time of year, high temperatures have struggled to get above the -15F to -20F range. Expect temperatures to plummet each evening after sunset as lows make a run into the -30F to -40F range for the majority of Northern Alaska. Interior valleys have the best chance at dipping below -40F each morning through this weekend, while locations right on the coast in Western Alaska may remain a few degrees warmer than areas further inland.

Watching strong northerly gap winds through the Alaska range passes the rest of today and into Thursday. Strong winds upwards of 45 mph have resulted in blowing and drifting snow and ground blizzard conditions. Therefore, a Blizzard Warning has been issued for Isabel Pass through Thursday afternoon...with rising visibility and diminishing winds thereafter. Cold Weather Advisories also remain in effect for the Alaska Range and Upper Tanana Valley as windy conditions have resulted in wind chills at or below -50F at times.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- An extended stretch of drier and much colder conditions persists into the first week of March. Daily lows in the -30F to -45F range expected, coldest locations in Interior valleys. Highs during the day should peak in the teens below zero.

- Blizzard Warning is in effect for Isabel Pass through Thursday afternoon for white out conditions from blowing and drifting snow.

- Cold Weather Advisories remain in effect for the Alaska Range passes and Upper Tanana Valley for the next several days for wind chill values at or below -50F.

- Large amounts of snow on frozen rivers and streams is leading to areas of water overflowing the ice. Use caution while travel along or on frozen waterways.

West Coast and Western Interior...

- Northwesterly winds through the Bering Strait will gust up to 40mph through Thursday morning. Strongest expected from Wales to Nome as well as St. Lawrence Island. Blowing snow will reduce visibility at times.

- A extended period of below normal temperatures continues through the weekend with lows in the -15F to -40F range. Highs during the day should peak in the teens or single digits below zero.

- Large amounts of snow on frozen rivers and streams is leading to areas of water overflowing the ice. Use caution while travel along or on frozen waterways.

North Slope and Brooks Range...

- Winter Storm Watches for blizzard conditions have been issued for the Northeast Arctic Coast, including Nuiqsut, Deadhorse, and Barter Island. The threat begins Friday morning and may persist into the following week for areas east of Deadhorse.

FORECAST ANALYSIS AND DISCUSSION

A deep polar airmass has settled into Northern Alaska today with many areas struggling to rise above -20F this afternoon. Satellite imagery shows clearing skies across the north and west, while the upper level low, which ushered in this airmass, has traversed the state and is now centered over Kayak Island. Upper level moisture from the Pacific has rotated around the upper low back into the Eastern Interior as seen on satellite imagery today. 500mb vort maps depict an upper level boundary stretching from the Northern Yukon to Ft. Yukon to near Bettles which has sparked light snow showers along and south of the Brooks Range. Any snow shower activity should be fairly light, but since temperatures through the column are well below the dendritic growth zone, fine snow grains will result in reduced visibility under any snow shower in the SE Interior today. Expect clearing for the Eastern and SE Interior over the next 12 to 24 hours as the upper low weakens and pulls off into Canada, shutting off upper level moisture advection into the state.

Leeside troughing off the Alaska Range should keep a surface low pressure system in the Northeast Gulf of Alaska for the next 24 to 48 hours. With a strong 1046mb+ high in Siberia continuing to overspread Alaska, the northerly pressure gradient along the Alaska range should keep northerly winds through the passes. Winds to 45 mph combined with the recent heavy snow has already resulted in blizzard conditions from blowing and drifting snow. These conditions will likely persist into Thursday before winds diminishing Thursday evening and visibilities improve. In addition to blowing snow, Cold Weather Advisories remain in effect for the Alaska Range and also Upper Tanana Valley for wind chill values at or below -50F.

For the rest of the state, well below normal temperatures continue through at least this weekend as surface high pressure remains in place and reinforcing shots of cold air pivot southward from the high arctic. The core of the incoming polar airmass will be directly overhead through Thursday with 850mb temperatures as low as -30C to -37C, well below normal for this late in the winter. Fairbanks 00z sounding today showed nearly the entire column at or below -30C, which is incredibly cold and deep, even for Alaska standards. Despite a 2000ft mixed boundary layer this afternoon, surface temperatures are still hovering in the -15F to -20F range, even with diurnal heating. A cold airmass this deep supports lows each morning in the -30F to -45F range across the majority of Northern Alaska, with the coldest spots in interior valleys where temperatures may approach -50F in some locations. Still watching how fast clouds clear in the far eastern and SE Interior as any cloud cover will keep surface temperatures relatively warmer than those areas that clear out. Due to the increasing sun angle this time of year, expect afternoon highs to reach the teens below zero; however expect a rapid drop in temperatures each evening around sunset.

Issued Winter Storm Watches for the Northeast Arctic Coast beginning Friday morning and persisting into the weekend as numerous fronts rotate around an intense 465dm upper low over the Canadian Arctic Archipelago. The first front arrives Friday morning with a 50-60 kt barrier jet developing along the NE Arctic Coast. This is a classic set up for an extended period of Blizzard Conditions in this region. Issued Watches as far west as Nuiqsut, where Blizzard conditions are possible Friday into Saturday. Further east toward Point Thompson and Barter Island, Blizzard conditions may persist through Monday March 2nd as additional fronts rotate in from the north and impact the coast. Lower confidence exists for Deadhorse and points west for Blizzard Conditions the latter half of the weekend as the strongest barrier jet may remain to the east.

Mid range ensembles do show upper level moisture from these polar fronts sagging southward into the Central and Eastern Interior Saturday and Sunday. Any upper level clouds may significantly impact surface temperatures this weekend, so will have to watch closely if upper level moisture can make it over the Brooks Range. Cloud cover in these deep arctic air masses can prevent the surface from losing heat, making for less than idea conditions for radiational cooling, helping keep temperatures significantly warmer and the low level inversions weaker. Will keep an eye on this and adjust the forecast as needed.

EXTENDED FORECAST DAYS 4-7

The extended stretch of well below normal temperatures continues into the first week of March. While the upper trough over the state pushes into Northern Canada and weakens, a secondary upper low over the Canadian Arctic Archipelago retrogrades closer to the state, bringing a reinforcing shot of arctic air to Northern and Eastern Alaska this weekend and near blizzard conditions to the Northeast Arctic Coast. The core of the arctic airmass with 850mb temperatures below -30C, becomes centered over Northwest Canada and Eastern Alaska this weekend. While the majority of the state will remain well below normal, coldest temperatures remain in the east while temperatures moderate somewhat in Western Alaska with highs nearing zero and lows still in the teens to 20s below zero. Eastern Interior valleys likely have several more days with low temperatures at or below -40F, potentially lasting into the first week of March. Still expecting large diurnal ranges in this clear, cold, and dry airmass as the increasing sun angle allows for afternoon temperature rises into the negative single digits and teens.

Keeping an eye on cloud cover making its way south of the Brooks Range as waves of energy rotate around the polar low in the high arctic. Moisture from these systems is usually fairly limited in such a cold airmass; so confidence at this time remains only marginal for cloud cover and its impacts on temperatures Sunday into early next week.

As mentioned above, the NE Arctic coast will be dealing with an extended period of blizzard conditions into the long range period. Highest confidence remains from Point Thompson to Barter Island; with lower confidence in blizzard conditions from Sunday onward for Deadhorse to Nuiqsut.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Blizzard Warning for AKZ850. Cold Weather Advisory for AKZ848-850-851. Cold Weather Advisory for AKZ836. PK...Brisk Wind Advisory for PKZ806. Brisk Wind Advisory for PKZ807-854-856. Brisk Wind Advisory for PKZ817. Brisk Wind Advisory for PKZ851.