textproduct: Fairbanks

SYNOPSIS

A storm system approaching Bristol Bay is spreading mainly light snow north across southwest Alaska and the western interior today. Daytime heating is allowing for snow to mix with or change over to rain from south to north through this evening before nighttime cooling allows p-types to switch back to snow. Precipitation chances and amounts diminish as they shift east across the interior on Wednesday due to the Alaska Range scouring out moisture. The time of day and elevation influences precip types with the snow level lifting above 1000 ft Wednesday afternoon. The next system shifts eastward over the West Coast on Thursday then to the Western Interior on Friday. Mainly snow along the West Coast on Thursday transitions to an elevation dependent rain/snow mix across the interior by Friday afternoon. This frontal system also brings south winds gusting up to 45 mph along portions of the West Coast, particularly the western Seward Pen and Lisburne Peninsula. Temperatures trend above normal across all of northern Alaska by late this week with elevation depended highs in the 30s to 40s and lows mainly in the 10s to 20s.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Seasonable temperatures trend above normal by the end of the week as cloud cover increases. Highs range from the 30s to low 40s with lows mainly around 20 with cooler temperatures at higher elevations.

- Southerly Alaska Range gap winds gusting up to 50 mph continue through this evening then gradually decrease on Wednesday.

- A weakening front moves east into the Interior Wednesday into Thursday producing a mix of snow and rain showers depending on elevation and time of day.

West Coast and Western Interior...

- A front continues to bring a mix of rain and snow showers through Wednesday with snow favored at night and at higher elevations and rain favored farther south and at lower elevations during the day. - Highs are expected to climb to near 40 in the interior valleys with values mainly in the low 30s along the coast and at higher elevations. Lows in the teens/20s to low 30s further inland as cloudier conditions return.

- The next frontal system brings a period of steady wet snow to the West Coast on Thursday that transitions to an elevation dependent rain/snow mix across the western interior by Friday. Southerly wind gusts of 40 to 45 mph accompany the front on Thursday then diminish Thursday night.

- Additional chances for mainly light snow continue for the West Coast with mainly light rain chances for the Western Interior.

North Slope and Brooks Range...

- Mostly clear skies and dry conditions with light winds will continue across the North Slope and Brooks Range through Thursday. - A frontal boundary shifts east on Thursday with increasing southerly winds allowing temperatures to rise into the 20s to 30s above.

- Overnight lows will continue to be coldest across the Arctic Plains/Coast around -10F to -20F through Wednesday, with above zero lows by the latter half of the week.

- A light rain/snow mix arrives at the Northwest Arctic Coast and Western Brooks Range Thursday afternoon and continues east across the North Slope through Friday.

FORECAST ANALYSIS AND DISCUSSION

A closed low at the base of a positively tilted trough weakens while shifting east over Bristol Bay tonight. This system brought mainly snow to southwestern portions of our area today, but observations show temperatures warming into the mid 30s and snow mixing with rain on the southeastern fringes of the preciptiation shield. Southerly winds bringing these warmer temperatures are also resulting in southerly wind gusts up to 50 mph through the Alaska Range mountain gaps. Troughing associated with this low pressure shifts east across the interior Wednesday as ridging builds across the Bering Sea. Troughing results in low-end precipitation chances across the eastern interior Wednesday and Thursday. Precipitation type will depend on the time of day, elevation, and precipitation rates but total precipitation amounts are generally less than 0.1" across the interior and locally approaching 0.5" across the West Coast through Thursday night.

The Bering Sea ridging shifts east across northern Alaska on Thursday into Friday bringing a return to dry weather. This amplified pattern shifts east toward Canada on Thursday as a frontal boundary moves over the West Coast bringing a 6-12 hour period of steadier snow. The band of snow diminishes and mixes with rain while shifting inland on Friday. We will also see southerly winds through the Bering gusting up to 40 to 45 mph as the gradient tightens between the low over Siberia and high pressure reestablishing over Alaska. Given the time of year, accumulating snow is becoming more difficult at lower elevations especially during the afternoon and evening hours. Additionally, elevation factors into differences temperatures with larger diurnal temperature ranges in the valleys and vice versa at higher elevations.

EXTENDED FORECAST DAYS 4-7

At the start of the extended period on Friday, we see a weakening 980mb low north of Siberia. A frontal boundary and associated swath of moisture is directed from the northern Pacific into the Western Interior, producing a band of mainly snow from the YK Delta to the North Slope that mixes with rain as it shifts inland. The front shifts ridging east over the Gulf of Alaska, sweeping eastward across the state through Friday. The lows westerly trajectory will result in weakening winds through the northern Bering Strait on Friday. However, flow into western Alaska will remain southerly as another low arrives in the Bering Sea on Friday. Temperatures warm above seasonal averages through the weekend and into the start of next week. In the Interior, expect peaks in the 40s above, with overnight lows still dipping below freezing at night. Along the West Coast, temperatures should get above freezing more regularly but still remain cooler, below 40F. Along the North Slope, temperatures will be well above average, with the western half potentially getting above freezing Friday and Saturday. Otherwise, temperatures in the 20s above are expected through the weekend.

Confidence has improved with respect to another surface low that arrives in the Bering Sea Saturday morning. Ensemble low locations are in fairly good agreement on the feature advancing slowly along the Siberian coast on Friday, then model solutions diverge between having it continue north or take a detour through the Bering Strait. The main difference between these two paths is the extent of precipitation along the West Coast, with the Bering path producing more substantial rain/snow showers farther into the Western Interior. Regardless, the system should be low impact and the Interior and North Slope remain generally clear and calm through the extended.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. PK...Brisk Wind Advisory for PKZ816. Brisk Wind Advisory for PKZ851.