Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 PM EST Thu Feb 15 2018 Valid 12Z Mon Feb 19 2018 - 12Z Fri Feb 23 2018 Latest guidance indicates a sharp and amplified upper-level ridge extending up through the state of AK this coming weekend. ECMWF and GEFS means suggest these 500mb heights being 2 to 2.5 standard deviations above average. A split flow upper trough does slide through this ridge and state on Sunday. However, this feature has very little influence on the anomalous ridge, while most of the upper dynamics dive southeast and pool over the northeastern Pacific. Thus the dome of upper high pressure builds back up and covers the majority of the state Monday through part of Tuesday. The operational and ensemble guidance capture this scenario quite well and added confidence in the upcoming forecast into early next week. By next Tuesday or Wednesday, the models begin to diverge on short wave details and whether the upper ridge survives. The ECMWF is very bold and aggressive in driving upper dynamics from the Pacific and Bering Sea through the state with the upper ridge reappearing west of AK next Friday. The last few runs of the GFS are slower in driving a swath of upper dynamics through AK but also depict a broad upper ridge re-appearing south or southwest of the state. Meanwhile both means pretty much carry some resemblance of the ridge over the state throughout with more subtle upper dynamics/short wave passing through. WPC followed more of a mean pattern for Wednesday through next Friday with small percentages of the operational GFS/ECMWF sprinkled in. The heaviest qpf over the 5 days will occur across most of the Aleutians with pockets of heavier precipitation across west central AK. 850mb temperatures will be slightly above normal, mainly a .5 to 1 standard deviation above average. Musher