Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EDT Sun May 14 2023 Valid 12Z Thu May 18 2023 - 12Z Mon May 22 2023 ...Spring warming to advance central/eastern Interior snowmelt runoff and river ice breakup threats this week... ...Guidance Evaluation/Predictability Assessment... The 12 UTC ECMWF/UKMET/Canadian and ECMWF ensemble mean solutions seem best clustered for later this week. A composite blend was preferred for this time period. Recent GFS/GEFS runs now offer more outlier solutions seemingly emanating across the forecast domain from less likely system/flow stream phasings out from the northern Pacific. Forecast spread remains problematic, lending a switch to the ECMWF ensemble mean that best provides day to day continuity into next weekend. This overall strategy also maintains reasonably good WPC product continuity despite a pattern still generally with below average forecast predictability. The blending of compatible guidance tends to mitigate small-mid scale system variances consistent with predictability. Applied manual edits to ensure sufficient surface low pressure center depths and wind speeds as supported aloft, but otherwise muted by the blending process and forecast spread. ...Overview and Weather/Hazard Highlights... Expect a warm and dry pattern over Southeast Alaska into later this week under an upper ridge. Upper ridging and warmer temperatures are also forecast farther north into the central and especially eastern Interior/Yukon Flats this week that will broadly increase the rate of snowmelt runoff and river ice breakup and lead to flooding threats. Please refer to ongoing advisories and watch/warnings from your local weather offices for impacts, details and needed actions. Slow pattern translation and uncertain splitting and phasing of Bering Sea/Aleutians and northern Pacific upper trough/system energies will also bring surface low pressure systems to coastal western/southwestern Alaska into Thursday before retrogression away from the area through the Aleutians. Expect some lingering wrapping precipitation. Meanwhile, this pattern will also support the rotation of organizing maritime systems to settle from the northern Pacific to across the Gulf of Alaska to linger and offer renewed sweeping precipitation chances for the full Alaskan southern to southeastern tier late week into next week, albeit dependent on low positioning that remains uncertain in guidance. Schichtel Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html