Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 626 PM EDT Fri Apr 11 2025 Valid 12Z Tue 15 Apr 2025 - 12Z Sat 19 Apr 2025 ...Another in a series of deep storms to offer heavy precipitation and high wind/wave threats for the southern tier of Alaska and the northern Gulf of Alaska Tuesday-Thursday... ...Guidance/Predictability Assessment... Prefer a composite blend of the now well clustered 12 UTC GFS/ECMWF/UKMET/Canadian models to provide maximum detail as consistent with a pattern with above normal predictability valid Tuesday-Thursday. Forecast spread has decreased from prior run cycles, trending deeper and with a westward shifted main low track up toward the Mainland from the North Pacific. This trend seems reasonable given the already well defined nature of the current system off of Japan. Forecast spread increases slower than normal over longer time frames in the wake of the main low this period,but added to the composite blend minority influence from the 12 UTC ECMWF/NAEFS ensemble means to smooth the less certain smaller scale rough edges. ...Weather/Hazards Highlights... A leading northern Gulf of Alaskan low will lose influence and weather focus by Tuesday. However, the guidance signal has risen in support of the development and northward track of a deep low from the Northern Pacific towards the eastern Aleutians and Alaska Peninsula/Bristol Bay Tuesday into Thursday, with weakening system energies and precipitation possibly lingering over the northern Gulf of Alaska next Friday into Saturday. The surface system will have potent upper low/trough support aloft and coupled downstream upper ridge amplification will act to slow eastward progression more than indicated over the past few guidance run cycles. Mean moist southerly flow wrapping near and east of the low will focus a multi-day period with locally heavy precipitation potential from southern Alaska into portions of Southeast Alaska, mainly Tuesday into Thursday. In this period of deepest low strength and pressure gradients, northerly winds and gap winds on the backside of the low both over the eastern Aleutians and the Alaska Peninsula as well as with leading winds up through Kodiak Island and southern Alaskan coastal areas through especially the Alaska Range may prove quite strong and gusty. The low will also present a well organized maritime hazard to monitor. While additional influx of upper through energies will meanwhile work up into/over the Interior, significant moisture or more than localized pockets of snow are not expected there. 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