Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 614 PM EDT Sat Apr 10 2021 Valid 12Z Wed Apr 14 2021 - 12Z Sun Apr 18 2021 ...Locally heavy rain possible for parts of Southcentral Wednesday... ...Guidance/Uncertainty Assessment... The upper pattern will feature anomalous and blocky flow next week with troughing along 160W and ridging over the Bering and NW Canada/AK Panhandle by Friday. An upper low is forecast to sink south-southeastward with multiple embedded vortices around it, suggesting lower predictability on the smaller to medium scale. The trend over the past day or so has been toward a bit quicker progression of the trailing shortwave that tugs the upper trough southward late next week into the weekend, which allows folded over ridging to connect along 55N late in the period. This would open up the flow to the north from the northern Bering across the North Slope and Beaufort Sea to more zonal flow. Though the GFS and Canadian were a bit removed from the better clustering (and better consensus) of the 12Z ECMWF/UKMET/Canadian ensembles and 00Z ECMWF ensembles, they were not too far from consensus around the edges of the domain. Therefore, a small minority weighting of the GFS/Canadian rounded out the larger consensus weighted mostly toward the ECMWF/UKMET and Canadian/ECMWF ensembles. This did nudge the systems around here and there as smaller timing differences at the onset grew with time, but overall the pattern evolution remained much in line with continuity. ...Weather/Hazards Highlights... Southerly flow Wednesday coincident with the system through the Gulf will sustain well above normal precipitable water values, perhaps nearing as high as they can reach for this time of year, as low pressure moves across Kodiak. Widespread modest to heavier rain (and elevation snow) are possible for parts of Southcentral (southern Kenai to Prince William Sound) where 1-2 inches of rain will be possible with locally higher amounts on south-facing terrain. Once that system lifts northeastward out of the region, upper ridging will nose in from the southeast as the upper low sinks southward through the northeastern Pacific. This should introduce a drying trend for most of the state starting Thursday into Saturday. A system will skirt through the North Slope with little precipitation. Temperatures will be milder than average for especially northern areas of Alaska as southerly flow brigs warmer air northward. The Panhandle and parts of Southcentral/southeastern Alaska may see an extension of below normal temperatures with high pressure nearby. Fracasso Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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