Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Wed Mar 30 2022 Valid 12Z Sun Apr 03 2022 - 12Z Thu Apr 07 2022 ...Overview... Alaska will begin next week with an overall pattern of upper troughing/lows over the state, which should persist particularly over western Alaska through the medium range period. At the surface, low systems are expected to track across the northern Pacific/Gulf of Alaska while additional low pressure may linger near the southwestern mainland. This will promote a wet pattern for southern Alaska, particularly over the Panhandle, though amounts do not look to be terribly heavy. Meanwhile a reasonably tight surface pressure gradient with an arctic high and southern Alaska lows could lead to some moderate to strong winds over the North Slope during the early part of the week, along with some breezy conditions possible along other low tracks as well. ...Guidance/Predictability Assessment... Recent model guidance shows fairly good clustering with the initial pattern Sunday-Monday over Alaska, with upper low centers over the Bering, northern mainland, and the northern Pacific/Gulf. Most models also seem to capture two surface lows in the northern Pacific/Gulf reasonably well, with one in place early Sunday and another south of the Alaska Peninsula moving east by Monday. With the second low, the 12Z UKMET appeared to be a bit of an outlier by day 5/Mon with its position farther south of consensus, but the GFS/ECMWF/CMC all seem within reasonable spread for a medium range forecast. It also still appears that separate, likely weaker low pressure will hover near the southwest mainland. Ensemble means seem to capture this better in recent model cycles compared to previous ones that showed (probably erroneously, given the deterministic guidance) a mean position for more combined low pressure. Given the fairly good initial agreement, utilized a blend of the GFS, ECMWF, and CMC deterministic runs for the early part of the forecast period. Flow upstream shows more significant differences beginning Monday and through midweek. Energy across Siberia should move eastward toward Kamchatka and the Bering Sea Monday into Tuesday, but with notable timing issues, as the ECMWF remains a slower solution. This causes models to be out of phase by Tuesday and beyond. While yesterday it was just one run of the ECMWF that was different from consensus, the EC runs have stayed consistent with their ridge pattern in the western Bering Tuesday and the UKMET is pretty similar, as opposed to the GFS runs carrying an upper low that tracks over the Aleutians by Tue-Wed and a separate upper low nearer the Panhandle by midweek. On the other hand, the EC shows one trough axis across western Alaska Wednesday-Thursday stemming from the upstream differences. The ensemble means are flatter of course but generally follow the deterministic models' pattern. The 12Z CMC may be the best compromise, but this is all quite uncertain given the flow's origin. These upper-level differences affect the timing/positioning of a relatively strong surface low coming from the southwest toward the Panhandle midweek. For the latter part of the WPC forecast, leaned slightly away from the ECMWF/UKMET cluster partly due to continuity, but with low confidence. Had the greatest weight on the GEFS mean by days 7-8. ...Weather/Hazard Highlights... Precipitation is possible over southern parts of Alaska from the Aleutians and Alaska Peninsula east into Southcentral Alaska and the Panhandle through much of next week near low pressure systems. Precipitation amounts should vary from day to day and place to place. Some rain/snow amounts could be enhanced at times, but the heaviest totals through the period will be dependent on exact low tracks that are uncertain at this point. The current forecast indicates southern portions of the Panhandle may receive the most precipitation overall, with local enhancements elsewhere. Interior Alaska should see generally dry conditions as the storm track stays to the south. Periods of gusty winds are also possible along low tracks, and the gradient south of Arctic high pressure may support a period of strong winds across the North Slope. Near average to below average highs are forecast over much of the state early in the week, with the greatest anomalies across the North Slope and lower elevations of the interior. The cold anomalies could ease by the middle of next week, but troughing over the southwest mainland could shift highs from above normal Sunday closer to normal as the week progresses. Low temperatures should be closer to normal over the North Slope and Interior compared to the cool highs, while milder than average lows are predicted in the southern mainland and the Brooks Range. The Panhandle can expect to see below normal highs and around average lows through the period. Tate Hazards: - High winds across portions of northern Alaska, Sun-Mon, Apr 3-Apr 4. 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