Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EST Thu Nov 16 2023 Valid 12Z Mon Nov 20 2023 - 12Z Fri Nov 24 2023 ***High winds and heavy precipitation expected for south-central Alaska early next week*** ...Synoptic Overview... A large Arctic surface high will be entrenched across eastern portions of the mainland and into the Yukon Territory for early next week. An incoming strong low pressure system from the North Pacific is progged to enter the central Gulf by Tuesday, and this will create an unusually steep pressure gradient across the south-central and southeast portions of the state, particularly near the coast, generating very windy conditions and an onslaught of deep maritime moisture towards the coastal mountain ranges. By midweek, this low weakens and a second storm system crosses south of the Alaska Peninsula and towards the western Gulf towards the end of next week, bringing more inclement weather to the region. Farther west across the Bering, an intense surface low on Monday is forecast to weaken steadily going into the middle of the week, but most of the wind and precipitation should stay west of the mainland. ...Guidance Evaluation and Preferences... The 12Z model guidance suite is generally in good overall synoptic scale agreement, with the exception of the UKMET that is displaced well to the east of the model consensus with the Gulf low early in the week. Looking ahead to the end of the week, the GFS is a little southeast of the consensus with the next low pressure system approaching the Gulf, but close enough to be a plausible solution. The greatest degree of model spread is across the western Bering and Aleutians with the next system to affect the region. A non-UKMET compromise was used through late Tuesday, followed by gradually increasing percentages of the ensemble means going through Friday. ...Weather/Hazards Highlights... A high impact weather event is looking increasingly likely for south-central portions of the state on Tuesday and into Wednesday as a potent surface low tracks northeastward into the Gulf. The 1040+ mb high over western Canada will create quite a pressure difference, and this will generate strong east to southeast winds across the northern Gulf and the coastal areas, with gusts into the 50-60 mph range possible and extremely rough seas. Additionally, strong onshore flow from the Alaska Peninsula to the Chugach Mountains will hammer this region with very heavy precipitation during this time, and models have trended higher compared to yesterday's guidance. Several feet of snow is likely for the higher elevations, and 4-8 inches of a cold rain for portions of the coast. More bad weather is possible later in the week as well, but this will be dependent on the eventual track and intensity of the second Gulf low. In terms of temperatures, a frigid start to the week across the Interior is forecast to modify some going into midweek as the Arctic high slides southeast away from the state. Milder air will likely be the case for the south-central portion of the state with more onshore flow and maritime air mass influence. Hamrick 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