Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 708 PM EDT Fri Sep 27 2024 Valid 12Z Tue Oct 01 2024 - 12Z Sat Oct 05 2024 ...Strong winds, significant waves, and some moderate to heavy rainfall expected to accompany a strong storm system into the Panhandle Monday-Tuesday... ...Overview... The main system of concern will be early in the period as an upper low through the Gulf early next week spins up a rather deep surface low which tracks into the Panhandle region around Tuesday. This will bring a low end atmospheric river, with periods of moderate to locally heavy rainfall, strong winds, and significant maritime hazards/wave heights to portions of the southern Coast and especially Southeast Alaska. The pattern remains fairly progressive into mid next week as the next system slides across the Alaska Peninsula into the Gulf, keeping south-central to southeast Alaska somewhat unsettled. Another deep surface low will move into the Bering Sea late next week, likely bringing some rainfall and more uncertain wind/maritime hazards. ...Guidance Evaluation/Preferences... Models overall show good agreement with the large scale pattern through the period, but plenty of uncertainty in the details. There has been a trend westward with the initial deep system in the Gulf, now bringing possibly more impacts to parts of the southern Coast. The UKMET was farthest east/south with this system and was not used in the blend today as it seemed an outlier compared to the other deterministic guidance and ensembles. There are also some timing differences with the next system as it enters the Gulf mid week, though the 12z CMC tracks it more southward than eastward like the better consensus would suggest. The GFS and ECMWF bring this system into the Panhandle, with agreement from the ensemble means, but significantly weaker than the prior storm. Models also continue to show good agreement on the existence of a deep Bering Sea system late next week, but with a lot of uncertainty on the track and timing. There is good agreement right now with the 12z GFS and ECMWF with the ensemble means, so that was used as the basis for the late week forecast. Overall, the forecast maintained good consistency with yesterdays forecast. ...Weather/Hazards Highlights... The early week surface low into the southern Panhandle region of Southeast Alaska will bring with it maritime hazards, rainfall, and gusty winds. While periods of heavy rainfall are possible, the winds will be the true hazard with this storm. Some model guidance suggests likely storm to near hurricane force winds are possible in some locations along with significant wave heights. The storm should move quickly inland late Tuesday. Some strong winds may impact parts of the Kenai Peninsula and Kodiak Island as well. After this, the remainder of the Southeast/Southern Coast area should remain generally unsettled with light rain expected as another weaker system passes from Bristol Bay into the Gulf mid week. A large and deeper storm system should enter the Bering Sea late in the period, with increasing rain chances along the West Coast and through the Aleutians Thursday into Friday, and more uncertain but possible maritime hazards and coastal flooding depending on the exact track of this storm. In a broad sense, cooler than normal high temperatures are likely over southern parts of Alaska and warmer than normal temperatures are likely for the northern two-thirds of the Mainland during the period. 40s to low 50s are forecast for highs in most lower elevation areas, with an overall warming trend as next week progresses. Most areas should see greater coverage of above normal morning lows though. Santorelli 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