Alaska Extended Forecast Discussion National Weather Service College Park MD 603 PM EDT Sun Sep 7 2025 Valid 12Z Thu 11 Sep 2025 - 12Z Mon 15 Sep 2025 ...Moderate rain into parts of coastal Southcentral Thursday... ...Guidance Evaluation/Preferences... Upper troughing between 150-160W will largely remain anchored in place later this week into next week, initially by a modestly deep system in the Gulf and then reinforced by an incoming upper low out of the North Pacific. The downstream pattern will be blocked by strong upper ridging over northern Canada while upstream the ensembles show building ridging over eastern Asia/Kamchatka. Combined with an upper low currently between Siberia and the North Pole that will retrograde into central Russia, the jet will transition toward split flow into the Dateline which lowers confidence in any specifics. However, the 12Z deterministic guidance offered reasonable clustering even out to next Monday (Day 8) but will see if this holds in future cycles. For the first couple of days in the forecast, a deterministic blend sufficed to handle the decay of the system in the Gulf. Thereafter, there remains a good deal of spread with the incoming North Pacific system and the models continue to waver on speed/track/depth. The GFS/ECMWF offered good agreement with the ensemble means in principle, and used that along with some Canadian guidance to round out the forecast through next weekend into next Monday. Though this did modify the timing of the next system, opted to follow with the latest thinking per the ensemble consensus. ECMWF AIFS was close by as well, though perhaps a bit quicker overall which is not unreasonable given the pattern orientation/setup. ...Weather/Hazards Highlights... The system near the Aleutians should promote lingering breezy conditions over favored areas across the AKPen on Thursday, with modest to heavier rain eastward across coastal Southcentral to around Yakutat. This area will see the greatest moisture surge ahead of the cold front combined with enhanced lift from the terrain. Rainfall totals of a few inches are possible along the coast with several inches (3-6"+) toward Yakutat per the NBM/models. For the rest of the Interior, scattered showers will linger through the period thanks to lingering upper troughing. With a trend toward a bit lower heights, temperatures will be cold enough for snow over the Brooks Range where a few inches are possible. Temperatures will be the most below normal over the North slope beneath the upper low, but above normal over the Panhandle ahead of the cold front. Temperatures will trend cooler than normal for much of the mainland with perhaps some moderating starting next week. Fracasso 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