Alaska Extended Forecast Discussion National Weather Service College Park MD 549 PM EDT Sun May 18 2025 Valid 12Z Thu 22 May 2025 - 12Z Mon 26 May 2025 ...Overview... Troughing will dominate the northeastern Pacific late this week through the weekend, with successive reloading of the Gulf upper low. Weak troughing will be present over much of the mainland, and a quasi-zonal/progressive flow across the Bering/Aleutians will bring in chances of rain to the island chain. For much of the state, it will be seasonable to perhaps cooler than normal with scattered showers beneath the troughing and steadier rain accompanying/preceding the more coherent systems (mostly over the Aleutians, coastal Southcentral, and into the Panhandle). ...Guidance Evaluation and Preferences... Ensembles remain in good agreement through the medium range, but the faster flow smears out much detail by later in the period. Overall pattern shows that any attempted ridging along 180 will be transitory as the main positive anomaly will stay just south of the Aleutians and the northern portion over northeastern Russia will meander in place. This opens the door from the NW Pacific across the Bering Sea/Aleutians for two to three systems in this 5-day period on a WNW to ESE path, ultimately ending in the Gulf. The GFS was close to the broad/ensemble consensus, but did differ in the track of the systems days 6-8. The 12Z ECMWF was closer to the preferred track/continuity and had support from its machine learning counterpart. Used this heavily in the weighting to add detail to the blurry ensemble means, but confidence was lower in specifics due to the quick flow. ...Weather/Hazards Highlights... Weak troughing over the mainland will promote near to below normal temperatures amidst mostly cloudy skies and widespread showers with perhaps some thunder over the interior. More focused rainfall can be expected over the Aleutians with the passing systems and along the northern Gulf Coast into the Panhandle, depending on how close the parent low wobbles northward. Rainfall should be on the lighter side with any surge in mid-latitude moisture aimed into central/southern BC, but could lift northward into parts of the Panhandle. 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