Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 647 PM EDT Wed Mar 20 2024 Valid 12Z Sun Mar 24 2024 - 12Z Thu Mar 28 2024 ...Much warmer than normal temperatures expected especially for northern and western parts of the Mainland... ...Moderate to heavy precipitation potential for parts of Southwest and coastal Alaska through the weekend... ...Overview... The pattern across the Alaska domain should stay fairly amplified through the period with a strong ridge across the Mainland, mean troughing across the Bering, and several shortwaves rotating through the mean flow south of the Aleutians and into the Gulf. This should result in warmer than average temperatures across much of the state, with precipitation mainly confined to coastal areas as well as into southwest Alaska. Most systems look to stay far enough south to keep most of the precipitation light in nature, but an early period low pressure system may bring more enhanced rain/snow this weekend. The ridge over the mainland is forecast to gradually weaken next week, but the general pattern should remain in tact much of the period. ...Guidance Evaluation and Preferences... The latest model guidance shows general agreement on the large scale pattern of reinforced troughing/upper low over the Bering/Aleutians and slowly retreating ridging across the Mainland. There remains plenty of uncertainty in the details though, especially concerning individual systems moving south of the Aleutians and into the Gulf. The 12z GFS and ECMWF are the most consistent through the period with each other, as well as the ensemble means and formed the majority basis for today's blend. The UKMET was a little different early on with the placement of a surface low in the Bering as well as a system sliding well south of the Aleutians into the southern Gulf Monday-Tuesday. The CMC for the most part was consistent enough with the ECMWF and GFS on southern stream systems, but was an outlier with dragging a cut off low south along the western Alaska coast and a stronger surface reflection. There are some timing differences with the next system south of the Aleutians on Wednesday (especially the CMC), and another stronger system behind it on Thursday, but for the most part the agreement on these systems is very good for the day 7-8 time frame. The GFS is quite a bit stronger with one system Monday-Tuesday that breaks off the parent upper low and moves into the Gulf, while the ECMWF and CMC show better agreement on just a weak shortwave through the region. Behind this, the ECMWF gets really fast with another shortwave south of the Aleutians. Given the uncertainty in these smaller scale lower predictability systems, the WPC blend for today trended from a purely operational blend on Days 4 and 5, to an increasing reliance on the ensemble means later in the period to help mitigate and smooth out these differences. Overall, this maintains good continuity with the WPC forecast from yesterday as well. ...Weather/Hazards Highlights... Expect the most active area for precipitation to be across the Aleutians and Alaska Peninsula and the western coast of the Mainland, where rounds of low pressure and frontal systems will help focus moist Pacific southerly flow this weekend and into early next week. The most active day should be Saturday-Sunday with some potential for moderate to heavy rainfall across parts of southwest Alaska into the Kenai Peninsula. Given warm temperatures, much of the precipitation should be rain, but snow is possible in the higher elevations. After this, the general pattern should stay unsettled and showery from the Aleutians to the Southern Coast and Panhandle, but most systems should be weak enough or far enough south to limit anything in terms of hazardous weather. Much warmer than average temperatures will likely last through the entire period for much of the Mainland due to the ridge aloft and warm mean southerly flow underneath/on the western side. Temperatures look to gradually moderate early next week but remain well above normal, especially across northern and western parts of Alaska. The eastern interior may trend back towards normal/below normal by mid next week, and Southeast Alaska may be near or below normal much of the period due to influence of multiple systems weakening as they reach the coast. 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