Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Sun Jul 09 2023 Valid 12Z Thu Jul 13 2023 - 12Z Mon Jul 17 2023 ...Overview... A stacked low pressure system is forecast to meander around the northern Pacific for the latter half of this week into the weekend, and the initial surge of moisture with this system should lead to some moderate rain amounts around the southeastern quadrant of the Mainland into Thursday. Farther north, the upper-level flow should be a little more progressive, with a ridge over western Alaska Thursday while likely weakening somewhat while it tracks eastward ahead of troughing moving from the Kamchatka Peninsula into the Bering. The strength of the upper ridging moving across the Interior will help determine how much temperatures could warm there, but the relative warmup may end up somewhat brief or with only slightly above average anomalies. ...Guidance Evaluation/Preferences and Predictability Assessment... Model guidance remains in good agreement with the persistent low pressure aloft and at the surface in the northern Pacific. Farther north there are larger model differences. Upper ridging across the western part of the state seems agreeable on Thursday, extending from a strong upper high in the Pacific on Thursday. But how strong the ridge stays as it tracks eastward depends at least partially on energy farther east, with small-scale troughing generally across the North Slope on Thursday. Occasional model runs from multiple model suites have been showing energy there dropping into the Interior possibly with a small closed low--for the 12Z cycle the UKMET did so, while the CMC did as well but farther north. While it does not seem prudent to show a closed low at this time, it does seem to suggest that energy could be strong enough to erode some of the ridging as it moves east. Meanwhile farther west there is a fairly good consensus for troughing to track from the Kamchatka Peninsula into the Bering Sea and western Alaska with time, but models start to diverge with the potential of hanging up energy there or dropping it southeast across the Aleutians into the northern Pacific early next week. Given these considerations, the WPC forecast was based on a blend of the 06Z and 12Z GFS runs, the 12Z ECMWF, and a bit of the 12Z CMC, while also incorporating the GEFS and EC ensemble means. As is typical, increased the means percentage as the forecast period progressed as model spread increased. ...Weather/Hazards Highlights... Low pressure over the northern Pacific/Gulf of Alaska will allow for some precipitation to affect the southeastern part of the Mainland on Thursday. Rainfall amounts do not look to be too heavy but could be relatively enhanced over the eastern Alaska Range. A swath of moisture ahead of the upper trough and a cold front could bring some rain chances to the Aleutians and western Alaska Thursday-Friday and into the Alaska Peninsula Friday-Saturday. Scattered mainly light showers are possible across much of the Interior on most days likely following a diurnal pattern, which could be relatively enhanced but still likely just light to moderate over the Alaska Range. Temperatures at the start of the forecast period Thursday are likely to be a bit above average across western Alaska underneath upper ridging. The ridge tracking eastward should transition the above normal temperatures to the eastern Interior for late week, while the western part of the state becomes closer to average. Areas of the eastern Interior could see temperatures rising into the 80s, though model guidance still varies on how warm temperatures could get dependent on the strength of the ridge. Southeast Alaska is also likely to warm above average late week before a cooling trend. Tate 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