Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 709 PM EDT Fri Jul 19 2024 Valid 12Z Tue Jul 23 2024 - 12Z Sat Jul 27 2024 ...Hazardous heat possible for parts of Interior Alaska early next week with increasing heavy rain threat late week... ...Overview... A strong upper ridge over the mainland as the period begins Tuesday will continue to promote well above normal temperatures for much of interior and northern Alaska through about mid next week, bringing some of the hottest temperatures of the season thus far. South of the ridge, a deep upper low will bring a period of moderate to locally heavy rains to parts of the Panhandle before it shifts inland on Wednesday. Another deep upper low will meander in the Bering Sea through about mid-week, then shift eastward eventually bringing heavy rainfall and significantly cooler temperatures into parts of the western to central/southern Mainland later next week. ...Guidance Evaluation/Preferences... The latest guidance continues to have a good handle on the overall synoptic pattern, and a general operational model compromise worked well for the day 4-5/Tuesday-Wednesday time frame. After Wednesday, differences in the operational guidance increases with respect to interactions with the upper low over the Bering Sea and additional energy dropping southward through eastern Russia. 12z GFS and CMC show a stronger system into Russia which should pull the upper low northward and sending troughing eastward into the West Coast quicker. The 12z ECMWF however shifted to a much slower progression/evolution of the upper low and troughing into the West. The ensemble means (along with some support from the AI models) favor the faster GFS and CMC and thus is how the WPC forecast leaned late period. However, compared to a day ago, there has been a trend for a slower trough progression, so timing of the rainfall into Alaska is still very uncertain. The WPC forecast leaned heavily on the ensemble means late period, with some inclusion of the operational GFS to help add some detail where feasible. ...Weather/Hazards Highlights... The surface low pressure system lifting towards the Panhandle region will bring some wet and unsettled weather to the region around Wednesday next week, with locally heavy rainfall possible. An initial weakening front through the Aleutians early week will bring some generally light precipitation, but additional shortwave energy and a secondary low pressure system behind this will spread rain west to east across the Aleutians into mid week. The cold front should reach the West Coast around Thursday or Friday next week, with an increasing threat for more widespread rains progressing steadily eastward with time across the Mainland into early next weekend. Some of the rainfall could be heavy in spots, especially along/near the favored terrain. Gusty winds may accompany this system, depending on exact strength, but should remain below hazards thresholds. Well above normal temperatures will continue through Wednesday, with parts of the Mainland/Interior seeing some of the hottest temperatures of the season so far, bringing daytime highs into the 80s to near 90 degrees, with an increased wildfire threat as well. The ridge breaks down by Thursday and the next cold front will usher in cooler temperatures. By next Friday, much of Western and Central/Northern Alaska could be 10 to 20 degrees below normal. The exception to the heat will be across Southeast Alaska, where temperatures may be near or below normal for much of next week. 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