Alaska Extended Forecast Discussion National Weather Service College Park MD 644 PM EDT Tue Jul 1 2025 Valid 12Z Sat 05 Jul 2025 - 12Z Wed 09 Jul 2025 ...General Overview... An upper high will remain parked over the Arctic and North Slope through the weekend, resulting in above average temperatures that will contribute to heightened thunderstorm chances and fire weather concerns from the Interior to the North Slope. To the South, a few low pressure systems are expected to track east across the Aleutians into the Gulf, which will result in unsettled weather and enhanced precipitation chances for the southern coast and Southeast Alaska. ...Guidance Evaluation/Preferences... Overall, model guidance is in fairly good agreement on the upper level pattern with some uncertainty in the evolution of individual upper lows and associated surface features. Ensemble means from the GEFS/ECENS/CMCE are in very good agreement through the entire period, and the deterministic guidance from the GFS/ECMWF/CMC/UKMET are well clustered through the weekend. By early next week, the influence from the strong northern ridge wanes as the ridge weakens and the evolution of upper lows tracking to the south becomes uncertain. All models are in good agreement on the low tracks, moving east across the Aleutians and into the Gulf, but details such as timing and strength are still somewhat unclear. The largest differences appear Monday into Tuesday with the main low in the Gulf. The general consensus among the deterministic and ensemble guidance is to slow/stall the main low over the Gulf while a secondary low drops into the Gulf behind it and ridging builds ahead of it over western Canada. The 12Z GFS diverges significantly from the consensus, pushing energy from the leading low into Canada and bringing the second low into the Gulf much faster than expected. As the secondary low strengthens in the Gulf late Tuesday into Wednesday, model agreement increases again with an expected amount of model spread for this time range. For WPC's forecast blend, a near even blend of the deterministic GFS/ECMWF/CMC/UKMET was used through the weekend, then ensemble means from the GEFS/ECENS/CMCE were added in increasing amounts through early next week. Some influence from the deterministic guidance was retained Monday-Wednesday, with the ECMWF/CMC making up a minority portion of the blend. The GFS was phased out early next week as it seems to be an outlier from the general consensus. ...Weather/Hazards Highlights... The influence of the strong upper ridge over the Arctic and North Slope will be felt well into the Interior as high temperatures rise into the 70s and 80s each day through the weekend. Temperatures will decrease slightly but still remain warm early next week as the high weakens. Above average temperatures will support isolated thunderstorm chances over the Interior, which may also lead to heightened fire weather concerns as lightning could spark new fires amid dry antecedent conditions. For southern portions of the state, lows tracking into the Gulf will result in unsettled weather and daily precipitation chances. Heavy precipitation is expected to focus over the southern coast, Kenai Peninsula, and Kodiak Island this weekend, then the focus should shift into Southeast Alaska early next week as an upper low stalls over the Gulf. This pattern is expected to direct a plume of moisture at Southeast Alaska, which could result in heavy rainfall Tuesday and Wednesday. Chances for light to moderate precipitation will likely linger along the southern coast through early next week as well. Forecast precipitation and cloud cover should keep temperatures cooler in these areas with daily high temperatures in the 50s and 60s. Dolan 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