Alaska Extended Forecast Discussion National Weather Service College Park MD 714 PM EDT Mon Jul 21 2025 Valid 12Z Fri 25 Jul 2025 - 12Z Tue 29 Jul 2025 ...Overview... At the start of the period Friday, a closed upper low will be located over the south-central Alaska Mainland within an elongated upper trough stretching toward Southeast Alaska (the Panhandle). This upper low is forecast to track into the Gulf of Alaska and deepen over the weekend, along with a surface low pressure system, which should lead to rounds of precipitation for the Alaska Range southward along the southern coast to Southeast. The lows will be slow to move in the blocky pattern with an upper high north of the state, lasting into early next week while gradually weakening. Meanwhile upper ridging is forecast to reorient from the northern Pacific and build northward across the Aleutians and Bering Sea, causing temperatures to warm from west to east. ...Guidance Evaluation/Preferences... Individual model and ensemble guidance is pretty agreeable with the large scale pattern described above through the weekend. The pattern is quite blocky with an upper high over the northeast Pacific and another in the Arctic Ocean, with Alaska's upper trough/low in between. The primary upper low emerging into the Gulf shows good agreement in 12Z guidance through Saturday, with a little more spread as it meanders into Sunday and beyond. The 12Z CMC was a bit southeast of consensus with the surface low by Sunday while the UKMET was southwest, so favored the 12Z GFS/ECMWF and their means. Models also align well regarding ridging aloft and at the surface from the northern Pacific northward into the Aleutians and southern Bering Sea through much of the period. Broader model differences arise early next week with the possibility of upper troughing emerging from eastern Siberia and the Arctic Circle to the west of the Beaufort Sea upper high. It is uncertain how much headway the trough(s) will make in displacing the ridges that are in place and how long that will take. Models and ensemble members generally show some troughing reaching at least the Seward Peninsula if not to the Y-K Delta by Monday-Tuesday. This will likely continue to be a forecast challenge in future days. The WPC forecast used a multi-model blend favoring the ECMWF and GFS early to mid period. As the forecast progressed, used some GEFS and EC ensemble means in the blend and reduced the proportion of individual models, reaching just over half ensemble means by Day 8 given the increasing model spread. ...Weather/Hazards Highlights... The low aloft and a frontal system will promote precipitation across much of the state into Friday. Moderate rainfall amounts are forecast in the Alaska Peninsula to the Alaska Range and Southcentral, with lighter amounts in the Brooks Range/Interior before a drying trend there. Additional rain is likely to focus in the Alaska Range and Southcentral into Southeast Alaska over the weekend and early next week with the upper and surface lows nearby. Rainfall totals are not currently expected to reach hazardous levels anywhere, but will continue to watch as rain over multiple days could add up. Wet snow is possible in higher elevations of the Alaska Range. A front approaching, along with potential upper troughing coming into the Bering Sea and vicinity, could lead to rain chances across the Alaska Peninsula and western Mainland into next week, possibly spreading east across the Mainland. Due to the upper low, cooler than normal temperatures may linger into Friday for portions of the Interior into Southeast Alaska. But ridging aloft and continental easterly flow at the surface should bring a return to above normal temperatures for most Mainland areas by the weekend. Highs will generally be in the 70s in most Interior areas. Temperatures may cool back down in the western Mainland early next week depending on the evolution of the upper trough. Southeast Alaska can expect temperatures to remain near to below average with the low in the vicinity. 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