Alaska Extended Forecast Discussion National Weather Service College Park MD 738 PM EDT Sat Jun 14 2025 Valid 12Z Wed 18 Jun 2025 - 12Z Sun 22 Jun 2025 ...Warm temperatures will persist across the Interior through next week... ...Overview... An omega block will set up over the Alaska domain next week, consisting of an upper low in the Bering that slowly drifts south while merging with a shortwave, another upper low in the northeast Pacific midweek moving east, and a persistent and anomalously strong upper ridge/high atop much of the Mainland in between the two lows. The upper high will bring long-lasting warm temperatures to the Interior in particular through much of next week, along with scattered convection. Meanwhile a low pressure/frontal system should lead to a round of rain moving from the Aleutians Wednesday-Thursday into the Alaska Peninsula Thursday-Friday. ...Guidance Evaluation/Preferences... Individual model and ensemble guidance is quite agreeable with the large scale pattern described above. Minor model differences appear with the shortwave rounding the southern side of the larger Bering upper low that will likely track across the northern Pacific along with its surface low. Some models close off a separate upper low south of the Aleutians around Thursday before merging the lows as they interact sometime on Friday. The 12Z UKMET seemed to disagree with the position of the upper lows, as it showed the upper low centered atop the Aleutians Thursday, but could not rule it out completely since the latest available (06Z) GFS Graphcast was similar. By Friday the CMC seemed to favor the southeastern low (originally the shortwave) unlike other guidance. By next weekend, model spread just increases further with the details as GFS runs split the upper lows and the ECMWF just lingers farther west than consensus. At that point the CMC is perhaps the closest to the ensemble means. These model differences are all pretty minor within the broader pattern agreement even through the extended range, fortunately. Upper ridging sticks around farther east until the Bering lows may gradually push it east next weekend, depending on the model. The WPC forecast preferred a blend of the ECMWF/GFS/CMC for the early part of the forecast. As the period progressed, used some GEFS and EC ensemble means, reaching half models/half means by Day 8 to mitigate the increasing model spread. ...Weather/Hazards Highlights... Warm to hot temperatures will be ongoing underneath the upper high as the period begins Wednesday. The Yukon Flats can expect the highest temperatures, nearing 90, while temperatures will be in the 80s through Interior areas like Fairbanks. These temperatures are above average by around 10 to 25 degrees across the Interior toward the North Slope. The multiple days of hot conditions could lead to fire concerns, especially in areas where it does not rain. The Y-K Delta and vicinity may cool down closer to or just below average by next weekend as upper troughing could finally approach. Meanwhile, Southeast Alaska should see close to average temperatures much of the period. Many Mainland/Interior areas can expect diurnally forced convection given the instability create in part by hot temperatures. Rain and thunderstorms will likely be scattered from day to day, and there may be locally heavier rainfall amounts in higher elevations of the Brooks and Alaska Ranges with some orographic enhancement. Around Wednesday-Thursday, Southeast Alaska may see modest rain as the upper low moves overhead. Then farther west, moist inflow ahead of a low pressure system and its associated fronts will spread moderate to locally heavy rain across the Aleutians Wednesday-Thursday into the Alaska Peninsula Thursday-Friday, with more modest amounts reaching Southcentral by next weekend. 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