Alaska Extended Forecast Discussion National Weather Service College Park MD 702 PM EDT Sun Jun 15 2025 Valid 12Z Thu 19 Jun 2025 - 12Z Mon 23 Jun 2025 ...Warm temperatures will persist across the Interior through next weekend... ...Overview... An omega block will set up over the Alaska domain later this 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 moving more quickly 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 the week, along with scattered convection. Meanwhile a low pressure/frontal system should lead to a round of rain moving from the Aleutians 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 way the Bering upper low and the northern Pacific shortwave and surface low interact and combine by around Friday. At the 12Z Friday timeframe, the surface low shown by the 12Z ECMWF and CMC is near/just north the Aleutians while the GFS runs are just to the south over the northern Pacific. The model averaging puts the low just atop the eastern Aleutians but AI models are generally favoring a slightly southern solution. The low positions late this week are a bit farther west than yesterday's. Over the weekend, the upper and surface lows are forecast to meander near the eastern Aleutians. The main outlier appears to be the 12Z GFS that shows a farther southwest position with the lows. Preferred to use the 06Z GFS run in the model blend instead, which was more aligned with consensus, especially because AI models were east even of the deterministic model consensus. This continues into early next week, where the AI models and ensemble means were east with the upper low position closer to Bristol Bay compared to farther west deterministic models. Overall the most uncertain forecast area is the western Mainland at the interface of the trough/low and ridge to its east. But at least the western trough/eastern ridge pattern remains agreeable on the large scale. WPC preferred a multi-model deterministic blend (including the 06Z GFS) for the early part of the forecast. As the period progressed, used some GEFS and EC ensemble means, reaching over 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 Thursday. The Yukon Flats can expect the highest temperatures, with some 90s possible, 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 Y-K Delta and 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 Seward Peninsula and vicinity should cool down close to average by next weekend and early next week as upper troughing could finally approach. The slowly weakening upper ridge will also allow for temperature anomalies to lessen somewhat, but remain warm over the Interior. Meanwhile, troughing moving across Southeast Alaska should lead to below normal temperatures there later this week, but by the weekend temperatures are forecast to rise as the upper ridge builds in, reaching 70F in some areas. Many Mainland/Interior areas can expect diurnally forced convection given the instability created in part by the hot temperatures. Rain and thunderstorms will likely be scattered from day to day through the period, and there may be locally heavier rainfall amounts in higher elevations of the Brooks and Alaska Ranges with some orographic enhancement. Into Thursday, Southeast Alaska is forecast to 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 Thursday and across the Alaska Peninsula Thursday-Friday, with more modest amounts reaching Southcentral by next weekend. Winds are likely to peak around 30-40 knots with a front in the Aleutians/Alaska Peninsula vicinity Thursday-Friday. 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