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Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
650 FXAK02 KWNH 182327 PMDAK Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 727 PM EDT Tue Jun 18 2024 Valid 12Z Sat Jun 22 2024 - 12Z Wed Jun 26 2024 ...Overview and Guidance Evaluation/Preferences... There will be three main low pressure systems of interest in the extended forecast. The first will be a slowly retrograding polar upper low across eastern Siberia, a surface low/upper low tracking in the general direction of the southern Southeast Panhandle this weekend, and a third system tracking south of the Aleutians. There may be a fourth system on the distant horizon that approaches the western Aleutians by next Wednesday. Meanwhile, most of mainland Alaska will be between these Pacific storm systems and an arctic upper trough north of the state, with pleasant early summer weather expected south of the Brooks Range. The 12Z model guidance, along with the 18Z GFS, are in good overall agreement across the Alaska domain to start the forecast period Saturday, with a general deterministic model blend sufficing as a good starting point for fronts and pressures, and mainly a GFS/ECMWF blend for QPF with some ensemble biased corrected QPF. Going into Sunday, there are some minor placement differences with the polar low over eastern Siberia, but more noticeable with the weaker upper trough/surface low near the central Aleutians with the GFS stronger and more progressive. Model differences grow quite a bit going into the first half of next week across the North Pacific, and also across the northern half of the mainland as a potential second polar low drifts south. There is a broader signal in the guidance for another low pressure system approaching the western Aleutians next Wednesday, albeit with limited confidence on specifics. The ensemble means accounted for about half of the forecast blend going into early-mid next week. ...Weather/Hazards Highlights... Light to moderate rain will be on the increase this weekend across the Southeast Panhandle with the approach of the Gulf low along with gusty southerly winds, followed by more showery conditions Sunday as the low weakens. Some showers are also likely across the central and eastern Aleutians as the next low pressure system passes by to the south. Isolated to scattered showers and storms are expected for portions of the Interior and the Alaska Range, mainly during the afternoon and evening hours. Given dry fuels for portions of the Interior, there are some potential fire weather concerns with dry lightning strikes. Most areas north of the Brooks Range should remain dry through the forecast period. In terms of temperatures, afternoon highs are expected to reach well into the 70s for many areas across the Interior, perhaps reaching 80 degrees for the Yukon Flats, and also just north of the Alaska Range. Overnight lows here should also be rather mild with readings bottoming out from the upper 40s to upper 50s. The Arctic Coast will likely remain chilly with onshore flow from the Arctic Ocean, with highs generally from the upper 30s to upper 40s. Hamrick 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 $$