Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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590 FXAK02 KWNH 232242 PMDAK Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 541 PM EST Sat Nov 23 2024 Valid 12Z Wed Nov 27 2024 - 12Z Sun Dec 01 2024 ...Much colder airmass to focus over the Interior next week... ...Protracted Wet/Snowy Pattern through the extended Thanksgiving weekend for Southeast Alaska... ...Guidance Evaluation/Preferences... Guidance forecast clustering has increased through medium range time scales, limiting confidence. Prefer a larger scale compatible 12 UTC GFS/ECMWF/UKMET and GEFS/ECMWF ensemble means composite to maximize forecast continuity amid growing system uncertainties. The flow pattern next week should be highlighted by a much below normal cold airmass focus over the Interior and an uncertain intensity and overall protracted wet/snowy pattern for Southeast Alaska. There is some guidance that offers stronger potential from Thanksgiving northern stream energy to monitor and subsequent impact from later extended holiday weekend slow approach of a major and moist Gulf of Alaska storm well offshore that will also support evolving and long duration maritime threats. ...Weather/Hazards Highlights... Upper ridging in place up into the Interior will break down and retrograde over the Bering Sea next week, leading to a much colder and unsettling trend for especially Interior Alaska under renewed mean upper troughing. As is typical, the coldest readings will be on the North Slope and central to especially the eastern interior where below normal temperature anomalies will be most prominent. Post-frontal gap winds may periodically strengthen in flow over the southern to southeastern Alaskan tier. Guidance spread next week becomes more significant over time with the handling of deep offshore storms re-developing/working from south of the Aleutians to the Gulf of Alaska. This impacts the timing for emergence of a subsequent downstream deeper moisture and enhancing precipitation pattern for the Southeast, perhaps with heaviest onset and possible heavy snow threat next weekend to be monitored. Schichtel 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 $$