Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 707 PM EDT Thu May 18 2023 Valid 12Z Mon May 22 2023 - 12Z Fri May 26 2023 ...Synoptic Overview and Guidance Evaluation... An elongated upper ridge axis is forecast to be in place across much of central and eastern mainland Alaska going into early next week with warm conditions for this time of year across much of the Interior. This ridge then breaks down some going into the middle of the week as a col develops in response to the quasi-stationary upper level gyre over the general vicinity of the Alaska Peninsula. This slow moving upper low should gradually move very slowly eastward towards the northern Gulf of Alaska by the end of the week, and a separate low may develop over the southern Bering mid-late week with a cold front approaching the Aleutians. The 12Z model guidance suite is initially in decent synoptic scale agreement across the Alaska domain with some minor differences in mesoscale features. By Wednesday, the UKMET is out of phase with a stronger trough over the eastern Gulf, whereas the model consensus has this trough back to the west, so it was not used after Tuesday. Meanwhile, the CMC is on the western side of the model spread with the upper low/trough, so it was weighted less for the second half of the forecast period. The use of the ensemble means increased to about 50% for the Thursday-Friday time period with the increase in deterministic spread. ...Sensible Weather and Potential Hazards... Temperatures will likely feel more like June compared to May with readings generally expected to be 5-15 degrees above average for most areas north of the Alaska Range through the middle of the week, and the opposite is likely to hold true for southern portions of the state with highs up to 10 degrees below normal owing to increased cloud cover from the slow moving low pressure system over the Alaska Peninsula and northern Gulf. In terms of rainfall potential, there will likely be a plume of enhanced moisture advected northward ahead of the main upper low, affecting primarily windward facing terrain across the Alaska Peninsula, Kodiak Island, and the Kenai Peninsula during the Monday to Tuesday time period with a few inches of total rainfall possible. Hamrick Hazards: - Heavy precipitation across portions of southern mainland Alaska, Mon, May 22. 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