Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 744 PM EDT Sun Jul 31 2022 Valid 12Z Thu Aug 04 2022 - 12Z Mon Aug 08 2022 ...Overview... Strong high pressure in both the upper levels and at the surface is forecast to retrograde and meander across the midlatitudes of the Pacific between Alaska and Hawaii through early next week. This will allow for a fairly progressive pattern across southern Alaska to the north of the high, with the main upper/surface low of the medium range period forecast to move across the Bering Sea and toward the southwest mainland around Thursday-Friday, then across the Gulf of Alaska into Saturday. These features will bring chances of rain across the southern mainland and Panhandle. Then an Arctic upper low is forecast to edge southward toward Interior Alaska late this week, bringing cooler temperatures and some light to modest precipitation. ...Guidance/Predictability Assessment... The upper low and associated surface low moving across southern Alaska have waffled somewhat with their timing. Today's guidanceÂis somewhat slower with the upper/surface low compared to the previous couple of days, though the most recent 12Z guidance did speed up a bit compared to the 00Z/06Z guidance, so hopefully models are settling on a middle ground for the timing. This shows the lows moving into the southwestern mainland early Friday rather than Thursday and then eastward, so slower than the previous WPC forecast. The early part of the forecast period was based on a blend of 40 percent 12Z ECMWF/30 GFS/20 CMC/10 UKMET. Then models agree that troughing is forecast to sink southward from an Arctic upper low, but with some variability in amount of troughing and timing. The 12Z GFS especially seems too aggressive and fast, so favored the EC/EC mean and a bit of the GEFS mean/CMC instead for the latter part of the forecast period. There is low confidence with the flow for southern Alaska in terms of possible separation of a late week/weekend shortwave from the main trough. The 12Z model cycle seems to keep energy more phased compared to some previous cycles, but with low confidence in the details at this point. ...Sensible Weather... Modest rainfall amounts are forecast to shift from the Aleutians into the southern half of the interior around Thursday into Friday, moving west to east with the low system, and spreading into the Panhandle Friday and lingering through the weekend. Precipitation totals could be enhanced in Southcentral Alaska and the Alaska Range (with possible snow in the highest elevations) and into the Panhandle. Additionally, a cold front moving just ahead of the trough into the northern mainland could cause some showery conditions across the North Slope and into the Brooks Range, which in higher elevations could fall as snow. As the period begins Thursday, some clearing of clouds before the trough systems will allow for some milder, above average temperatures over coastal regions of the North Slope and from the Seward Peninsula eastward into the Tanana Valley, where temperatures could rise into the 70s. Temperatures will trend considerably cooler late this week into early next week as troughing spreads eastward from the southern upper low and southward from the Arctic upper low. The largest anomalies will likely be over the northern interior, where high temperatures could be over 20 degrees below normal. 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