Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 641 PM EDT Tue May 04 2021 Valid 12Z Sat May 08 2021 - 12Z Wed May 12 2021 ...Overview and Guidance Evaluation... Most guidance continues to show a deep-layer mean low over the Aleutians/southern Bering Sea that persists through the weekend before weakening early next week. Shortwaves ejecting from the mean low should produce a series of wavy frontal systems that cross the Aleutians through the Alaska Peninsula and Gulf of Alaska, producing precipitation across these areas, and eastward along the southern coast/Panhandle. Although the consensus clusters a little better than average, individual solutions suggest numerous uncertainties with the forecast that would affect sensible weather over the coastal areas, and islands. The first wave ejecting from the main low drifts north across the Gulf of AK Day 4 in its weakening phase, decaying on Saturday. On Sunday, the next of the series of wave moves north across the Gulf of AK, with the 12z GFS and ECMWF trending a few hours faster than their prior runs. The next cyclone develops Sunday south of the main Aleutians low. On Monday to Tue the low moves northeast,gradually merging with the old parent low. The 12z GFS becomes an outlier in moving the low further north/faster,so more weighting was given to the 00-12z ECMWF/Canadian/12z GEFS Mean cyclone position. By mid week, the next 500 mb low moves from south of Kamchatka east near 50N, spawning cyclogenesis, with the low approaching the lower Aleutians and possible arriving by the middle of next week. There is better than typical agreement the low will develop, with typical timing/location differences. The agreement lead to a blend of the last 2 ECMWF and GFS runs, along with the ECMWF Ensemble Mean to mitigate the differences among solutions. ...Sensible Weather... Expect the highest probability of precipitation and moderate totals to extend from along the Alaska Peninsula to the Kenai Peninsula, with another max in southeast Alaska/panhandle in tandem with each wave of low pressure/associated fronts. Scattered diurnal convection is possible inland as a quasi-stationary front lingers over interior AK. The Aleutians will likely see unsettled conditions with periods of rain with each low later this week and again in the middle of next week. With above normal heights across interior and northern AK, temperatures are favored to be above normal in most areas, with near normal in far northern AK. The Panhandle and coastal areas west to the Aleutians may see temperatures near normal in periods of clouds and showers (but below normal highs on cloudier days). Petersen No significant hazards are expected over Alaska during this forecast period. Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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