Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 801 PM EDT Mon Apr 22 2024 Valid 12Z Sat Apr 27 2024 - 12Z Wed May 01 2024 ...Overview... An upper/surface low is forecast to track across the eastern Aleutians and the Alaska Peninsula at the start of the period Friday, and then east across the Northeast Pacific over the weekend into early next week before pushing into British Columbia. North and east of this feature, upper ridging will stretch from Southeast Alaska northwest into the northern part of the state late week but erode with time. Then upstream a round or two of energy and troughing could move across the Bering Sea toward the western coast next week, but with ample uncertainty. ...Guidance Evaluation and Preferences... Guidance is in reasonably good agreement with the pattern through late week as the aforementioned low undercuts an upper ridge over portions of eastern to northern Alaska. Recent guidance has maintained its trend of a steadier progression of the low eastward that began with the 12Z Sunday models. Thus for the early part of the forecast period, used a blend of the deterministic guidance favoring the 12Z ECMWF and GFS. Model spread increases rapidly into next week. First, by Sunday there is some uncertainty with how much energy may remain/come in near Bristol Bay. This makes the ECMWF (which has a ridge) out of phase with the CMC that lingers a small upper low there and the GFS runs that push additional energy in. Then a larger scale trough may push into the Bering and the Aleutians and western Alaska, but the timing is quite variable. GFS runs are faster to bring the trough east than the ECMWF and CMC and leads to more out of phase issues. There is certainly low confidence in the forecast for Sunday-Tuesday. Quickly ramped up the proportion of the EC and GEFS ensemble means in the blend to over half by Monday and 80 percent by Tuesday. The means are pretty zonal due to the differences across the ensemble members but hopefully models will converge with time. ...Weather/Hazards Highlights... The upper and surface lows late this week will promote some precipitation cross the Aleutians to Alaska Peninsula into the southwest Mainland toward Kodiak Island and the Kenai Peninsula, with moderate amounts Friday lowering on Saturday. Some gusty winds are possible late in the workweek for the Aleutians to Alaska Peninsula and maritime areas, but are likely to stay below hazards criteria. Some precipitation is likely over the weekend for Southeast Alaska as moist inflow increases ahead of the low moving east. Generally light amounts are forecast in northern parts of the Panhandle with more moderate amounts in southern parts. By next week, precipitation chances may get renewed in the Aleutians toward southwestern and south-central Alaska, but will be dependent on the eventual flow. Meanwhile the northern half of the Mainland can expect generally dry conditions. Most of the state should see above normal temperatures during the period, with the highest anomalies tending to be over the Interior. To the north of a front settling over the north-central mainland, cold high pressure over the Arctic may keep temperatures near to somewhat below normal, especially across the North Slope. Locations near the Southcentral coast and northern Panhandle may also see near or slightly below normal readings. 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