Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 744 PM EDT Sun Apr 02 2023 Valid 12Z Thu Apr 06 2023 - 12Z Mon Apr 10 2023 ...A general troughing pattern over Alaska will lead to colder than normal temperatures across much of the mainland and wet weather from Southcentral Alaska into the Panhandle... ...Overview... Overall an upper troughing pattern is likely across much of Alaska through the latter half of next week and into early next week, as an upper low drifts atop the northwestern mainland and a couple of shortwave energies combining to produce troughing in the Gulf of Alaska/northern Pacific by the weekend as well. Meanwhile rounds of low pressure in the Gulf of Alaska should lead to a wet pattern for Southcentral Alaska into the Panhandle. ...Guidance Evaluation/Predictability Assessment... Model guidance appears fairly agreeable on the large scale but with some small scale differences certainly within typical spread at the medium range lead time. Today's guidance for the most part has trended toward an upper low initially just north of Alaska as the period begins Thursday drifting southward such that it is atop the northwestern mainland through the weekend, a more southerly trend with the center of the feature compared to yesterday. With this trend, there seems to be less separation with this feature and the upper/surface low shifting southeastward across the Bering Sea and Aleutians around Friday. Recent models have trended toward all this except the UKMET, which continued the farther north upper low and allowed for a more consolidated northern Pacific wave that was separate from the northern flow pattern. Thus the UKMET was considered an outlier at this point and not favored. Guidance continues to show general agreement that the notable energy tracking from the Bering Sea into the Gulf/Pacific should combine with other energies in the northern Pacific for upper troughing and possibly an embedded low there. The pattern looks to stagnate like that (with mainland to northern Pacific north-south oriented troughing) through early next week while ridging comes in behind over the Bering Sea and Aleutians. The early part of the forecast was based on a blend of the 12Z ECMWF/GFS/CMC, with some inclusion of the ensemble means by days 6-8. ...Weather/Hazard Highlights... Multiple rounds of precipitation are likely especially across the Panhandle and back into Southcentral Alaska as surface lows and deep layer southwesterly Pacific flow direct moisture into the region. There may be some potential for flooding if there are multiple days with heavy amounts in the same area and/or rain falling on areas with snowpack and rising dewpoints promoting quick snowmelt, but this remains uncertain. Snow is possible farther inland across the eastern part of the mainland through mainly Thursday. Meanwhile the Aleutians is likely to see light precipitation around Thursday/Friday as a low passes over, with some threat of windy conditions too. Moderate to strong winds are possible over the weekend on the backside of the Gulf lows with possibly some gap winds in favored areas from the Aleutians east to the Kenai Peninsula depending on the low tracks. Temperature-wise, the trough/low aloft will cause colder than normal temperatures across at least western and central Alaska that have trended even colder in today's forecast given the track of the upper low directly over the northwestern mainland. Thursday-Sunday are likely to see temperatures of around 10-30F below average in terms of lows, with departures for high temperatures possibly even larger locally. Actual temperatures are likely to be below 0F for lows into the southwestern mainland. Meanwhile, while highs should be cooler than normal all the way east into the Panhandle, lows could stay warmer than normal with the mild moist inflow there. Tate 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