Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 754 PM EDT Mon Oct 30 2023 Valid 12Z Fri Nov 03 2023 - 12Z Tue Nov 07 2023 ...Overview... A pattern change is in store over Alaska later this week into early next week, with troughing aloft replacing short range ridging across the Interior. This and a cold front pushing through the state will moderate temperatures much closer to normal after the mild spell. Farther south, mean low pressure at the surface and lower heights aloft will be in place across the northern Pacific. This pattern will favor some periods of precipitation across the Alaska Peninsula to Southcentral and Southeast Alaska, but nothing terribly heavy is expected. Some light snow is possible into the Interior as well. Additionally, recent model guidance has shown a stronger signal for a surface low to track southeast over the Bering Sea and cross the Aleutians early next week, for some possibly windy and wet conditions for the Aleutians to Alaska Peninsula. ...Guidance Evaluation and Preferences... Models are agreeable that the pattern change to upper troughing will take place across the Interior, with typical differences in the details. Today's 12Z guidance suite shows better consensus for a compact upper low near the Bering Strait Friday-Saturday, except for the 12Z UKMET that had a weaker shortwave. Preferred the 12Z GFS/ECMWF/CMC with this feature early in the period. This low looks to gradually drift east into early next week into the western Mainland. But the 12Z ECMWF takes the low farther south, crossing the state and showing it in the Gulf of Alaska by early Monday. WPC and the Alaska WFOs agreed that this outlier seemed unlikely given the lack of support from other guidance. Farther south, upper and surface lows will track eastward across the northern Pacific into the weekend, with some spread but looking to stay south of the state until perhaps next week when they could pivot northward toward Southeast Alaska. With more of a westward trend of the northern upper low, phasing of this trough/low with the northern one seems less likely. Meanwhile, model guidance is trending stronger with energy spilling into the Bering Sea from Russia for early next week, creating troughing that may phase with the northern low by around Monday-Tuesday as it drops south across the Aleutians and into the northern Pacific. This could support a reasonably strong surface low taking a similar track across the Bering Sea southeastward across the Aleutians and near the Alaska Peninsula. The low does show spread in its depth and track; GFS runs are somewhat south of the ECMWF/CMC and stronger, but all tend to develop or redevelop a low south of the Alaska Peninsula by early Tuesday. If the surface low ends up as strong as what the 12Z GFS indicated, this could lead to some concerns for strong winds over the Aleutians to Alaska Peninsula. Thus the WPC forecast was based on a blend of the 12Z GFS/ECMWF/CMC early in the period. Decreased the proportion of the deterministic models, especially the ECMWF, as the period progressed in favor of the GEFS and EC ensemble means. ...Weather and Hazards Highlights... Precipitation across the state should be generally light to moderate through the period, and timing of the precipitation will depend on the details of upper and surface low positions particularly in the northern Pacific. Around Friday precipitation may be locally enhanced for Kodiak Island into Southcentral and parts of Southeast Alaska, with rain in the lower elevations and some snow in the Alaska Range, but amounts are not likely to be very heavy. Late this week into the weekend, some limited moisture may spread farther north into the Interior and allow for some rounds of light snow. Chances for light precipitation may last into early next week for Southcentral and Southeast Alaska, while precipitation chances also go up for the Aleutians and Alaska Peninsula. Windy conditions may be possible there as well with a surface low Monday-Tuesday, so this will continue to be monitored. Temperatures will be gradually dropping closer to normal late week, but may remain slightly above average for most of the Mainland (except the Brooks Range) until early next week when the upper low goes more overhead, flipping highs to a few degrees below normal in many areas. Lows on average should stay near to above normal in most areas though. The North Slope is likely to stay above average with some milder onshore flow. Meanwhile Southeast Alaska and the Aleutians look to see temperatures generally within a few degrees of average. Tate 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 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