Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 758 PM EDT Tue Jul 16 2024 Valid 12Z Sat Jul 20 2024 - 12Z Wed Jul 24 2024 ...Somewhat wet pattern for Alaska Panhandle and Aleutians... ...Overview... Latest guidance continues to show surface low pressure tracking north into the Gulf late this week, weakening as it approaches the Panhandle region. This may spread some moisture into at least the Panhandle, but models have backed off on any sort of heavy rain threat. Meanwhile, expect a Bering Sea upper ridge to build eastward over the mainland by the weekend, replacing an initial trough and promoting a warmer trend for temperatures over most areas aside from the Southcentral coast and Panhandle. Along the southern periphery of progressive high latitude flow, a mean frontal boundary may set up near the northern coast from the weekend into early next week. Finally, a deep-layer low will make gradual progress from the northwestern Pacific through the western Aleutians and into the central Bering Sea, spreading a broad area of rain across the region and perhaps eventually into the southwestern mainland. ...Guidance Evaluation/Preferences... In general, the models have a decent handle on the large scale pattern with typical spread in speed and location with some of the smaller details of the forecast. For the early part of the forecast period, there is some uncertainty in the exact placement/speed of the deep low into the western Aleutians, but good agreement on its track into the central Bering. And the 12z CMC is a little slower to bring the upper low in the Gulf eastward compared to the ECMWF and GFS. By early next week, the GFS is a little more bullish on bringing weak troughing across the Northern Coast, and there are some small scale differences in individual shortwaves/surface lows traversing through the base of the mean low in the Bering. The start of the forecast was comprised of general model blend between the GFS, ECMWF, CMC, and UKMET. By the start of the new week, added the GEFS and EC ensemble means and gradually increased their weighting to help mitigate the smaller scale differences while also keeping operational input to add detail where feasible. This maintained good agreement with the previous WPC forecast as well. ...Weather/Hazards Highlights... Most of the guidance depicts a surface low pressure system lifting towards the Panhandle region that will usher in lighter QPF amounts each day and then the Panhandle and vicinity should trend drier during the weekend. A northwestern Pacific low drifting into the Aleutians and Bering Sea along with associated fronts will spread areas of rainfall gradually eastward across the region during the period. The leading edge of this moisture may reach into the southwestern mainland by next weekend. This system (along with the northeastern Pacific low) may produce some brisk winds but with speeds likely staying well below hazardous criteria. Expect increasing coverage of above normal readings by the weekend as an upper ridge builds over the mainland, but the Panhandle and parts of Southcentral may see greater persistence of below normal highs. Parts of the Mainland/Interior will have some of the hottest temperatures of the season so far during this period. Southwestern areas may also trend back below normal with the arrival of some clouds/rainfall. Negative anomalies for min temperatures should be more moderate than those for highs early in the period, followed by increasing coverage of modestly above normal lows by next weekend and early next week. Santorelli/Campbell 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