Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
370 FXAK67 PAJK 181619 AAA AFDAJK Southeast Alaska Forecast Discussion...UPDATED National Weather Service Juneau AK 819 AM AKDT Tue Jun 18 2024 .UPDATE...Just shipped new grids and marine forecasts for fog along the outer coast from near Yakutat southward along Cross Sound and to just offshore of Sitka. Visibilities in some areas are 1/4sm as the Cross Sound FAA Webcam shows. Fog is more patchy out past 20 miles offshore. Expect the fog to lift somewhat by mid afternoon before ceilings lower again tonight in the same areas. W ebcams over the inner channels of SE Alaska show mostly a low cloud deck around 2500 ft above ground level at several places with breaks in the cloudcover noted southern Lynn Canal south through Stephens Passage to Frederick sound and the Petersburg area. 05/JG && .&& .PREV DISCUSSION......ISSUED AT 446 AM AKDT TUE JUN 18 2024 .SHORT TERM...High pressure remains over the gulf this morning allowing for the associated marine layer to expand in coverage from yesterday morning. This marine layer will continue to persist and allow for cooler temperatures compared to locations not affected by the clouds. Some areas will see the marine layer break up during the daytime hours before the coverage returns during the overnight hours. Temperatures today look to be a rinse and repeat of yesterday across the panhandle. With observed temperatures yesterday not nearly as warm as what was forecasted for the same time frame, went ahead and lowered todays highs to reflect this outcome. Cloud cover was also expanded to reflect the increase in marine layer clouds during the overnight and morning hours across the panhandle. Overall though, summer will continue to persist for the panhandle with warm temperatures, afternoon sea breezes, and little to no rain in the short term forecast. LONG TERM...Summer continues across SE Alaska through the first half of the week, though more active weather is on the horizon. Get out and enjoy it while you can. A ridge will continue to hover over SE AK through Wednesday, with the axis slowly moving E over the Gulf and across the area. Dry, with afternoon sea breezes in the inner channels is the main theme over the next few days. By Thursday, a weak wave will attempt to advance through the ridge, bringing with it chances of rain, though operational guidance is likely overemphasizing PoP chances with this system. Anticipate fairly minimal QPF totals and wind impacts, if the system isn`t largely eroded away by the ridge itself. By the end of the week, an extension of a closed low over the Aleutians attempts to form into a longwave trough and move into the Gulf, bringing some onshore flow, cooler temperatures, and increasing PoPs through the weekend. Think that there is a good chance that much of the energy will move S of the panhandle, but still anticipate at least some chances of rain for the area. Afterwards, some clearing is increasingly likely for the latter half of Sunday or Monday, though this is not set in stone, with the GEPS being more pessimistic. Threats to coastal and gulf waters remain low through Thursday, with our swells significant deep ocean wave heights remaining largely under 8ft. With that said, stout 15 to 20 knot northwest winds along the coast will bring short period wind driven waves to the west coast of Prince of Wales and into Dixon Entrance. AVIATION...Marine layer low clouds continue their daily dance in and out of the inner channels. Lowest conditions this morning are along the outer coast and in Clarence Strait where ceilings have dropped to around 900 to 1500 feet. No fog below the cloud deck has been reported though. These lower conditions have gotten as far inland as Angoon, Hoonah, Gustavus, and Ketchikan overnight. Areas farther north and east have seen some clouds but they have all been above 4000 feet. Expect the low clouds to retreat again today with all, but the outer coast, Cross Sound, Western Icy Strait, and possibly Gustavus, becoming VFR by late afternoon. The clouds will then invade again tonight with a similar area seeing lower ceilings late, though the area covered could be somewhat larger then tonight. MARINE...Marine layer continues to persist over the Inner channels and outer gulf coast as high pressure remains over the gulf. The extent of the clouds this morning is greater than yesterday morning but many areas still remain cloud free. This trend is expected to continue until the high pressure over the gulf shifts to the east allowing for a low to move into the western gulf. Otherwise, diurnal sea breezes are expected to continue during the daytime hours for locations not affected by the marine layer. HYDROLOGY...The Flood advisory for the Chilkat River continues due to snowmelt from warm temperatures. Flooding conditions are expected to continue with warmer temperatures persisting across the Chilkat Valley. Temperatures are expected to decrease by late week as more clouds return to the area limiting daytime highs. This should allow for flows on the river to decrease. Otherwise,, the river is expected to continue to show a diurnal trend in response to temperatures. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...None. && $$ Visit us at http://www.weather.gov/Juneau