Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
365 FXAK68 PAFC 161248 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 448 AM AKDT Mon Sep 16 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A shortwave trough is moving across Southcentral and the Gulf this morning. Isolated to scattered showers are continuing across the northern Susitna Valley, eastern Prince William Sound, and the mountains along the Chugach and the Talkeetna. Gusty winds through Kenai and Anchorage from southwesterly flow up Cook Inlet should start to decrease this afternoon along with the showery activity. The exception to this will be along the Alaska Range and the Wrangells north of Gakona. Precipitation will likely linger until early Tuesday morning for those locations as a central low passes through the central Interior of the state and a weak shortwave dips slightly into the Susitna Valley and Copper River Basin. A brief weak ridge will help to clear some skies later tonight as the next front reaches the western Gulf and Kodiak Island. Cloud cover will become more important tonight into Tuesday morning as cooler, drier air filters into Southcentral. For areas that clear, light winds and weak ridging will allow for good radiational cooling overnight and Tuesday morning temperatures may feel a bit chilly as temperatures drop into the 30s to lower 40s for most areas in Southcentral. The Copper River Basin will likely see the coldest morning temperatures will lows looking to bottom out in the low 30s. Patchy valley fog and patchy Cook Inlet fog is possible for some of the locations that manage to clear. Increasing mid and upper level cloud cover, moving in from the south, should keep temperatures from dropping too low for areas along the Cook Inlet up through the Mat-Su Valley, but timing of this will factor heavily into how low temperatures drop. One thing to note, is that we are now reaching that time of year when we start seeing our first temperatures of 32 degrees for the upcoming cold season. Now is a good time to start thinking about how to protect those cherished warm season plants that are still outside as we start to increase our chances reaching low temperatures of 32 degrees or lower. The next system will be another wet one with south to southeasterly flow for Southcentral Tuesday and Wednesday. Winds could be gusty through the Copper River and Turnagain Arm. The front will spread across the Kenai Peninsula late Tuesday morning, then to Anchorage, Prince William Sound, the Matanuska and Susitna Valleys in the early afternoon. Rainfall intensity will increase Tuesday night into Wednesday for eastern Prince William Sound. Precipitation will gradually diminish for much of Southcentral later Wednesday as the low starts to move across the northern Gulf. Thursday looks to be a little bit quieter, with light showers lingering around the mountains. Overall, temperatures will remain on the cooler side through the rest of the week. - PP / rux && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)... Forecast remains on track for a stronger system to move into the Bering Sea this afternoon and trek eastward towards Southwest Alaska through Tuesday. Models are slow to agree on the track for this system and some uncertainty remains. There has been a gradual southerly trend, pushing somewhere onshore into Greater Bristol Bay. The current forecast leans toward the EC and Canadian, which are reasonably aligned. The GFS, however, continues to be the southern outlier, though consistently southern. The NAM is more of a middle ground solution but does ultimately trend closest to the GFS. There is better agreement on higher winds pushing into Bristol Bay, with gusts to storm force likely, and waves reaching 13 to 17 ft. Questions that need to be resolved, however, are the placement of the low and duration of winds. A further north and deeper solution of the low would extend the duration of winds into Bristol Bay and possibly necessitate some flood products. A more southerly track, such as the GFS solution, would still bring very strong winds into Bristol Bay, but for a shorter duration as the GFS solution is more progressive with the low. As low as it occludes, it does so in a bent-back fashion, pulling colder, northerly air along the backside and increasing winds to storm force. There is decent agreement for the Pribilof Islands to be impacted by these storm force winds Tuesday afternoon. Saint George has the greatest chance for strongest winds. && .LONG TERM FORECAST (Days 4 through 7: Thursday through Sunday)... By the start of Thursday morning a building ridge over the eastern Bering Sea appears to settle in. The resiliency of ridges is usually a point of contention in the model solutions, however agreement is currently strong regarding a fairly strong ridge remaining over the area, warding several low pressure systems off south of the Chain into the early portions of the weekend. Model uncertainty is much higher to the east in Southcentral and the Gulf of Alaska. By Friday morning, the GFS solution pulls a fairly strong low pressure system up from the northern Pacific into the Central Gulf, spreading wind and rain across the coast, whereas the Euro and Canadian models keep a mild trough in the northern Pacific, with Southcentral staying clear. By Sunday morning, solutions comes back into better agreement with the ridging over the eastern Bering weakening as a strong low pressure system fills over the western Aleutians and a new low over the the Gulf of Alaska. A broad troughing pattern looks to resume thereafter, which will keep shower chances in play for both Southwest and Southcentral Alaska through the remainder of the long term period. -CL && .AVIATION... PANC...VFR conditions persist. Southerly winds around 25 to 35 kts this morning will remain gusty but gradually diminish through today. Isolated to scattered showers move through this morning but should be mostly focused along the Chugach Front Range, away from the terminal. From this afternoon through Tuesday morning, high confidence in a spell of fairer conditions with no rain, lighter winds, and VFR conditions expected. The is a small possibility for patchy fog after midnight into Tuesday morning if skies clear and overnight temperatures cool. Later on Tuesday, a front will bring a return of rain and stronger winds. && $$