908 FXAK68 PAFC 191314 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 514 AM AKDT Tue Oct 19 2021 .ANALYSIS AND UPPER LEVELS... A stacked low over the Gulf ushers strong winds and rain across the Gulf this morning. A robust frontal system anchored across the eastern Gulf through Prince William Sound is latched to the aforementioned low, creating a vigorous barrier jet leading to much stronger high-end gales and low-end storm force gusts mainly south of Cordova and Valdez overnight. Over the Bering, a broad frontal system from the North Pacific extends across the eastern Bering to a complex low west of Saint Matthew Island. Meanwhile, an upper level ridge extends from the western Gulf through the north- northeast flank of the Gulf low. Multiple shortwaves associated with these two separate upper lows increased the potential for more clouds, rain and gusty winds especially for Prince William Sound, eastern Aleutians and Southwest Coast today. && .MODEL DISCUSSION... Model solutions show favorable agreement between surface and upper-level features moving across the Bering and Gulf of Alaska through the week until Friday morning. A robust front wrapped across the eastern Gulf through Prince William Sound is well advertised among the models, creating multiple micro-scale lows to en route north-northwest through the northern Gulf until the front tapers off Wed afternoon. Over the Bering, solutions are still on track with the placement of the existing Bering low and its associated front today through Tue night. As the next Northwest Pacific low enters the Bering Sea Wed night, most guidance highlights a broad area of strong gales and potentially storm- force winds on the west and south flank of the low. After Friday morning, synoptic patterns begins to fizzle out for both the Bering and Gulf which creates a low forecast confidence. Essentially, the aforementioned short-term pattern will still bring active weather across the region especially along the coastal areas. && .AVIATION... PANC...VFR conditions will persist, with gentle northerly winds continuing this morning. As Turnagain winds pick up a notch this afternoon, gusts could make its way near the airfield in the evening. The potential for reduced ceiling and light rain could occur around 03Z Wed, leading to a low end MVFR conditions. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... A tightly-wrapped low is moving rapidly through the Gulf of Alaska from Southeast to Northwest today. This low is just to the south of Middleton Island early this morning can be seen quite well on both satellite and radar. There has been some uncertainty as to where this low will make its landfall over the kenai Peninsula, with the difference between a northerly track and on e off the southern tip having a large difference in today and tonight's weather from Kodiak Island through the Anchorage area. It has taken a while, but it does appear that this system should take the more northerly track as was discussed yesterday morning. This will bring it just south of Seward and then it will rapidly weaken as it moves over Kenai and then farther northwest. Winds will be strong especially to the north of this low, but the winds around the low will rapidly weaken today as it loses strength. The Whittier and Portage areas will be interesting to watch as this low moves through. Lows taking a track similar, but just a little farther north (coming onshore between Seward and Whittier have sometimes brought a periods of very strong winds to these areas. In this case, the little bit farther south track and the lack of strong pressure rises behind the low (due to the weakened stationary front along the north Gulf coast, this one probably will not be a strong as the one from about three years ago in October. However, still went with a Gale warning for Passage Canal and increased winds there and in Portage above all model guidance. The next weather feature to track will be the 500 mb longwave trough as it slowly moves into and through Southcentral Wednesday through Thursday night. This will keep south-to-southeast flow aloft over Southcentral with some embedded shortwaves in the flow aloft that may bring some additional shots of precipitation. With the Southerly flow, most of the precipitation at sea level should be rain, but will need to see how this develops as these short waves are rather weak and not well defined at this point. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)... The front off a large broad system in the Bering has pushed over the Southwest Coast early this morning. Snow has pushed as far inland as Bethel, and will likely continue through the rest of the morning before tapering off. Precipitation reaches the Bristol bay area later this morning, and will likely consist of primarily rain for the lower elevations, with a rain/snow mix or all snow along the higher elevation and foothills of the Kilbuck Mountains. The front continues across the Southwest Mainland, fizzling out as it approaches the Alaska Range late this afternoon. Inland areas of Southwest, such as Sleetmute and Iliamna will see daytime temperatures above freezing today, meaning any precipitation that falls this afternoon will be rain and then transition to a rain/snow mix or all snow for the overnight hours. Conditions behind the longwave trough are drier, but will remain cool and cloudy Wednesday and Thursday. The next front off a new incoming Bering low reaches the Southwest Coast by Thursday evening. There are still a few inconsistencies yet with this system, but current guidance shows the main impacts and brunt of impactful weather may be confined to the Coastal areas. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)... A broad low pressure system is set up in the northern Bering, while a high pressure ridge enters the western Bering today. The two are creating a tight pressure gradient and creating gusty gale force northwesterly winds across the western and central Bering today and tonight. Winds die down to widespread small craft by tomorrow morning once the transient ridge moves into the central Bering. A new system develops west of Attu and moves into the western Bering by late Wednesday night. Model guidance is hinting as strong cyclogenesis as the low tracks eastward across the Bering, meaning it is strengthening as it travels. Anticipate strong storm force winds along the front as well as the back side of the system beginning early Thursday morning. Significant cold air advection is pulled behind the low, aiding in the strengthening of the winds behind it, with models hinting towards at least hurricane force gusts Thursday evening and Thursday night between the Pribilof Islands and the Eastern Aleutians. Additionally, expect heavy precipitation (mostly rain) along the frontal boundary tracking from the Western Aleutians to the Southern AKPen starting tomorrow evening and persisting through Thursday evening. && .MARINE (Days 3 through 5/Thursday through Saturday)... Bering/Aleutians Forecast confidence is moderate during the 3-5 day period as a strong low pressure system moves through the southern Bering Sea on Thursday and Friday. Minor differences exist between guidance with respect to the placement and intensity of this low. There is high confidence that widespread gale force winds will occur during this period. In addition to the strong winds, large long period northwesterly swell is expected along the coastal waters on the north side of the Aleutian Islands Thursday and Friday. These winds and seas will gradually ease and abate on Saturday. Gulf of Alaska Forecast confidence remains above average for Thursday with winds remaining under gale force and no high seas. Confidence decreases on Friday as the next low moves in from the North Pacific. Gale force winds are possible along the coastal waters throughout the northern Gulf on Friday and Saturday. && .LONG TERM FORECAST (Days 4 through 7/Friday through Monday)... A cloudy, cool and wet pattern is expected for Southcentral Friday through Monday as upper-level troughing extends from the northern Bering Sea into the central Gulf. This orientation of the upper trough will allow for moisture to enter Southcentral as the trough-axis remains southwest of the Kenai Peninsula and thus resulting in broad south-southeasterly flow from the Gulf. With respect to precipitation type, the chance for snow increases with elevation. The Bering/Aleutians will be in a cloudy and cool pattern as broad upper level troughing continues to extend across the region. Strong northwesterly gap winds are expected in the eastern Aleutians and western Alaska Peninsula on Friday and Saturday in the wake of a strong low pressure system moving into the Gulf. These winds will eased Sunday and Monday. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Gale Warning: 119, 120, 125, 129, 131, 155, 165, 170-179, 185, 351, 411-414 FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...CB SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM MARINE/LONG TERM...ED