964 FXAK68 PAFC 081518 CCA AFDAFC Southcentral and Southwest Alaska Forecast Discussion...CORRECTED National Weather Service Anchorage AK 718 AM AKDT Thu Apr 8 2021 .ANALYSIS AND UPPER LEVELS... Two upper level shortwave troughs exist over Alaska this morning, both of which will be responsible for the active weather over the mainland the next two days. The southern of the two lows, which brought blizzard conditions and widespread snow to Southwest Alaska yesterday, has shifted southeast over the AKPEN this morning. This shortwave will help to pull an unseasonably cold airmass and polar low over northern Alaska to the south, thus amplifying the pattern over our Area of Responsibility (AOR). The cold airmass can be seen well on infrared satellite with cold brightness temperatures measured at the surface and cloud streets streaming south of the Bering Sea ice. Meanwhile, the next frontal system is rapidly approaching the western Aleutians. Widespread snow has been observed on radar and surface observations across Southcentral with the northerly extent reaching as far as Talkeetna and Glennallen. Northerly winds have been picking up throughout Southcentral as the low shifts into the Gulf. && .MODEL DISCUSSION... Overall, models are in excellent agreement in synoptic scale features in the short term. Thus, forecast confidence in the short term is high. Minor discrepancies exist in the strength and southern extent of the polar trough as it moves over the Copper River Basin on Friday. The NAM is the most aggressive and coldest of the models over this area. However, the differences are minor and have little impact on forecast confidence. && .AVIATION... PANC...VFR conditions at 12z this morning are expected to lower to MVFR as light snow redevelops over the airport complex by 14z. IFR conditions are then expected between 14z and 18z as bands of snow move from west to east across the terminal. By 18z, snow is expected to be east of the terminal, falling over the Anchorage Hillside. By this afternoon, gusty northerly winds will develop over the airfield. These winds will increase in intensity through the evening and overnight hours, with gusts approaching 50 mph. The northerly winds will slowly diminish Friday but are expected to remain gusty. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 3: Thursday through Saturday)... Model guidance is very much on track with a late-season storm event that is making an impact on our area since late last night. A potent shortwave trough has moved over the southern AKPEN, with an associated triple point low developing along a frontal boundary northeast of Kodiak Island. An initial push of moist, southwesterly flow aloft allowed snow to fall over the western Kenai Peninsula, Anchorage Bowl, and Mat-Su Valleys. As the low moves over the central Gulf this morning, the easterly flow along the north Gulf will allow snow to fall along the immediate coast. A deformation band along the back side of the low will also allow a band of snow to move across Cook Inlet and the Anchorage Bowl this morning. This band of snow is expected to linger across the Anchorage Hillside and upslope regions of the Chugach and Kenai Mountains through most the day, with a couple of inches of snow possible. Moist, cyclonic flow will keep the chances of scattered snow showers going over the Copper River Basin as well as north and west facing mountain slopes through Friday afternoon as the low exits to the eastern Gulf. Thereafter, a polar shortwave trough will move south from the northern half of the state on the heels of the aforementioned Gulf low late Thursday night and into Friday. Very cold, arctic air will spread across the southern mainland and create gusty, northwesterly winds funneling through the usual gaps and passes, with Anchorage Bowl potentially reaching up to 50 mph or more by Thursday night. A High Wind Warning has been issued for Thompson Pass, Seward, and Kodiak Island to account for this significant wind event. Additionally, northwesterly storm to hurricane force winds with heavy freezing spray concerns will blow across the usual gaps and passes, including Resurrection Bay, Kamishak Bay, Shelikof Strait, and Lower Cook Inlet, from Thursday afternoon into Friday morning (please see Marine Weather Statement for details). Wind chills will be another area of concern associated with the strong winds and colder temperatures for Thursday night and into Friday night in the low-lying and surrounding high elevations. The gusty, northerly winds are expected to diminish by Friday night into Saturday morning, allowing overnight lows to plummet anywhere from the single digits to sub-zero. Some of these overnight lows will have the potential to approach or break daily cold temperature records for early to mid April. A low-level amplitude ridge of high pressure will bring fair, mild weather over the southern mainland by Saturday. Looking ahead, a storm system with a deep fetch of tropical moisture is expected to arrive late Saturday and into Sunday. Some uncertainty exists with precipitation timing and duration with subsequent model runs needed to iron out specific details. Suffice it to say that unsettled weather will return late this weekend, so stay tuned for the latest updates! && .SHORT TERM FORECAST SOUTHWEST ALASKA (Today through Saturday)... Blizzard conditions will persist across the Kuskokwim Delta coast early this morning on the backside of a low. Conditions will improve through the day as winds diminish. The pressure gradient will tighten over interior Bristol Bay into this afternoon, leading to blowing snow in the Iliamna area. Otherwise, mostly sunny skies are expected. An extremely cold airmass will drop temperatures well below zero overnight across much of the region. Conditions will remain quiet through the day Friday. A front will move onshore Saturday morning, bringing more accumulating snow to Southwest Alaska. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Today through Saturday)... Strong, cold northwesterly flow on the backside of a low centered in the Gulf is expected to bring hurricane force gusts out of bays and passes south of the Alaska Peninsula through today along with heavy freezing spray. A front tracking west to east across the Bering will lead to blizzard conditions for the Pribilofs Friday morning. Precipitation will quickly change to rain by mid-morning and persist through the afternoon. Brief snow is possible across the central and eastern Aleutians ahead of the front, changing to rain in southwesterly flow behind it. Colder air wrapping around the associated low will bring widespread snow showers through Saturday. && .MARINE (Days 3 through 5: Saturday through Monday)... An active pattern is expected to continue for the forecast period with a large gale force low anticipated to slowly traverse the Bering Sea. Differences arise after the Saturday night time period in regards to exact strength and placement of the low. The one thing that looks to be fairly certain is that gale force winds are expected on the northwest to southwest side of this low the duration of the forecast period subsiding Monday. More uncertainty arises for what happens on the eastern side of this low as another piece of energy is expected to move northward from the North Pacific and towards the Gulf of Alaska. The low in the Bering may transfer some of its energy to this other system. The less energy transferred the weaker this other system will be, keeping the system in the Bering stronger for a longer time frame. The strength of this other system that will move into the Gulf is uncertain at this time ranging from small crafts to potentially gale force. One thing that is certain is the track that this feature will take moving from the southwest part of the Gulf towards Southeast Alaska Sunday through Monday. && .Long Term Forecast (Days 4 through 7: Sunday through Wednesday)... Model guidance is in fairly good agreement on the upper level features early on in the forecast time period before diverging for Tuesday and Wednesday. All guidance agrees that there will be an upper level trough present across the Bering and western Alaska. This will extend southward from another upper level low present over the Arctic for Sunday into Monday with some slight placement differences. Model guidance agrees on an upper level ridge nudging up into eastern Alaska and along the ALCAN border with Southeast Alaska under the axis of this ridge early on before pushing off to the east. Beyond Monday night, model guidance spreads widely on the strength of these features, though, placement looks to be in fairly good agreement. Basically, the main takeaway will be that a fairly active pattern will return to southern Alaska. There is the potential for an atmospheric river aimed somewhere in between the eastern Kenai Peninsula and southeast Alaska as multiple systems will impact the region over a couple days. Temperatures look to slowly warm each day, possibly reaching the upper 40s maybe even 50 degrees for some areas of Southcentral towards the end of the forecast period, though, this will all be determined by the exact strength and placement of upper level features Tuesday and Wednesday. There is also the chance temperatures may not drop to or below freezing which may impact the continuing running tally for consecutive nights at or below freezing for Anchorage which by this time frame will be in the top 5. Therefore, expect near average temperatures to start the period, rising to above normal for the second half of the period. As these systems come up, precipitation types may be an issue across the area as warm air tries to overcome the very cold air mass present out ahead of it. Also, potential exists for some fairly high precipitation amounts in the four day period mentioned, especially in the mountainous terrain. Lastly, with this upcoming pattern next week, rapid snowmelt is anticipated especially if temperatures get as warm as currently progged to do. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...Blizzard Warning 155 195. Winter Weather Advisory 161. High Wind Warning 125 131 171. MARINE...Hurricane Force Wind Warning 130 131 138. Storm Warning 120 121 127 128 150 155 352. Gale Warning 119 125 126 129 136 137 139 140 160 165 173 177-181 185 351 411-414. Heavy Freezing Spray 119-121 125 127-131 137-141 160 180 185 FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...CJ SOUTHCENTRAL ALASKA...MF SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AP MARINE/LONG TERM...MV