187 FXAK68 PAFC 230059 CCA AFDAFC Southcentral and Southwest Alaska Forecast Discussion...CORRECTED National Weather Service Anchorage AK 459 PM AKDT Sun Mar 22 2020 .ANALYSIS AND UPPER LEVELS... High pressure over the eastern Bering continues to bring calm and sunny weather across much of the state. In the Panhandle, a surface low continues to drift off to the southeast. Between the high in the west and the low in the Panhandle, a tightened pressure gradient has caused gusty northerly wind through much of the forecast area. Along the North Gulf Coast, channeling has increased the wind strength and winds through Valdez were gusting up to 45 mph this morning. Some blowing snow occurred through colder areas like Thompson Pass overnight, but with warming surface temperatures today, conditions have improved. Fog occurred overnight in the Susitna Valley and along Cook Inlet, but has since burned off this morning. Out west, sunny conditions persist over most of the Bering Sea, with clouds creeping in just south of the Aleutians. A trough dipping down from the Arctic is bringing some clouds and westerly winds to the Kuskokwim Delta, but little precipitation. && .MODEL DISCUSSION... Models are in fairly good agreement in the short term. Starting Tuesday, there are some differences in the effects of the northerly trough. NAM seems to be the quickest and brings the most precipitation in, while the GFS lags slightly behind. Today's forecast attempted to strike the middle ground between those solutions. && .AVIATION... PANC...Light winds and VFR conditions will persist. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Strong northerly outflow winds will continue through the next 24 hours due to the tight pressure gradient between a surface ridge extending across the interior of the state and an elongated trough of low pressure over the northern Gulf. These winds will begin to diminish in intensity tomorrow as the trough dissipates and a ridge of high pressure extends across the western half of the Gulf with more of westerly flow aloft developing. Clear and dry conditions will also persist across the region due to the ridge and northerly flow. A few mid and high level clouds will skirt the northern portions of the Susitna Valley and Copper River Basin tonight through Monday as a series of upper-level shortwaves track east across the Alaska Range. Although it will remain dry across much of the area, patchy fog is once again possible overnight along Cook Inlet and around Talkeetna, as weak surface winds have yet to scour away all of the lingering low- level moisture. A more significant shortwave moves across Southcentral overnight Tuesday into Wednesday. This system will spread clouds over the region along with areas of light snow for interior locations and a mix of rain/snow for the Kenai Peninsula and Gulf coast. There is still some model uncertainty as to how widespread the precipitation will be, but given the uniform westerly flow and lack of deep moisture advection, the bulk of the precipitation will likely occur along the upslope areas of the mountains. A second shortwave then drops south from the interior later on Wednesday with better upper-level support. This will help maintain the cloud cover across Southcentral and produce additional light snow for the northern half of the Susitna Valley, Copper River Basin, and higher elevations. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)... A 1046 mb high over the Bering Sea will keep things quiet for the next 24 hours for southwest Alaska. An upper level disturbance will bring precipitation chances back to the Kuskokwim Delta on Monday night. Temperatures should be cold enough for snow during this event. A north Pacific low will lift into the Bering by Tuesday afternoon and things will shift, as the high pressure of recent days weakens. Warm air advection pushing onshore will likely deliver some freezing rain chances late Tuesday night before switching over to rain. An active pattern will keep precipitation chances in the forecast through Wednesday and beyond for Southwest Alaska. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)... High pressure will keep much of the Bering and eastern Aleutians quiet for the next 24 hours. A frontal boundary from a north Pacific low will lift into the western Aleutians tonight and bring precipitation and some gusty winds. As this boundary spreads northeastward the Pribilofs can expect some rain and snow chances Monday morning. As the parent low lifts across the western Aleutians precipitation will increase for the eastern Aleutians and the Pribilofs on Tuesday. As the system weakens into a series of upper level troughs Tuesday night, precipitation chances in the Bering will continue for the Pribilofs and eastward through Wednesday. && .MARINE (Days 3 through 5)... Winds should not exceed small craft advisory through Thursday. && .LONG TERM FORECAST (Days 3 through 7)... Strong confidence remains that an upper level ridge will remain over the southern part of Alaska through the middle of the week. Early Tuesday morning, a North Pacific low will get caught up in the backside of the ridge, which will bring it northwest across the western Aleutians and into the Bering Sea. This low will weaken the ridge, thereby flattening it, and will force the low southeastward across the eastern Aleutians and right back into the North Pacific through Thursday. Following this, zonal flow aloft will be the dominant feature into Friday. Afterwards, an upper level ridge will build across the Bering Sea until an upper level trough upstream enters the western Aleutians Friday night. This will bring precipitation to the western Aleutians/Bering and across into the eastern Aleutians through Sunday. During this time, an upper level trough looks to dip down from northern Alaska and into Southcentral before becoming a closed off low Saturday. If this solution holds, chances for precipitation will return to Southcentral through Sunday. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Gales 130 and 131. FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...LF SOUTHCENTRAL ALASKA...TM SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...LB MARINE/LONG TERM...CK