214 FXAK67 PAJK 092245 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 245 PM AKDT Tue Oct 9 2018 .SYNOPSIS...A front will weaken along the outer coast Wednesday before a second, gale force front overtakes it from the west. The second front will cross the panhandle from west to east Wednesday night. && .SHORT TERM...Other than some dense fog this morning around Wrangell, Southeast Alaska enjoyed a benign fall day as a weak shortwave allowed a thin deck of cirro-stratus to stream eastward across the region. Winds have also been relatively light as high pressure across northwest Canada continues to weaken, even as a weak front approaches the central gulf. Tonight the weak front will stall over the eastern gulf bringing the first chances of rain into Yakutat. However, a second front with much deeper moisture will follow, spreading moderate rainfall from Yakutat Wednesday into the northern Panhandle Wednesday evening, and the entire Panhandle by late Wednesday night. Yakutat could get 1 to 2 inches with this system while the northern Panhandle will see between a quarter around Haines/Skagway to 0.5 to 1 inches from Sitka to Juneau. This feature will benefit from the dynamics of a 130-kt jet aloft and well- defined baroclinicity. A wave forming along the front will help stall the front across the southern Panhandle from Wednesday night into late Thursday, and this is where we committed most of our forecast changes. First we increased the duration of rain over the south from Wednesday night into Thursday and thereby raised amounts as well. All told, we are expecting 1 to 2 inches of greatly beneficial rains across the south where utility companies among others desperately need it. Second we extended the brisk southeasterlies through Clarence Strait and Prince of Wales Island during the period and delayed the eventual onset of northwesterlies until late Thursday afternoon. In fact southeasterlies were extended across much of the Inner Channels outside the south even though winds will be generally lighter here. Thursday night, a fairly nice northwesterly jet behind the system mandates brisk northwesterlies at the surface. Right now, we have no small crafts, but if the jet appears similar to what happened Monday, we may need to consider a few. Even as the southern Panhandle deals with a wave overrunning a stalled front, the northern Panhandle will not be completely dry as weak convection amid onshore flow will support scattered rain showers across the area. Forecast remains on track and confidence is relatively high. Changes were mainly reserved from Wednesday night into Thursday night for slowing down the system across the south. .LONG TERM.../Thursday through Tuesday/...A large upper level ridge will have a strong positive tilt to it with the main axis extending northeast from west of Washington State, across British columbia, and into the southwestern portion of the Northwest Territories at the start of this long range forecast period. . A southwesterly 130 kt jet will be positioned over the far northern Panhandle. The jet will shift south through Thursday as an upper short wave progresses east and displaces the ridge. An even larger upper ridge will build in behind the short wave on Friday with the strongest jet energy arcing over the top of the ridge north of the Panhandle. A second short wave will ride up over the second ridge on Sunday...and this pattern will repeat itself for the remainder of the long range forecast period...possibly longer. At the surface, this progressive pattern will yield 5 discrete front over the coming week with the first departing the forecast area to the south on Thursday morning. Long range models are picking up on what may turn into a heavy precipitation training event late Friday night and going into the weekend. As they often do, this training front will waver back and forth north and south as short wave energy transits along the frontal boundary. Good agreement in the long range models on the existence of heavy precipitation and the previous RFC forecast shows this as well. Not so good agreement on the location of maximum QPF. Opted to blend heavily to the ECMWF for this portion of the forecast with the caveat that the preferred model solution may change over the next few days. Fairly high confidence in a heavy precipitation event. Model agreement is consistent and improving on a dry day on Friday, so reduced PoP for this period - again blending heavily to the ECMWF. Model spectrum spreads for forecast highs and lows indicated that the existing long range forecast was too warm. Adjusted temps down by a few days across the board. Adjusted down by several degrees in the Whit Pass area. And so, if the heavy precipitation works out, the Klondike Highway may see a significant snow event this weekend. Still no snow on the Haines Highway or anywhere else at lower elevations. Blended NAM and the Canadian NH for updates to pressure and wind Thursday and Thursday night. Used GFS and ECMWF for Friday and Friday night. PoP and QPF as discussed above. Overall forecast confidence is average, trending above average on the potential for a heavy precipitation event this coming weekend. && .AVIATION... && .MARINE... && .AJK Watches/Warnings/Advisories... PUBLIC...None. MARINE...Gale Warning for PKZ052. Small Craft Advisory for PKZ022-043-051. Small Craft Advisory due to Seas for PKZ041-042-053. && $$ JWA/Fritsch Visit us at http://www.weather.gov/Juneau