Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
542 FXAK67 PAJK 171309 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 509 AM AKDT Tue Sep 17 2024 .SHORT TERM...A lull in the active weather pattern on Tuesday begins drawing to a close Tuesday night as another front moves into SE AK. Satellite and radar imagery as of the time of writing (12z) show clearing skies across most of the panhandle as a low which is still bringing chances of rain to the southern half of the area departs through the morning hours. In the place of the departing low, ridging will briefly rebuild as energy races downstream of an approaching system. The ridge won`t be very impressive, with 500 mb decameter heights struggling to get above 654 decameters through the day. This will contribute to widespread clearing skies across the area. The weak ridge will be displaced Tuesday night as another system approaches from the west. Northerly flow will prevail for most locations through the daytime hours, though flow will veer to the S Tuesday night as the system approaches. Winds and chances of rain will increase Tuesday night into Wednesday as the system arrives. For additional details, see the long term forecast discussion. .LONG TERM.../Wednesday through Sunday/...This extended range forecast period sees Southeast Alaska situated on the north side of the upper level jet stream with periods of upper level zonal flow punctuated by pronounced upper level troughs. The single exception to this will be on Friday when an upper ridge transits the area from west to east. What this means: No less than three lows pressure centers will transit across the Gulf of Alaska and Southeast Alaska over the next five days with the only meaningful chance of dry weather occurring on Friday when the upper level ridge passes overhead. Model divergence gets rather large on Friday going into Saturday with regard to a low over the far southeast Gulf. Details on how strong and precisely where it will make its closest approach to the southern outer coast are lacking big time. Fortunately we have several days to pin down this potentially storm force low. As is often the case, GFS is offering the strongest solution. If the worst case GFS solution pans out, potential exists for the first high wind warning of this Autumn season for the southern outer coast. Stay tuned. && .AVIATION...Patchy fog and low clouds north and east of Kupreanof Island is creating a few areas of IFR conditions this morning as higher level clouds have cleared out. Areas farther south are still dealing with higher overcast so those areas are seeing VFR or MVFR conditions due to a lack of low clouds or fog developing. Once the morning fog dissipates today most areas should be VFR through the evening hours. An incoming front late Tue night into Wed will start to bring ceilings and vis down to MVFR or lower due to precipitation. Winds will also be increasing especially in the northern Lynn Canal area. Some light turbulence and low level wind shear may be possibly into Wed as the front moves in. && .MARINE...Wind speeds largely remain on the lower side until Tuesday night across most of the area. By late Tuesday night, the next front will move in from the west, causing wind speeds to increase. 20 to 25 knots in the gulf with 10 to 20 knots in the inner channels. The exception for the inner channels is Lynn Canal where wind speeds will increase to 20 to 30 kts by late Tuesday night with elevated winds lasting into Wednesday. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...Strong Wind late tonight for AKZ318. MARINE...Small Craft Advisory for PKZ012-013-641-661-662-671-672. && $$ SHORT TERM...GFS LONG TERM....Fritsch AVIATION...EAL MARINE...GJS/GFS Visit us at http://www.weather.gov/Juneau