Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
601 FXAK67 PAJK 122241 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 241 PM AKDT Sun May 12 2024 .SHORT TERM... Key Points: -Increasing marine winds by Monday morning as a front approaches the area, reaching Small Craft Advisory for inner channels by Monday afternoon. Discussion: No significant changes to the short term forecast at this time. A weakening system has pushed inland from the Northern Gulf this afternoon, bringing a wide swath of post-frontal on-shore winds and scattered rain showers across the AOR. Anticipating this soggy and unsettled pattern to continue to kick off the work week as a mid-lvl low traverses over southcentral Alaska with a deepening low over the northern Gulf keeping persistent southwesterly flow over the area. As this low traverses eastward, it will push another front across southeastern Alaska, bringing another round of rain and elevated winds. Main concern through the short term will be for N/S oriented inner channels by Monday afternoon as southerly winds increase up to 25kts as another system and front pushes into the area with Small Craft Advisories for Stephens Passage and Chatham Strait. As for temperatures, continuing cloud cover will prevent low temperatures near sea level from reaching freezing tonight, with expected lows in the low 40s to upper 30s. By tomorrow afternoon, high temperatures should warm up to the upper 40s to low 50s under mostly cloudy to overcast skies. .LONG TERM... The primary feature of the mid range forecast is a weak atmospheric river (AR) for the southern panhandle Tuesday into Wednesday. Ensemble guidance continues to be in two camps for how this system will proceed: The first, mainly held by the GEFS and GEPS, is a slower progressing trough which will increase rain totals for the southern panhandle. With this solution, 80% of ensemble members indicate rainfall rates of up to a half inch every 6 hours with totals of up to 2 - 2.5 inches over 48 hours. The EPS and deterministic EC continue to prefer a progressive trough, which will push the heavier rates south of the southern panhandle, near Haida Gwaii. At this time, there is good confidence that a low end AR will occur, mainly due to the duration of the event, but overall rainfall rates do not look impressive to support any major impacts. One tidbit of information to add is the 80-100 knot jet associated with this weak AR at 500 mb. Naturally, high vorticity advection and lift exist, meaning that there is the possibility of a rapidly developing surface low feature near the southern panhandle. LREF progs have trended up wind speeds, with the spread of gusts varying wildly between 25 mph and 60 mph at the 10th and 90th percentile respectively around Metlakatla, Ketchikan, and southern PoW Island. While the chances are still low, the general progression towards a more windy system is definitely something to keep in mind as more details become clear. && .AVIATION...MVFR conditions persist tonight, with IFR under more robust showers into late Monday morning. Widespread rain and some LLWS begin to impact the coast near 20z Monday, moving east over Monday night, reducing CIGS and VIS. && .MARINE...Post-frontal on-shore precipitation and southwesterly winds up to Moderate Breeze will continue through tonight for the Gulf and outer waters with wave heights up 7-9ft. Main concern will be for N/S inner channels by Monday afternoon as southerly winds increase up to Fresh to Strong Breeze as another system and front pushes into the area with Small Craft Advisories for Stephens Passage and Chatham Strait. Winds decrease by Tuesday morning. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...Small Craft Advisory for PKZ012-031>033-641>644-651-652-661>664- 671-672. && $$ SHORT TERM...NM LONG TERM...NC AVIATION...AP MARINE...NM Visit us at http://www.weather.gov/Juneau