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Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
769 FXAK67 PAJK 162353 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 353 PM AKDT Tue Jul 16 2024 .SHORT TERM.../Through wed night/ Active short range period today as a new moderate atmospheric river takes aim at the central and northern panhandle starting tonight and lasting into Wednesday. Rainfall totals look to range from around 1.5 to 3 inches with higher totals in isolated and high elevation areas over a 24 hour period. Area of highest confidence for moderate to heavy rainfall is from around Gustavus and Hoonah eastward to Petersburg. Some uncertainly on where the eastern and western edges of the heavy rainfall will be, especially the western edge. General trends over the last 24 hours have edged the rainfall slightly further west then where they were depicted yesterday which put Hoonah and Gustavus right on the western edge. The eastern edge is complicated by the eastward movement of the moisture plume Wednesday into Wed night which will spread at least a brief period of rain across the southern panhandle Wed night which could drop up to 1 to 1.5 inches of rainfall there. The moisture plume is then expected to be exiting the panhandle by late Wed night. The target for the highest rainfall is the Juneau area. Wind wise, expect elevated winds for most of the inner channels starting tonight and lasting into Wed. Most inner channels will likely see a brief period of 25 kt small craft wind conditions at some point through Wed afternoon. Highest winds will likely be late tonight for the south and Wed morning/mid day for the central and northern panhandle. Northern Lynn and Skagway winds will last the longest possibly lasting into late Wednesday night before diminishing. .LONG TERM.../Thursday through Tuesday/... Overview: A relatively quite weather period is likely for SE AK. A number of breaks are in the mid to long range, not exactly dry but not the intense rainfall and stronger winds we have been seeing. Mid level low with trough extended into the AK Gulf moves eastward then drops to the south into the weekend. As part of a blocking pattern, to the west a ridge then another low, this mid level pattern will shift in position somewhat by likely not change until late next week. For Thursday remnants of the Wednesday front will be over the southern region keeping rain going. Points north of Frederick Sound not have higher chances of rain breaks that day. With the 500 mb low in place flow pattern will move a low extending from a deeper system over the far SW Gulf northward into the SE Gulf by Friday. For now winds around the low expected to be in the 20 kt range with lighter winds to the north. Light to moderate rainfall amounts move in with the system with most models keeping precip over the south with diminishing rates as the low moves northward. GFS tracks furthest north with highest winds and pop. By late Saturday this low will have dissipated, but the main low remains in place into next week and thus can keep pushing precip bands over the panhandle. The southerly flow and weather breaks will let day time highs pick back up into the upper 60s to low 70s. With the run to run inconsistencies seen that past few days not fully jumping on any one solution so overall keeping with SE AK climatology: mostly cloudy chance of rain. && .AVIATION.../Until 00Z Thursday/...Generally expect continued lowering of CIGs and VSBYs into the MVFR / IFR category range into Wednesday morning as the next frontal system moves through the Alaskan Panhandle region. Those conditions will begin to improve toward Wednesday afternoon. SFC winds may become a bit gusty as the front pushes through from this evening into the morning over some locations. LLWS values of up to around magnitudes of 30 to 40 knots are possible out of a southeasterly direction along with the passage of that front, as well. && MARINE...Highest winds and seas in the marine areas will be mainly confined to the extreme SE Gulf waters and across most of the inner channels Tonight into Wednesday. Highest expected winds will top out at 25 to 30 kt small craft criteria winds especially in Clarence Strait. Seas will top out at 10 ft late tonight for the extreme SE gulf waters. Inner channel seas will likely be around 5 to 6 ft at the highest with higher seas in areas of long fetch. && .HYDROLOGY...Rivers and streams are running high with Auke Lake in Juneau still hovering around minor flood stage and the Chilkat River still over minor flood stage from the previous event. The forecasted rain amounts of 1.5 to 3 inches for the area from Tuesday night through late Wednesday afternoon and the saturated soils will cause rivers and streams to rise rapidly. There is good ensemble agreement on this heavy rain event with 50 to 70% chance the area will see the forecasted rain amounts and these values are very anomalous for this time of year. With that said there are flood advisories out for the Chilkat River area, Taiya River area and the Mendenhall valley area for minor flooding through Thursday morning. Flooding is expected to develop through Wednesday afternoon and persist into the evening time frame. A flood watch is still in affect for the full Juneau borough as other non gauge rivers/streams that may flow out of their banks. For other areas outside of the flood advisories, there is a special weather statement out for significant river rises but not flood is expected for those areas. Some of the large rivers may stay above flood stage longer due to the lag in draining all the rainfall runoff and melted ice. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...Flood Watch from 7 PM AKDT this evening through late Wednesday night for AKZ325. MARINE...Small Craft Advisory for PKZ011>013-021-022-031>036-641-642-644- 661-662. && $$ SHORT TERM...EAL LONG TERM....PRB AVIATION...JLC Visit us at http://www.weather.gov/Juneau