Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
728 FXAK67 PAJK 161239 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 439 AM AKDT Mon Sep 16 2024 .SHORT TERM...Chances of rain showers continue across the northern half of the area through the day on Monday, while a stronger low passing across the southern half of the panhandle brings widespread rain to areas south of Sumner Strait. Drier weather is in store Monday night into Tuesday. Satellite and radar imagery as of the time of writing (12z) depict a developing low moving into the southern panhandle, with its associated cloud shield reaching as far N as the Icy Strait Corridor. Upper level analysis reveals the culprit behind the low as a weak upper level shortwave trough moving within a broader area of troughing across the gulf. Overall dynamics aren`t all that conducive to a strong system developing, and the primary impact of this system will be the rainfall it produces across the southern half of the area through the day. The rainfall itself will also be less than outstanding, with amounts near sea level between 0.25 and 0.75 inches of rain expected through the daytime hours. Across the northern panhandle, chances of rain showers are expected given continued onshore flow, although these will be less widespread in nature. Chances of rain will diminish through the evening and overnight timeframe on Monday across most of the area as northerly flow develops, with most locations drying out save for a few passing showers by Monday night. The exception to this will be parts of the far southern panhandle like Revillagigedo Island and Hyder, where PoP chances will remain more robust until Tuesday morning. As PoPs diminish, increasing breaks in the clouds will set the stage for fog or low stratus development across parts of the area, though this will largely dissipate through the morning hours on Tuesday. Winds will continue to diminish through Monday, with Lynn Canal, the Icy Strait Corridor, and Clarence Strait likely remaining the last holdouts for elevated winds, through even these areas, barring Clarence Strait, will drop below 15 kt by late Monday night. Primary changes to the forecast were to add some additional detail to the PoP and QPF fields for the low moving in across the south, as well as to extend the duration of elevated winds for a few locations given a continued sharp pressure gradient. .LONG TERM.../Tuesday through Friday/... Quick Notes: -Rainy weather continues. -24 hour rainfall amounts are not out of the ordinary for this time of year. -Marine winds will be elevated late Tuesday night through Wednesday night with sustained winds around 15-25 kts for some of the inner channels. Details: The active pattern will continue across the panhandle through next week. To start off, an exiting system on Tuesday with brief 500mb ridging may give the area a short break in the rainy weather, and even some breaks in the clouds, on Tuesday. The short break will come to an end Wednesday as the next front pushes through. There will be both wind and rain with this front. That being said, rainfall amounts aren`t all the impressive for this time of year, with 24 hour rainfall amounts around 0.50 to 1 inch. Wind speeds will increase as the front tracks through, but nothing too out of the ordinary with frontal passes this time of year. Beginning late Tuesday night, most inner channels will see speeds increase to around 10 to 20 knots for Wednesday. The exception will be Lynn Canal where sustained speeds upwards of 25 knots are possible based on forecasted pressure gradients. Once the front clears the area, lingering light, on/off rain will last through Friday with decreasing wind speeds. Ultimately, what is currently on the radar as the next impactful rain event could possibly be next weekend, into early next week. There are early indications of a long duration rain event. At this time, there is 40-60% chance of IVT values exceeding 250 kg/m/s for three days. Unfortunately, details are scarce, but it will be monitored closely. && .AVIATION...Areas of rain and some fog/low clouds are making for a mixed bag of aviation conditions this morning. Ceilings and visibility range from VFR (6000 ft ceilings and 10 mile vis) all the way down to LIFR (200 ft ceilings and 1.5 mile vis) in some areas. Winds are mostly light except for the northern Lynn Canal area where gusts to 40 mph are being observed. The forecast is for general improving conditions through the day with most areas becoming VFR by late afternoon. The southern panhandle will be the slowest to improve as there is a disturbance moving through that area this morning. Winds near Skagway will likely persist through the day before diminishing this evening. Tonight will possibly bring a mixed bag of ceilings and vis conditions again. This time due to fog possibly developing in many areas and persisting into Tuesday morning. Expect areas of VFR with IFR or lower conditions where fog develops. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...Strong Wind until 7 AM AKDT this morning for AKZ318. MARINE...Small Craft Advisory for PKZ012-013-022-641>644-651-652-661>664- 671-672. && $$ SHORT TERM...GFS LONG TERM....GJS AVIATION...EAL Visit us at http://www.weather.gov/Juneau