Area Forecast Discussion
Issued by NWS Juneau, AK
Issued by NWS Juneau, AK
516 FXAK67 PAJK 181339 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 539 AM AKDT Thu Jul 18 2024 .SHORT TERM...A contrasting forecast is in store for SE AK, as two separate weather patterns result in sharply differing conditions across the panhandle. Across much of the northern half of the area including locations like Juneau, Sitka, and Angoon, an interlude of drier weather will be present through much of the day on Thursday. The band of precipitation responsible for the rainfall on Wednesday has moved into the southern panhandle as it continues to weaken and synoptic NW flow behind it has resulted in some clearing of the main stratus deck across the area. Overnight, many areas with otherwise clearer conditions saw fog or low level stratus decks develop as light winds and saturated soils combined with cooling temperatures. Anticipate that the fog will largely dissipate through the morning hours on Thursday, with much of the low level stratus deck which developed in the wake of the departing system following suit. This will clear the way for significant breaks in the clouds and subsequently warmer temperatures, for the northern half of the panhandle through the day on Thursday. The southern panhandle will feature a sharply different pattern as chances of rain and a layer of stratus continue to remain courtesy of the aforementioned decaying band of precipitation. Although QPF totals will be substantially lower today than they have been through the past few days, still anticipate that as much as 0.25 to 0.5 inches of rain could fall in some locations. The cloud deck will inhibit daytime heating, and so high temperatures will likely be cooler than across the N half of the panhandle for many locations. Thursday evening and night will see a pattern reversal, as the band of precipitation moves N, bringing chances of rain and widespread cloud cover back to the N half of the panhandle, while drier conditions and some breaks in the clouds become possible for the southern panhandle. Chances of rain will continue on Friday as moderate mid-level support helps fuel a shortwave which will move into the area from the S as it orbits around a broad area of low pressure in the Gulf. The primary changes made to the forecast were to decrease high temperatures for the southern half of the area on Thursday, and to increase categorical precipitation coverage in conjunction with the band of precipitation currently over the southern half of the panhandle. Wind speeds were increased in a few of the inner channels, but the forecast continues to remain largely on track. .LONG TERM.../Friday through Wednesday/... Overview: A relatively quiet weather period is likely for SE AK. Friday will see additional moisture being funneled up from the south, which will then be followed by drier air from the south. An easterly, wet wave is possible late in the weekend and into next week. 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 rainfall amounts move in with the system with most models keeping precip over the south with diminishing rates as the low moves northward. 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. Looking towards late weekend and into next week, there is increasing confidence of an easterly wave making it over the mountains. Areas of interest include communities in the northern panhandle and possibly Juneau at this time. && .AVIATION...Early this morning, impacts to aviation can be split between two very different areas. South of Frederick Sound, continued rain streaming in from the south is keeping the lowered clouds and visibility in place. Clouds as low as a few hundred feet and visibility as low as a couple miles. For this area, not expecting much in the way of improvement today but some improvement is possible later tonight as this area of rain pushes northward. So generally expecting overall IFR to low-end MVFR today with some improvement tonight. Areas north of Frederick Sound, the clearer skies that moved in caused foggy conditions to develop. Reported visibilities overnight have bounced around from the full 10SM to 1/4SM. Going forward, once the fog fades out later this morning, expecting VFR conditions through today. Tonight, the incoming rain and clouds from the south would lower flying conditions to generally MVFR. && .HYDROLOGY...Rivers across the northern inner channels are largely on their way down or expected to be begin falling later on Thursday, with the possible exception of the Chilkat River which continues to rise as of the time of writing. Hydro issues should improve over the next few days as much less rainfall is expected over the area. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...Dense Fog Advisory until 8 AM AKDT this morning for AKZ325. MARINE...None. && $$ SHORT TERM...GFS LONG TERM....NC AVIATION...GJS Visit us at http://www.weather.gov/Juneau