Area Forecast Discussion
Issued by NWS Juneau, AK

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000 FXAK67 PAJK 161335 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 535 AM AKDT Mon May 16 2022 .SHORT TERM...
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/Through Mon night/ Rain showers from a frontal band moving through this morning are spread across the southern and central panhandle up to Gustavus, Hoonah, and Angoon. Satellite rain rate and radar imagery does show that the northern edge of the showers is just south of Juneau as of 5 am and slowly moving north. This band of showers should spread over the rest of the northern panhandle by midday. Behind it, a few more short waves are expected to move north across the panhandle through tonight as they wrap around a weakening low in the southern gulf keeping the area mostly damp. The strongest one moves into the south this afternoon and has a bit more dynamics associated with it. First off some higher southerly winds are likely ahead of it as southerly pressure gradients briefly tighten. Areas like Stephens Passage and Lynn Canal will likely see a step up in winds to 20 or 25 kt this later this morning and into the afternoon hours. Second, a mass of cooler air aloft combined with an area of enhanced vorticity is moving in with the short wave and is expected to destabilize the atmosphere enough that some thunderstorms could occur across the southern panhandle this afternoon and evening. Not a great chance of this happening but the best chance will be in areas where some clear breaks show up this afternoon especially along the higher terrain. Forecast changes were mainly focused on local effects from winds though inner channel winds were increased for the late tonight, Tue, and Tue night time period as stronger southerly flow still exists from the remaining low in the gulf at that time. Otherwise changes were mostly minor. .LONG TERM.../Tuesday through Friday/...Major themes in the extended range forecast are diminishing precipitation through Tuesday night followed by decreasing clouds and significantly warmer daytime highs for the balance of the week. Small craft easterlies/southeasterlies over the coastal marine zones of the eastern Gulf will persist through Tuesday night and end early Monday morning. Although the current forecast does not have small craft winds on the inside, it may become necessary to include them for Clarence Strait Tuesday and Tuesday night. At the start of this long range forecast, models are in good agreement and depicting a large upper level low centered over the Gulf of Alaska. This low will drop south and then be ejected east by a 150kt jet. Strong and deep upper level ridging will then shift east, become negatively tilted, and develop into a large omega block. At the surface, this feature is not nearly as well defined, but can be identified easily enough when comparing the surface pressure pattern to the 300mb and 500mb heights. Additionally, an inverted surface trough will remain situated over the Panhandle for most of the coming week. A significantly warmer continental low level airmass will move in from the east beginning on Wednesday courtesy of the inverted trough and this will be the basis for the warmer daytime highs and clearing skies that Southeast Alaska will experience during the second half of the upcoming week. Highs in the low to mid 50s on Tuesday will be replaced by mid 60s, or possibly even higher, by Thursday. Owing to the continental source region of this warmer air, relative humidity values will drop as well, getting down to the mid 30s in some places. Fortunately, green-up is well under way across Southeast Alaska as a whole, which will act to mitigate, but not completely, eliminate any fire danger.
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PUBLIC...None. MARINE...Small Craft Advisory for PKZ012-033>036-041>043.
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