textproduct: Juneau

SYNOPSIS

Key Messages:

- Diminishing trend in winds and precipitation tonight into tomorrow. Lingering rain primarily across northern panhandle.

- Another front arrives late Tuesday into Tuesday night, bringing predominantly rain and continued warmer-than-normal temperatures into midweek.

- Late week into next weekend, long range models are still hinting at a weather pattern that has been known to produce heavy snow. High uncertainty at this time but worth watching closely.

LONG TERM.../through this weekend/

The upcoming week is looking like another cloudy and rainy week. There will be lulls between the frontal passages, with precipitation chances mainly limited to western facing mountains, but the overall trend in the long term forecast is cloudy and rainy this week. But late this week into next weekend, ensembles are hinting at a weather pattern that has been known to produce heavy snow.

Friday into the weekend, the overall weather pattern looks to change. Ensembles are hinting at a upper air low pressure descending south out of central Alaska. Run to run ensembles have increasingly placed this low to the west of Anchorage, but cluster analysis has this low as far east as Prince William Sound, around a 40% or less chance of occurrence. What this translates into sensible weather for the panhandle is how deep will the cold pool in Canada get. The further east the low center is, the more the cold pool in Canada will be developed, and the further south the southwesterly flow will be. The stronger the cold pool in Canada is, the further south the associated arctic boundary will be, which will dictate what part of the panhandle will get the most snow. At this point, guidance is backing off on the low placement to west of Anchorage as the more likely scenario, which would bring warmer temperatures further north, keeping the arctic boundary near the northern panhandle.

Confidence is low for placement of heaviest snow, with confidence intervals for the northern half of the panhandle being between all rain with little to no snow accumulation to nearly 12 inches of snow in 24 hours.

Furthermore, there is evidence that if this upcoming weekend system does not generate substantial snowfall for the panhandle, early to mid next week is shaping up to keep this pattern going, which would result in multiple rounds of snow. These upcoming systems will be carefully watched over the following days.

Stay tuned.

AVIATION

For the latest 3 PM aviation update, CIGS have dropped a little faster than expected over SEAK, with several locations AOB IFR. Where MVFR is hanging on, we expect to see IFR CIGS overnight through late Tuesday morning, with periods of IFR to even LIFR VSBYs at times in drizzle and fog. The moist onshore flow will continue through Tuesday with some improvement in CIGS and VSBYS to MVFR in the afternoon, but again quickly trending down toward sunset. 05/Garmon

MARINE

Outer waters: Persistent westerly flow to 20 knots in the gulf waters are expected to continue through the evening and slowly diminish into the morning hours Tuesday. Seas look to follow this trend, enhanced by the long fetch and duration of westerlies in the gulf. Primary swell is currently a southwesterly direction to around 8 ft, for a combine wave height of around 11-13 ft. Not expecting any improvement in seas as winds collapse and shift to the SE for the frontal passage tomorrow. Along the front, expecting to see 25-30 knot sustained winds moving eastward across the gulf into the evening hours tomorrow, before moving overland tomorrow night.

Inside waters: The diminishing trend continues for the inside waters as gradients relax and winds aloft reduce in lieu of the incoming front tomorrow. Expecting to see around 10 knots maximum across the panhandle tonight with plenty of low clouds. The one exception is Lynn Canal, as westerly flow aloft looks to keep southerlies up to 15-20 knots in the channel. That being said, Taiya Inlet down to Eldred Rock have high uncertainty on how stable the low level atmosphere will be. Currently, expecting a relatively stable environment, which will result in decoupled winds near Haines and Skagway and relatively light winds. South of this point; however, southerlies up to 20 knots are currently occurring.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ022-053-641>644-651-652-661>664-671- 672.