textproduct: Juneau

UPDATE

Update to aviation section to include 18z TAF issuance...

SYNOPSIS

Key Messages:

- Another front arrives late Tuesday into Tuesday night, bringing predominantly rain, some increased wind, 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

Widespread lowered conditions continue to be prevalent through Tuesday morning as fog and low CIGs AoB 1000ft stick around preceding a front moving into the panhandle Tuesday evening. Many TAF sites are currently seeing MVFR to IFR conditions with Petersburg and Ketchikan holding onto LIFR conditions with VIS AoB 2SM and calm winds. Conditions are expected to remain lowered through the day with little improvement through the 24 hour period, as light winds and low sun angle helps to reinforce the lowered cloud layers. As the front reaches the outer coast of the panhandle Tuesday afternoon, winds are expected to increase to around 10 kts with potential for 20 kt gusts and moderate rainfall rates. Lowest CIG layers may attempt to rise as the higher cloud deck associated with the front moves in, though MVFR conditions or lower are still expected to prevail through the period. Near 2000-2200 local time Tuesday night LLWS threats begin along the coast from southeast winds 30 to 40 knots at 2500ft.

MARINE

Gulf Waters: Incoming front is already starting to switch wind directions across the gulf as winds at buoy 46085 have already turned to the SE while the buoys closer to shore are starting to turn SW this morning. Expect those winds to continue to turn to the SE with an increase in speeds to around 25 kt by this afternoon and evening from W to E with winds near the coast staying near 25 kt through the night. Winds are then expected to switch to the S and then SW at 20 kt again for Wednesday in the post front environment. Seas are rather high with 10 ft wave heights mainly from a SW swell of 8 ft (period 14 sec). Not much change is expected for seas heights overall with 10 ft wave heights common. The increased winds from the front will briefly take over wave generation duties as SW swell diminishes to 6 ft later today. However as the wind diminish, the SW swell picks up to 8 ft again into Wednesday before starting to slowly subside into Wednesday night.

Inside waters: Lighter winds to 15 kt from the south will rule the inner channels for Tuesday. These lower winds are helping form some patchy fog in some areas with visibility down to less then a mile at times. Fog is expected to persist through the morning and may even last into the afternoon in some areas due to the low winds and low sun angle. Expect winds to start increasing this evening as a front approaches likely getting rid of most of the fog, but heavier precip will start moving in with the wind increase. Max winds will be around 20 to 25 kt late tonight mainly over the southern 2/3rds of the inner channels before diminishing into Wednesday afternoon. Seas (mainly wind wave) will build to 5 ft tonight before subsiding into Wednesday. SW swell from the gulf will lead to higher seas in ocean entrances exposed to the SW and W with up to 8 ft seas encountered in these areas through Wednesday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Dense Fog Advisory until 9 AM AKST this morning for AKZ326. MARINE...Small Craft Advisory for PKZ022-033-034-036-053-641>644-651-652- 661>664-671-672.