textproduct: Juneau

SYNOPSIS

Key Messages:

- Widespread cold temperatures and cold wind chills last through through early workweek.

- A Taku wind event in Downtown Juneau and Douglas will be weakening Monday morning.

- Increasing potential for an overrunning snow event by late in the workweek into next weekend.

LONG TERM

This week, we'll be watching the potential for a slight shift in the weather pattern that could would the next round of snow to Southeast Alaska along with some marginally warmer temps.

The long range computer models, both deterministic and ensembles, are trying to put a low pressure center in the northern Gulf of Alaska in the second half of next week. This would allow for the flow to switch to a more onshore pattern, or at the very least a weaker outflow. This would weaken the pressure gradient over area, allowing for wind speeds to weaken a bit beginning around the Wednesday/Thursday time frame. If/when the low continues its journey southeastward, the pressure gradient would tighten up again, allowing for wind speeds to pick back up for the later days of the week.

As far as snow potential, the EURO and Canadian develop a low in the northern Gulf as early as Wednesday. Their respective ensembles mirror this story. The outlier is the GFS. The latest GFS deterministic run keeps the area dry until late Thursday into Friday. The GFS ensemble average, however, closer matches the EURO and Canadian.

For now, moisture amounts are hinting at if the panhandle sees any snow later this week, it would start out as light snow until Friday and the weekend.

The 75th percentiles for the EURO and GFS ensembles give the panhandle less than a tenth of an inch of QPF for Wednesday through Wednesday night, which would give around 1 inch of snow at most. For Thursday into Thursday night, the 75th percentiles are giving the area around a tenth to about a third of an inch of QPF, with the greater amounts in the EURO, which would give around 1 to 5 inches of snow over 24 hours. For Friday into Friday night, the 75th percentiles are giving the area around one to two inches of QPF, which would give upwards of 12+ inches of snow over 24 hours. The 50th percentiles are giving the area around a half inch to one inch, which would give around 6 to 12 inches of snow. Saturday's QPF is even greater with the 50th percentile around one to two inches, which would give over 12 inches of snow and the 75th percentile is over 2 inches, which would be well over 15 inches of snow. The issue with Saturday's snowfall forecast is warmer air aloft may slide in, which would lower total snowfall amounts and some areas in the far south may even see rain mixed in.

So what are the main takeaways off all this data? For starters, the 75th percentile is an upper bound. So the amounts mentioned above are on the high-end for current estimates. Secondly, snow is possible as early as Wednesday but majority of the data is pointing to it not being much much if it does happen. Thursday could be a wildcard day that is worth watching closely. Friday and next weekend could be a very snowy couple of days so that will be worth watching closely, especially with the jump in 75th percentiles from yesterday to today.

As far as the slightly warmer temps are concerned, there is a warming trend but most of Southeast is still likely to be below freezing. Wednesday's highs will be generally in the single digits to teens but by the weekend, highs could be in the teens in the far north, 20s and 30s elsewhere. For overnight lows, Tuesday night's forecasted lows are in the single digits to teens with warmer low temps in the teens to 30s for the weekend nights. So warmer but still colder-than-normal.

AVIATION

Widespread VFR conditions, with Generally clear skies and outflow winds continuing through Monday and into Tuesday, albeit with some weakening of the outflow winds expected. What clouds are present are largely limited to the southern panhandle, but these are generally above 5K feet. The bigger story will be winds. While outflow will remain, some weakening is expected, and low level turbulence and LLWS will diminish through Monday, though cannot rule out some sporadic mountain wave activity lingering. The strongest winds will remain entrenched within the inner channels and standard outflow areas.

MARINE

Inside waters: Outflow conditions and freezing spray remain the concerns for the inside waters. North/south oriented channels are expected to remain mostly the same, wind speed wise, through there will be a slight diminishing trend before outflow starts to shut off on Wednesday. East/west oriented channels will see a faster diminishing trend especially along the outer coast as pressure gradients become more north/south orientated allowing winds in these areas to diminish by late Monday night or Tuesday. Overall though freezing spray still remains a problem for a large part of the inner channels due to the winds, high seas (due to the high winds blowing down the long linear channels), and cold air. Heavy freezing spray still plagues Lynn Canal, Taku inlet, and Glacier Bay through Monday night at least.

Gulf waters: Outflow conditions persist with the highest winds still coming out of the passes east of Yakutat, Cross Sound, and to a lesser extents out of Chatham Strait. Higher seas (up to 14 ft) as well as freezing spray are also found in these outflow areas. This strong outflow is expected to diminish today into Tuesday as pressure gradients become not as favorable to sustain them. The higher seas and freezing spray will diminish as the winds do. Otherwise, winds over the gulf waters are expected to remain mostly out of the north for the next few days with seas diminishing down to 6 ft or less as the outflow diminishes by Tuesday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Extreme Cold Warning until noon AKST today for AKZ317. Cold Weather Advisory from noon today to noon AKST Tuesday for AKZ317. Extreme Cold Warning until noon AKST Tuesday for AKZ318>322-324- 325-327-329. Cold Weather Advisory until noon AKST Tuesday for AKZ323-326-328- 330>332. High Wind Warning until 9 AM AKST this morning for AKZ325. MARINE...Heavy Freezing Spray Warning for PKZ011>013-021-031-032. Heavy Freezing Spray Warning for PKZ022-033. Heavy Freezing Spray Warning for PKZ033. Heavy Freezing Spray Warning for PKZ034-035-643-671. Heavy Freezing Spray Warning for PKZ034. Heavy Freezing Spray Warning for PKZ053. Heavy Freezing Spray Warning for PKZ644-651. Gale Warning for PKZ011>013-022-031-643-644-651-663-664-671. Small Craft Advisory for PKZ021-032>035-053-641-642-661-662-672.