Tuesday, December 17, 2013
A storm in the Gulf of Alaska is currently affecting the northwest. Energy will split as it moves west, with a piece of energy traveling south along the coast and another piece skirting to our north. We will be spared the coldest part of the approaching storm as most of the cold air slides north and east of us.
Tomorrow should be another nice day before clouds build ahead of the approaching storm later in the day. The wave to our southwest is forecast to eject some energy over our area late Wednesday night or early Thursday leading to some accumulating snows by Thursday afternoon in the 2-4” range.
Precipitation should let up later Thursday before a cold front approaches from the north late in the day. It does not appear there will be good overrunning around the front as the flow aloft is very weak in the vicinity of this split system. Generally unsettled weather with light snow of around 1-3” is expected.
Another wave approaches from the northwest early Saturday, and this one appears to have a slight split to it as well. Slightly heavier snowfall is expected with this cool push of air, though amounts are still expected to be light and in the range of 2-4” each day of the weekend. Temperatures should continue to cool through Sunday morning continuing the light snowfall.
Skies don’t look to clear until late Monday as we remain in cool and moist northwest flow. A nice Tuesday before another approaching storm influences our area mid-week.
Saturday, December 14, 2013
A weak wave passes over us in northwest flow tonight, but there is minimal cool air associated with it so I would expect even lighter amounts tomorrow than the 2-4” that fell by this morning’s report. Skies should clear during the day ushering in a very pleasant week of warm and dry weather.
By midweek, a large storm enters the west coast of the US. Models are now trending towards splitting this storm as it moves over the Great Basin, sparing us from the coldest air of Big Blue. We will, however, experience a significant cold front currently timed for late Thursday as the northern portion of the wave passes through the area. Unfortunately, the southern portion of the wave is currently forecast too far south to affect our weather, and the event will be relatively short-lived as it ends by mid-day Friday.
The ridge in the Gulf of Alaska forcing the northwest flow over our area is forecast to build behind this passing storm before a Pacific wave is forecast to travel through it early in the following work week. This may bring colder temperatures and some snow, but the forecast is too far out for much confidence in that model solution.
Thursday, December 12, 2013
Mountain slopes have warmed nicely while the valleys remain cold while trapped in strong temperature inversions. In fact, warming temperatures aloft counter-intuitively strengthen lower-level inversions as vertical mixing in the lower levels is suppressed in the stabilizing airmass. The cold air in the valley bottoms then stays cold as the surface warming is minimized by the shallow sun angle and reflective snow surface.
There are some weak disturbances influencing our area starting tomorrow, though there is very little chance of significant accumulations. A wave to our south crosses too far south Friday morning for any snow, while another wave from the northwest is forecast to split as it moves over us later Friday, perhaps producing some light snow showers. Yet a third wave is forecast for early Sunday morning and that may produce a bit of snow as well.
Waves graze our area in warm and dry northwest flow Tuesday and Wednesday, but only a slight moderation of temperatures are expected. The developing story is the likely return near the end of the work week of Big Blue, the meteorological euphemism for an arctic outbreak similar to what we observed last week.
Lots of details are still to be resolved by the numerical models, but agreement between the models is trending stronger with this major cold and likely snowy pattern change near the end of next week.
Tuesday, December 10, 2013
Very light snow is currently falling on the hill as a weak wave in northwest flow grazes our area today. Temperatures on the hill are running about 10F warmer than yesterday, and they will warm further, especially Wednesday and Thursday. Mountain valleys, however, will remain cold as temperature inversions maintained by the clearing skies expected tomorrow and Thursday allow for strong nighttime cooling of the snow surface.
Our next chance for snow occurs late Friday as another weak Pacific wave from the northwest is forecast to cross our area. Snowfall is expected to be light at this time, but the bigger effect may be that valley inversion are moderated as the storm passes.
Seasonal weather is expected to continue into the following week before another arctic surge may impact us near the end of the work week. This outbreak may be similar to the current one with sharply colder temperatures and moderate to heavy snows, though a 10 day forecast is likely to change as the event nears.
Sunday, December 8, 2013
Most of the remaining part of the storm is currently moving through the area as temperatures up top have dropped from 0F at 5am to -7F at 8:30am as light snow continues. Temperatures will likely continue to fall or remain this cold until tomorrow morning when a trailing wave finally pushes the coldest part of the storm east of the area. Snow showers on the hill will likely continue until tomorrow afternoon, though additional accumulations after noon today will be minimal due to the very cold temperatures and drying airmass.
Another grazing wave in northwest flow will keep temperatures cold and start light snow showers on the hill again during Tuesday afternoon and evening. There should be some warming on the mountain slopes by Wednesday, but it will be most noticeable on Thursday as the trough that had been sitting over the western part of the US moves east. Mountain valleys, on the other hand, are likely to remain cold as strong inversions develop and persist.
Models currently forecast a weak storm for the following weekend. A flat ridge looks to build in the Gulf of Alaska which may shunt Pacific energy to our north and create mostly dry conditions after that.