Grazing storm for tonight, tomorrow briefly interrupts warm and sunny weather
Wednesday, April 8, 2015
The storm that brought two feet of snow to the Sierra Nevada mountains yesterday is on our doorstep. Clouds are increasing and there may be some showers late this afternoon ahead of the main push of cool air expected around late this evening or midnight. Snows should increase around then and last through the morning, with the heaviest snows staying just north of our area where the atmosphere is the most unstable and upward forcing is strongest. I would expect 1-4” for the morning report with maybe another inch or two during the morning hours.
Non-accumulating showers will likely continue through the afternoon before drier air filters into the region. Additional weaker grazing waves will pass well north of us on Friday morning and each of the weekend mornings, but warming temperatures and sun should overcome the slight cooling from these waves giving us some beautiful weather for closing weekend.
Another storm crossing the Baja peninsula around mid-weekend will eventually pass south of us by late Monday and bring significant precipitation to the Colorado plains and possibly the southern mountains, likely leaving us with dry weather. Concurrently, a major storm is forecast to cross the west coast around Monday, and there is a lot of model uncertainty with the evolution of this storm. While is is nearly certain that California and the western Great Basin will receive significant precipitation, our forecast is considerably murkier for next week.
Cold front later Wednesday should bring snow
Tuesday, March 31, 2015
A storm currently crossing the Pacific Northwest coast will bring a cold front through our area around Wednesday afternoon, temporarily ending the abnormally warm and dry conditions for a few days. The atmosphere will destabilize tomorrow and we will be prone to gusty winds with falling temperatures, with even the possibility of some thunder and lightening later in the afternoon or early evening. Some of these showers may produce an inch or two or snow on the hill which would be reported Thursday morning.
While most of the energy stays north of us for Wednesday, by Thursday a trailing wave brings a reinforcing surge of cold air into the area. There is a much better chance of snow as the storm is forecast to move more directly over the area by Thursday night. Winds do look like they will turn to the northwest for a period of time between Thursday night and Friday morning, and this will be the best time for snow. I expect 2-6” by the Friday morning report and another inch or two during the morning hours. While we are likely to see snowflakes even in the valley, the very warm temperatures of the past few weeks have warmed the ground surfaces and will preclude accumulating snow.
Skies should clear later Friday and temperatures should warm during the day after a chilly start. Another spectacular weekend is on tap as dry air in generally westerly flow invades the area.
Another Pacific Northwest wave approaches our area early next workweek and brings some cooler temperatures, but this storm will pass well north of our area and likely be responsible for some windy but dry conditions.
Temperatures will warm again behind this grazing wave, but there is a lot of model uncertainty heading into closing weekend. The American GFS has a strong trough crossing the West Coast around Friday and threatens significant snow during the latter half of the weekend. The European ECMWF has a similar trough slightly further west at the limit of its 10 day forecast, but the forecast beyond that has not been generated yet.
Storm on track for Tuesday and Wednesday
Monday, March 23, 2015
The storm advertised in last week’s blog is on track to deliver snow tonight and tomorrow night through Wednesday. There is a slight change in the forecast as the last wave timed for Wednesday night, though still cold, will be drier than originally predicted.
The atmosphere has destabilized ahead of the cold front currently moving through Utah, and any showers that form this afternoon will likely fall as liquid below 9500 feet or so. Upward forcing will increase just ahead of the front by late this afternoon, increasing showers and lowering snow levels until the front moves through around 6pm or so.
Rain will change to snow in the valley around sunset while moderate to sometimes heavy snow should fall on the hill. We should continue accumulating snow in the cool and moist northwest flow into the early morning hours before the snow decreases and becomes more showery during the day Tuesday. I would expect 3-6” on the Tuesday morning snow report.
Another wave bringing more snow is currently forecast to move across the area around sunset Tuesday, leaving another 3-6” on the hill by the Wednesday morning report. Conditions will remain unsettled and showery Wednesday before the last and coldest, but driest wave moves over the area Wednesday night. I expect accumulating snows to end by midnight, with 1-4” reported Thursday morning.
There may be some isolated snow showers in the cool and unstable airmass Thursday before a building ridge brings much warmer and dry weather for Friday into Saturday morning. Current forecasts have the northern portion of a splitting Pacific wave moving through the ridge by later Saturday, bringing some cooling, though showers are currently forecast to remain north of us.
The warmer southern portion of this split wave is then forecast to approach the area Sunday afternoon, increasing the chance of showers later in the day and into the evening and bringing another unsettled start to the next workweek.
Chance of precipitation Thu. / Fri. and again in about a week
Wednesday, March 11, 2015
High clouds in advance of a spitting West Coast storm have invaded our area today as temperatures stay warm. The northern portion of the split storm will move eastward tonight and graze the northern half of Colorado tomorrow and Friday, bringing some cooling and the chance of light high-elevation snows. I expect only 1-4” of snow above 9000 feet from this system between Thursday and Friday afternoons before dry and warm weather returns for the weekend and the beginning of next week.
Interestingly, the southern portion of this storm is forecast to move south into the Baja area by this weekend and loiter for a few days before being nudged inland by another possible Pacific storm timed for mid-next week. As might be expected for a forecast a week away, there is a lot of uncertainty with not only the Pacific storm itself, but how it will interact with the West Coast ridge and the Baja low.
There is hope that an active pattern will return around mid-next week, though there is a lot of model disagreement on whether that will happen.
Continued dry with warming for the next week
Friday, March 6, 2015
The arctic air mass brought by the last storm is still influencing our weather today with cold morning temperatures even as it is being rapidly moderated by the strengthening early March sun. Though we are in a warming trend for the next week, a couple of weak waves embedded in the fast northwest flow north and east of us will keep temperatures near normal Saturday and then again Sunday. The stronger and further west Sunday wave will bring more cooling than Saturday and also showers to southern Colorado.
Temperatures will warm to above average beginning Monday and last through much of the workweek as the West Coast ridge builds. A weak and disorganized Pacific wave interacts with the ridge by the end of the workweek increasing the chances of light showers for then and into the next weekend. Another significant push of Pacific energy is forecast to attack the ridge early in the next workweek, possibly beginning another storm cycle.
