Thursday, June 1, 2017
A splitting Pacific storm is currently moving across the Great Basin. While most of the storm will avoid Colorado, increasing moisture and upward motion ahead of the storm will bring good chances for showers to the Steamboat Springs area this afternoon and tonight.
Lingering energy and moisture will fuel the chance of afternoon thunderstorms on Friday as the northern part of the storm moves towards the Great Lakes.
The last forecast discussed the possibility of the southern part of the split possibly affecting our weather on Saturday, but numerical weather forecasts now have that area of low pressure well to the south of northern Colorado. Drier air moves over our region behind the departing northern part of the storm leading to a very pleasant Saturday.
Late in the weekend another storm crosses the Pacific Northwest coast. As earlier predicted by the European ECMWF, a building ridge of high pressure over the Rockies will shunt the slow-moving storm first to our northwest and then to our north. The ridge will be flattened over our area by the grazing storm, and this will lead to a small chance of afternoon storms on Sunday and a better chance on Monday and Tuesday as the airmass is destabilized by cool air aloft associated with the storm.
Temperatures will warm again starting on Wednesday and continuing through the rest of the work week as a ridge of high pressure rebuilds over the Intermountain West behind the grazing storm.
Monday, May 29, 2017
Energy traveling southward along the western periphery of a large storm near the Great Lakes has kept seasonably cool temperature in place for the Steamboat Springs area. There will be a threat of afternoon and early evening storms today, with gusty winds likely as most of the precipitation will evaporate in the dry sub-cloud layer before reaching the ground (virga). This evaporation will cool the air beneath the cloud, forcing it first downward as it becomes negatively buoyant and then outward as it encounters the ground.
The diffuse area of low pressure talked about in the last forecast looks to stay south of northern Colorado through midweek, allowing a ridge of high pressure to build over the Intermountain West. Mostly sunny skies and warm temperatures are expected with only a slight chance of afternoon storms for Tuesday and Wednesday.
A splitting Pacific trough of low pressure approaches the West Coast midweek, and the first effects will be much increased chances of afternoon storms on Thursday as some moisture to our south is carried northward by the southwest flow ahead of the trough.
The southern end of the splitting trough looks to move over Colorado on Friday, bringing a weak cool front through the area with showers likely during the day.
By Saturday, Colorado will be caught in the somewhat chaotic and slow-moving area of the split flow, leading to more chances for showers, though likely less numerous and intense than on Friday.
On Sunday, the Steamboat Springs area looks to be in either drier flow from the southwest or moderately unstable flow from the north as some of the northern split interacts with more energy rotating southward from central Canada. At this point, the forecast could be either dry or unsettled.
Models agree that another storm will cross the West Coast late in the weekend, but disagree on its position. The Amercian GFS has the further south solution compared to the European ECMWF, and would bring another round of cooler temperature, showers and unsettled weather for the beginning of the new week.
Thursday, May 25, 2017
While the bulk of a storm currently affecting the Steamboat Springs area is located in the southern Canadian Prairies, just north of Montana and North Dakota, a cold front moving into the Great Basin on the backside of that storm will keep a somewhat stationary front over the northern borders of Utah and Colorado through Saturday. Showers will be the heaviest and longest-lasting with cooler temperatures today and Saturday, as the stationary front moves southward, with Friday being a less active and warmer day as the once-cool front retreats northward back over our area as a warm front.
Some energy lingers over the southern Great Basin even as the storm passes east of our area by Saturday night, and that will contribute to the possibility of much lighter afternoon showers for Sunday and Memorial Day along with near-average temperatures.
Around Tuesday, a large diffuse area of low pressure crosses the northern Baja coast. Though the exact track of this low pressure is in question, models agree that subtropical moisture will be drawn northward across New Mexico and Colorado on the front-side of the storm, leading to heavier afternoon showers on Tuesday and Wednesday.
More uncertainty exists around midweek as the European ECMWF has uncharacteristically changed its solutions from earlier runs and now has the storm moving over Colorado later in the work week. The American GFS, on other hand, keeps the bulk of the storm south of us in the Chihuahuan Desert over northern Mexico and southern New Mexico. Continued afternoon showers are likely with this solution while a wetter period later Thursday or Friday is advertised by the ECMWF.
Monday, May 22, 2017
The slow-moving storm that started affecting the Steamboat Springs area last Wednesday is currently spinning north of the Great Lakes. A couple more waves of energy will move southward along the western periphery of the large storm bringing reinforcing surges of cold air and more precipitation across our region today and tonight.
Showers will increase again around mid-afternoon and become heavy at times during the late afternoon and early evening. While the bulk of the precipitation will be rain in the valley with more accumulating snows above 8000′ or 9000′, there may be enough cold air for some non-accumulating snow at the lower elevations later in the evening when the last wave of energy moves over the area.
Precipitation should end by midnight followed by some much-welcomed clearing for Tuesday and Wednesday. Temperatures will still be below normal on Tuesday, but warming on Wednesday should bring a classic sunny late-spring day with pleasant temperatures.
Meanwhile, another strong storm is forecast to travel across the Gulf of Alaska tomorrow and mix with more cold air from western Canada as it moves eastward. By Wednesday, the storm will undergo a modest split, with the northern portion moving across the Canadian border and the southern portion elongating across the northern Great Basin as additional energy moves southward from Canada.
The end result will be another prolonged period of unsettled weather likely lasting through at least some of the Memorial Day weekend, as earlier suggested by the European ECMWF and discussed in the last forecast. Periods of heavier showers will occur as a couple of waves of energy move through the Great Basin, followed by partial clearing behind each wave and the usual afternoon showers.
The timing of the waves will almost certainly change by my next forecast on Thursday, but right now the heaviest showers are likely to occur during the day Thursday and again later on Saturday. The periods of heaviest precipitation will also be influenced by quick moving waves of energy from a decaying storm system off the southern California coast, and these may or may not phase with energy from the north.
Lastly, in order to thoroughly complicate the prognostication, the European ECMWF has just forecast a faster eastward movement of the storm, bringing drier and warmer weather for the latter half of the long weekend while the American GFS still holds on to the cool and unsettled weather through Memorial Day.
Thursday, May 18, 2017
A large, powerful and slow-moving late-season winter storm that is currently spinning over the central Rockies has brought close to a foot of snow to the Steamboat Springs area so far. Light to sometimes moderate snowfall is forecast to continue through this evening before tapering off after midnight.
The slow movement of the storm means that we will still be in the cold, moist and unstable northwest quadrant of the storm through tomorrow, leading to showers, moderate to heavy at times, through the day Friday. Some additional snowfall accumulations above the valley bottom are likely.
Only light showers may be possible for Saturday in still below normal temperatures as northwest flow keeps the cool temperatures around. Concurrently, a wave of energy from the Pacific phases with some cool air from western Canada before splitting just upstream of our area by Saturday night. There will be enough moisture and instability to bring a good chance of storms later Sunday lasting into the evening.
A stronger wave of energy moves southward from western Canada on Monday and phases with some energy from the current storm which by then is forecast to be over the Great Lakes. This will keep the cool unsettled around for Monday with another chance of showers and storms throughout the day.
A last wave is forecast for late Monday night or early Tuesday, with showers ending early in the day before drier air overspreads the area in still cool, though warmer, temperatures.
A transitory ridge is advertised to be over the central Rockies by both the American GFS and European ECMWF for Wednesday and Thursday, bringing much warmer temperatures and sunny skies to the region. There is very considerable model disagreement for the end of the week as another storm approaches the Pacific Northwest coast. The European ECMWF phases this with cool western Canadian air and digs the storm toward the Great Basin while the American GFS keeps the storm moving north of the central Rockies. The end result is opposite forecasts for Memorial Day weekend, with the ECMWF forecasting a trough over our area while the MRF forecasts a ridge.