Here comes the North American Monsoon
Thursday, July 11, 2019
The warm, dry and sunny weather we are currently experiencing in Steamboat Springs this Thursday afternoon will give way to increasing moisture starting Friday. Clouds will increase along with increasing precipitation chances that will persist through the weekend and into the next work week.
An expansive ridge of high pressure is currently covering the western two thirds of the country, with Tropical Storm Barry threatening the Louisiana coast on the southeastern side of the ridge and continued storminess in the Gulf of Alaska on the northeastern side of the ridge.
Contributing to the strength of the ridge is the strong summer heating of the elevated Mexican Plateau, and the on-time appearance of the North American Monsoon is due to moisture originally from the Caribbean being pulled first westward and then northward around the ridge of high pressure. While we do not see the intensity and persistence of precipitation associated with the Indian Monsoon (which is much stronger due to the higher and broader Tibetan Plateau), our area will see increased clouds with a greater likelihood of locally moderate to heavy precipitation, due to not only the increased moisture but also the relatively slow storm movement thanks to the light winds under the ridge. Another hallmark of the North American Monsoon is warmer overnight temperatures as the increased moisture acts like an earth-blanket, and possibly slightly cooler afternoon temperatures if the clouds are persistent and thick enough to block some of the sun.
And its not certain we will see any precipitation as these monsoonal surges of moisture produce relatively spotty coverage, but there will be some chance on Friday, with more of a chance on Saturday and better chances on Sunday and Monday.
By Tuesday, the Gulf of Alaska storminess is forecast to move inland well north of our area, but the increased westerly flow will not only flatten the ridge of high pressure over the west, but sever our fetch of moisture from the south. The end result is decreasing precipitation chances for Tuesday and Wednesday, along with some breezy westerly afternoon winds.
Subtle changes in the strength and position of the ridge of high pressure can drastically affect the northward extent of monsoonal moisture and the resultant forecast, but right now moisture may begin to increase again for the end of the work week before a more robust surge of monsoonal moisture may occur around the following weekend or soon thereafter.
Best shower chances this Sunday and Monday
Sunday, July 7, 2019
The sunny skies this Sunday morning in Steamboat Springs have given way to increasing clouds as moisture moves over our area in southwest flow. Showers will be possible later today and again tomorrow before drying occurs on Tuesday. The dry air will stick around through the workweek along with our warmest temperatures of the summer so far, before moisture returns around the weekend.
Currently, we are seeing increased moisture in the southwest flow ahead of a cold storm near Vancouver. There will be a chance of afternoon and evening showers today and again Monday before the Vancouver storm travels across Montana on Tuesday and drags a weak cool front through our area. The air will cool and dry as we see breezy westerly winds, keeping high temperatures on Tuesday comfortably below our average of 81 F.
But as the storm travels eastward across the northern U.S. border through the workweek, a ridge of high pressure will build over the Rocky Mountains starting on Wednesday. Temperatures will be the warmest of the summer so far, with high temperatures around five degrees or so above average and almost no chance of rain through Thursday.
By Friday, additional incoming Pacific energy flattens the ridge of high pressure over the Rockies, and this is important for our area as subtle changes in the position and strength of the ridge influence the fetch of moisture from the south associated with the North American Monsoon. But these subtle differences make for a tough forecast as relatively minor changes in the upper level flow may mean the difference between a wet and dry prediction.
With that said, shower chances are currently advertised to return around Friday. Though a ribbon of dry air is forecast to be just to our north through the following weekend, if that stays to our north as currently forecast by some weather prediction models, then the chance for showers will continue through the weekend and into the following workweek.
Warm and dry until moisture returns near the end of the weekend
Thursday, July 4, 2019
The Steamboat Springs area is currently experiencing a beautiful warm, dry and sunny Independence Day. More of the same is expected through most of the long Fourth of July weekend before precipitation chances increase for later Sunday and Monday. The chances decrease for a couple of days before increasing again toward the end of the workweek and heading into the following weekend.
Counterclockwise flow around a strong and cold storm centered near Vancouver has brought warm and dry southwest flow to our area. While cold air from western Canada and additional incoming Pacific energy will periodically energize the storm over the next few days, a ridge of high pressure building northwestward from the Louisiana coast into Texas and the Rocky Mountains will keep any weather associated with the storm at bay. So the warm and dry days and cool nights will continue through the first half of the weekend.
By later Sunday, clockwise flow around the Texas ridge of high pressure will carry some moisture from the Mexican Plateau northward as the light winds turn to be more from the south. This pattern is representative of the beginnings of the North American Monsoon, and there will be increasing chances for showers from later Sunday through Monday.
Meanwhile, part of the Vancouver storm will move eastward across the northern Rockies early in the workweek and suppresses the Texas ridge of high pressure southward. Drier air will return for Tuesday and Wednesday as the winds turn back to southwesterly or even westerly.
The old Vancouver storm is then forecast to travel east of the northern Rocky Mountains around midweek, allowing the Texas ridge to rebuild to the west and northwest. The strong summer sun will allow the ridge of high pressure to prevail over any storminess to our northwest, and the North American monsoon looks to become better established over mostly New Mexico and Colorado. The forecast moisture over our area will increase precipitation chances for the end of the work week and the following weekend, with a stronger and wetter monsoon signature forecast by some weather forecast models for the following workweek.