Wetting rains more likely for the end of the work week
Monday, August 1, 2016
A Pacific Northwest storm will cross the coast Tuesday morning and travel well north of the Steamboat Springs area along the US-Canadian border on Wednesday. Drier air ahead of this storm has spread through northern Colorado in westerly flow and will reduce, but not eliminate the threat of afternoon storms for Tuesday.
As the northern storm swings north of our area on Wednesday, winds will increase ahead of a weak cool front forecast to move through northern Colorado late Wednesday or early Thursday. The storm will be drier than I thought in the last forecast, so the meteorological concern will be wind rather than rain for Wednesday and Wednesday night.
Though Thursday will start cool and dry, a relatively well-defined wave from the southwest will travel across the Four Corners later Thursday and western Colorado by Thursday night into Friday. Moisture will rapidly increase ahead of this wave, increasing the chance of locally heavy rainfall by Thursday afternoon and possibly extending into the night.
By Friday, another Pacific Northwest storm carves out a trough of low pressure off the West Coast, keeping the moist southwest monsoonal flow going for the weekend. A currently ill-defined wave may move over our area on Friday, again increasing the threat of locally heavy rainfall that may last into the evening.
Earlier forecasts had dry air overspreading our area for most of the weekend, but current forecasts have the West Coast trough deeper and more persistent, keeping the still moist, but drying, monsoonal moisture plume over our area through Monday. This will continue the threat of afternoon storms through Monday before the Pacific Northwest storm moves inland, bringing dry air and likely eliminating the chance of afternoon storms for the rest of the next work week.
Moisture returns for Sunday and next week
Friday, July 29, 2016
Cool air currently moving into the Gulf of Alaska will nudge the western ridge eastward, keeping the current hot weather around for most of the weekend. By Sunday, some of this cool air in the Gulf and associated energy will break off and move across the the US - Canadian border, moving the western ridge further eastward and allowing a surge of monsoonal moisture from the southwest to be carried over Colorado starting as soon as Saturday. Initially, storms will be high-based and mostly windy, though wetting rains become more likely by Sunday afternoon as the atmosphere continues to moisten.
The threat of afternoon storms will continue for at least the next week with cooler daytime highs and warmer overnight lows as the moisture and associated clouds reduce solar heating during the day and trap surface heat during the night.
Another lobe of energy crosses the Pacific Northwest coast late Monday and may be strong enough to drag a weak cool front through the Steamboat Springs area on Wednesday as it travels along the US - Canadian border. The stronger winds and decreased atmospheric stability may allow for better storm organization and an increased threat of locally heavy rainfall for Wednesday and lasting into the night.
Though moisture will decrease behind the front early Thursday, the western ridge quickly redevelops over our area as more cool air drops in the Gulf of Alaska. The humid conditions will quickly return by Thursday afternoon and last through the weekend as longer-range models keep the storm off the Pacific Northwest coast with moist southwest flow over Colorado until the following work week.
Mostly dry and warm work week growing hotter by next weekend
Sunday, July 24, 2016
A weak wave off the Pacific Northwest coast will allow a low-amplitude ridge to rebuild over the western states, which will increase temperatures to above normal again for the beginning of the work week. As this wave moves inland around Tuesday, this shallow ridge elongates eastward, allowing a modicum of moisture from the south to move northward over Colorado on the western periphery of the ridge. This will result in a very weak monsoonal pattern, increasing the chance of afternoon storms for Tuesday.
This brief and unimpressive surge of moisture will be replaced with dry air by Wednesday as the wave moves through the northern Rockies. An additional wave taking a similar path will also pass north of our area by the end of the work week. Models have trended this wave further north as it is deflected by the western ridge and it no longer looks to bring any cooling to our area as was the possibility in the last forecast. Instead, more cool air forecast to move into the Gulf of Alaska will allow the western ridge to grow even stronger, bringing hot temperatures well above normal to the Steamboat Springs area by next weekend.
Longer-range models do have relief from the heat after next weekend as more cool air is forecast to move into the Gulf of Alaska and produce an upper level trough off the West Coast that may again allow monsoonal moisture to be drawn northward over Utah and Colorado from western Mexico. The longest-range model I regularly view hints that this wetter pattern may persist through at least the first week of August.
Drier weather ahead
Friday, July 22, 2016
Another Pacific Northwest storm made landfall near Washington state last night, and looks to drag a weak cool front across the Steamboat Springs region tonight as the storm moves through Montana.
Winds will become breezy and veer from the previous southerly direction to the westerly or northwesterly direction by Saturday, effectively ending the influx of monsoonal moisture from the south as the western ridge flattens. Remaining moisture will continue the threat of afternoon storms for the weekend, especially for Saturday, under much less humid conditions and warming temperatures.
A weak wave redevelops near northern California late in the weekend allowing a low-amplitude western ridge to rebuild which will increase temperatures to above normal again. As this wave moves inland around Tuesday, this shallow ridge also moves eastward, allowing some moisture from the south to move northward over Colorado on the western periphery of the ridge. This will result in a very weak monsoonal pattern, increasing the chance of afternoon storms for Tuesday and Wednesday.
This brief surge of moisture will be replaced for Thursday and Friday with dry air as several Pacific Northwest waves phase with a storm moving across the Canadian Plains and bring some cooling to the area in dry and breezy westerly to northwesterly flow. Currently, the last wave timed for Friday will be the strongest and may be strong enough to increase the threat of showers as the cool front moves through.
Drying weekend follows showery week
Monday, July 18, 2016
A large storm currently off the Pacific Northwest coast has forced a ridge to build over the western US, allowing south-southwesterly flow to carry monsoonal moisture from Mexico northwards over Colorado. This moist flow is a day or two faster than my previous forecast, keeping temperatures closer to normal today as clouds periodically inhibit the sunshine.
Very short range models indicate showers redeveloping overnight as old storm boundaries interact and force storms in the moist and unstable airmass.
Additional ill-defined waves from the south will continue to travel over Colorado for the work week, keeping a mix of sun, clouds and showers around with near normal temperatures.
Though models have pieces of energy ejecting from the Pacific Northwest later in the work week, the western ridge will deflect them to our north with minimal impact on the monsoon. However, the storm finally makes landfall late in the work week, and looks to drag a cool front across the Steamboat Springs region late Friday or early Saturday.
Winds will veer from the southerly direction to the westerly or northwesterly direction, effectively ending the influx of moisture from the south as the western ridge flattens. Remaining moisture will continue the threat of afternoon storms for the weekend under much drier conditions and warming temperatures.
