Drying trend interrupted midweek and still followed by cool front
Monday, August 8, 2016
A storm currently located in in Washington state will first move east through the Idaho panhandle tomorrow and then northeast to the north of Montana by Wednesday. Energy ejecting from this storm earlier today gave us a couple of rounds of much needed early-morning thunderstorms today.
Additional Pacific energy will travel southwards along the West Coast and keep a trough of low pressure extending from the eventual north-of-Montana low back towards northern California. Ahead of this trough, the drying southwest flow evident this afternoon will continue Tuesday, though there is still a threat of late afternoon storms as lingering moisture is heated by the sun.
The dry Wednesday promised in last Friday’s forecast is in jeopardy as moisture from Tropical Storm Javier, currently located near southern Baja, is drawn northeastward ahead of the California trough. It again looks like the best moisture will remain south of northern Colorado, but there may be enough in proximity to Steamboat Springs to allow for a round of afternoon and evening storms in more humid conditions.
This moisture plume will be quickly shunted to our east as the California trough moves inland and then across the Great Basin on Thursday. Pieces of energy ejecting from this Great Basin trough will likely induce more afternoon storms for Thursday before a cool front moves through the area late Thursday night or early Friday morning.
There is some Pacific moisture within this trough, the first of this late-summer season, and there may be enough upward motion to induce some Friday storms in the relatively cool and unstable northwest flow behind the front.
Though there is mid and upper-level drying behind this trough, trailing energy in northwest flow looks to move over the area on Saturday and may spark another round of weaker afternoon storms. Temperatures should return to normal to above normal by Sunday and heading into the next work week as a flat western ridge builds behind the departing system.
Wet start to weekend followed by modest drying
Friday, August 5, 2016
A Pacific Northwest storm and associated trough of low pressure extending southward along the West Coast continues to draw monsoonal moisture over Colorado and southern Utah in the southwest flow ahead of the storm. While Steamboat Springs is on the northern edge of the moisture plume and heavier rain, ill-defined waves of energy either ejecting from the West Coast storm or embedded in the southwest flow will keep good chances of wetting rains around through Saturday.
A wave of energy traveling along the southern end of the West Coast trough will nudge the entire storm eastward around Saturday night, shifting the highest moisture to the east as well. Though a significant drying trend starts then, a weak ejecting wave looks to travel close enough to our area on Sunday to continue the threat of afternoon storms, possibly strong, that may continue into the evening.
Additional Pacific energy keeps parts of the storm to our west, with continued southwest flow keeping the driest air to our west through at least Tuesday. The remaining moisture will keep the threat of afternoon storms around for Monday and Tuesday under noticeably drier conditions.
Much drier air looks to finally intrude by Wednesday as what remains of the West Coast trough moves bodily inland. Though the storm will stay mostly to our north, it will be close enough to create dry and breezy weather for Wednesday and part of Thursday. The southern part of the storm is forecast to drag a cool front over our area by later Thursday or early Friday, and may be the focus for thunderstorms for the end of the work week, especially Friday.
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.
