Former hurricane Blanca influences our weather starting tomorrow
Tuesday, June 9, 2015
Former hurricane Blanca, currently in the Gulf of California, will travel northeastward across the Great Basin today and tonight as a Pacific storm crosses the West Coast tomorrow morning. It appears that the former hurricane will first move over our area tomorrow afternoon and evening before being quickly followed by what will end up being a slow-moving Pacific storm which may affect our weather through mid-weekend.
First, high clouds will invade our area tonight, and thicken and lower tomorrow before showers or a more persistent light to moderate rain arrives for the afternoon. Rainfall intensity will decrease overnight as I expect our heaviest precipitation to occur behind this initial event as a significant amount of moisture is left behind for the Pacific storm.
As the Pacific storm begins to move eastward towards our area on Thursday, some cool air from the Canadian plains mixes with the system, leading to a slower and stronger storm. There is some uncertainty when the cool air reaches our area, but current forecasts have moderate to heavy showers later Thursday and overnight before they diminish by early Friday. An additional surge of cool air is forecast to again increase the intensity and duration of showers by Friday afternoon and overnight.
Saturday looks to be cool with some light showers behind the finally-departing storm. Some dry air is forecast to sneak into parts of northern Colorado on Sunday, and this may lead to the typical afternoon thunderstorms after a sunny morning.
Monday looks to be very similar to Sunday before a much drier regime is advertised to occur over our area around Tuesday. The dry air may be interrupted by the end of next week as some models have a wave traveling to our north, but longer-term models keep this dry air mostly intact through next weekend and into the following week.
Update to yesterday’s forecast
Friday, June 5, 2015
As a storm currently along the West Coast draws moisture from once-hurricane Andres over our area. clouds will thicken during the day and showers will occur later this afternoon and through the evening. There will be a small break early Saturday before a lobe of energy is ejected over our area ahead of the eastward progressing West Coast storm, bringing another round of moderate to heavy rain for Saturday afternoon and extending into the night.
There may be another break early Sunday before the storm to our west lifts toward the northeast and travels across the Great Basin. Though the storm weakens considerably, there is still enough moisture and upward motion to to produce showers during the day.
We will still be under the influence of the weakened storm on Monday, leading to more showers, especially in the afternoon. Tuesday and Wednesday look to be the nicest days of next week, though there will still be the threat of the typical afternoon thunderstorm.
There is a wildcard for the forecast next week in the form of hurricane Blanca, which is forecast to move up the Baja coast early next week. Earlier model runs had the moisture moving over our area, but current runs keep most of the moisture to our south. However, models also forecast a complicated interaction between the former hurricane, another storm entering the West Coast around midweek, and a surge of cool air from the Canadian plains. These three entities may conspire to increase the threat of heavy rain by Thursday afternoon and lasting through Friday. That forecast will no doubt evolve as we get closer to the event.
After that, some models predict a far-western Caribbean storm that may help draw moisture northward and lead to a monsoonal-like surge of moisture over our area for late next weekend or early the following workweek. Furthermore, there will likely be additional Pacific energy crossing the West Coast keeping our June weather active.
More wet weather for Saturday and the end of next week
Thursday, June 4, 2015
The current warm and dry weather will end by tomorrow as a storm along the West Coast draws moisture from once-hurricane Andres over our area. Clouds will thicken during the day and showers will occur tomorrow afternoon and through the evening. There will be a small break early Saturday before a lobe of energy is ejected over our area ahead of the eastward progressing West Coast storm, bringing another round of moderate to heavy rain for Saturday afternoon.
There will be another break Sunday before the storm to our west lifts toward the northeast and travels across the Great Basin. Though the storm weakens considerably, there is still enough moisture and upward motion to to produce showers by Sunday afternoon.
We will still be under the influence of the weakened storm on Monday, leading to more showers, especially in the afternoon. Tuesday and Wednesday look to be the nicest days of next week, though there will still be the threat of the typical afternoon thunderstorm.
There is a wildcard for the forecast next week in the form of hurricane Blanca, which is forecast to move up the Baja coast early next week. Earlier model runs had the moisture moving over our area, but current runs keep most of the moisture to our south. However, models also forecast a complicated interaction between the former hurricane, another storm entering the West Coast around midweek, and a surge of cool air from the Canadian plains. These three entities may conspire to increase the threat of heavy rain by Thursday afternoon and lasting through Friday. That forecast will likely evolve as we get closer to the event.
After that, some models predict a far-western Caribbean storm that may help draw moisture northward and lead to a monsoonal-like surge of moisture over our area for late next weekend or early the following workweek.
Summer weather begins Saturday
Thursday, May 28, 2015
Our long-delayed summer weather begins on Saturday, but not before the wave currently affecting our area leaves more rain today and Friday. Rainfall should end by early Saturday as the wave moves east of our area.
Saturday should start out cool, but temperatures will begin to warm during the day. The cool airmass left behind will likely support storms of minimal strength and it’s possible we may even have a rain-free day for the first time in about 3 weeks, though that hope may be threatened by a very weak wave passing north of our area by late in the day and overnight.
The upper-elevation snowpack will see its first above-freezing low temperatures in three weeks Saturday night, signaling the beginning of its melting and contributing to increasing river flows, especially early next week as it may take a day for that water to make it to the Yampa river.
The warming temperatures will certainly make the weather feel summer-like, and yield typical summer afternoon thunderstorms Sunday through Tuesday.
A wave traveling across the northern third of the US will clip our area and knock temperatures back on Wednesday, as well as the strength of the afternoon storms. There is a possibility, however, that rain will be more persistent late in the day and overnight.
A much stronger storm crashes into the California coast around Thursday, though there is a significant amount of dry air ahead of the storm that will be brought over our area through the end of the workweek as the flow backs to the southwest. The evolution of this wave is complicated as it is not clear how much splitting will occur and how much of the cold air still in the Canadian plains will be drawn into the system, but this may threaten next weekend’s weather.
Generally, for the longer term, there is additional Pacific energy forecast to enter the West Coast as well as a westward expansion of the cool airmass over the Canadian plains. The combination of these is forecast to inhibit the West Coast ridge from building, keeping our weather on the seasonably wet side through at least mid-June.
Rinse and repeat
Thursday, May 21, 2015
The forecast is sounding like a broken record (remember those?!), but the rain looks to continue as four more waves move over our area through mid-next week. For water managers out there that believe the snowpack does not accumulate moisture after May 1, 
note that the Snotel remote measuring site near the top of Buffalo Pass called Tower registered a local low in snow depth on May 8 of 69” with about 28” of liquid water. In twelve days, the snowpack increased about 8”, but remarkably the liquid water content increased by 3.5”! The end result is that the below average water year for Routt county that began on October 1 is now above average over most of the county. The southern part of the county is between 10 and 30% above average, while a small area in the extreme northeast is still lagging at between 10 and 30% below average, with the rest of the county as much as 10% over average!
In the short term, rain starts up again early this afternoon as the morning heating interacts with substantial low-level moisture and produces another round of scattered rain showers. However, unlike the previous 2 nights, rain should increase tonight and become moderate to heavy as the first wave from the southwest ejects over our area this evening.
There is a small amount of drying advertised by some models early in the day tomorrow, but again any heating will act on a very moist airmass to produce another round of afternoon rainstorms.
Some more drying is forecast early Saturday as a strong storm that ejected the Thursday night wave approaches the area, but again we will be susceptible to scattered afternoon rainstorms. As the storm moves over the area early Sunday, some cool air from the Canadian plains related to a wave to our north and east will be mixed into the storm, lowering snow levels to around 9000′ and again leading to a wet day.
Skies will briefly clear by Monday morning before the fourth wave, forecast to be located over the Four Corners region by Monday afternoon, again increases rainfall later in the day and overnight.
The parade of relatively organized storms will be briefly interrupted midweek, but clear mornings should give way to the typical afternoon thunderstorms as the strong May sun interacts with a very moist atmosphere.
Additional Pacific energy enters the West Coast later in the week, though forecasts are uncertain as to the amount of mixing between the southern stream over central California and the northern stream over the Pacific Northwest. Nonetheless, it looks likely the unsettled weather will continue into next weekend, with the pattern likely continuing into at least the first week of June as additional Pacific energy is forecast to crash into the West Coast.
