Friday, May 5, 2017
The beautiful weather in the Steamboat Springs today will hang around for most of tomorrow before the current ridge of high pressure is nudged to our east by an approaching Pacific wave. This wave will split as it approaches the West Coast, with much of the energy diving south along the California Coast and forming a closed low pressure system cut off from the main jet stream.
Moisture and limited energy will eject over our area starting later tomorrow, bringing breezy southwest winds and afternoon clouds. The dry lower levels of the atmosphere will allow rain that falls to evaporate before reaching the ground (virga), bringing gusty afternoon winds in places.
By Sunday, the now well developed cutoff low will assume a relatively long-lived position along the California - Arizona - New Mexico border. As the lower atmosphere moistens, and more moisture and energy eject from the spinning low to our southwest, thunderstorm chances and coverage will increase for Sunday.
These cutoff lows are notoriously difficult to predict since there is no strong upstream forcing to move the storm along. The end result is that timing and position of precipitation is nearly impossible to get right this far out, and a slight southern shift in the storm southward would greatly diminish our precipitation chances while a shift further north would increase the chances.
That being said, current forecasts have the chance of afternoon storms for both Monday and Tuesday before the cutoff low lumbers eastward through most of the work week. Models have the storm more or less over Colorado around midweek, bringing cooler and much wetter weather to Colorado for Wednesday and some or most of Thursday.
A very complicated pattern then ensues, with interactions between additional Pacific energy approaching the coast, the cutoff low and even energy swinging back westward from an East Coast storm that developed from our storm this past Monday and Tuesday. While earlier in the week it looked like summer-like weather would return after the cutoff low moved east of us, more unsettled weather now looks more likely heading into next weekend.
Monday, May 1, 2017
Winter looks to be finally done with us by midweek, but not before another disturbance in cool northwest flow moves over the Steamboat Springs area on Tuesday. Showers will start in the morning and continue through the day, and though we may see the last snowflakes of the season in the Yampa Valley near the beginning of the storm and again near the end of the storm Tuesday evening, accumulating snows of 2-5” will be confined to elevations above 8000′.
If skies clear by Wednesday morning, temperatures will start out quite chilly with some moderate warming during the day that will bring temperatures towards average.
More pronounced warming will increase temperatures to above average on Thursday and even warmer summer-like temperatures are expected to last through the weekend as a deep and strong closed low that is cut off from the Pacific jet stream forms over southern California late in the weekend
It’s meteorologically remarkable that we flip from a long-lasting winter-like pattern to a summer-like pattern in a few short days, but the southwest flow ahead of the eventual southern California cutoff low will bring an increase in atmospheric moisture that will begin our thunderstorm season. These are expected as soon as Saturday afternoon, with coverage, intensity and duration increasing on Sunday and Monday as waves of energy eject out of the loitering cutoff low to our southwest.
It looks like we go from cold and wet to warm and wet as that cutoff low will continue to influence our weather during next week. There is model disagreement as to when that cutoff low moves east, but models have the storm moving near or over Colorado sometime during next week.
Thursday, April 27, 2017
A broad upper level trough extending across almost the entire continental U.S. has brought a series of strong spring storms across the Steamboat Springs area this week. The last wave in this series is currently traveling southeastward through the Great Basin and will form a strong closed low around the Four Corners region by Friday night.
The track of the storm will carry most of the weather to our south on Friday and east along the Front Range by later Friday and Saturday, but cold, moist and unstable northerly to northwesterly flow will keep snow showers going on Friday. These will be capable of producing localized moderate to heavy precipitation, especially in the afternoon.
Showers will diminish through Saturday, ending by sunset, in still cool temperatures. There is some dry air lurking to our north, and if it makes it over the Steamboat Springs area Saturday night, I would expect a quite cold Sunday morning. Temperatures will warm on Sunday, though they will still stay below average.
As the storm continues moving to our east across the central U.S. through the remainder of the weekend and early next week, a couple of waves in northwest flow will keep our weather unsettled and likely bring showers from Sunday night through Monday and again Tuesday night through Wednesday.
For those weary of winter, strong warming and drying is advertised for Thursday and Friday making those days feel relatively summer-like. Lots of uncertainty for next weekend, though, as another Pacific storm moves the ridge of nice weather eastward. There is disagreement among the models as to whether the Pacific storm makes landfall as a consolidated system as indicated by the American GFS, bringing another period of unsettled weather, or as a split system as per the European ECMWF, preserving the nice weather into the weekend.
Monday, April 24, 2017
A persistent trough of low pressure will remain over the western U.S. this week, continuing the unsettled spring conditions over the Steamboat Springs area. There will be plenty in the weather grab-bag this week including sun, clouds, rain, snow and possibly thunder.
Northwest flow associated with the trough will drive at least three disturbances through the west this week, with the first moving over our area tonight. Showers will be most numerous this evening, with snow at the higher elevations lowering to the valley bottom overnight. Normally, cooling northwest flow is our ideal snow-producer, but moisture wanes after midnight limiting the on-mountain accumulations to around 2-5” by the morning.
The second wave is forecast to move southwest of our area through the Four Corners region tomorrow and is responsible for diverting the moisture away from northern Colorado tonight. The end result is we will be between the initial wave to our north and the second wave to our south, leaving a cool Tuesday with a mix of sun and clouds and possibly some showers.
More pronounced drying will appear for Wednesday as the pair of waves moves to our east, providing for more sun especially early in the day before the threat of afternoon showers once again appears.
The third and coldest wave in this series of storms noses into our area Wednesday night in the still prevalent northwest flow. Another round of accumulating snows is expected for the mountain in the range of 2-5”, with some light accumulations on the grassy surfaces of the valley by Thursday morning.
Additional energy feeding into the storm will keep snow showers going on Thursday before the storm again splits by Thursday night, with energy centers over southwestern Nebraska and the Four Corners by Friday morning. The complicated nature of the storm combined with it being several days away makes the details of the forecast uncertain, but right now the storm system is not forecast to be east of our area till the second half of the weekend. This keeps the cool and unsettled weather around through Saturday with snow the likely precipitation type in the valley for both Friday and Saturday.
While we will see some warming and drying behind the storms by Sunday as they are forecast to be east of our area by then, some moisture in northwest flow quickly returns by later Sunday and will keep the possibility of light rain showers around for the beginning of the next work week.
Thursday, April 20, 2017
A cold Gulf of Alaska storm is currently on our doorstep, and some showers have popped up today in advance of the main storm. While snow levels are currently near 9500′, temperatures will drop this evening and bring snow to the Yampa Valley floor overnight. I would expect to see accumulations on the grassy surfaces by the morning of an inch or two, with a more substantial 4-8” at the higher elevations.
Cool and moist northwest flow will follow for Friday and Saturday. Showers, most likely snow even at the valley bottom, will be heaviest through Friday night, with an additional inch or two expected at the higher elevations.
Decreasing moisture on Saturday will limit the showers, but seasonably cool and still unstable northwest flow will make them most likely in the afternoon.
Sunday should be a spectacular day as temperatures warm under a transient ridge bringing mostly sunny skies.
However, a strong and progressive Pacific jet stream containing several embedded waves will move that ridge of nice weather eastward, with the first weakening wave bringing a chance of light showers by Monday afternoon.
Behind that, a stronger wave moves over the Steamboat Springs area on Tuesday, bringing heavier precipitation and the chance of snow down to the valley floor again.
It does not appear there will be much of a break in the weather as the strongest wave in this series moves across the central Rockies on Wednesday. Additional energy will keep the cool and wet weather around for the rest of the work week, with impressive precipitation accumulations likely across all of Colorado by week’s end.
The timing and details of these waves in the fast Pacific jet stream are notoriously difficult to predict, and I expect changes to the forecast for my next update on Sunday or Monday.