wxgeek's weather-Weather Outlook April 21-30-Update 4/26

Update Sat Apr 26

Upper low currently centered in central AZ, and cold front now extends from northern UT south through eastern UT into eastern AZ. Precip extends along and ahead of the front with embedded thunderstorms. Precip currently extends into western CO east to about the Divide. Models in overall good agreement on progression of this system. Basically a good precip event along and west of the Divide as well as the far northeast plains. For the foothills and Urban Corridor a relatively light precip event. Cold front expected to move into the foothills tonight between 9 pm and midnight. Precip will intensify west of the Divide through tonight, with some precip along the cold front as it moves east. Precip is expected overnight in the foothills and Urban Corridor, then will remain mostly east of I-25 Sunday morning as well as west of the Front Range Crest. Strong westerly winds will be across much of CO from this afternoon through Tuesday. Snow level currently around 10,000 ft west of the Divide, but is expected to lower to near 7000 ft tonight into Sunday morning, then remain 7000-8000 ft during the day on Sunday. Winter Storm Warning for most of CO west of the Front Range Crest. For snow amounts, still looking like 6-12 inches for the mountains, with 1-3 inches for the foothills above 7000 ft. With very warm ground temps, not expecting much accumulation on roads, mostly on grassy surfaces. I do not think roads will be an issue in the foothills, High Country is a different story. By Sunday evening, most precip will have exited state except across far northeast plains and the mountains where showers will persist. very strong west to northwest winds expected to develop Sunday afternoon into Tuesday evening, with speeds of 20-45 mph, and some stronger gusts. Monday and Tuesday will be cool and blustry, with some showers mostly along and west of the Divide, with a slight chance for showers in the foothills and Urban Corridor. Snow level will remain in the 6000-7000 ft range daytime hours, and 5000-6000 ft overnight. Temps will be well below seasonal norms through Thursday as upper level low meanders in the Great Plains and Midwest most of next week.

Conditions finally clear and temps begin to warm Friday, with dry conditions and temps climbing back above seasonal norms through next weekend. Next chance for precip would be towards the middle to end of the following week.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Update Fri Apr 25

Fairly nice Spring day across CO today, temps above seasonal norms and some breezy winds. Next system is providing some challenges for details of the weekend forecast. Models are generally in good agreement on the track of the upper level trough/low, but precip differences are fairly large. It all depends where the surface low develops and whether the foothills see any upslope flow, or whether it remains westerly. NAM is the most abundant for precip in the foothills, while the GFS has less, and WRF has very little. Areas of CO will likely see some decent precip with this system, the challenge is pinpointing these exact locations. Mountains are a good bet as all models forecast robust precip along and west of the Divide. Far northeast plains also likely to see between 0.5 and 1.0 inches of precip, mostly rain but some snow. Areas in-between are more difficult. Using a blend of the NAM and GFS, forecast looks something like this:

Precip moves into western CO during the day on Saturday. Snow level around 9000-10,000 ft through Saturday afternoon. Cold front moves into eastern CO Saturday afternoon, and precip will fill in behind front in the foothills and Urban Corridor by Saturday evening with snow level lowering to around 8000 ft. Most likely precip for the foothills and Urban Corridor will occur Saturday night with snow level lowering to 6500-7500 ft by Sunday morning. Despite the upper level trough moving from the 4 Corners to Southeast CO, surface low remains over northeast CO through Sunday afternoon. Precip will move east into the eastern plains during the day on Sunday, with showers lingering in the mountains, but foothills should dry out from late Sunday morning into Sunday night. Snow level remains 7000-8000 ft during the day on Sunday. Strong westerly winds will also be likely from Saturday night through Monday as strong surface pressure gradient develops across CO. Upper level low moves into western KS on Sunday, then western NE Sunday night into Monday, while surface low remains just north and a little east of upper low. Showers likely to persist Sunday night in the mountains. For snow amounts, mountains above 8000 ft looking at 6-12 inches of snow. For the foothills, currently thinking 2-5 inches of snow above 8000 ft, although some models would suggest amounts of 1/2 to 2 inches while others suggest up to 6-8 inches. Without significant upslope flow, the lower amounts seem more reasonable. Really all depends on where the rurface low develops. If it remains farther north, lower snow amounts, while farther south higher amounts.

Upper level low is expected to meander from the Central Plains into the upper Mississippi Valley from Monday through Thursday. This keeps a cool northwest flow over CO through this period, so temps expected to remain below seaosnal norms Monday through Thursday, with a chance for afternoon showers each day, primarily over the mountains, foothills and Palmer Divide, but some could move onto the plains as well. Snow level remains in the 6000-7000 ft range during this period.

Dry and warmer conditions expected Friday through the middle of the following week. Next precip chances would be late the following week.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Update Thu Apr 24

Very nice day across the state today with temps slightly above seasonal norms and mostly sunny skies. Friday should be another very pleasant day with warmer temps, but some breezy conditions developing in the afternoon.

For the weekend, attention turns to deep upper level trough passing through the west coast. Models in decent agreement today on track and timing of this system, but because of the proximity of this system in CO, a few hundred miles of difference in the position could mean the difference between very little precip versus a lot of precip. Current models bring the upper trough to near Las Vegas by Saturday morning, near the 4 Corners region Saturday evening, and then somewhere from southeast to northeast CO Sunday morning as a closed upper circulation. If the system remains farther south, much better chance for upslope flow and increased precip across eastern CO. If the system tracks farther north, western CO still gets plenty of precip, but eastern CO would only get light amounts. Until this system makes it onshore, it is tough to determine which model has the best track. Given the time of year, I am preferring the southern track and will use the NAM model for the following forecast. Know that the forecast could change significantly in the next day or two.

Precip expected to move into western CO Saturday morning mostly west of the Divide, with snow level 9000-10,000 ft. Precip will spread east to the foothills by Saturday late afternoon/evening with snow level remaining 9000-10,000 ft. Some isolated thunderstorms will be possible Saturday afternoon and evening from the foothills east as cold front moves into this area. Precip could become heavy at times Saturday night from the mountains to the Urban Corridor. Snow level expected to lower to 7000-8000 ft overnight, so areas above 8000 ft could see some significant accumulation. Precip accumulations in the 0.25 to 0.75 inch range possible, which would translate to 3-8 inches of snow, although with such warm ground temps, much of the initial snow likely to melt, especially on pavement. During the day on Sunday, precip moves into eastern plains, continues in the mountains, and becomes showery in the foothills with snow level 8000-9000 ft. As surface low wraps up in western NE, some strong westerly winds likely across CO, especially eastern plains. Most precip moves out of CO Sunday night with only mountains flurries remaining, but strong westerly winds expected to persist. Models then keep the upper low in the Central Plains and Mid Mississippi Valley through next Wednesday. This keeps temps below average across CO, and will keep a chance for showers mostly in the mountains, but also across the foothills and plains into Wednesday evening with snow level 7000-8000 ft. Strong westerly winds also likely through this period.

Upper low finally moves farther east and builds upper ridge over CO by next Thursday, so temps come back to seasonal norms. Conditions warm and remain dry through next Saturday. Next upper level trough expected to move into CO by late next Sunday into early the following week, so precip comes back into the forecast.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Update Tue Apr 22

Warm and breezy day across CO. Temps already into the 80's on the plains with upper 70'salong the Front Range. Showers and thunderstorms developing and will move eastward through the afternoon and evening hours. Upper level trough currently in the Great Basin and will move into the northern Rockies Wednesday. Southerly winds will increase across CO ahead of this system into tonight and early Wednesday, then shift to westerly as cold front moves through CO Wednesday morning. Westerly winds expected to increase Wednesday afternoon into Wednesday night. Not much precip expected for CO with this system. Some showers across the northern mountains Wednesday morning, then isolated showers across the northeast plains Wednesday afternoon and evening. Snow level 7000-8000 ft west of the Divide Wednesday, 9000-10,000 ft east of the Divide. Fire weather concerns for southeast CO today through Wednesday.

Conditions clear and winds die down on Thursday with temps closer to seasonal norms. Warm and dry conditions expected Friday with temps back well above seasonal norms.

For the next system, GFS has come into agreement with the ECMWF model as expected, which will bring a vigorous upper level trough into CO on Saturday, but will keep the surface Low over northeast CO, thus limiting precip potential for eastern CO. The open trough also moves through faster, so precip will be out of the picture by Sunday evening. Precip will move into western CO Saturday morning moving east to the Front Range Crest by Saturday afternoon. Snow level expected to be 9000-10,000 ft Saturday, lowering to around 8000-9000 ft Sunday. Precip lingers west of the Divide Sunday into Sunday evening, but little if any precip expected to make it east into the foothills and plains. Best chance would be Saturday afternoon/evening with front, but any amounts would be light. Mostly strong westerly winds with cooler temps from Saturday afternoon into Sunday evening for the foothills. Models may still tweak the forecast some, and if upper low develops farther south, precip forecast could change significantly, but current forecast keep eastern CO pretty dry this weekend. Beyond that, models keep CO mostly dry and warm through next week into next weekend with temps well above seasonal norms by the end of next week and next weekend.

It certainly appears that our snow season is mostly over. Some snow will likely be possible in May, but at this time does not look like much will fall as most precip appears to be of liquid variety from here on. If this pattern holds, this will be our third lowest snowfall on record since 1993, with only the meager 2001-2002 and 2005-2006 seasons being lower. I will hope that the building El Nino in the Pacific takes hold and provides for a much bigger snowfall next season. In the mean time, hope the rain can continue until Monsoon season, as May and June have the highest fire potential of the year.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Mon Apr 21

Typical April day in CO, some sun, some clouds, some showers. Showers most prevalent south of I-70 today and west of I-25, although some have moved through the southern Metro area and Palmer Divide. Snow level around 12,000 ft today. Temps will increase Tuesday as upper ridge pumps up ahead of upper trough off the west coast. Temps expected to be 10-20 degrees above seasonal norms Tuesday. Showers and isolated thunderstorms also expected to develop in the afternoon and persist into evening hours, beginning in the mountains and spreading east into the foothills and plains. Precip amounts generally expected to remain below 0.10 inches, but could see 0.25 or more in heavier isolated showers/thunderstorms. Snow level Tuesday expected to remain above 12,000 ft, but small hail will be possible in thunderstorms. Gusty southerly winds expected to develop Tuesday afternoon and persist into Tuesday night with speeds of 20-45 mph possible. Increased fire danger Tuesday afternoon across southeast CO.

On Wednesday, upper trough will move into the northern Rockies and drag a cold front across CO during the day. Some showers will be possible along and behind cold front, mostly north of I-70 and west of the Front Range Crest, but some showers will be possible into the foothills and northeast plains by Wednesday afternoon and evening. Snow level behind front will lower to 7000-8000 ft Wednesday evening. Strong westerly winds expected behind cold front with speeds of 25-50 mph from Wednesday afternoon into Wednesday night, increasing fire danger again over southeast CO. Winds should calm down after midnight.

By Thursday, temps back near seasonal norms under mostly sunny skies statewide. Dry conditions should persist into Friday with temps even warmer, and well above seasonal norms.

By Saturday, some big changes to our mild Spring weather in store. Saturday should start out fairly nice, but a potent upper level trough is expected to make it's way into CO by Saturday afternoon. Precip is expected to develop over western CO Saturday afternoon with snow level 9500 - 10,500. Precip is expected to move into eastern CO Saturday night into Sunday as well, with snow level lowering to 8000-9000 ft by Sunday afternoon. Models still differ in the handling of this system. GFS develops a closed upper low and tracks it across southern CO into Monday morning, while the ECMWF and UK models bring an open upper trough through CO by Sunday evening. There is precip with each system, but there would be much more with the GFS solution, and lower snow levels. GFS would continue precip into Tuesday morning, while European models clear things out by Monday morning. Not sure which way things will go, typically the GFS aligns with the European models eventually, but I could see things going the GFS way this time of year, so will have to wait and see how they evolve this week. For sure, temps will be much cooler, below seasonal averages Sunday and Monday, and precip will be likely. Amounts will depend on the track and intensity of the upper level system. If the GFS solution verifies, foothill areas above 8000-9000 ft could see significant snow from this system, and lower elevations could see well over 1 inch of rain.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

Bump for 4/22 update

Bump for 4/24 update

Bump for 4/25 update

Bump for 4/26 update