wxgeek's weather-Storm Forecast Wed-Sat Update 11/23

Update Sat Nov 23

Upper level low continues to spin over southeast CA this morning. For CO, mostly cloudy conditions with snow across southern portions of the state. Farther north in deformation zone, only very light precip past 24 hours. Wold Creek picked up an additional 13 inches past 24 hours, while central mountains picked up 1-6 inches. Not much snow north of I-70. Upper low is forecast to slowly moves east into AZ by Sunday, then into west TX on Monday. Low is far enough south that only southern portions of CO will get significant precip from this system. Another surge of moisture will push north tonight, so areas up to I-70 could see another light dusting to an inch, while areas south of US 50 will see more significant snowfall. Another 6-12 inches possible across the southwest and south central mountains. Mostly dry conditions north of US 50 on Sunday, although a few light flurries still possible in the foothills, and central mountains could pick up a few more inches on Sunday south of I-70. More clearing expected on Monday with a return to mostly sunny skies and any snow limited to far southern CO. Rather funny I saw the sun the entire time in Seattle this week, and haven't seen the sun here since returning.

Portions of AZ, NM and southern UT receiving substantial precipitation from this system. Mountain areas have received 1-2 feet of snow, while Phoenix received 1.6 inches of rain the past 24 hours and over 2.25 inches past 48 hours which has caused some flash flooding.

Latest models continue to downplay system for Thanksgiving, so currently expect mostly dry conditions for all of Thanksgiving week into the weekend across CO. Maybe a few light flurries Friday and Saturday over the High Mountains west of the Divide, and temps should be close to or slightly above seasonal norms into next weekend. Latest long range models continue the dry pattern into early December.

_________________
"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 Nov 22

Back from a cool and clear Seattle, rare and beautiful. Snow amounts across eastern CO have generally ranged from 2-5 inches in the foothills and Urban Corridor, with some areas receiving up to 6-8 inches north of I-70. Central and Northern mountains have received 3-9 inches, while southwest mountains have received up to 23 inches at Wolf Creek.

Upper level low currently spinning off the southern CA coast this morning, and the low is expected to slowly move east over the weekend into AZ on Saturday, and along the NM/CO border Sunday and into the TX/OK panhandle region Monday. This system will produce large precip amounts across the Desert Southwest, southern CA and NV, as well as southern UT and CO today through Sunday. Heavy snow will be likely across northern AZ and NM as well as southwest CO and southern UT. For eastern CO, snow will move farther north this afternoon into Saturday afternoon and evening, but I expect any additional accumulations for foothills and Urban Corridor to be light, generally less than 2 inches with many areas just seeing a dusting. The farther south you are, the better chances you have to see more snow. Southwest mountains and areas south of US 50 could see an additional 10-20 inches today into Sunday. By Sunday, most snow should remain across southern and central mountains, with only partly cloudy conditions for eastern CO. Temps likely to remain below seasonal norms through Sunday across CO.

For next week, mostly dry with temps near seasonal norms Monday through Wednesday statewide. By Thursday, next system will begin to affect CO bringing snow to western CO By Thursday afternoon with snow level 5000-6000 ft. Snow will spread east By Thursday night into eastern CO with snow level down to plains level. Periods of snow to persist Friday statewide into Friday night, clearing by Saturday morning with dry conditions expected Saturday and Sunday, except for some mountain flurries possible by Sunday afternoon and evening. Snow amounts look fairly light for this next system. Extended range models have been vacillating between snowy and cold to dry and mild for early December, so will have to wait and see how that transpires.

_________________
"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 Wed Nov 20

Some interesting models trends this morning. Briefly, before I have to depart for Seattle, models have delayed the initial onset of snow for the foothills and Front Range until after midnight tonight, but have moved the upper low that was forecast to be off the Baja coast into southeast CA and western AZ. Latest models runs bring precip into southwest CO this afternoon with snow level 7500-8500 ft, into eastern CO tonight after midnight with snow down to plains level, but keep snow going across southwest CO through Saturday, with some snow south of I-70 into Friday afternoon and Saturday morning. This will be a significant storm for southwest CO, and a decent snow for the remainder of the state. Least amount of snow across the far eastern plains. Forecast goes like this....

Snow moves into southwest CO this afternoon, and cold front moves south into eastern CO after midnight tonight. By Thursday morning, moderate to heavy snow across most of CO. Snow persists most of the day Thursday statewide, with snow beginning to diminish across northeast CO by Thursday evening, but continues west of I-25 and south of I-70 into Friday night, with some snow lingering into Saturday morning. Nearly all areas should clear by Saturday night as upper low moves east into OK/TX panhandle regions. Heaviest snow for foothills and Urban Corridor will be from midnight tonight through Noon Thursday. Could see periods of 1-2 inches per hour during this time. Lighter snow after that, but there could be periods of moderate snow Thursday night into Friday morning again.

Updated snow amounts:

Southwest mountains: 12-24 inches
Central and Northern Mountains: 6-14 inches
Foothills and Palmer Divide: 3-8 inches
Banana Belt: 2-6 inches
Urban Corridor: 2-5 inches
eastern plains: 1-4 inches

Currently NWS has Winter Storm Watch and Winter Weather Advisories out for the southwest mountains.

Driving all day Thursday into Friday will likely have snow and ice packed roads across most of the state, so allow some extra time for traveling and use your winter driving skills.

Conditions should clear by Saturday afternoon and currently Sunday through Wednesday next week look dry. Next system now looks weaker for late next week with precip chances diminished on Saturday and Sunday. Thanksgiving day now looks dry and mild statewide.

_________________
"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 Nov 19

Fair amount of mid and high clouds drifting across CO today under westerly flow aloft. Some snow showers have developed across the northern and central mountains, and these will persist into this evening with generally 1-3 inches of accumulation on primarily west facing slopes. Temps east of the Divide will remain well above seasonal norms today.

Wednesday will start off nicely across most of the state, but change is looming. Upper level trough will move down from the Pacific Northwest on Wednesday. This trough will split, but both branches will have some affect on our weather Wednesday through Friday. Precip will move into southwest CO Wednesday afternoon with snow level near 8000 ft and spread to most of western CO west of the Divide by Wednesday evening with snow level lowering to near 7000 ft. A cold front associated with northern branch of upper trough will begin to move south across CO Wednesday evening/night. As this front begins to interact with moisture from southern upper trough branch, precip will move into eastern CO Wednesday evening after 6 pm. Upslope flow will develop behind cold front and temps will drop dramatically. Snow level will quickly lower to plains level after about midnight Wednesday night, and snow will intensify overnight becoming moderate to heavy at times. Snow will persist across pretty much the entire state during the day on Thursday into Thursday night, although intensity will be mostly light snow on Thursday. Temps will fall during the day on Thursday as colder air moves south. Snow begins to diminish overnight Thursday and ends by Friday morning, except some lingering snow across southern portions of CO into Friday afternoon. Temps remain cool on Friday and well below seasonal norms. Skies should begin to clear by Friday afternoon.

For snow amounts, always the hardest part, but models are currently in pretty good agreement, so here is my forecast from Today through Friday:

Southwest Mountains: 6-14 inches
Central and Northern Mountains: 5-12 inches
Foothills and Palmer Divide: 3-8 inches
Urban Corridor and plains: 2-5 inches

Currently no warnings, watches or advisories out from the NWS, but I expect that to change either later today or Wednesday. Looks like Winter Weather Advisory criteria for the foothills and Urban Corridor, and potential for Winter Storm Warning criteria for some mountain areas.

Heaviest snow for the foothills and Urban Corridor will be from 8 pm Wednesday through 6 am Thursday. Wednesday evening commute should be fine. Thursday morning commute likely to be slow and slick with snow and ice packed roads all the way onto the Urban Corridor. With warm temps early this week, initial snow likely to melt, especially at lower elevations, and then will ice over as snow falls Wednesday night into Thursday morning, so roads may be extremely slippery. Roads likely to have snow on them Thursday evening, but crews will have all day to get some work done on major routes so should be somewhat better than the morning commute. Roads could still be slick for the Friday morning commute, but should be much better Friday evening. Low visibility also likely in the foothills due to snow and upslope conditions.

Weekend currently looks mostly nice. Southern upper trough branch will form a cutoff low off the northern Baja coast, then eject northeastward late this weekend. Some precip is possible across southern CO, mostly south of US 50, Sunday afternoon into Monday with snow level 6000-7000 ft. Slight chance some showers could drift as far north as the central mountains and southern foothills on Monday. Tuesday through Thursday of next week currently look mostly dry statewide with temps near seasonal norms. Snow is possible statewide from next Thursday night into Saturday as upper trough moves down from the Pacific Northwest. Long range models bring snow back into CO early the following week as well.

_________________
"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 Nov 18

Nice day across the state today with just a few high clouds drifting by. Temps will be 5-10 degrees above seasonal norms today and Tuesday. A few light snow showers possible Tuesday over the northern and central mountains, but little if any accumulation expected.

Big change in the weather will occur late on Wednesday. Wednesday starts off mild and mostly dry statewide, then an upper trough will approach from the northwest late in the day. The upper trough is forecast to split, with the southern branch becoming a cut-off upper low off the northern Baja coast late this week. A cold front associated with the northern branch will move from north to south across CO Wednesday night. Upslope flow will develop over eastern CO behind the front, and snow will move over the entire state late Wednesday night into Thursday morning. Snow level will be 5500-6500 ft Wednesday night, lowering to plains level on Thursday, except 6000-7000 ft south of US 50. Snow is expected to persist during the day on Thursday into Thursday night, diminishing by Friday morning. Snow could cause some slow and slick commutes Thursday and Friday morning. Cool temps will persist on Friday with temps well below seasonal norms. For snow amounts, tough to say at this point. Models are predicting decent amounts (4-10 inches), but there is limited support aloft from this system, so snow will be generated primarily from upslope flow that is not all that deep. It looks to me to be a case of a long duration event with limited accumulation. My best guess right now would be 4-8 inches for the mountains west of the Divide, 1-4 inches for the foothills and Palmer Divide, and 1-2 inches for the Urban Corridor and plains. Will have to watch future model runs and see if things change one way or the other.

Friday looks cool and mostly dry statewide. The weekend looks to have temps back near or slightly above seasonal norms under mostly sunny skies. The cutoff upper low is forecast to move northeast across AZ and NM early next week, which would bring some precip chances to CO Sunday night into Monday night, but mostly south of US 50 with snow level 8000-9000 ft.

Looking ahead for the Thanksgiving Holiday, models currently predicting chances for precip from next Wednesday into next weekend with temps below seasonal norms. Doesn't look like anything significant, but many areas of CO could see snow on Thanksgiving day and into the weekend.

Latest seasonal outlook from CPC calls for above average temps for the Nov-Jan period across CO, and near normal precipitation over CO. Above average precip is forecast over the northern Rockies, and below average precip across the southern Rockies and Texas.

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

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

Bump for 11/19 update

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Bump for Sat Nov 23 Update