wxgeek's weather-Weekend storm forecast-Update 3/8 evening

Update Sat Mar 9 Snowman2::

So timing of the system a bit slower, so taking longer to get things in full gear this morning, but satellite and radar showing good upslope and snow moving down from the north across the Front Range and foothills now. Dry slot, as some models predicted, kept overnight snow from developing in southerly flow ahead of main system, which implies snow totals will be on the lower side of earlier ranges. Heavy snow will be likely between 9 am and 5 pm today, with snowfall rates of 1-2 inches per hour at times, so this system will still be a powerful storm, and as surface low in southeast CO developes, northerly winds of 20-45 mph will increase this afternoon and evening creating whiteout conditions at times, especially east of I-25, but foothills will also have these conditions, making travel difficult. Roads in the urban corridor remain wet, but could become slushy later today wiyth heavy snow. Roads in the foothills will be snow and ice packed for the most part with temps in the mid to upper 20's. Models keep snow going until about 8 pm tonight in the foothills, longer on the plains.

Currently looks like 8-16 inches for foothill areas a good bet, with lower amounts in the banana belt. Urban Corridor amounts of 6-12 inches look good, with 5-10 inches on the plains. Wolf Creek ski area picked up 16 inches the past 24 hours, lower amounts elsewhere in the mountains. Sunday continues to look mostly sunny, breezy and cool. Next week will be dry and mild, with precip chances returning late next weekend or early 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 Mar 8

Updated note from 3:45 pm Friday: Just looked at the 18Z run of the NAM and GFS, and they are more robust with this system. NAM, which had been the dry model, now has up to 2 inches of liquid equivalent over the foothills, which translates to this storm has the potential to dump 20-30 inches of snow across the foothills if the NAM is correct. Amounts will likely be lower, but be prepared for the best/worst case scenario. Heavy snow still looks like it waits until after midnight, very heavy between 3 am and 5 pm Saturday, tapering off and moving east by Saturday night.....

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Update Fri Mar 8

Very colorful map across CO with regard to warnings today. NWS has issued a Winter Storm Warning that covers much of western CO, and now extends to the foothills and Urban Corridor. A Blizzard Warning has been issued for much of the eastern plains. Warnings go into effect beginning at 5 pm today for the foothills, and at 2 am Saturday for the Urban Corridor and plains and extend until 5 pm Saturday for the foothills and 11 pm Saturday for the plains. Models are in generally good agreement on timing and track, although snow amounts vary quite a bit. NWS seems to have gone on the high side for storm totals, and with enough model data to support that, understand their thinking. Some models still favor lower snow amounts. So the bottom line is that it's gonna snow, beginning sometime tonight and through all day Saturday, and it could be a lot of snow. Liquid equivalents on models range from 0.50 inches to 1.25 inches near the foothills, and with spring snow to water ratio is between 10 to 16 inches of snow per inch of water.

System is currently just moving onshore in southern CA, with precip extending into southern CA and NV, AZ, southern UT and western CO. System on satellite loops looks like is has rounded the corner and is beginning to move fairly quickly eastward now. Models have the upper low over the CA/AZ border this evening, then near the 4 Corners Saturday morning, across southeast CO and into western KS by Saturday evening. If this system moved slower, we would be looking at 2-3 foot snow amounts, but we will have to be grateful for what we get. Forecast looking like this now...

Snow will intensify across western CO today, mostly south of I-70. Snow level 7500-8500 ft west of the Divide today. Snow will become heavy west of the Divide tonight with snow level lowering to 6000 ft. For eastern CO, models differ on when snow begins. NAM holds snow off until early Saturday morning, while the GFS, Euro and WRF bring snow to the foothills later this evening, between 8 pm and midnight. Snow amounts overnight vary a lot, with some model guidance giving 4-8 inches overnight, while some in the 1-3 inch range. What is for sure, is that heavy snow will become likely by 5 am Saturday across all of eastern CO north of the Palmer Divide, and persist into Saturday evening. Heaviest snow will be from 5 am until 3 pm, with snowfall rates of 1-2 inches per hour possible during this period. Strong northerly winds will accompany this system as a deep surface low develops in southeast CO, so blowing and drifting of snow likely Saturday afternoon into evening. Winds of 20-45 mph possible, hence the blizzard warning for the plains. Snow level will begin around 8000-9000 ft Friday afternoon/evening, then lower to near 6000 ft by midnight, and plains level by Saturday morning. However, temps will be relatively warm with this system, so snow will be wet and heavy spring snow. Temps near freezing on the plains, and mid to upper 20's in the foothills. Roads below 6000 ft will remain wet to slushy, while above 70000 ft roads may become snow and ice packed. Since there is such a range of snow amounts possible with this system, I will take a probabilistic approach to amounts, so we'll see how this works....

Area: 15% probability / 70% probability / 15% probability
Southwest Mountains: 6-12 inches / 12-24 inches / 24-30 inches
Central and Northern Mountains: 4-8 inches / 8-16 inches / 16-24 inches
Foothills and Palmer Divide: 4-8 inches / 8-16 inches / 16-24 inches
Banana Belt: 3-6 inches / 6-12 inches / 12-18 inches
Urban Corridor and plains: 3-7 inches / 7-14 inches / 14-20 inches



The bottom line is that unless you have an emergency or urgent situation Saturday, a good day to stay off the roads. Travel pretty much anywhere in CO will be difficult to impossible from tonight into Saturday night. Since snow will be wet and heavy, power outages will be possible, although since winds will be fairly strong, accumulations on trees and lines should remain low, but be prepared for some power outages.

Skies will clear Saturday night and be mostly sunny on Sunday, with cool temps. Next week will see temps rise to back above seasonal norms for most of the week under sunny and dry conditions across the state. Next precip chances will be 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 Mar 7

Beautiful day across the state today with temps well above seasonal norms. The weather picture will begin to change Friday. The challenging aspect of this upcoming system is not whether it will snow, but how much snow will various areas receive. This is not a slam dunk forecast, although any forecast in CO rarely is.

Overall models are in decent agreement on the track of the system, but some timing differences are emerging which complicate the forecast. In general, latest model data is suggesting this may not be as big a storm as previously anticipated, despite the NWS issuing a Winter Storm Watch over most of eastern CO. I suspect many of these areas may only see Winter Weather Advisories by tonight or Friday. Winter Storm Warning will likely be issued for the mountains west of the Divide, especially the southwest mountains.

Latest forecast looks something like this. Upper level low currently spinning off the CA coast will continue south to near Pt. Conception Friday morning. Upper low is then forecast to be near the 4 Corners region by Saturday morning and into central KS by Saturday evening. Latest NAM has the upper low over south central CO Saturday morning, so the NAM is becoming even faster with this system. GFS and ECMWF in good agreement so will continue to base forecast more on these models, although the NAM solution makes me even more skeptical of a significant snow event. Snow is expected to move into western CO during the day on Friday, with snow level 7000-8000 ft. Snow looks to move east to between the Divide and Front Range Crest by 6 pm Friday. Some showers and isolated thunderstorms may pop up across eastern CO Friday afternoon and evening, but snow level expected to be 8000-9000 ft Friday across eastern CO. Heavy snow is expected over the mountains west of the Divide Friday night with snow level lowering to valley floors. Across eastern CO, some showers but heavy precip is not expected until Saturday morning after 6 am. Period of heavy snow looks like 6 am to 2 pm Saturday across eastern CO as surface low sets up over southeast CO bringing good upslope flow, with snow continuing over the mountains Saturday as well. Snow level should be down to plains level Saturday, although temps below 6000 ft will hover near freezing, so given very warm temps this week and daytime snow, I expect roads below 6000 ft to remain mostly wet Saturday, perhaps some slush. Roads above 6000-7000 ft likely to have slush and some ice, especially secondary roads. Snow should end by 5 pm to 8 pm Saturday with overnight clearing. Now for snow amounts, the most difficult aspect of the forecast:

Southwest Mountains: 1-2 feet
Central and Northern Mountains: 8-16 inches
Foothills and Palmer Divide: 5-10 inches (higher amounts possible north of I-70, lower amounts in the Banana Belt)
Urban Corridor and plains: 4-8 inches (highest amounts north of I-70)

Obviously these amounts can change if the track of the system changes, or the speed. Given the latest model consistency and trending, I am fairly confident, at least as confident as any sane meteorologist can expect to be, in the above snow totals. I will continue to check latest models and provide another update Friday. Travel on Saturday likely to be difficult, especially heading west across CO. Delays and road closures will be possible. Eastern plains may also have some strong northerly winds during the snow on Saturday, so visibility issues may cause some problems on the eastern plains as well.

Sunday should be a cool start but warming under mostly sunny skies. Next week continues to look dry and mild. Weak system passing north of Co will lower temps slightly mid week, but very warm temps expected late next week. Next chance for precip looks to be late next weekend or early 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 Wed Mar 6

Another warm and dry day across the state today, and even warmer temps expected Thursday. Models in better agreement today on our weekend storm, so confidence is growing. Our weekend system is currently spinning off the OR coast, and has begun to drop south. Models move the upper level low south along the CA coast to near Pt. Conception Friday morning, then move it east to near the 4 Corners region by Saturday morning, and then into central KS on Sunday morning. Although this is a favorable track for eastern CO snow, it is trending a little farther north than ideal. The NAM model has the track even farther north than the GFS and ECMWF, but will base my forecast on the two global models at this time. The system is also moving through fairly quickly, so this limits snow amounts as well. Forecast for CO now looks like this:

Snow will move into western CO during the day on Friday, but remain west of the Divide through Friday evening. Snow level will be 7000-8000 ft initially with heaviest snow in western CO Friday night into Saturday afternoon,. Snow level drops to valley floors by Saturday morning. Winter Storm Watch currently in effect for most of western CO, and expect this will become a Winter Storm Warning Thursday. Currently looks like 1-2 feet for the southwest mountains, and 8-16 inches for remainder of mountain areas with snow ending Sunday morning. For eastern CO, snow moves in Friday night, with initial snow level 6000-7000 ft. Snow becomes heavy during the day on Saturday, with snow level 5000-6000 ft. Snow persists but lightens Saturday night with snow level down to plains level , then comes to an end Sunday morning with clearing through the day. Currently looks like heaviest snow across eastern CO will be from the Palmer Divide north. If the track of this system moves farther north like the NAM suggests, heavy snow area will accordingly move farther north. Snow amounts using the current GFS/ECMWF model would bring 5-12 inches to the foothills, with up to 14 inches in favored areas, and areas north of I-70, and 4-9 inches to the Urban Corridor and plains, with heaviest amounts being at higher elevations and the Palmer Divide. With warm temps this week, and elevated snow levels, lower elevation roads may remain mostly wet or slushy on Saturday, possible freezing Saturday night. Roads above 7000-8000 ft likely to become snow and ice packed Saturday into Sunday morning. Overall a nice spring snow, but not an epic system, so no major outages expected.

Warm and dry weather expected next week, with high temps possibly into the 70's on the plains by late next week. No significant precip expected in the extended forecast. As our weekend system moves east Sunday into early next week, severe weather potential will exist across the mid and lower Mississippi Valley and deep South.

Major snowstorm affecting the mid Atlantic region today, and expected to affect the Northeast through Friday. Lots of cancelled flights in this region, so if you have travel plans, call ahead. Also a good Nor'easter, so lots of heavy surf and beach erosion for an area that is still impacted from Sandy.

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

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

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So we get to enjoy a few warm and dry days before a potential snowstorm this weekend. Temps will be well above seasonal norms today through Thursday, with Thursday being the warmest day of the week with temps 10-20 degrees above seasonal norms.

System to affect us this weekend is currently off the WA/OR coast, and is forecast to drop south along the CA coast this week and then turn east into AZ by Saturday and into the OK panhandle by Sunday. Models are still going through their usual iterations with the track and timing. ECMWF was the slower model, and today has the system moving out faster than the GFS. So this model dance will likely continue through this week. The general consensus at this time is that snow will move into western CO Friday, but remain west of the Divide with snow level 7000-8000 ft. As the system nears the 4 corners region on Saturday eastern CO will begin to get the majority of our snow. So snow moves into eastern CO Saturday as surface low sets up in the TX panhandle and we get deep upslope flow. Snow looks to persist into Sunday morning, then exit the state Sunday afternoon. As usual, snow amounts will depend on the track and timing of the system. The slower it moves, the more snow we would get. Latest models are trending towards a faster moving solution, so lower snow amounts today versus yesterday, but I am confident models will vary with track and timing all week. It will be hard to pin down snow amounts until we have better model consistency and consensus. Model output from today would have somewhere between 6 and 14 inches for the foothills, and 4-10 inches for the Metro area and plains. Yesterday snow amounts were higher. Currently looks like a good snow event, but nothing major, but of course that could change during the week. I will continue to monitor and provide daily updates.

Beyond the weekend, most of next week currently looks mild and dry. Medium range models hint at bringing more snow to CO by the following weekend (St. Patrick's Day weekend).

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

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

Bump for Wednesday 3/6 update

Bummer, two weekends in a row messed up. Oh well, the dogs love going for walks in the fresh snow.

Messed up nothin'!!!! I actually wish we would get another huge load of snow. 36"+ would be fine with me!!!

Bump for Thursday March 7 Update

Bump for Friday March 8 Update

Buy your bread and milk tonight! French toast Saturday.

RenegadeCJ wrote: Messed up nothin'!!!! I actually wish we would get another huge load of snow. 36"+ would be fine with me!!!

Me too!

Same here.

Bump for evening Friday 3/8 update