wxgeek's weather: Cold and Snow on the way-Update 12/4-Noon

Update Wed Dec 4

Update 12:00 pm:

Perhaps I was a bit harsh on the models prematurely. Nice CSI snow band associated with upper jet stream came through this morning and dumped 3-6 inches of additional snow. Snow amounts now generally 2-6 inches along the Urban Corridor and plains, and 6-14 inches in the foothills, and 6-18 inches in the mountains, so forecast was not as bad as I earlier thought. Generally only light snow this afternoon with minimal additional accumulation expected. Skies should begin to clear by this evening and tonight, with temps plummeting. Lows tonight should be in the -5 to -20 F range in the foothills, and 0 to -15 range on the plains. High temps Thursday and Friday in the single digits if temps even get above zero. Light flurries possible Thursday into Friday morning. Next disturbance looking a little stronger on latest model runs, and is expected to swing across CO this weekend. Currently looks like 2-5 additional inches possible in the mountains, and 1-3 additional inches for the foothills and Urban Corridor. Arctic air mass expected to remain in place over CO through Monday, then temps expected to gradually warm, but remain well below seasonal norms.

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Update Wed Dec 4

Latest observations show from 1-7 inches of snow across the foothills and Urban Corridor overnight. Models need a program to stop them from blatently lying, I apologize for another busted forecast. Should have stuck with earlier instincts and ignored models.

Looking at radar and satellite data, good surface low over southwest CO will move east along the CO/NM border through the day. Snow will persist through the morning and then begin to diminish this afternoon. Perhaps another 1-3 inches for most foothill and Urban Corridor locations today. Very cold air in place up to about 10,000 ft MSL, then a strong temperature inversion from 10,000 to 14,000 ft MSL which is why it is still snowing with temps below zero at the surface. Currently -7 deg F on Conifer Mountain.

Arctic air will remain in place through the weekend. Some light flurries possible late Thursday into Friday, mostly south of I-70. Better chance for accumulating snow from Saturday into Sunday, with maybe an additional 1/2 to 2 inches. Models now hold off any additional significant systems next week, so cold temps early next week, then temps begin to warm Wednesday into next weekend. Some mountain snow possible late next 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 Tue Dec 3

The warm and calm before the storm this morning. Latest observations and model guidance delay the passage of the arctic front a bit. Arctic front currently in southern WY and will push south into CO later this morning and afternoon. Front is expected in the Metro Area between 1 pm and 4 pm this afternoon, and cold temps and snow will follow. In the mountains, snow will increase this morning and afternoon as this snow is associated more with a Pacific cold front. The two fronts merge this evening. NWS has now issued a Winter Storm Warning for the mountains, foothills and Palmer Divide through 6 pm Wednesday. Winter Weather Advisory has been issued for the Metro Area. Snow amounts will fall off rapidly as you get farther east away from the mountains, as snow will be more associated with very strong jet stream aloft versus surface upslope flow, as upslope flow will remain fairly shallow, below 9000 ft. Thus, snow will become heavy in the mountains later today and persist through Wednesday evening. For the foothills and Urban Corridor, snow will develop later this afternoon and evening, becoming moderate to heavy tonight and Wednesday morning, diminishing by Wednesday evening. New snow amount forecast as follows from today through Thursday morning:

Mountains up to the Front Range Crest: 12-30 inches
Foothills and Palmer Divide: 6-16 inches
Banana Belt: 2-8 inches
Urban Corridor: 3-9 inches (heaviest west of I-25)
Eastern Plains: 2-6 inches

Bitter cold temps still on tap for Wednesday through Sunday, with a second system expected to bring some light additional snow to CO Saturday afternoon into Sunday, and keep temps very cold. Models then suggest another stronger system for next week with more cold arctic air, so we may not see warmer temps until late next week.

Roads will be snow and ice packed from this evening through the weekend, with toughest commute Wednesday morning and evening. Today may not get too bad until after 6 pm, so if you can leave early, that would be advised.

Stay safe and warm through this extended cold and snowy period.

_________________
"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 Mon Dec 2

Strong westerly winds buffeting the High Country and foothills today with wind speeds of 50-80 mph being reported. Winds are expected to remain strong and gusty today into tonight with temps 10-20 degrees above average due to katabatic flow. Winds should begin to die down after midnight. In the High Country, snow is accompanying these strong winds making for tough travel across the state.

The Arctic Express is fast approaching. Models are in good agreement on the evolution of this system, yet the snow forecast remains difficult. Snow will increase west of the Divide tonight ahead of the system. Arctic front expected to move south through CO during the day on Tuesday, arriving near the WY border near daybreak, and moving south of I-70 in the afternoon and to US 50 by midnight. Shallow upslope flow will develop behind the front and snow will develop shortly after front moves through. Snow will begin tonight west of the Divide, and intensify during the day on Tuesday. East of the Divide, snow will begin after arctic front moves by. SO for the Metro Area and foothills, snow likely to develop by late Tuesday afternoon and intensify by evening, then persist overnight into Wednesday afternoon. Heaviest snow for the foothills and Urban Corridor looks to be from 8 pm Tuesday to Noon on Wednesday. Snow will begin to diminish across the state by Wednesday evening. Now for the tough part, snow amounts. It is becoming more difficult to disregard model precip output, yet the upslope flow is only expected up to about 9000-10,000 ft. However, upper level trough has good dynamics and fairly deep moisture, so my snow total forecast has been bumped up accordingly. There is the possibility models have overplayed this system, but will go with the model consistency and agreement amongst almost every model out there as they output from 0.50 to 0.75 inches of liquid equivalent for the foothills. Using a conservative 14:1 ratio, we could see a decent snowfall. In response, NWS has issued a Winter Storm Watch for mountain areas east of the Divide and foothills, while a Winter Storm Warning has been issued for mountain areas west of the Divide. My snow forecast now looks like this from Tuesday morning through Thursday morning:

Mountains: 10-24 inches
Foothills and Palmer Divide: 4-12 inches
Banana Belt: 2-6 inches
Urban Corridor: 3-7 inches
Eastern plains: 2-5 inches

Arctic air will be firmly in place by Wednesday night, and has no plans on leaving through Sunday. Low temps during this period will be from +5 to -15 deg F, and high temps will be from 0 to +15 deg F. Some light snow or flurries will be possible at times from Thursday through Sunday, but any additional accumulation would be light, generally less than an inch or two. For the commute, Tuesday evening, Wednesday morning and Wednesday evening will be the worst with ice and snow packed roads pretty much everywhere. Tuesday evening into Wednesday morning could be especially difficult due to initial snow melting on warm roads then freezing underneath snow. Roads crews will likely have the majority of snow plowed from Thursday and beyond, but cold temps will limit melting so ice and snow likely to remain in spots through the weekend.

Now would be the time to insure pets have a warm place to reside and pipes are properly insulated to avoid freezing.

Extended range models indicate temps will begin to moderate early next week, yet remain below seasonal norms. Models then suggest the possibility of another decent storm affecting CO by mid to late next week with more arctic air making it's way into CO. If models are correct, I think most of CO is assured of having snow on the ground for the Holidays.

_________________
"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 Sun Dec 1

Before the cold and snow, there will be wind. NWS has issued a High Wind Warning for the foothills from 6 am Monday to 5 am Tuesday. Westerly winds will strengthen early Monday morning and persist into early Tuesday morning. Sustained wind speeds of 20-50 mph likely, with gusts in the 60-80 mph range possible over prone areas. Strongest winds will be north of I-70, but foothill areas south of I-70 will still experience very strong winds that may cause downed trees and power outages.

Now on to the cold and snow. Models have moved arctic front into CO earlier, so now expected to move into northern CO Tuesday morning and move south of I-70 by early afternoon. Snow will develop behind arctic front and upslope flow will strengthen. Snow could become moderate to heavy by Tuesday evening and continue into Wednesday afternoon. Snow looks to diminish by Wednesday evening but temps will become much colder. Models bring a decent upper level disturbance through Tuesday night with decent precip amounts, more than would normally be expected with an arctic type system. Of course, last storm models over predicted precip amounts as well, so will continue with lesser amounts, but know snow amounts could be higher if model precip amounts come through. Snow amount forecast from Tuesday morning to Wednesday evening look like this...

Central and Northern Mountains: 6-18 inches
Foothills and Palmer Divide: 3-8 inches
Banana Belt: 1-5 inches
Urban Corridor and plains: 2-5 inches

With snow now developing by Tuesday evening, commute back up the hill could be slick and slow as well as all day Wednesday. Basically travel anywhere in CO this week may be difficult at times. As skies clear Wednesday night, temps will plummet with lows Thursday morning likely to be below zero in many foothill areas. High temps Thursday in the 5-15 deg F range, with low temps Thursday night through Sunday night in the 5 to -10 range. High temps will struggle to get out of single digits through Sunday. Some light snow is possible again Saturday afternoon through Sunday evening, although additional accumulations expected to be light, generally less than 2 inches. Temps will begin to moderate early next week, with more snow chances late next week.

Mini Nor'easter now looks to stay off the East Coast early this week, so likely will not cause any travel issues.

_________________
"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 Sat Nov 30

Enjoy another beautiful day across the state today with temps 5-15 degrees above seasonal norms. Sunday will be similar, except for gusty westerly winds developing by Sunday afternoon into Monday morning across the foothills. Gusts could reach 50-60 mph in prone areas mostly north of I-70. Also, light snow and flurries still expected from Sunday afternoon into Monday morning over the northern mountains with 1-2 inches possible.

Models beginning to refine the big chill for next week. Latest model runs now bring the arctic front into northern CO by Tuesday evening, so snow likely to develop Tuesday night and persist into Thursday afternoon. Heaviest snow now looks to be Tuesday night into Wednesday evening, with light snow persistsing into Thursday evening and night. Models then dry things out with only very limited snow now expected Friday and Saturday with cold arctic air in place, with a chance for another disturbance to bring some additional snow on Sunday. Temps look to drop 20-30 degrees as arctic front makes initial push through CO on Tuesday. On Wednesday with snow, temps likely to remain between 5-15 deg F all day. By Thursday, colder air penetrates CO so high temps likely in the 0-10 deg F range, with overnight lows in the 0 to -15 range. Arctic air remains in place Friday and Saturday, so temps will likely remain in the -15 to +10 deg F range statewide. Models bring some light snow in Sunday afternoon into Monday evening, but with cold air still in place, any snow would be light.

For snow totals, looks like lesser amounts now, which is not surprising given the cold arctic air with this system. Mountains still look to pick up the most snow with 6-18 inches possible from Tuesday through Thursday. Foothills look to pick up 3-7 inches, while the Urban Corridor and plains could see 2-5 inches. The biggest impact will be the cold temps next week. Litttle if any melting expected, so roads could remain ice and snow packed much of the week and Mag Chloride loses much of it's effectiveness when temps are below 10 deg F. Animals will remain another concern. Any animals normally left outside may need to be brought inside. Temps begin to moderate by the following Wednesday.

So from my records, I have received 9.5 inches of snow so far on Conifer Mountain. Normal snowfall at the end of November is 30.5 inches, so we are at 31% of normal snowfall. Despite snowfall on 11 days in November, we only received 2.5 inches of snow. Since 2006, we average 31 inches of snow in December on Conifer Mountain, so we are once again beginning to fall woefully behind in our snowfall. It is a bit scary to depend on a snowy Spring to save us, as without that, we know what our early fire season looks like.

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

"It is better to be roughly right than precisely wrong".
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Fri Nov 29

Hope everyone enjoyed a very pleasant Thanksgiving and you are able to enjoy this beautiful late November weather. Sunny and mild weather to persist across CO through Saturday with temps 5-15 degrees above aseasonal norms. Sunday will start out nice, then some clouds will increase across western CO and some gusty westerly winds will develop east of the Divide Sunday afternoon and persist into Monday morning. Wind speeds of 15-35 mph with gusts to 50 mph possible across foothill areas with strongest winds north of I-70. Some flurries possible mostly over the northern mountains Sunday afternoon and night with snow level 6000-7000 ft and accumulations of only an inch or two possible.

Models in decent agreement on the big patten change for next week. Monday should be mostly sunny with mild temps statewide. Tuesday also looks to start out mostly sunny, with some clouds increasing across northwest CO by Tuesday afternoon and some snow possible over the northern mountains by Tuesday evening. Acrtic front looks to push south across CO Tuesday night, with snow developing behind the front across most of CO. Cold temps and snow to looks to persist statewide Wednesday, although amounts look to remain on the light side, with a dusting to a few inches most areas. Models agree that as large and deep upper level low moves south into the northern Great Basin early next week, the energy will split. Northern branch is forecast to move into the Northern Plains Wednesday and continue into Ontario Thursday. The southern branch forms an upper trough over CA/NV Wednesday and moves across CO Thursday into Friday, and another piece of energy moves south out of Canada and moves across CO on Friday into Saturday. At the surface, once arctic front moves through, cold arctic air will remain in place over CO through at least next Sunday. Periods of snow will exist from Wednesday into Sunday statewide. Heaviest preiods of snow look to be Wednesday night into Thursday, then again Friday afternoon into Saturday evening, although with such cold air in place, snow amounts will likely not be all that heavy, but snow will be light and fluffy with a 16:1 or 20:1 water ratio. At this time, for the period Tuesday night through Sunday, snow amounts look to be in the 10-20 inch range for the central and northern mountains, 6-14 inches for the southwest mountains, 4-9 inches for the foothills and Palmer Divide, and 2-5 inches for the Urban Corridor and plains. Know that these amounts are likely to change by early next week and models have a better handle on the evolution of this system. If the southern disturbances develop more and advect some moisture we could see higher amounts in the foothills and plains, whereas if only the cold arctic air produces snow, amounts would be lower due to limited moisture in this very cold air. Temps are likely to plunge below zero by late next week, with high temps remaining in the single digits. A return tpo warmer temps does not seem likely until mid week of the following week.

For anyone traveling to the East Coast next week, models are suggesting a mini-Noreaster will develop off the North Carolina coast on Monday, and move up the Atlantic coast affecting the mid Atlantic region late Monday into Tuesday, then affect the Northeast Tuesday into Wednesday. Rain/snow line will be very close to the coastline with strong northeast winds that will push waves and seas onto immediate coastal areas. Inland areas could see significant snow from this system. This system has the potential to disrupt travel across this region next week.

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

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

Bump for 11/30 update

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Bump for 12/4-Noon update