wxgeek's weather-Dry/Warm this wk. Possible snow this wknd-Update 12/11

Update Wed Dec 11

Beautiful day across the state today with temps 15-25 degrees above seasonal norms. This will begin to change on Friday as we will see more high clouds and more wind, although temps will remain well above seasonal norms with downsloping flow. West to souwest winds will increase Friday afternoon into Saturday afternoon with speeds of 15-35 mph and gusts up to 50 mph, hence fire danger will be quite high for December Friday into Saturday.

As for the incoming storm, this one is not revealing itself very easily. As usual, some model differences, which translate to big differences in potential snow amounts. CA is getting hammered today, with rainfall amounts generally in the 2-6 inch range so far in northern and central CA. System will move into SoCal Friday, then into the Great Basin on Saturday, and finally into CO on Sunday. In general, models have slowed system down a bit. GFS and ECMWF in good agreement tracking the upper trough near the 4 Corners late Saturday, then a closed upper low over northeast NM Sunday. The NAM/WRF tracks the upper low farther north, across southern CO, and hence has higher snow amounts than the GFS and Euro. The GFS and Euro have been pretty consistent tha past 24 hours, so my forecast will trend towards that solution, but know if the NAM/WRF solution is more accurate, snow amounts will be higher. Hopefully we will get better overall model concensus Friday into Saturday and be able to pin this thing down. The GFS and Euro are also warmer, so snow on the plains likely to be a mix and mostly melt due to warm tenmps this week, wile the NAM/WRF brings colder temps and accumulates snow over the plains. Using mostly GFS and Euro, forecast currently looks somegthing like this:
Precip will move into western CO Saturday afternoon with snow level 7000-8000 ft and precip will remain west of the Divide through midnight. Precip moves into eatsern CO by early Sunday morning with snow level 5000-6000 ft. Snow persist most of the day then diminishes by Sunday evening, and end by midnight Sunday. Snow amounts for the mountains look to be in the 6-18 inch range. For the foothills, 2-6 inches possible, and for the Urban Corridor and plains, from a trace to 3 inches. If the NAM/WRF solution is correct, snow amounts could be 50% higher, and near winter weather advisory criteria for the foothills. Time will tell.

For next week, model consistency is horrible, so very low confidence.Models bring another system into CA early next week, but trajactories have varied from into CO to way south of CO the past 2 days. Latest model runs keep majority of precip south of CO Wednesday into Thursday, but if track moves farther north, good snow chances for CO. Similar system for next weekend, models keep system south currently, but if father north CO could see snow next Sunday. Models then not sure abouth xmas week. Was dry yesterday, but latest runs have a system nmoving into CO Wednesday, so snow would be posible xmas eve into xmas morning. Again, it is likely forecast will continue to change radically beyond next 2-5 days.

_________________
"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 Dec 10

Bookend storms on each coast today. Noreaster continues to pound the Northeast, while powerful Pacific storm hammers the Pacific Northwest today and will move into CA on Thursday. With each system, lots of rain, snow and high winds along with flooding. Winds in the 60-75 mph range buffeting WA and OR today, while 3-5 inches of rain possible in northern CA and 1-3 inches elsewhere, along with 2-4 feet of snow in the Sierras. Likely to hear about a lot of landslides in burn scars in SoCal by Friday.

For CO, lots of sunshine today will lead to very warm temps. Some mid and high clouds will filter across the state today, but temps will still be 10-20 degrees above seasonal norms. Even warmer temps expected Thursday and Friday as upper ridge dominates Rocky Mountain region. Some gusty westerly to southwesterly winds will likely develop Friday afternoon into Saturday afternoon in advance of approaching West Coast system.

Another day and some different solutions from models for our weekend storm. Somewhat better consistency last few runs and GFS and Euro are in decent agreement, so confidence slightly higher today. Both models now track the upper trough to near the 4 Corners region by Saturday afternoon then along the CO/NM border to southeast CO/northeast NM by Sunday morning. this also develop a surface low across southeast CO which is a much better snow scenario for eastern CO. If current forecast holds, precip will move into western CO Saturday during the day. Snow level around 8000 ft initially lowering to 7000 ft by Saturday evening. Precip should remain on the west side of the Divide through Saturday evening. Precip then spreads east to about the I-25 corridor Saturday night into Sunday morning with snow level lowering to 5000-6000 ft by Sunday morning. Snow will persist during the day on Sunday across eastern CO with snow moderate to heavy at times. Snow diminishes by Sunday evening and moves east of the state Sunday night. If latest models are accurate, mountains could receive 6-12 inches of snow, while the foothills could see 3-7 inches of snow, and Urban Corridor and plains 2-5 inches of snow. If models continue this track, I would expect the NWS to issue some winter weather watches/warnings/advisories in coming days. However, since models have been so erratic with the track of this system, no one is quite ready to begin blowing the whistle yet. Need another day of consistent runs before this becomes more believable, but I like the trend. Will continue to monitor and update.

For next week, latest models bring another upper trough into the central Rockies mid next week, so more snow possible Wednesday into Thursday statewide, then again next Sunday into Monday. So enough snow for a white xmas for most of CO, but xmas eve and day currently look dry across CO.

_________________
"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 9

Dry and mild day across CO once again. CO is currently under the influence of what we weather people call a dirty ridge, meaning there is an upper ridge, but it is allowing clouds to spill through the ridge axis and downstream. Hence, temps today will be a little cooler than expected due to the high clouds, and an inversion exists across the plains and has trapped the cooler air under the inversion, which extends up to about 7000 ft, so warmer temps in the foothills, with grungy air below the inversion top. The upper ridge is expected to amplify Wednesday through Friday, which should eliminate most of the clouds and allow temps to rise even further above seasonal norms. Near record temps will be possible Friday. As upper level trough from the West Coast moves inland on Friday, CO will see very warm temps along with some gusty west to southwest winds. Winds in the 15-35 mph range will occur, with gusts to 50-60 mph possible from Friday afternoon into Saturday afternoon. Thus, fire danger will be elevated Friday and Saturday in the foothills and plains.

As for our next system, models continue to vacillate on the timing and position from run to run, so overall confidence in weekend forecast is pretty low at this point. In general, model runs today kept the southern branch of the upper trough slightly farther north over northern NM, which is a little better for precip for eastern CO, but the split in the upper trough will take a lot of the energy out of the system until it regroups farther east on Monday. The European model is a little better for precip than the GFS which keeps the energy farther south. Until this system moves onshore on Thursday, I doubt the confidence will increase much. Once models can incorporate data from the West Coast, a better forecast should percolate up. Given the latest forecast, precip would move into western CO during the day on Saturday with snow level around 8000 ft. Precip moves east Saturday night into Sunday morning, with some precip over eastern CO possible during the day on Sunday. Snow level would be 5000-6000 ft, but any amounts would be very light, generally less than 1 inch. Precip would move east of CO by Monday morning. Since there is still so much uncertainty in the forecast, if the upper level system tracks farther north across southern CO, eastern CO could receive greater snowfall, while the system could move farther south and not provide any precip to eastern CO. Mountains likely to receive 1-3 inches either way, with perhaps up to 6 inches in the southwest mountains. CA is looking for 1-5 inches of rain Thursday into Friday, with the Sierras receiving 2-4 feet of snow.

For next week, models remain pretty inconsistent, so confidence lower than usual for a long range forecast. West Coast will continue to receive abundant Pacific moisture Monday through Wednesday, with some of this moisture forecast to move into CO next Wednesday into Thursday. Snow level would be down to plains level, and amounts would remain on the light side statewide. Models then suggest upper ridge will amplify along the West Coast next weekend, which would allow for a system to slide down from the Pacific Northwest into CO the following Monday and Tuesday, providing enough snow for a white Christmas for most areas in CO. As stated previously, this is about as likely as most fairy tales of coming true, but with time will come a better forecast.

Elsewhere, the mid Atlantic and Northeast are experiencing some tough winter weather as a NorEaster is under way. This system is expected to move very slowly to the north northwest over the next 72 hours, so very difficult weather for the Northeast through Friday is expected. Some inland areas of NY as well and VT and NH and ME could receive several feet of snow before this is over, while coastal areas getting pounded by heavy rain and high surf from strong winds. All precip will turn to snow overnight and persist through Friday morning. Travel delays at major airports already in the 1-4 hour range, with cancellations likely.

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

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

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Our dry and mild December will continue this week, with mostly sunny skies and temps well above seasonal norms statewide. Attention then turns to whether we will get any snow this weekend. Latest models runs are not overly optimistic on the upcoming system unfortunately. GFS and Euro have converged on a solution, and it does not favor much snow in CO. Vigorous upper trough will bring heavy rain to CA this week, but as the system moves east, models indicate energy in the upper trough will split, which is never a good sign for us. Some goes north, and another branch will dig south into NM. This split will leave CO with only light snowfall amounts, and most of that will be in the mountains. Models could of course change between now and then, but the latest forecast seems to go along with how this season has progressed for us. If the current forecast is accurate, some precip would move into western CO Friday night with snow level 7000-8000 ft. Some precip would push east to about the Front Range Crest Saturday with snow level remaining in the 7000-8000 ft range. Some flurries would persist Saturday night west of the Divide with snow level lowering to 5000-6000 ft as upper trough passes. Foothills and plains would be left high and dry if the current forecast is accurate, and amounts in the mountains would likely only be a few inches. Conditions would clear out Sunday, but temps would remain near seasonal norms.

For next week, models now bring a chance of snow into CO from Wednesday night into Thursday night, with some snow possible for the foothills and plains with much cooler temps. Models then bring another chance for snow into CO next weekend with temps remaining on the cool side. Hopefully the wet weather along the west coast will begin to make it's way farther east as December progresses.

As previously posted, the driest December since 1993 on Conifer Mountain was December 2002 when only 3 inches was recorded. This was also a season with a late building El Nino, and those who lived here, will remember what happened in March of 2003. For those not around at that time, March 2003 was the snowiest month on record on Conifer Mountain with 103.75 inches. I'm not saying there will be a repeat of that, but if the building El Nino does make progress, conditions will favor a snowier late Winter and Spring.

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

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

Bump for 12/9 update

Bump for 12/10 update

Bump for 12/11 update