The Official 2009-2010 Denver winter weather thread

[PTPatrick]

0z nam and 18z GFS looking much better for post frontal upslope precip with this system late tomorrow into Wednesday. Also seems like temps will be plenty cold for fluffy dry snow. the 1/4 to 1/2 inch of precip could easily be 3-6 inches I think . Per Nam snow would start around 06z tomorrow night. Wednesday....once a little accum happens in the early morning hours, looks to light flurries and snow fallling through a very cold airmass for the rest of the evengin. By early thursday morning 510 decimeter core of the cold air sitting over the black hills south dakota. That should easily make for widespread single digits across eastern Colorado on thursday morning and highs in the teens. Friday could be the coldest as GFS has core of the cold even closer over central nebraska on Friday morning. Wouldnt be surprised to see Greeley go below zero is current models pan out. .

[Dencolo]

I can't believe the total duration of precip the 18z GFS wants to give the Denver area. It never gets too heavy, but we're talking nearly 40% of the period of the 384 hrs w/ some precip.

Completely different then our 1st two storms. All of it in one big chunk. Now the possibility of light snow on and off the next two weeks. And we could see some serious cold as well.

Also, there still seams to be about 3" of snow on the north facing yards in the neighborhood. It is really interesting to drive East West through the neighborhoods. One side has been snow free for 10 days+ while the other side has 3" of snow on the grass and still has icy driveways.

[PTPatrick]

0z GFS is even wetter with tomorrow night system...closer to .5 with some .5-.75 inch precip probably only in the foothills. But even .5 in the metro could translate to up to 8 inches with cold enough temps I think .

Friday and Saturday seem to be the only real break in precip between systems...but GFS no longer shows the warming in that period that it once did...pretty much highs in the 30s or lower through 7 days.
Sunday into MOnday looks like a 2 day flizzard in arctic temps followed by a doozy of a storm on tuesday. Too early to get excited but the closed low moving into a good upsloap spot combined with frigid temps and high liquid to snow ratios...

[SCMedic]

NOAA discussion is no where near as bullish on the models as I would expect. Still calling for 1-4" tonight and Weds...


It's the Saturday - Tuesday systems I'm really interested in. Keep the fingers crossed.

[VoodooCadillac]

1.5" in FC this AM. Very light & fluffy and COLD!.

YTD snow:
First storm - 3"
Big storm - 21.5"
3rd storm - 6.5"
12/2/09 - 1.5"

Total = 32.5"

[PTPatrick]

With all this cold air and not much snow know this forum has been dead the past couple days. Quick and dirty model updates on coming weekend and next week systems.

Tomorrow and Saturday, still cold but warmer...low to mid 30s highs and sunnier Should get melting tomorrow and saturday.

Saturday night front comes in, Snow on Sunday ranging from around 3 inches NAM, to 4-6 on GFS. Light snow lingers into Monday morning, temps stay frigid until the storm comes in monday night with the pacific air things warm up a bit to 20s.

Bigger storm comes in Monday afternoon, although per GFS flurries never really stop on Monday. The main batch of QPF seems to come in very late Monday night and the storm wraps up into plains by overnight tuesday. Tuesday is a snow day. QPF for the main portion of the storm, looks like .5-.75 for the metro. The caveat is this will be falling into air that is in the teens for second half of the storm. That could make for dry fluffy snow maybe on the order of 6-10 inches. As the storm winds up tuesday evening temps should be in the single digits. Also this storm looks windier than our previous so perhaps there could be some drifting and wind chills could be an issue.

You might as well combine the 2 storms for a total 10-16 inches from Sunday to Tuesday night, and not much melting should be occuring, even on roads...although long duration and lack of any really heavy looking periods should help.

[SCMedic]

Nice summary Patrick. I was just thinking about doing the same thing.

Hopefully this QPF on the GFS pans out. Another 10-16" would be fun. I'd be at 42-48" this year already!

[PTPatrick]

Not too much change in the forecast reasoning for tomorrow for our area. Front comes in tonight and puts us in the deep freeze for the next 4 days with Tuesday being one of our coldest days yet. Cheyene is calling for them to be below 0 by dinner time tomorrow so I think our forecast could be colder than its even shown right now.

Snow looks good for tonight and tomorrow...in fact the disc sounds like we should start having snow tonight and barely stop until the second storm leaves on tuesday overnight. During that entire period it wont be heavy. Most accumulation looks to end though later tomorrow evening, with probably near 6-7 inches for most of the metro by day break monday.

Second storm on monday afternoon and tuesday...unless the low closes off a little more south orographics are never "great" east of the mountains. It could happen but fairly good model agreement so far that it wont. That would put is with another long period of light fluffy snow of low liquid content. Models painting around .25 for that storm for this area. In that cold air that could still translate to another 4-6 nches, but thats on top of the 6-7 we will already have...so I guess, take home point is...its going to be snowing for the better part of the next 3 days. While none of it should be heavy, it will be very cold and WILL stick on the roads. Commuters on monday and tuesday morning take head!

[SCMedic]

I agree, I still see the Monday night/Tues storm as the heavier snow and wouldn't be surprised to see it close off and pull in some gulf moisture into a true upslope event. We will have to wait and see. Next weekend looks fairly interesting too!

Stay off the roads on Monday!

[Dencolo]

WWA in affect. Previous discussion said we'd be looking at a 15 or 20-1 precip to snow ratio - that is huge! This snow is going to be super light. I'll probably be able to use my leaf blower to clear the driveway this time...

Edit: BTW, I checked on Vail's website and they have received 37" of snow for the season. I've had more than that at my house! Looks like by the end of the week they'll be on top, but how often do parts of Denver have more snow than Vail through nearly mid December?

...WINTER WEATHER ADVISORY IN EFFECT FROM 8 PM THIS EVENING TO
8 PM MST SUNDAY...

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 8 PM THIS EVENING
TO 8 PM MST SUNDAY.

SNOW WILL START THIS EVENING AND CONTINUE THROUGH SUNDAY AFTERNOON.
SNOWFALL AMOUNTS OF 4 TO 8 INCHES IS EXPECTED THROUGH SUNDAY EVENING
WITH THE HEAVIER AMOUNTS EXPECTED NEAR THE FOOTHILLS

[PTPatrick]

Winter weather advisory out for tonight and tomorrow. Calling for 4-8 inches in the metro by late tomorrow. Looking at latest 18z models, NAM is not much changed. Still a bit drier down in the metro than GFS, but would still probably get us tot he 4 inch. GFS is closer to the 8 inch range with closer to .5 inches of QPF by 12 z monday. We are talking most likely a 20:1 ratio here.

The 18z models are looking a little different than 12z and 06z runs for tuesdays system. NAM is looking a little wetter...a little. painting close to .25 inches for the 0z tuesday-06 wednesday time frame mostly do to a brief period of heavier precip in the tuesday afternoon time frame. Still though...for the whole 84 period NAM only squeezes out .5 inches or about 10 inches of snow for us. Not sure why the tuesday storm looks slightly wetter as the features don't look all that different.

18z GFS also came in slightly wetter for the second storm, do to a slightly stronger and further south system (at 18z tuesday its just se of Trinidad, CO with the surface low, vs between La Junta and Lamar on the 12z run of the model). That roughly 100 mile difference could mean a world of difference for us in the metro. Even so, 18z run only got us into the .1-.25 range for Tuesday. That subtle difference is probably less important now, but if the trend further south continues we could be looking at more than 4 or 5 inches on tuesday.

for what its worth 12 euro and 12 z canadian were drier for us for Tuesdays storm. CMC had almost no QPF tuesday. In any case, HPC has us in the risk of 4 inch range on Tuesday.


EDIT: 0z NAM came in a little wetter for tomorrow. much closer to GFS. 0z GFS looks a little wetter...maybe the diff between 4-8 and 5-10 so not a huge difference for tomorrow and tomorrow night. Still waiting on the rest of GFS for tuesdays storm

[PTPatrick]

As of 6 this morning I had barely gotten anything at my house. there was a dusting and light snow then. Woke up a bit ago again now looking like things finally picked up and already have about 3 inches of fluff. Dont know if we just got a late start or if the precip amounts will be lower. GFS at 0 z still has some good lift for the next 6 hours or so. In any case, doubt metro will realize 8 inches...perhaps 6 in the western burbs, and east of I 25.

12z not looking good for accumulating snow with Monday and tuesday. Monday is clear from downsloaping all day tomorrw...we may even get sun which would help the road situation. Tuesday's storm just doesnt give us good upsoap all level. GFS is .1-.25 inches, and NAM is about the same, and that is for a pretty brief period on tuesday morning. In any case, still some time to watch but there is excellent agreement. My guess at this point is 2-5 inches in the metro with tuesdays system. Nothing to write home about , but hey, snow is snow.

[VoodooCadillac]

9" of very, very fluffy snow @ 10:00 AM in Fort Collins. Light snow is continuing.

Edit:
Snow generally tapered off around Noon. We'll call it 9" for the total.

Edit #2:
It never totally stopped snowing yesterday afternoon/evening, and we had an additional 1" this AM, so I'm revising the 12/6 total to 10."

YTD snow:
First storm - 3"
Big storm - 21.5"
3rd storm - 6.5"
12/2/09 - 1.5"
12/6/09 - 10"

Total = 42.5"

[SCMedic]

Only 4-5" here in Broomfield. Still snowing and damn cold. Thus is some of the driest snow I've seen down here.

[PTPatrick]

I'm up to 4.5 in the yard here. Definately dry. Roads werent bad if drive like a sane person.

I wont beat the models to death tonigth but suffice it say they are still keeping the urban corridor from Ft Collins south pretty dry with this storm. 0z nam has NO QPF from tonight into tuesday morning, and then just has a brief shot of light snow on tuesday afternoon. I suspect we will see some sun tomorrow after all. 18z GFS would still give the front range a few inches of powder in the tuesday to tuesday evening time frame but still not much. HPC and discs seem to be leaning more toward GFS for the tuesday storm.

0z GFS is in up until 48 hrs. Still wetter than NAM with the urban corridor. shows around .25 range for QPF...so 4-6 inches seems reasonable for the period from tomorrow evening onward. Heaviest period of precip comes in tuesday between rush hour and lunch. All and all I think this tuesday system will come out very similar to todays storm.

[PTPatrick]

looked at the forecast for the area and was a little surprised...calling for 1-2 today, 3-5 tonight, 3-5 tomorrow. That seems pretty high given that even the more optimistic GFS only paints under or right at .25 inches of precip for the rest of this event. Even with a higher than 20:1 ratio that would still only get most of us into the 6 inch range total and I am not particularly optimistic on that, let alone possible accums of a foot for the next 2 days. Oh well, it could certainly verify, esp for the western southern surburbs...just doesnt seem likely.
It continued to snow here last nigh, and I did have about another half to an inch of snow overnight. I might add, that is weird to see a forecast forecast for 7 to 12 inches of snow and NOT have an advisory...just odd.

[SCMedic]

They have 1-2 today for me, 3-7 now tonight, and 3-5 tomorrow with a WWA being issued later this afternoon!

I had a feeling this second storm would be bigger than they expected! I picked up 2" more overnight and it's still snowing.

[Dencolo]

looked at the forecast for the area and was a little surprised...calling for 1-2 today, 3-5 tonight, 3-5 tomorrow. That seems pretty high given that even the more optimistic GFS only paints under or right at .25 inches of precip for the rest of this event. Even with a higher than 20:1 ratio that would still only get most of us into the 6 inch range total and I am not particularly optimistic on that, let alone possible accums of a foot for the next 2 days. Oh well, it could certainly verify, esp for the western southern surburbs...just doesnt seem likely.
It continued to snow here last nigh, and I did have about another half to an inch of snow overnight. I might add, that is weird to see a forecast forecast for 7 to 12 inches of snow and NOT have an advisory...just odd.

I am kind of doubting the snow totals expected, as I have the same forecast. The models don't appear to support that much QPF. So far this year is seams the big storms were a little under predicted and the medium storms are slightly overpredicted. While 7 to 12 is predicted, I'm going to guess 6". But I'd like to see the 12"!

[Dencolo]

Now calling for 3" to 7". We'll see...

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 5 PM MST
TUESDAY...

A WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 5 PM MST
TUESDAY.

LIGHT SNOW WILL CONTINUE TO SPREAD ACROSS THE FRONT RANGE URBAN
CORRIDOR AND NORTHEASTERN PLAINS OF COLORADO TONIGHT AND INTENSIFY
BEFORE DAYBREAK TUESDAY. TOTAL ACCUMULATIONS OF 3 TO 7 INCHES CAN
BE EXPECTED BEFORE THE SNOW DECREASES TUESDAY AFTERNOON. THE
HEAVIEST AMOUNTS CAN BE EXPECTED ACROSS LARIMER AND NORTHERN WELD
COUNTIES.

[PTPatrick]

my prediction for downtown is 5 inches. that would look nice on top of the 4 thats on the ground. meanwhile its SOOO cold. 7 outside right now. We never hit the expected upper teens highs today. I suspect that tomorrow will end up in the single digits for the better part of the day. Still nothing like the cold shot we had this time last year though when the high was barely above zero and lows in the minus teens...but given all that cold air building in canada I think that could be in our future. Highs are not looking like they will rebound very quickly. Probably Friday before we get above freezing.