mayjawintastawm Posted March 9, 2021 Share Posted March 9, 2021 GFS is playing a game of high-stakes chicken with the other models. Though none are saying it'll be a total bust. Then again, the No Accumulation Model has not weighed in yet. Tomorrow evening is when our fantasy may blow up. Link to comment Share on other sites More sharing options...
ValpoVike Posted March 9, 2021 Share Posted March 9, 2021 Snow ratios could really be impactful this weekend. It will be interesting to see as even some of the lower qpf's of "only" 2.5" could be crippling at 12 or 15:1. Even 10:1 for that matter. For what it's worth, GFS seems to be factoring at 16 or 17 in spots. When I lived in the Midwest, ratio forecasts seemed to be a bit more accurate than in Colorado. Link to comment Share on other sites More sharing options...
Chinook Posted March 10, 2021 Author Share Posted March 10, 2021 For the weight of snow on rooftops, basically QPF would matter, and the ratio wouldn't. Of course, that's not the only factor, but we are starting to get to a point where weight could collapse some roofs. Link to comment Share on other sites More sharing options...
skierinvermont Posted March 10, 2021 Share Posted March 10, 2021 0z GFS ups total... over 6" QPF from Golden north to Fort Collins. But the southern edge of the storm has been creeping north on nearly every model run. Any farther north and total will start to decrease south of Boulder. Thinking there is a decent chance this ends up being a FOCO to Cheyenne jackpot. GFS ensemble mean is 4"+ from Boulder to Cheyenne. Which is a 1" bump from the 12z mean over the same area. Link to comment Share on other sites More sharing options...
WeatherAg99 Posted March 10, 2021 Share Posted March 10, 2021 On 3/8/2021 at 3:05 PM, ValpoVike said: You could go to Black Hawk and stay at one of the casinos...maybe a jackpot either way. This is the answer! Up to 40” in the forecast in Black Hawk and not a bad way to enjoy it! Link to comment Share on other sites More sharing options...
Chinook Posted March 10, 2021 Author Share Posted March 10, 2021 The 00z Euro still has a very significant amount of snow for the area, particularly near and east of Cheyenne. The GFS does have much more for Larimer/Boulder Counties. As for most of Wyoming to the Black Hills, there is a first storm that is happening right now. So the snow totals reflect both storm systems. Link to comment Share on other sites More sharing options...
smokeybandit Posted March 10, 2021 Share Posted March 10, 2021 Suddenly I want to hug the Euro and not the GFS with its sharp cutoff east of 25 Link to comment Share on other sites More sharing options...
ValpoVike Posted March 10, 2021 Share Posted March 10, 2021 And the GFS this morning must have been offended by our incredulity and added even more QPF to Larimer. Over 8" liquid. Link to comment Share on other sites More sharing options...
mayjawintastawm Posted March 10, 2021 Share Posted March 10, 2021 Anybody who was around in the floods of 2013 see a similar QPF pattern on the GFS with this storm? Seems spooky. Link to comment Share on other sites More sharing options...
mayjawintastawm Posted March 10, 2021 Share Posted March 10, 2021 1 hour ago, ValpoVike said: And the GFS this morning must have been offended by our incredulity and added even more QPF to Larimer. Over 8" liquid. Yeah, a difference between 2" and 4"+ in perhaps 20 miles doesn't make a ton of sense. Would not take this verbatim. You know, I was thinking about what might make models better that would incorporate probabilities and "time to event" that would inject some climatology into the craziness of predicting weather 168+ hours out. The NWS does this in their forecasting, ramping up POPs etc as events get closer. I do some stats in my job but have no idea about complex modeling. Does this ring a bell with anyone? Link to comment Share on other sites More sharing options...
MidlothianWX Posted March 10, 2021 Share Posted March 10, 2021 12z GFS QPF: Denver: 2.3" Boulder: 4.6" FoCo: 5.7" Seems like a pretty harsh gradient. Also, Denver and Boulder flirt with the rain/snow line briefly on Saturday. Link to comment Share on other sites More sharing options...
ValpoVike Posted March 10, 2021 Share Posted March 10, 2021 The Euro just crapped on the QPFs, and the GFS came down a bit too but not as much. Link to comment Share on other sites More sharing options...
smokeybandit Posted March 10, 2021 Share Posted March 10, 2021 At this rate you'll have to go to Wyoming to see the good stuff. Link to comment Share on other sites More sharing options...
ValpoVike Posted March 10, 2021 Share Posted March 10, 2021 15 minutes ago, smokeybandit said: At this rate you'll have to go to Wyoming to see the good stuff. I haven't had a chance to really look at it, but it appears that the Euro is not as deep. Even Wyoming is lower. Link to comment Share on other sites More sharing options...
MidlothianWX Posted March 10, 2021 Share Posted March 10, 2021 Forecast discussion from Boulder: Quote The main event that has caught eye of weather enthusiasts will begin late Friday and into Saturday. It is also when the models begin to have larger disagreements. What models agree upon is that thunderstorms will develop along a dryline across western Texas to western Kansas as a surface cyclone depends over southeast Colorado and northeast New Mexico. Meanwhile, the cut off trough will move slowly eastward providing ample QG ascent for a long duration of moderate to heavy snowfall across much of our forecast area. What the models differ on is how quickly the cut off trough progresses eastward and how strong the upslope flow is. The GFS and Canadian are more progressive with the cut off trough and have stronger easterly winds at 700 and 500 mb meaning there would be better upslope flow. The ECMWF is slower with the progression of the trough and has weaker upslope flow. To give an example of the difference in upslope flow between the models, the 00Z GFS has an area of almost 60 knots of due easterly 700 mb flow across the northeastern plains of Colorado at 21Z Saturday while the 00Z ECMWF has between 25-30 knots of southeasterly flow during that same time. Considering the GFS has 60 knots of upslope flow screaming towards the mountains and foothills with strong warm air advection and QG aloft, it`s not that hard to believe the QPF output near Boulder is around 1.75 inches between 18Z and 00Z Saturday evening. The question is, are the 60 knot easterly winds at 700 mb in the GFS realistic? It seems unlikely. But could the upslope component of the wind be in the 35-45 knot range for a 12-24 hour period? That is much more likely. What peaks my interest is that the model that has the lowest ensemble mean for QPF in Denver is the ECMWF with a mean of 2 inches. That means at this time there are two main solutions, with one being a more intense but quicker moving solution (GFS and Canadian) and the other being the less intense but slower moving solution (ECMWF). With the models becoming more consistent with their solutions, confidence is growing quickly that there will be a high QPF output from this storm perhaps in the 1.5 to 3 inch range for Denver. There is high confidence that snow ratios will be quite low from a climatological standpoint across our forecast area. Soundings show low to mid level lapse rates will be near the moist adiabatic lapse rate while any isothermal layer that develops would likely be above -10 degrees Celsius. In addition, the warm ground temperatures and compaction will aid in lowering snow ratios. It is possible the average snow ratio may end up in the 8 or 9 to 1 ratio with this storm. Therefore, the messaging of 1 to 3 feet of snow for much of our forecast area is still on track. Winds will increase late on Saturday and through Sunday with gusts up to 45 mph possible across the eastern plains near Limon. Link to comment Share on other sites More sharing options...
skierinvermont Posted March 10, 2021 Share Posted March 10, 2021 4 hours ago, mayjawintastawm said: Yeah, a difference between 2" and 4"+ in perhaps 20 miles doesn't make a ton of sense. Would not take this verbatim. You know, I was thinking about what might make models better that would incorporate probabilities and "time to event" that would inject some climatology into the craziness of predicting weather 168+ hours out. The NWS does this in their forecasting, ramping up POPs etc as events get closer. I do some stats in my job but have no idea about complex modeling. Does this ring a bell with anyone? There are models that do this, but it’s a layer on top of the underlying physical modeling Link to comment Share on other sites More sharing options...
skierinvermont Posted March 10, 2021 Share Posted March 10, 2021 1 hour ago, ValpoVike said: The Euro just crapped on the QPFs, and the GFS came down a bit too but not as much. 1 hour ago, smokeybandit said: At this rate you'll have to go to Wyoming to see the good stuff. The gfs ensembles didn’t budge with the 4” from Boulder to cheyenne. Link to comment Share on other sites More sharing options...
smokeybandit Posted March 10, 2021 Share Posted March 10, 2021 Areas the GFS had getting 40" of snow it now wants to give almost all rain to. Link to comment Share on other sites More sharing options...
mayjawintastawm Posted March 10, 2021 Share Posted March 10, 2021 Now might be a good time to take a holistic, Zen-like approach (is that possible here?) and let the atmosphere do what it wants to do for a while before locking anything in. Spring Front Range storms: 1) Quite uncommonly are mostly rain 2) Almost always overperform in the foothills; Boulder County usually wins 3) Seldom leave anybody out completely. Namaste. Link to comment Share on other sites More sharing options...
skierinvermont Posted March 10, 2021 Share Posted March 10, 2021 Wow unbelievably the GFS ensembles bumped another full 1" of QPF from Boulder to FOCO.. 5"+ now on the mean. The mean also shifted maybe 25 miles south, so the north trend is over for the moment. Link to comment Share on other sites More sharing options...
smokeybandit Posted March 10, 2021 Share Posted March 10, 2021 NWS doesn't seem to buy into the GFS hot air Link to comment Share on other sites More sharing options...
skierinvermont Posted March 11, 2021 Share Posted March 11, 2021 1 hour ago, smokeybandit said: NWS doesn't seem to buy into the GFS hot air Yeah I mean until 18z it was shifting towards the Euro. Hoping 00z provides some answer now that the trough is really starting to set up over CA. Big difference between 2" and 4.5" Link to comment Share on other sites More sharing options...
ValpoVike Posted March 11, 2021 Share Posted March 11, 2021 Well, 00z juiced up again. Even the para. Link to comment Share on other sites More sharing options...
mayjawintastawm Posted March 11, 2021 Share Posted March 11, 2021 Just now, ValpoVike said: Well, 00z juiced up again. Even the para. Where do you get your numbers? I can't get anything yet. Link to comment Share on other sites More sharing options...
ValpoVike Posted March 11, 2021 Share Posted March 11, 2021 00z is thru Monday on Pivotal. 1 Link to comment Share on other sites More sharing options...
MidlothianWX Posted March 11, 2021 Share Posted March 11, 2021 QPF totals for 0z GFS: Regular: Boulder: 7.3" Denver: 3.9" FoCo:5.0" Para: Boulder: 5.3" Denver: 4.3" FoCo: 3.5" This run seems a bit colder - I would presume this is all snow. Also, the storm keeps getting pushed back - light snow begins early Saturday, heavier stuff moves in late morning. Link to comment Share on other sites More sharing options...
WeatherEmperor Posted March 11, 2021 Share Posted March 11, 2021 5 minutes ago, MidlothianWX said: QPF totals for 0z GFS: Regular: Boulder: 7.3" Denver: 3.9" FoCo:5.0" Para: Boulder: 5.3" Denver: 4.3" FoCo: 3.5" This run seems a bit colder - I would presume this is all snow. Also, the storm keeps getting pushed back - light snow begins early Saturday, heavier stuff moves in late morning. What am I missing with temps? The latest tropical tidbits looks like a crazy rainstorm over the Denver area haha Link to comment Share on other sites More sharing options...
MidlothianWX Posted March 11, 2021 Share Posted March 11, 2021 25 minutes ago, WeatherEmperor said: What am I missing with temps? The latest tropical tidbits looks like a crazy rainstorm over the Denver area haha You might be right. I could be looking at the wrong data on Pivotal. I'll leave the temp discussion to those who are more well versed in local climo. Link to comment Share on other sites More sharing options...
skierinvermont Posted March 11, 2021 Share Posted March 11, 2021 Thinking Euro will step south with this run looking at 500 thru 48 Link to comment Share on other sites More sharing options...
skierinvermont Posted March 11, 2021 Share Posted March 11, 2021 Eyeballing it looks like the Euro ups the metro from around 1.5" to 1.9". Decent ~50 mile southward shift in the overall QPF field. And the 500mb looked closer to the GFS than it did before. Still need another 50-75 miles south shift to really focus the upslope over the NW metro area. Link to comment Share on other sites More sharing options...
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