Thursday, April 09, 2009

Aerial Views of Red River Ice Jams

See more photos from the Free Press flyover here. (click on full screen view.. excellent images!)


  1. Great inclusion on your site Rob!
    Post more of the same if & when they become avbl.
    Chris in Westwood

  2. Better break out the sun screen tomorrow with a high of 7 C

    14C by next week~~~!!!!!!

    Does anyone have any guess on how much rain we will see on Sunday into Monday????

  3. GLB model has a band of showers moving through Winnipeg/RRV late Sunday into Sunday night, out by Monday morning with about 5-10 mm. GFS is giving us about 10 mm but over a longer time period, while NAM is dry with very little amounts. Ensemble average gives less than 5 mm to Winnipeg for the event. GLB continues to be the most aggressive with upper support for this system while others show weaker support aloft. Based on the look of the system, I would expect marginal amounts of 5 mm or less falling over Winnipeg and RRV, mainly Sunday night.

    Further out, MRF is showing a more southerly track on the April 15-16 system.. with main pcpn impact south of the US border. This is more in line with Cdn and European solutions as well.

  4. By the way, MB Ag-Wx has added real time precipitation on their mesonet website for the 2009 growing season. Handy to keep track of precip amounts in real time. You can access their data on my site under "CURRENT OBS>>LATEST OBS"

    CWB mesonet also very handy to show real time precip amounts.

  5. Rob
    Excellent visual, but ....I notice the hydro towers are missing from the Fort Garry Bridge (Bishop Grandin and Pembina Hwy) Were they victims of the Ice jam??

  6. The NWS yesterday predicted 35mm rain for the Border area between ND and central Sask. as far east as Estevan

    Will that occur in the RRV by Friday.

  7. Not sure about those hydro towers at the Fort Garry bridge.. didn't hear anything about damage there due to ice jams.

  8. Models weaken that system as it moves east over MB.. ensembles giving a 50% chance of 5 mm or more for Winnipeg by Friday, and a 25% chance for up to 15 mm.

  9. First precip chance for RRV will come on Sunday/ Sunday eve. A subtle wave will interact with warm moist advection giving the potential for 10-15 mm of rain in N RRV and interlake region.

    By Monday, southern low starts closing off and moisture gets cut off for us. Tuesday and Wednesday look balmy, as upper ridge gets re-established over us. Warm, moist advection will re-commence into Saskatchewan along an inverted trough. Note that GFS has been consistent with this feature and the resulting QPF fields. We will be under the influence of a drier SE flow and I would expect little precip. Inverted trough appears to wash out as Rob mentioned...

    There after, the GFS and GEM completely part ways. GEM suggests a retrogression and amplification of the blocking pattern... resulting in backdoor cold, dry advection for us and a weaker more southern track for the Colorado low. GFS is more aggressive in ejecting potent low into central/ northern plains with significant QPF brushing S Manitoba.

    In fact of GEM verifies, Eastern Canada is looking at an arctic type outbreak.. So the potential is still there for significant precip next week.. just too early say exactly where.

  10. Are the models to aggressive with the warmth or does anyone see that 17 C is quite possible Tuesday and Wednesday??????

  11. Someone seems to expect a lot of heat as AHPS USGS predict a tremendous spike in water levels (from melting) on the Sheyenne river ..up to 5 feet higher than the record in the heart of the deepest snow in the ND RRV Basin. Thankfully (for GFKS and WPG) this flows south to Fargo

  12. Both GEM and GFS agree on warmth Tues and Wed. Given 850 hPa temps at 6 C and sun... temps would reach 20 C with dry topsoil. However the ground will still be waterlogged so highs in the high teens look good to me.

  13. Nice day in Steinbach, mainly sunny and +11.

    Still some pesky snow lingering around. It will be mid-week for sure until there is no visible snow left and it could be slightly longer than that.

    For the most part, the snow is gone.

  14. Officially 10.1 at YWG at 4 pm... yay!

  15. Daniel...I'll have a respectful disagreement with you on the high for Tuesday. The models show it being +21C in Steinbach, presumably +19 or +20 in Winnipeg. If Tuesday was tomorrow and the models were showing these temperatures, I would believe them. Today for instance, the models had advertised a high of +11 for Steinbach and the actual high was +12. Tomorrow the forecast is for +10, Monday +14, and Tuesday +21. I think the models will be right, since they have been extremely accurate with the temperature lately.

    Today 850mb temperatures were just a shade above zero, about +1 or +2. On Tuesday, the models show a 850mb temperatures of +6 to +8, which nicely corresponds to highs between +18 and +21. Obviously the fundamentals behind the model forecast may change by Tuesday (different upper-air pattern), however I don't think the soggy ground would actually lower the temperature below the NAM's forecast.

  16. Typically looking at the 925 mb temperatures will give you a better estimation of maximum temperature. At 850 mb you can still be influenced by an inversion between 925 and 850 mb but almost always you will have a dry adiabatic profile from 925 mb to the surface during the afternoon. For southern MB adding 6 degrees to the 925 mb temperature should give you an accurate afternoon high. For instance this afternoon the 925 mb temperature is 5C. Add this 6C to the 925 mb temp gives you a high temperature of 11c, which we got to today. Does anyone know where you can find model forecast temperatures for 925 mb?

  17. Scott...

    Never blindly follow model guidance... the past few weeks illustrate why one never should.

    Topsoil moisture has an enormous impact on the amount of surface heating that can take place. The more moist the soil, the more energy that goes into latent rather than sensible heat flux.

    In absence of the most efficient surface heating possible, one requires mechanical turbulence to mix down from 850 hPa... SE trajectory is not very good for this.

    Assuming we did get the best heating/mixing... mixing down 6 C air at 850 hPa along the dry adiabat (1 C/100m)just barely yields 20 C or so.

    Your point on the 850 hPa temps is contradictory. If surface temps are less than 10 C warmer than at 850 hPa today... how does this support your argument for a 15 degree spread on Tuesday?

  18. Anonymous is correct... 850 temps are only a rough estimate for potential highs in the warm season. The real situation is often more complex or subtle. But as anonymous mentions, access to more info is limited.

  19. I agree completely that one should never blindly follow model guidance.

    With my website I have followed the NAM and GFS all winter...both have been terrible all winter, yet I have kept my accuracy rating to 85%. When models start to get on a roll, like they have recently, there is no forecaster that can beat them. For instance...They have constantly been showing low temperatures close to zero (i.e. -2 to -5), while EC and other forecasters have been posting lows closer to -10. Almost every night the models have been correct, and the forecasters have been wrong. Again today the models have been suberb, not being off by more than one degree. Often looking at 850mb and 925mb temperatures is helpful, however looking at the previous day and the temperature trend is more helpful if the pattern is staying relatively constant.

    While Tuesday is still a ways off in model terms, if Tuesday was tomorrow and the forecast was calling for +20, I would believe it 100%. The actual high might be +19 or +21, but that is close enough to satisfy me and most other forecasters.

    Obviously this "debate", if you can call it that, is more about forecasting technique, rather than principle. My bottom line, as I have already stated, is that if Tuesday was tomorrow and the NAM was calling for a high of +20, I would believe it, based on the current trends. However since Tuesday is 3 days away, I am no where near prepared to call that my official forecast. If on Monday night the models still show a high of +20 for Tuesday, that will be my forecast.

    Models can be like the stock market...sometimes you have to ignore the company and follow the trend.

  20. First of all, the models have not been on a roll lately. The models are having all kinds of trouble resolving the complex blocking pattern that is evolving. Temperature guidance is performing better now because most of the snow cover is gone.


    "Often looking at 850mb and 925mb temperatures is helpful, however looking at the previous day and the temperature trend is more helpful if the pattern is staying relatively constant"

    ...but how do you determine if the pattern is staying constant without doing a thorough analysis of 850/925 hPa temps or soil moisture conditions? A proper analysis is the key to any good forecast.. not just what NAM or whatever model you think is hot at the time says.

    If a model outputs something which does not look right, one is obligated to question it. At the very least go back to your analysis and see how that particular model is initializing.
    You should always look at other guidance to see if it has a better handle on the situation.

  21. "First of all, the models have not been on a roll lately."

    The models haven't been on a roll in terms of tracking weather systems and forecasting QPF, etc, however they have been on a roll with forecasting temperatures, which is what I was referring to. Snowcover or no snowcover, the models are handling temperature well.

    "...but how do you determine if the pattern is staying constant without doing a thorough analysis of 850/925 hPa temps or soil moisture conditions?"

    I don't really know how to explain the way I determine whether the pattern is remaining relatively constant. Right now temperatures are in a gradual increase trend (with the exception of Sunday), which I expect to continue into next week. I do use the 850mb temps and sometimes the 925mb temps, but they aren't a make or break part of my analysis.

    "If a model outputs something which does not look right, one is obligated to question it. At the very least go back to your analysis and see how that particular model is initializing.
    You should always look at other guidance to see if it has a better handle on the situation."

    I constantly question model outputs. If I may brag for a second, that is the reason my website has been so successful in the past year(s). I also use as many as four or five model outputs for each forecast. I never use less than three models.

    Once again I'll just state that this conversion has more to do with technique than principle. In my opinion there is no right or wrong way to make a forecast. I believe that using the method which yields the most accuracy is the best and that is what I am doing. I think it is good that both of us use different methods, otherwise there would be no fun in predicting weather because all of our forecasts would be the same.

  22. Well let me interject while you are bragging about your site...

    Where is your discussion on the evolution of this whole pattern? You have steered well clear of this and have chosen to 'cherry-pick' a narrow topic.

    I am interested in hearing Rob's (or any other meteorologists) opinion... would you be hesitant to forecast highs of 21 C given the following:

    i) 850 hPa temps of 6 C,
    ii) SE wind
    iii)current surface conditions

    I look forward to hearing other views.

  23. Good discussion on temperature forecasting! Everyone makes good points. As anonymous and Daniel have mentioned, there is more to temperature forecasting than going with model guidance, no matter how well it may be doing! One should always use models to support one's forecast based on sound analysis and diagnosis. That being said, Scott is correct in noting that it is becoming increasingly difficult to beat model temperature forecasts for Day 1. Not to say it can't be done, it's just that opportunities to improve on model temperature forecasts in the short term are becoming less frequent as models and algorithms improve.

    Adding 10-12C to the 850 temperature works well in a dry snow-free environment here in southern MB, (sometimes up to 15C in a very dry environment) but if there's a lot of low level moisture (including moist soil conditions), or low level inversions, snowcover, etc. then the relationship doesn't work as well. In addition, you have to see where the source region of the airmass is.. a southerly valley wind in Winnipeg coming out of a snowcovered North Dakota will keep our temperature down even though 850 temperatures may be rising over us. Downslope flows will add 2-3C in places to the lee of the Pembina escarpment or the Riding Mtns. Sometimes model guidance will fail to pick up on these subtleties that human forecasters can pick up based on experience.

    Personally, based on current model data, I see 16-17C for Winnipeg on Tuesday. 20C seems a bit of a stretch given the moist low levels and lack of a favourable downslope west to southwest flow for us, but I won't be too upset if I'm proven wrong :)

    Anyways, nice to see us debating whether it's going to be 15 or 20C, rather than 15 or 20 cm!

  24. I agree, it is a good debate and thanks for helping to clear things up Rob.

    I look forward to hearing predictions on Monday evening.

  25. I'm looking forward to my first rumble of thunder!!!!!

    I see there is a chance of showers and rain tonight!!!!

    Any remote chance of a thunderstorm?????

  26. Rob ...Do you agree with the TWN pcpn forecast From Wednesday to Sunday of 23 to 34mm or (30 to 40 mm if you count 1 cm on Saturday) or is it too far out??

  27. Based on current models, those numbers look on the high side for Winnipeg/RRV for Wed-Sat. Models indicate there will be rain over southern SK/SW MB along an inverted trof (maybe 15-25 mm), then the main energy with this system shifts south bringing the bulk of pcpn over the Dakotas Thu-Sat. Still too early to say for sure though as this will be a complex slowly evolving system. FWIW.. current ensembles give a 50% chance of up to 10 mm for Winnipeg with this event, and a 25% chance of up to 20 mm.

  28. Well, looks like two days of double digit temperatures and now some rain has pretty much got rid of the snow in Winnipeg. Still plenty of snowbanks left in residential areas, but in general, I think we can say Winnipeg is generally snowfree as of April 12th. So I'll consider April 7-14th as the correct answer to the latest poll question. (FWIW.. I chose April 14-21)

  29. Rob!!!
    Does that mountain of dirty snow in the shopping center parking lot count as "snowpack"????? LOL

  30. Does anyone see the potential for any daytime heating type thunderstorms for tomorrow???

    With this departing rain system and with the colder air aloft with the warm April sun....any chance of a few thunderstorms "popping" up??

  31. Looks like EC is calling for a high of +16 tomorrow. That high sounds good to me, as models have been trending downward will temperatures over the past few days. However I wouldn't be at all surprised if some places hit +18, assuming we have sunshine for most of the day.

  32. I don't see much convective potential for tomorrow. Mid level temps should warm ahead of a disturbance off to our NW.

    Saskatoon punched up to 20 C this afternoon as they tapped the warm sector of that Alberta system. Temps shot up with good mixing and very dry air in SW flow. 850 hPa were depicted at around 10 C by RUC in those areas.

    850 hPa temps are progged at 4-6 C over RRV/SE Manitoba tomorrow with SSE surface flow. Wildcard is amount of cloud cover... both left over stratus and mid level clouds associated with lift/ warm air advection of a strengthening southern system.

    EC sky cover model shows fairly clear skies south and east of Winnipeg.. therefore I think 16-18 C is a good guess provided we do not get more cloud cover. The higher values are possible in the pine covered sandy ridges east of the RRV... the dark surface area provided by the trees and rapidly draining soils should allow for better surface heating.

    Wednesday actually looks like the warmer day to me.. 850 hPa temps warm to at least 8 C and trajectory looks a tad more favorable for mixing. I think some areas have a shot at 20 C provided clouds from advancing inverted trough stay away long enough.

    GFS is more aggressive in slumping inverted trough thru us by overnite Wednesday and shows significant QPF. GEM is much slower with this feature keeping us in a southerly flow until early morning Fri. GEM also weakens precip by the time trough reaches RRV.

    Models still all over the place with the evolution of main Colorado low as it slowly ejects out later in the period.

  33. Break out the sunscreen and swimming gear it nice and balmy out there!

    It is amazing how warm 15 C feels after a long winter!!!!!

  34. Amazing being able to go out with only a light jacket...

    Highs around 16 C this afternoon. Note that 850 hPa temps are depicted as high as 7 C for Winnipeg on RUC sounding. Light SE flow and low level moisture (surface td's as high as 8 C)inhibiting heating/mixing.

    GFS now proggs 850 hPa temps warming only slightly.. with a similar light SSE flow. As a result I think highs around 17 C are a good bet tomorrow.

  35. Note also that clouds may be on the increase tomorrow. I think we should be able to reach that high before the clouds move in.

  36. Interesting to note a band of higher dewpoints of 10-13C along the western RRV from Gretna to Portage.. coincident with a deck of fog and stratus this morning. Temperatures in this area were a couple of degrees cooler than the rest of southern MB today, around 13-15C this afternoon while most other areas got to 16-18C. This shows how low level moisture will cut down on the amount of heating available to warm the air. Could see some thick fog redeveloping in this area again tonight.

  37. Very interesting indeed. SE winds are a cool upslope flow for these regions. Pooled surface moisture is seemingly trapped beneath an inversion or isothermal layer. Big contrast from when a SW flow is present, and these areas benefit from enhanced mixing as Rob mentioned. If fog/stratus form tomorrow... it may not burn off before higher level clouds advect from the west.