Tuesday, April 27, 2010

Wet weather finally moving into southern MB..

Our dry April will end up on a wet note as a complex storm system over western North America slowly pushes eastward over the next few days. This storm system will spread an area of showers into southern Manitoba Wednesday night into Thursday with some isolated thunderstorms possible. Rainfall amounts will likely be in the 5-15 mm range with this first wave of precipitation. There should be a break in the rain Thursday night into Friday morning before another wave of precipitation moves in Friday afternoon into Saturday as an intensifying low pressure system moves through North Dakota and southern MB. There is the potential for heavy rain and strong winds over portions of southern MB with this second wave of precipitation Friday night into Saturday, with even the chance of some wet snow mixing in on the backside of the system as colder air wraps in. All in all, it looks like some much needed precipitation will finally be arriving over southern MB between Wednesday night and Saturday, our first significant rainfall event of the season. Cooler unsettled weather is expected behind this storm system for the first part of May.

51 comments:

  1. Hi ROB!

    Thanks for all the hard work in keeping us all informed on the upcoming storm!!

    Finally something exciting to talk about!!

    I have a feeling this storm is gonna be a good one....
    I'll be looking forward for thunderstorms tomorrow night!!

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  2. Well, if you believe the Canadian GLB model from last night, southern MB is in for a major soaking Friday into Saturday as they intensify and stall a deep low pressure system over North Dakota. They show a good 30-50 mm of rain over much of southern MB along with strong winds. Just miserable. On the other hand, the GFS and ECMWF are not as intense on Friday's low and are more progressive, tracking it into Northwest Ontario Saturday with less rainfall over southern MB as a result. Who's right? Who knows. But the development and track of this North Dakota low on Friday will be the key as to how much rain we actually get during this event. For now, we'll stick with the ensemble estimate of 20-30 mm for the RRV area between Thursday and Saturday.

    By the way, the last 2 days of the forecast (days 6 and 7) continue to show an awfully optimistic bias with sunshine and temperatures in the upper teens. The upper pattern would suggest a cooler and cloudier outlook.. with high temperatures more in the 10-13C range. Note yesterday, the Day 6 forecast for Sunday was calling for a sunny high of 14C in Winnipeg.. today, the Sunday forecast is now a rain/snow mix with a high of +5C. Note that the last 2 days of the forecast (day 6-7) are based on an ensemble model, while the Day 3-5 forecast is based on the GLB model. This can sometimes lead to significant inconsistency issues between the two forecasts if the driving models are at odds with each other.

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  3. Models still having hard time handling track and evolution of second low. However GFS, NAM, and GEMGlobal all agree on slug of precip associated with secondeary low coming up from Central Plains Thursday morning. Instability looks unimpressive as warm moist advection/ LLJ is focused SE of us. Evolution of deformation zone and steady, soaking precip dependent on low track as mentioned. GFS now shows a less progressive track up thru Manitoba. In this case deformation zone would retrograde NW and we may be influenced by dry slot before more precip wraps back in.

    Still a lot of uncertainty like always when there is a transfer of energy between two systems. Not only between the Alberta and Central Plains lows but also from a potential transfer to a third low which would tap moist advection regime off to our SE. Models depict second low suddenly jumping into Ontario... from past experience this is sometimes a hint of energy transfer to a nascent system tracking further SE.

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  4. If you take the average of the 12Z GEM, the 18Z GFS, 18Z NAM and the 00Z foreast by the HPC (QPF), you get 30 to 40mm of precipitation for virtually any point in southern Manitoba. The highest amounts are from the GEM, generally 40 to 50mm, while the lowest are from the HPC, at 10 to 20mm in general. The GFS and NAM fall somewhere in between. Also note that these number are total accumulations for the next 84hours. The GFS gives more precipitation past 84 hours, but that isn't included in these numbers.

    As a result of these average amounts, I voted for 30 to 50mm in the poll. I think 20 to 30mm could also win, but it will probably be at the high end of that (near 30mm).

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  5. The first showers have arrived. -shra started at 18:25hrs local time in the Silver Heights area of Winnipeg. Cvctv cld passing ovhd, trace of pcpn so far.

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  6. Narrow band of showers moving through this evening won't amount to much.. maybe 0.5 mm or less. I'm surprised they even reached the ground given the dryness of the low levels, but they were heavy enough to avoid evaporation on the way down.

    After this band moves through, looks dry for awhile before another band of showers over ND moves in overnight into Thursday morning. Showers and possible thunderstorms increase over southern MB Thursday afternoon into Thursday night with a good 10-20 mm possible before heaviest area of rain moves into interlake and southern SK on Friday as main low drifts over southern MB. We dry slot somewhat on Friday over RRV/SE MB with some scattered showers possible before wrap around rain works in Friday night into Saturday with another 5-10 mm possible. I went for the 20-30 mm selection, but this could be on the conservative side. We'll see how this unfolds..

    By the way, the Nipher snow shield was removed from the Winnipeg airport rain gauge yesterday, so rainfall amounts from the airport should be accurate with this event.

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  7. Rob!

    Sounds like Calgary is really gonna get a good snow storm out of this one!!!

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  8. Rob!

    I wonder why the winds were so much stronger today in Portage La Prairie
    than they were in Winnipeg???

    hmmmmm....?????

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  9. I was in Miami (MB) this afternoon (first showers btw 4:45 5:30) The winds were howling until after that first shower. We reckoned a two club wind and est'd 30 to 40K although one golfer was sure it was at least 50 with higher gusts. No anemometer in my golf bag LOL

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  10. The latest GFS is now falling in line with idea of very heavy rainfall and strong winds again!

    40 mm storm TOTAL almost looks certain!!!

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  11. Miami is due South of PLP. The Golf Course is 2k West of town and only a few km to the Manitoba Escarpment which might account for the winds.

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  12. How many times since the end of January have we pondered the imminent arrival of one of these systems only to be disappointed and ask.

    What have we done that ZEUS ignores us.

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  13. Curious Gal....

    I have a feeling this storm has it's sights set on Southern Manitoba!!!

    Red River Valley might be the
    Bulls - eye .

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  14. Precip amounts are tricky because they depend on a couple of things:

    1) How much embedded convection there will be within initial surge of moisture coming up with plains low. Best warm/moist advection looks to be further east but I suppose some elevated instability may bleed into our region.

    2) How far north and quickly will dry slot back in from SE and shut down precip over us.

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  15. Well, no rain overnight and radar looks awfully quiet throughout southern MB and ND this morning. There is some convection over northeast South Dakota, and this activity is expected to push into the RRV this afternoon into this evening, with 10 to 20 mm possible in this first wave. That however will be highly dependent on how much convection fires up as Daniel noted, but dynamics look good for getting something. We then get a break in the dry slot overnight through Friday, although you can't rule out a few scattered showers in the dry slot.. before wraparound rain moves in Saturday and Sunday. Overall, the 20-30 mm still seems reasonable for us between today and Saturday, but amounts could be lower if the convection today isn't as strong or misses us.

    And lo and behold, sunshine and 20 degree temperatures predicted on the last 2 days of the forecast again! Monday's projected high of 18C is now down to 7C! The ensemble model that EC uses for Days 6 and 7 appears to be having some difficulty adjusting to the pattern change expected behind this storm system for early May. Other model and ensemble guidance indicate highs no better than 15C through the first week of May over us. So for the time being, I would suggest treating the temperature guidance for Days 6 and 7 as suspect, and to consult other forecasts for second opinions.

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  16. 06Z NAM has backed off on amounts significant, it now shows only 10 to 15mm for most of southern Manitoba. However, the 06Z GFS and GEM are still quite heavy with precipitation, showing 25 to 40mm for SC and SE MB. The ensemble is giving a near 100% chance of more than 25mm between now and Monday, so a storm total of 30mm still looks likely.

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  17. Rob Why do the local Wunder Local Precip Map page stations Forks CXWN and a few others in southern MB (all "C's) show precip on the map of 10X the adjacent stations winter and summer?

    Fortunately ECs records don't reflect this.

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  18. Jim..

    Not sure why that is happening. Obviously some sort of coding error with the data sent to Weather Underground.. but I wouldn't know where the error source is. For a great map showing detailed station data, go to www.weatherfarm.com, and sign up with a free account. This is a site for Weatherbug data. Under the live data window, click on "analyze weather in your region" and it will display all Weatherbug data, including rainfall totals. They also display some EC and MB Ag data. Very handy.

    As for us, the rain is spreading northward throughout the RRV this afternoon pretty much as models advertised. Rainfall amounts of 2-5 mm over southern RRV as of 1 pm according to Weatherbug mesonet, with rainfall rates of about 1-2 mm/hr.. not heavy by any means, but a nice steady rain. Heavier rain falling south and east of Grand Forks moving north.. will likely spread into RRV and southeast MB this afternoon into this evening.

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  19. But, are we even going to get more rain after this? Everyone drastically changed the forecast, now only a slight chance of showers over next few days... Ugh, starting to say, so much for this storm! =Þ

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  20. Jewels, Address your Ugh to Zeus. Nothing else is working. lol

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  21. Thanks ROB. Helpful tool as they Hi-lite, and then supress info from those sites whose results are o/s sensible limits. eg(MAFARI)

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  22. Looks like another good band of pcpn pushing up from Steinbach. Total pcpn at my place - as of 6pm Thursday - 10.8mm.

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  23. Steinbach has received about 14mm so far.

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  24. Expect another 5 hours of steady rain which will push us close to 15 mm by nights end!!!

    Everything is already greening up!

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  25. Environment Canada forecast is calling for rain to end early this evening!!!

    I see no end in the rainfall until sometime overnight!

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  26. A general 10-15 mm over Winnipeg up to 9 pm with up to 20 mm over the southern RRV and parts of SE MB. Steady rain should continue for the next several hours with another 5 mm or so before it tapers off overnight. So looks like a general 15-25 mm over the RRV and SE MB with this first shot of rain. Things dry out for Friday as we get in the dry slot, although conditions will be unstable enough for some scattered showers and possibly a thunderstorm if we can get some sunny breaks. Some additional rain is likely this weekend in the wrap around behind this storm system (perhaps another 5-10 mm), with even some wet flurries possibly mixing in by Sunday morning. Overall, models overdeveloped the second phase of this system early on before getting a better handle on it in later runs.

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  27. 15.2mm up to 10:30pm this evening in Steinbach. I expected 10 to 20mm during the day on Thursday, then another 5 to 10mm overnight, which is right around what we should receive. It would take another 10mm over the next two days to hit the 30mm window that I was talking about before.

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  28. Rob!

    Any chance of seeing thunderstorms this afternoon in Southern Manitoba??

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  29. There's a chance of some isolated thunderstorms popping up in the dry slot that has cleared skies this morning over SW MB and central ND. Shear isn't that impressive and instability is weak, but there's enough low level moisture and a frontal trof that may kick up some weak tstms in that area. As for Winnipeg, I think we'll stay too cloudy and cool to see any thunderstorms forming over us.

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  30. Looks like Round 2 of the rain is set to settle into Southern Manitoba
    by afternoon!

    Another 10 mm????

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  31. Ooo. Some storms in ND developing. We finally get to see some action after boring April. =Þ Probably miss Winnipeg =,(

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  32. Jewels !

    I see those storms in North Dakota have very little motion to them.

    The chances of those storms hitting Southern Manitoba are slim to none!

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  33. Winnipeg right between two areas of precip right now.. the 'rain gods' not smiling down on Winnipeg lol. Lets see if radar fills in a bit more.

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  34. Temperature falling to 5 C tomorrow afternoon for Winnipeg.

    Break out the parkas!!

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  35. Looks like we might be getting April in May and we just had our May in April....LOL

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  36. 23.1mm storm total in Steinbach up to 5:30pm today.

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  37. Strange, where I am in south end, just got 3 heavy downpours of rain past hour, though, only light blue on the radar. 6 mm so far this afternoon, a good 3 mm past hour.

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  38. Rain has really picked up here is St James in the past hour or so !!

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  39. Approaching 30mm in Steinbach. Water is starting to collect on the surface, which isn't good. The last thing we need to go from extremely dry conditions to extremely wet conditions!

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  40. 8pm Friday, storm total is now 28.2mm in the Silver Heights area of Winnipeg. I had voted for 20-30mm on Rob's poll...looks like I will be wrong this time. Doing wonders for my lawn though!

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  41. Dan !

    28.2 mm and looks like a batch of heavier rain is just south of the city with another quick 5 mm

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  42. SPC has issued a high risk for storms in the U.S

    Tornado outbreak underway!!!

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  43. Ya, storms galore right now there!
    This storm will probably bring April rain totals above normal for us! Hides the fact that almost the whole month was very dry.

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  44. I was just thinking every precip event we've had since December have all had the exact same radar signiture. Moisture has come from the south east in reverse rotation. It may have been even longer but I can only remember from when the snow started. The radar signiture could pretty much be a rerun.

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  45. Officially, Winnipeg airport has picked up 26 mm of rain since Thursday.. with 28 mm at the Forks. I don't think we're going to see too much more today, with maybe another 2-5 mm by midnight, so looks like 30 mm rainfall totals will be the final tally for Winnipeg to midnight tonight. There has been heavier amounts reported nearby with 43 mm reported so far in Landmark, southeast of Winnipeg. Ironically, this rainfall puts our monthly pcpn total for April a little above average, even though we went almost the entire month with no rain!

    By the way, April finished with a mean of 8.4C in Winnipeg, tied with April 1906 as our 8th warmest April since 1872. Just 4 years ago in 2006, we had an even warmer April (9.4C), our 2nd warmest April ever. Warmest April on record in Winnipeg was in 1915 (9.5C)

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  46. Rob!

    Tuesday/Wednesday system looks like it will have a nasty bite to it!!

    I have feeling this could be a snow producer!!!

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  47. Chris - Windsor Park10:27 AM, May 01, 2010

    Indeed it looks as though we will be experiencing April weather in May. The ECMWF for North America shows a pattern change at least through till the 3rd week of May.
    Chilly and unsettled are a couple words they use.
    ECMWF was pretty much in the ballpark for predicting April's weather, here's to hoping it is wrong for May.

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  48. A bit off topic, i just wanted to say I just noticed that this April, we broke the record of having the earliest overnight low that was warmer than 10°C! (April 14th)

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  49. 33.5mm storm total so far in Steinbach. This is more or less in line with the average amount that I calculated back on Wednesday (35mm). The NAM is second best, having predicted 33mm for Thursday, Friday, and Saturday combined.

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  50. As of 2:40pm Saturday, the storm total (Thurs onward) for Silver Heights Winnipeg is 31.8mm. There is a bit of cvctv stuff about, so a few more shwrs can be expected.

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