Sunday, May 17, 2009

Enjoy today.. sharply cooler tomorrow

Today will be the mildest day of the holiday weekend as gusty southerly winds push temperatures up to 18-20C over southern MB with morning sunshine giving way to high cloudiness during the day. A southerly breeze will keep temperatures mild tonight, with lows of 10-12C . Early Monday however, a sharp cold front will sweep across southern MB from the north, bringing strong northerly winds and falling temperatures. In Winnipeg, the front is expected to pass through between 5 and 8 am, dropping temperatures from sunrise values near 12C to about 5C during the morning, remaining steady or recovering only slightly in the afternoon. This will lead to a widespread frost Tuesday morning across southern MB with morning lows of –2 to -5C likely under clear skies and light winds.

Cooler than normal weather is expected for much of the upcoming week with showers possible Wednesday. The good news is that long range guidance is finally indicating a nice prolonged warmup by next weekend with temperatures in the 20s, hopefully taking us through the end of May.


  1. .....and early this week the Winnipeg floodway will honor all those extreme weather events of the last 6 months by remaining open for the longest period in its history (43-44 days in 97) This occurs less than 6 months after it last closed in November the shortest winter shutdown in its history.

  2. Hey Rob

    Just looking at the radar and using the weather net radar that shows the projected rain fall it looks like around midnight we should be getting rain in Winnipeg and north of us tonight. Forecasters don't really say anything about rain. Am I missing something?

  3. Another cold front coming in tomorrow!
    Then a 1 day warm up....then another cold front!

    I just wish we can break this weather pattern and get into a extended "hot" weather!

    By the sounds of it I won't have to wait much longer.

  4. Daryl..

    Looks like most of that activity on radar is aloft, and drying out before it hits the ground (known as "virga") There may be a sprinkle of two north of us, but most of the pcpn should bypass us. There is precipitation further northwest over central SK that is reaching the ground, and that will spread into areas north of Winnipeg overnight.

  5. Oh I see. How far North is the moisture going to go are we talking Selkirk or further North than that?

  6. Here comes the cold air.. as of 8 am it's 13C in Selkirk, but drops to 6 C in Gimli. Large area of cloud moving in from the north will herald arrival of cold air with gusty north winds. Should be arriving in Winnipeg within the hour.. then say goodbye to sunshine and double digit temps.

  7. The models show an intriguing scenario for tomorrow night (Tuesday 06Z). A very strong LLJ will push 850mb tds to between +10 and +14C over the northern plains and southern Manitoba. This will create MLCAPE values between 1000 and 1500 J/kg south of the Trans-Canada.

    Helicity values will be extreme and shear is good at all levels. The main downfall is the temperature. Tomorrow at 06Z the surface temperature will be around +10. The temperature at 850mb will be slightly warmer. A warm front moving in overnight may serve as a trigger for storms. Since there is no capping, we may see elevated storms, certainly not surface based.

    If the surface temperature was higher, this is a sort of a MCS setup. However I don't know how things will react with colder will bear watching.

  8. Rob can you provide an explanation for why we have been below normal temps for so long and keep getting hit with cold front after cold front? Your insight always is appreciated and helpful. Thank you

  9. The simple answer is that the jet stream, or storm track, has been suppressed mainly south of us or over us for the past few months (actually for the past year and a half), which has kept us cooler than normal much of the time as we tap cooler air to the north more frequently than not. We occasionally bump up to near or above normal, but those episodes are of short duration as one cold front after another brings back the cool air for several days from the ever present Arctic airmass that is hovering just north of us.
    This month will mark the sixth consecutive month below normal, and 12th of the past 16 months that have been below normal. Only the 4 months from Aug - Nov 2008 were above normal.

    One could blame "La Nina" for this suppressed jet stream which is characteristic of a La Nina pattern. But there have been other La Nina episodes where we've been above normal for long periods, so there must be other climatic factors in conjunction with the La Nina that has made this year's below normal weather so persistent. That however gets into more complicated climate theory which is beyond my area of expertise.

    As of last month, they officially declared that this latest La Nina event is over and that the Pacific has entered an ENSO-neutral phase (i.e. no La Nina or El Nino) Hopefully this will allow the jet stream/storm track to assume a more normal position over the next few months and allow more prolonged episodes of seasonal or above seasonal weather over the southern Prairies. Sure hope that happens as this cool weather is really getting tiresome..

  10. A good example of how warm weather is being suppressed south of us.. 34-37C heat over southern Minnesota and southeast SD today!

  11. Thanks for your reply Rob. Always appreciated and always written in a clear and knowledgeable manner

  12. Looks like some thunderstorms are trying to form this morning!

    They re-issued there forecast stating that there is a 60% of thunderstorms!

  13. Second day of RECORD heat in Minnesota !
    Minneapolis hit 97 F yesterday which was a record!
    Today ....ummm looks to be about
    94 F

    Meanwhile we are socked in with the low clouds and rain showers....

    What's new!

  14. Our turn for hotter/humid weather will be next weekend (end of the month).

    Temps, Dewpoints and CAPE values will be on the climb starting Wednesday the 27th...

    In the mean time...the change towards normal temperatures looks to begin this weekend sometime! With the warm air probably establishing itself for Sunday pm.

  15. Justin/ Daniel

    Am I accurately reading the Radar ..will that rain hold off Charleswood Headingley from 3pm to 8pm tonight??


  16. Winnipeg is pretty much out of the rain as of 3pm as the low departs into Northern Minnesota/NW Ontario...

    The back edge of the main area of precip is over the Whiteshell area...

    You should be good!

  17. Could anyone provide an explanation as to why Thunder Bay is so warm today (30C!)....According to EC, temperatures rose from 16C to 28C in one is that possible? Strong warm front or what?

  18. Today's scenario was actually fairly well depicted by models last week before they flip flopped significantly. Main difference is warm front set up further south with continental tropical air staying off to the SE.

    Interesting to note the sudden intrusion of warm mid level temperatures acting to cap most convection south of us. Even elevated storms could not get going with good moisture only at mid levels and up. Trajectory of LLJ was mainly SW.. again not good for moisture return.

    As previously mentioned, given the amount of warmth building (including mid-level cap) to our south and a shift towards an upper ridge over the western prairies (and NW over us) precip chances look scant until the very end of the extended outlook (first days of June). At that time we will finally get back into a SW flow and moisture return on the back side of that upper ridge.

    Previous droughty summers have been characterized by anomalous upper ridges remaining anchored over Western Canada (1988 and 2006). Lee troughs and LLJ occurrence are suppressed leading to prolonged dry, sunny periods.
    Often there is also a noticable extension of high pressure back along the gulf cutting off low level moisture return (just like today). It is interesting to note that 1997 was a very warm, dry summer after a sudden pattern change in early June.

    We'll have to see if models remain progressive on the movement of the upper ridge... or if that SW flow can persist. Just too early to say yet.

  19. Daniel .. Given your analysis how does TWN arrive at occasional showers totaling 40 to 50mm for Sunday..and steady RAIN on Monday totaling 10mm..Are they late on their online updates?
    They appear to hsve had some major reality differences lately (or do they have typos) Link on my name..

    JUSTIN ...thanks for that confirmation..That big flag NNW of you and just South of the river was bathed in ggreat weather all afternoon.

  20. Jim...

    Those precip may be based on GEM guidance which is very wet with a system moving up from the central plains. However the latest 0000Z run of GEM Global keeps the bulk of the precip off to our SE.

    Interestingly... GFS has now picked up a QPF bullseye over us as well. The model is generating a MCS on the nose of a 40 kt LLJ and riding it along the 850 hPa warm front overnite Saturday into Sunday. There will also be a right entrance region of upper jet around. I think that represents the best chance for precip over Winnipeg if the complex can hold together Sunday during the day.

    QPF on GEM and to some extent on GFS seem overdone after this point. Both models put down a heavy swath of precip from the Black Hills of S Dakota to International Falls along the front stalled to our south.

    Moisture looks a bit better than today.. but the key will be much cooler mid level temps which will lead to greater instability. The catch is, dynamics will be lacking with only a few subtle shortwaves and a disorganized LLJ. This might be a case of 'convective feedback' ... but we will see.

  21. Daniel
    What I'm hearing is that 5 day QPF is about as accurate and together as the 5 day Hurricane predictions...

    It is the same thing n'est pas?

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  23. QPF should be taken with a big grain of salt. Precipitation results from the interplay of many different variables (moisture, lift, saturation, instability). Therefore an accurate prediction is difficult especially when convection is involved.

    Btw.. GFS at least hints at some showers early tomorrow morning associated with disturbance moving in from Saskatchewan. Moisture return looks limited tonite and LLJ remains weak and disorganized.. wouldn't expect more than a few sprinkles.

    By tomorrow, the American RRV will once again tap the warm sector of the system before the associated cold front slices thru. Cold pool settles back in over us for Saturday.

    Moisture return commences again on Saturday nite. As mentioned previously, GFS depicts an MCS rolling thru SE Saskatchewan and SW Manitoba. Yet again, the warm sector will elude S Manitoba with front stalling off to our SE. I still think QPF amount and coverage is suspect given orientation of LLJ and front. Surface based convection does not appear likely either with best SBCAPE staying will to the south... Rob, any thoughts?

  24. Yes, models have been having difficulty with impulses and convection over northern Plains/southern Prairies through the weekend into early next week, especially the Canadian GLB which has been most aggressive with convective QPF pushing all the way into southern MB Sunday night into Monday. As you say, upper dynamics weak and surface moisture will be better further south. My feeling is that there will be an area of showers and thunderstorms over SD Sunday spreading into ND with some activity possible over southern MB later Sunday into Sunday night. Models hint at more extensive moisture spreading into southern MB next Monday with 700 mb low moving across MB/ND border.. but confidence is low at this point. As mentioned, model QPF with convection is always suspect..

  25. Rob
    Are the cold(MEAN) Temps this month due to the Excessive soil moisture conditions. See Mean Temperature and Pcpn Anomalies, (OR)Are the inverse similarities of the Soil Moisture (Palmer Drought Index)and the Month to Date temperature Anomaly Maps of the US.. cause amd effect or coincidence.


  26. Daniel// Rob ... Those QPF numbers have had me twisting in the wind for weeks. Glad you picked up on my error.. confidence level not accuracy.