Hot and humid weather over southern MB today along with an approaching trough of low pressure will set the stage for the development of some strong thunderstorms this afternoon.. some of which may reach severe limits. A severe thunderstorm is defined as a thunderstorm producing one or more of the following..
- hail of 2 cm or more (nickel size or greater),
- wind gusts of 90 km/h or more
- rainfall of 50 mm in one hour or less, or 75 mm within 3 hours
- tornadoes
Today's thunderstorms will likely be slow moving storms given a weak flow aloft, so heavy rainfall will be the main threat, although some storms could produce nickle to quarter size hail given the instability levels. Storms are expected to develop over western MB this afternoon ahead of the low pressure trough, and move into the Red River valley by evening before dissipating tonight. Stay tuned for updates and possible watches and warnings on today's weather..
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ReplyDeleteWWCN11 CWWG 181534
SEVERE WEATHER BULLETIN
ISSUED BY ENVIRONMENT CANADA
AT 10:34 AM CDT THURSDAY 18 JUNE 2009.
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WATCHES/WARNINGS IN EFFECT FOR SOUTHERN MANITOBA...
SEVERE THUNDERSTORM WATCH FOR:
=NEW= SELKIRK - GIMLI - STONEWALL - WOODLANDS - ERIKSDALE
=NEW= PORTAGE LA PRAIRIE - HEADINGLEY - BRUNKILD - CARMAN
=NEW= MORDEN - WINKLER - ALTONA - EMERSON - MORRIS
=NEW= BRANDON - CARBERRY - TREHERNE
=NEW= DAUPHIN - ROBLIN - WINNIPEGOSIS
=NEW= MINNEDOSA - NEEPAWA - RUSSELL - RIDING MOUNTAIN NATIONAL PARK
=NEW= KILLARNEY - PILOT MOUND - MANITOU
=NEW= MELITA - BOISSEVAIN - TURTLE MOUNTAIN PROVINCIAL PARK
=NEW= VIRDEN - SOURIS
=NEW= STE. ROSE - MCCREARY - ALONSA - GLADSTONE
=NEW= ARBORG - HECLA - FISHER RIVER - GYPSUMVILLE - ASHERN.
STRONG THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AS A TROUGH OF
LOW PRESSURE MOVES ACROSS SOUTHERN MANITOBA.
THIS IS AN ALERT TO THE POTENTIAL DEVELOPMENT OF SEVERE
THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS.
MONITOR WEATHER CONDITIONS..LISTEN FOR UPDATED STATEMENTS.
IF THREATENING WEATHER APPROACHES TAKE IMMEDIATE SAFETY
PRECAUTIONS.
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==DISCUSSION==
A TROUGH OF LOW PRESSURE MOVING INTO WESTERN MANITOBA LATE THIS
MORNING WILL INTERACT WITH A WARM, HUMID AIRMASS OVER THE SOUTHERN
HALF OF THE PROVINCE. THUNDERSTORMS ARE EXPECTED TO DEVELOP EARLY
THIS AFTERNOON ALONG THE TROUGH AND SLOWLY PROCEED EASTWARD
THROUGHOUT THE DAY. SOME OF THESE STORMS WILL LIKELY BE SEVERE...
PRODUCING STRONG WIND GUSTS, LARGE HAIL, AND TORRENTIAL DOWNPOURS.
THE STORMS ARE EXPECTED TO REACH THE WINNIPEG AREA LATE THIS
AFTERNOON OR EARLY THIS EVENING, THUS THE WATCH WILL LIKELY BE
EXTENDED TO WINNIPEG AND AREAS EAST LATER THIS AFTERNOON.
PLEASE REFER TO THE LATEST PUBLIC FORECASTS FOR FURTHER DETAILS.
END
Nice little cell has popped up in the Interlake east of Gypsumville on what appears to be a lake breeze boundary.
ReplyDeleteI suspect PASPC will release a balloon today to get a better idea of the upper air enviornment this afternoon.
BTW, dewpoint sensor doing some strange things at YWG airport. 17c one hour.. 10 the next. Probably a faulty sensor. Dewpoints across the RRV are generally in the 15 to 18C range.
Rob.
ReplyDeleteNow I know what you mean by "SLOW" moving storms this afternoon!
That storm that has popped up in the interlake is basically stationary!!!
Heavy rain will be a real issue with these storms!
Shortwave in N Dakota is interacting with moisture/ instability to produce complex of t-storms SW of Grand Forks. Models prog shortwave to pass us to the SE.. however SE Manitoba may get brushed by the convection associated with it. This may the best chance at organized storms today.
ReplyDeleteI am not sure convection forming on the surface trough will reach RRV. With shear being so weak and a disorganized LLJ, storms will have a hard time getting far ahead of the trough or persisting after sun goes down.
Could be an interesting set up tomorrow.. with surface trough coming thru RRV early to mid afternoon. I would like to see what can happen today with that feature before speculating too much.
Just checked radar/ satellite... interesting cumulus fields developing S of Winnipeg along with some cells popping SW of Emerson.
ReplyDeleteElsewhere, cumulus development can be seen along the Manitoba escarpment and along the lakes. Its going to be an interesting afternoon... with scattered convection in areas of better mesoscale forcing...
*Riding Mtn area (slope effects)
*Interlake (lake breeze)
*Southern RRV/ SE MB (shortwave)
*City of Winnipeg ???
lets see what happens...
It is very hard to pinpoint where the storm will fire up this afternoon!
ReplyDeleteThere just all over the place!
One thing is the risk of VERY heavy rain amounts if you get stuck under one of these storms. Some place in Northern North Dakota got 3-4 inches of rain in a few hours!
WOW!
looks like some cells are building up the Red River Valley, perhaps towards the Winnipeg region?
ReplyDeleteOtherwise we'll have to wait and see what exactly happens with storms today and how they move.
Yes!
ReplyDeleteSevere thunderstorm warnings for those cells building up the Red river Valley!
Oh....I forgot to mention Winnipeg airport has finally hit 30 C
A almost 2 months earlier than last year!
Pretty good cell just east of La Salle as of 4:30 pm. Storms are nearly stationary but are not lasting too long.. heavy pulse type storms that do their thing and then die, while outflows kick off other cells.
ReplyDeleteThat La Salle cell is right over Victory Lane Speedway.. so much for racing tonight!
ReplyDeleteGetting a nice cooling outflow from that La Salle storm here in Charleswood.. temperature dropped from 31C to 28C, with a gusty south breeze.
ReplyDeleteA storm pretty much has to form right over top of you, because they ain't moving.
ReplyDeleteStorm Outflow!!!
ReplyDeleteRob take a look at the radar!
Notice how there is a "arc" shaped radar return that passes right through Winnipeg!!!
Is that an outflow Boundary????
Yep.. that's an outflow boundary.. pushing up to the north Perimeter now. Sometimes those boundaries can trigger new storms..
ReplyDeleteYou could see the LaSalle cell from U of M for over an hour.. sky looks pitch black to the south. I drove down to the floodway control structure to get a closer look... looked like torrential rain, but did not observe any lightining.
ReplyDeleteOutflow boundary showed up nicely on radar. Am a bit surprised it did not trigger other cells... but cumulus field looks to be building north somewhat. Most of the convection today is associated with the North Dakota shortwave. If we lack a similar feature tomorrow, it will be difficult to get much convection going before surface trough moves thru.
I cannot believe with the copious moisture present the last few days, Winnipeg may not even get a drop of rain this week...
Trigger a new storm that outflow boundary did!
ReplyDeleteA huge thunderstorm to my northwest
(around Rosser)!!
Another strong cell formed near the woodlands radar... likely at the intersection of outflow and lake breeze boundaries. Will be interesting to see what happens as the outflow boundary moves over the Lake Manitoba.
ReplyDeleteWhat is causing the storms to vaporize so quickly???
ReplyDeleteThis nothing one mintue...then out of nowhere..."BOOM" a storm!
Only for it to vanish 1/2 hour later!!!!
Daniel, Welcome to forecasting pulse storms ...
ReplyDeleteTomorrow is a real question mark...
ReplyDeleteOne thing to note is arctic front that has snuck down almost as far south as Swan River (further south than models were progging). Models show this shallow NE flow getting cut off and shunted eastwards tomorrow.. however, elongated mid-level trough may be able to tap at least some of that chilly air.
Models also show quite a lot of post frontal precip in region of mid level deformation associated with trough. Assuming there is no convective debris present, I would expect temperatures to soar early in the RRV, and by midday there could be a respectable west to east temperature gradient in place.
Best chance for severe convection would be along surface trough if enough heating can occur, I would expect transition to cooler temps and stratiform precip as we are influenced by deformation zone later in the afternoon.
Rob, whats your guess?
Highly underwhelming "severe weather" today. Storms didn't move an inch, which kept the excitement factor to a minimum. Tomorrow doesn't look much better. Storms may fire off again, but the circumstances will be much the same as they were today.
ReplyDeleteAttention then turns to Sunday. A potent system will position itself over central Saskatchewan by Sunday afternoon. A fairly strong cold front will be positioned south and east of the low. Moisture similar to today will surge into southern Manitoba and south-eastern SK. A strong jet stream (unidirectional) overhead will provide ideal conditions for a strong wind/hail event. It is currently unclear exactly how this system will orientate itself. Right now it looks like south-western Manitoba will see round #1 on Sunday, and south-central and south-eastern Manitoba will see round #2 on Monday. Thoughts?
Some storms are starting to fire off along the trough, outflow boundaries, and lake breeze convergence boundaries...and there are moving!
ReplyDeleteLooks like we will have an isolated severe risk in the RRV and south-eastern Manitoba. CAPE values are 1000 to 2000J/kg. Shear is still poor, but about 20 knots. This should support some slightly longer lasting pulse storms, with the risk for large hail.
Rob, have you seen the 3:30 radar image? There is an outflow arc that is right near Portage! There is one or two cells near the arc, lets see if they are pulse thunderstorms.
ReplyDeleteIs it safe to say that we have gone into a "HOT" weather pattern????
ReplyDeleteIt was quite the jump from cool spring into Summer if that is the case!!!
Got a chance to finally look at some model data for next week...
ReplyDeleteFirst in regards to daniel P's question; we have certainly switched into a 'summer' phase. Snowfields continue retreating in the arctic allowing for better heating to occur farther north. Coupled with the strong June sun, we have flipped (at long last) into a warmer phase. Does that mean we will be above average for a long stretch... possibly but very hard to say for sure. Keep in mind that near average temps are practically 'hot' anyways (27 C by July).
If we look to analogue summers after spring floods... we see that we have still experienced cool downs after finally switching into summer mode. The Hudson Bay Vortex has periodically built in sending us cool air. This is exactly what happened in early July of both 96 and 97 (I do not have time to track down the exact dates). In fact in early July 1997, YWG either set a record low or came very close.. I recall a frost warning being possibly being issued?
Now, due to the aforementioned bare ground and open water at higher latitudes, the arctic air will modify significantly until the nights start getting longer again in August. As a result we will not see single digit temps etc, but temps in the high teens/ low twenties.
I will comment on next week in the following entry...
Well, last week featured only a trace of rain for Winnipeg, we remained more or less under the influence of that Prairie upper ridge. The deepest layered moisture and shortwaves embedded in the SW flow moved into N Dakota leaving us with only widely scattered showers.
ReplyDeleteWe could use a bit of rain at this point (parts of the city have barely received any precip for the last 3 weeks)... but alas the first part of the week does not look promising for rain or severe weather.
Once again, the early period will be characterized by a splitting of the energy, with us sitting in the doldrums. Good LLJ/ dynamics wrap up around a dominant, cut off low that sets up over NW prairies. Transport of deep, tropical moisture and best surface warm front will be focused with a another disturbance tracking up thru Minnesota.
Surface trough between the two limps across the RRV sometime Monday.. after which point a westerly flow cuts off good moisture well to our south. With little in the way of mid level dynamics and shear, I do not expect much apart from debris cloud and scattered light showers.
We do get some decent upper shear and left exit region by Tuesday, but main juice and instability will be south of stalled surface front well off to our SE. We need that maritime tropical warm front to set up along the international border and a well focused LLJ intersecting it. That may eventually happen... I did not look in any detail at late week.