This Week May Start with a Bang

Brad Leave a comment

There will be a risk of strong to severe thunderstorms in Southern Manitoba to start the week – hence why it may start with a bang!

Positions of Fronts on Monday Afternoon

Monday

Monday

Mix of Sun and Cloud. Risk of a Thundestorm.
25°C / 12°C

Today’s weather will be dominated by a risk of thunderstorms in Southern Manitoba. These storms may become severe, with large hail, damaging winds, and heavy rain. Tornadoes will be possible, but the risk is quite low. The reason why thunderstorms are being forecast for today is due to an unstable atmosphere being in place over Southern Manitoba along with a jet stream overhead. When combined, these ingredients can produce strong storms. If you’re in the mood for a more details, please read the technical discussion below.

Technical Discussion:

There is a slight risk of severe thunderstorms in Southern Manitoba today. An overview is offered below:

Moisture: Surface dewpoints in the mid to upper teens will be in place over Southern Manitoba by this evening. At 850mb, dewpoints will be around 10C.

Instability: MLCAPEs of 1000-2000J/kg will be in place over the western half of Southern Manitoba this evening. This instability will likely be transported eastward through the rest of Southern Manitoba during the late evening to overnight period.

Wind Shear: 0-6km bulk shear is currently 25-30kts over Southern Manitoba. An upper-level jet at 250mb is in place along the International border, with speeds of around 70kts. In the low-levels a south to south-westerly low-level jet of 20-30kts will be in place this afternoon.

Trigger: A trough will be positioned through the western-most portions of Southern Manitoba today. In addition, models suggest a weak surface low may be located near Portage la Prairie by late evening. A pseudo-warm front will likely extend from this surface low north and eastward through Southern Manitoba during the day. In addition, the left exit of a 250mb upper-level jet will be position over Southern Manitoba during the day today.

Monday’s Thunderstorm Risk Map

Conclusion: There will be a risk of severe thunderstorms today through much of Southern Manitoba. This risk is contingent on sufficient daytime heating, with convective temperatures generally being in the mid-twenties. Should sufficient heating occur, storms should develop along the trough and possibly surface low during this afternoon. Storms will drift east and persist into the evening. Models suggest there will be some useable elevated instability tonight, so storms may persist after dark. However, the timing of storm evolution will be important, since the atmosphere does not destabilize in the Red River Valley, and points east, in a significant fashion until around/after dark. Thus, if storms move eastward too quickly, they may not be in phase with the plume of instability. Therefore storms may begin to weaken by late evening if the aforementioned factors are not in sync. Storms are generally expected to be multicellular in nature, however some supercells will be possible, particularly during the evening hours in south-central Manitoba.

Tuesday

Tuesday

Mix of Sun and Cloud. Slight risk of a Thunderstorm.
24°C / 10°C

The forecast for Tuesday is a somewhat tricky one. A cold front is forecast to lie somewhere near or in Southern Manitoba during the day on Tuesday. Depending on the character of this front, Tuesday may be a mostly cloudy and increasingly cool day, or it could be a rather nice day. At this point it appears most probably that Tuesday morning into the afternoon will be fairly nice, with temperatures in the mid twenties. However, at some point in the afternoon or evening rain and/or thunderstorms may move in, cooling things down and bringing an end to the nice day. There is still a fair bit of uncertainty with the Tuesday forecast, so we’ll update you again as necessary

Wednesday

Wednesday

Mix of Sun and Cloud
23°C / 8°C

Wednesday looks to be a decent day in Southern Manitoba. High temperatures are expected to be in the low to mid twenties with a breezy north-west wind of 20-30km/h gusting to 40-50km/h. Skies will be a mix of sun and cloud due to fair weather cumulus development throughout the day.

Elsewhere in Weather News: July 27th, 2013

Matthieu Leave a comment

France Faces Severe Storms; More Coming Today

France has had its fair share of severe storms this past week, with more of it expected to come today (Saturday). A level 3 “severe” thunderstorm, the highest risk possible, has been issued by ESTOFEX (European Storm Forecast Experiment) for the northern half of France. Conditions are favorable for tornadoes with a warm front draped across the region and incoming cold front from the west; an upper-level low spinning off the coast of France over the Atlantic will provide sufficient destabilization in the upper levels of the atmosphere.

ESTOFEX forecast

ESTOFEX forecast for today, risk 3 in northern France, Belgium, Netherlands and northwest Germany. Highest risk for large tornadoes resides here. (Source: ESTOFEX)

The only potential flaw in the setup could be due to the large MCS that fired up on Friday evening in west-central France as it continues to move northeast potentially leaving debris cloud in the region this morning. But with that said, as of Friday evening, the MCS was moving fairly quickly, and at this rate would be out of the region in time for tomorrow’s setup. With dewpoints in the low twenty Celsius range, shear plentiful with the approaching upper-level trough, and a great shear profile, all kinds of severe weather could be in play, including powerful tornadoes. The severe weather risk also extends into northwest Germany, Belgium and the Netherlands.

MCS and upper level low

Upper level low spinning off the coast of France and MCS in orange box that could hinder storm activity tomorrow. Infrared satellite image taken Friday evening. (Infrared satellite image source: Weather Online)

The expected severe weather follows a significant weather outbreak that occurred in France on Tuesday afternoon. Strong storms passed through the Burgundy region dropping large hail (between ping-pong and golf ball size) and causing significant damage to vineyards. In this region, crop losses are as much as 75% in the hardest hit areas. Flooding was also an issue, where some main roads such as the one between Pommard and Volnay were flooded out and impassable.

In 2008 an EF-4 tornado touched down around Hautmont, France and caused 4 fatalities and 18 injuries. Severe weather is not that common of an occurrence in France, with only a couple outbreaks per year.

Sunny Weekend Ahead

Brad Leave a comment

Sunny weather will dominate the Red River Valley as a ridge of high pressure moves into Manitoba. Temperatures will be below-normal through the next 3 days as we remain entrenched in a cooler air mass originating from the north while the jet stream remains locked up in the United States.

Friday

20°C / 7°C
Mainly sunny.
Saturday

22°C / 11°C
Mainly sunny.
Sunday

24°C / 13°C
Mainly sunny.

Temperatures will slowly climb back towards the mid-20’s by the end of the weekend, while overnight lows will start at an extremely unseasonably cool 7 or 8°C and warm to around 13°C by Sunday night. Skies will be mainly sunny the next several days with no precipitation in sight.

Showery Weather Ahead

Brad Leave a comment

A persistant Arctic vortex over the Eastern Arctic will continue reinforcing a westerly to northwesterly flow over the Prairies which has been bringing cooler summer weather to Southern Manitoba. Multiple disturbances are forecast to track down in the northwesterly flow which will produce a showery second half to the week.

Wednesday

22°C / 13°C
Increasing cloudiness then showers with a risk of a thunderstorm in the afternoon.
Thursday

21°C / 11°C
Cloudy with scattered showers. Windy.
Friday

22°C / 10°C
Mainly sunny.

We’ll see a fairly cloudy day today as temperatures climb to only around 22°C. A trough of low pressure will work it’s way into and through the Red River Valley bringing scattered showers with the risk of a thunderstorm through much of the day and the early evening. No severe weather is expected. Skies should clear overnight as we drop to a low of around 13°C.

On Thursday a second – more potent – system will begin working it’s way through the province. Clouds will roll in early on Thursday as an upper disturbance tracks an area of rain through the Interlake. Here in the Red River Valley we’ll likely see another round of scattered showers starting midday with the winds picking up out of the north to around 30km/h with gusts to 50 or 60km/h. Thunderstorms aren’t expected and we’ll see a high near 21°C. Things will clear out overnight as we head to a low of about 11°C.

Friday will bring more stable weather with mainly sunny skies and a high of 22°C. Winds will continue to be breezy through the morning but should begin to let up in the afternoon. Things look very pleasant through the weekend with mainly sunny skies and highs in the mid–20’s with overnight lows in the 12–13°C range.