Tag: Humid

Friday’s Surge of Heat & Humidity Leads to Unsettled Weekend

Brad

Heat & humidity will begin moving into the region today as a breezy southerly wind develops over the province, tapping into a much warmer air mass over the Northern Plains of the United States.

A potent low pressure complex developing over the western Prairies & Northern Plains will bring a thunderstorm threat back to Southern Manitoba today with the southwestern corner of the province under the threat for thunderstorms—potentially severe—this afternoon and this evening, while the Red River Valley and southeastern Manitoba seeing the threat move in this evening and into Saturday morning.

Before that, though, Winnipeg & the Red River Valley will have a fairly nice day ahead. Temperatures will soar through the morning, reaching within a degree or two of today’s high temperature of 28°C by lunch. Skies will be mixed today with cloudier conditions developing in the afternoon. Southerly winds to 30-40km/h will pick up through the day across much of Southern Manitoba, drawing moisture from the United States northwards into the province. By late afternoon, dew point values in the Red River Valley will climb to the 16-18°C range1 while in the southwest corner of the province, dew point values may reach the 20°C mark, making for very humid feeling conditions.

AWM Convective Outlook for June 24/25, 2016
AWM Convective Outlook for June 24/25, 2016
As the afternoon wears on, a leading shortwave lifting out of Montana will destabilize conditions over southern Saskatchewan and southwestern Manitoba, bringing a threat of thunderstorms to the region. There’s a slight chance that some of these thunderstorms may become severe. The threats from these storms will be:

  • Rainfall: Precipitable water values of 35-45 mm combined with storm motions of 20-30km/h will produce very intense rainfall, but the storms will be moving quickly enough that the overall rainfall accumulations will be limited.
  • Hail: With MLCAPE values in the 1500-2500 J/kg range and ample shear present, storms will likely take the form of discrete supercells early in their life cycle. These storms will be capable of producing large, damaging hail.
  • Wind: Overall, wind won’t be a widespread threat with these storms, but isolated damaging wind gusts are possible.
  • Tornadoes: The supercell thunderstorms in southeastern Saskatchewan and southwestern Manitoba will be in environments with very strong directional shear. A small chance of a tornado or two exists with these storms.

As we move into the evening, scattered showers or thunderstorms are possible over the Red River Valley while the thunderstorms closer to the SK/MB border continue onwards and grow into a larger complex of thunderstorms that will push eastwards overnight. Instability actually increases overnight as moisture continues to be pumped northwards along the low-level jet ahead of the incoming shortwave. As a result, a large area of rain and thunderstorms will likely progress eastwards overnight, reaching the Red River Valley between 3 and 6AM. These thunderstorms will present a slight risk of severe weather with primary threats of rain and large hail, with a secondary threat of damaging wind gusts.

Worth noting: if the western shortwave offering support to this system ends up slowing down, the overnight thunderstorm activity may diminish over southwestern Manitoba.

Temperatures will remain very warm on Friday night with overnight lows near 20°C in the Red River Valley.

Saturday: Muggy with Continued Thunderstorm Threat

Saturday will start with whatever convection moving through on Friday night exiting the region, and we’ll be left with very humid conditions with dew point values likely climbing to 20-21°C. Temperatures will climb towards the mid-20’s through the morning under fairly cloudy skies, but conditions will undergo a fairly significant change midday as a cold front sweeps through. The passage of this front will bring another threat of showers and thunderstorms to the region and with MLCAPE values near 1500-2000 J/kg and ample shear, these will also have bring the threat of severe weather with rainfall, winds and hail a concern.

4km NAM Dewpoint Forecast valid 15Z June 25, 2016
High dewpoint values over 20°C will be in place on Saturday morning in the Red River Valley.
Once the front passes, gusty westerly winds will usher in drier air as dew point values plummet into the single digits, bringing relief from the humidity. Skies will begin clearing as well, likely providing some afternoon/evening sunshine. Temperatures will likely top out at only 24 or 25°C, though, and a cooler night will be ahead with lows near 15°C.

Dreary End to the Weekend

Saturday night’s clear skies will be replaced by cloud on Sunday as the main upper-level low of this whole weather system moves through the region. It will bring showers to much of Southern Manitoba with most of the activity through the morning hours and then tapering off through the afternoon. Temperatures will be much cooler with a high near 17 or 18°C and strong northwesterly winds of 40 gusting 60 km/h picking up by the end of the morning.

The winds will taper off overnight as the valley heads to a low near 11°C.

Winnipeg’s seasonal daytime high is currently 24°C while the seasonal overnight low is 12°C.

  1. At a dew point of 16-18°C, it begins to feel mildly muggy. ↩

Mixed Conditions Through Remainder of Week

Brad Leave a comment

Conditions will be mixed across Winnipeg & the Red River Valley through the remainder of the week with today's wet weather & seasonal temperatures giving way to warmer conditions with unsettled conditions building back in for the end of the week.

Today will start off with showers across the southern Red River Valley; there's a chance that we'll see some of the activity here in Winnipeg, but so far this system has been very difficult to get a handle on. Winnipeg may see the precipitation edge into the city this morning, but there's about an equal chance that it will stall just to the east of the city and never make it in.

Radarscope – Woodlands 0.3° Reflectivity
An area of rain is pushing towards Winnipeg this morning.

By this afternoon, the rain should head back off towards Ontario and Winnipeg will be left with cloudy skies that will clear through the afternoon. Temperatures will climb towards a high of 23°C in Winnipeg today, with highs of 22-25°C across the Red River Valley. Expect a low near 15°C tonight under mainly clear skies.

Thursday will be a very nice day through the Red River Valley with a few clouds and much warmer weather. Daytime highs will climb around 28°C while a breezy south-to-southeasterly tap into higher moisture to the south, pushing dew points into the upper teens. This will make things feel slightly muggy, and that high of 28 feel closer to something in the mid-30's. A frontal wave passing through in the late afternoon will bring a risk of thunderstorms to Winnipeg & the Red River Valley through the evening hours. Temperatures will fall towards a low of 18°C under mixed skies overnight.

This simulated RADAR image shows precipitation moving through the Red River Valley on Friday night.
This simulated RADAR image shows precipitation moving through the Red River Valley on Friday night.

Friday will bring mixed skies to Winnipeg with drier air moving in behind the passage of a cool front in the morning. Temperatures will still climb to a high near 28°C once again, but by late afternoon significantly more cloud will begin moving into the region as the cool front rebounds and begins pushing back through the region. In the evening, showers and thunderstorms will be possible across the Red River Valley as the warm front slowly pushes northwards. Temperatures will fall to a low near 18°C once again on Friday night.

Long Range

The weekend is looking like it could be a wet one once again. Currently a low pressure system is forecast to move through the region on Saturday, which would likely bring a rainy day to the region with 15-25mm of rain possible. Things will improve a bit on Sunday as the system leaves the region, but a slight chance of showers may linger through the day.

Daytime highs will be in the low- to mid-20's and overnight lows will dip down to the mid-teens.

Winnipeg’s seasonal daytime high is currently 24°C while the seasonal overnight low is 11°C.

First Summer Blast Will Bring Muggy Weather & Severe Thunderstorm Threat

Brad Leave a comment

The first real notable surge of summer air is on the way for Winnipeg as a broad southerly flow develops ahead of a slow-moving low pressure system moving across Saskatchewan. This organized flow of southerly air will tap into Gulf moisture[1], bringing the first notably humid spell of 2016 to Winnipeg. Alongside the heat and humidity that will move in, there will be a threat of thunderstorm development across Southern Manitoba, of which severe storms are certainly possible.

Today marks the start of the summer surge moving into Southern Manitoba as light southerly winds develop over the Red River Valley and warmer air aloft begins to move into the region. Skies will partly cloudy to mixed through much of the day as temperatures climb to a high near 24°C. The humidity will still be fairly comfortable today with dewpoint values in the low teens.

Heading into the late afternoon and evening, cloud cover will thicken up over Winnipeg & the Red River Valley as some precipitation develops associated with instability ahead of the approaching warm front. Winnipeg will see a decent chance of seeing some light rain overnight, but amounts will likely remain under a few mm. Temperatures will dip to a low near 14°C tonight.

RDPS Forecast Temperatures valid Wednesday Afternoon
The RDPS shows very warm temperatures in Southern Saskatchewan this afternoon, indicative of the hot air mass set to move into Manitoba tomorrow.

Thursday will be the most significant day over Southern Manitoba as the full brunt of a hot and humid air mass settles over the province. Temperatures will soar to a high near 28°C while the humidity becomes particularly swampy, with dewpoint temperatures likely to climb to the 19-21°C range. This will feel quite sticky, especially as the first humid spell of the year, as humidex values climb toward the mid-30’s for the afternoon.

With the heat and humidity in place, attention turns towards thunderstorm potential. This setup has been interesting to watch develop over the last week as models have struggled to resolve exactly how much moisture would arrive in the province and how warm temperatures aloft would get. That said, there’s a severe thunderstorm risk today that will start over southeastern Saskatchewan with afternoon thunderstorm development possible. The threat will then shift eastwards through the evening and overnight with thunderstorms transitioning from surface-based to elevated as the low-level jet strengthens, helping the scattered afternoon activity grow upscale into a larger area of rain and thunderstorms.

AWM Day 1 Convective Outlook valid June 9-10, 2016
AWM Day 1 Convective Outlook valid June 9-10, 2016

Taking a more technical look at it, as usual we return to the basic MIST principles:

  • Moisture: With surface dewpoints climbing towards or even over 20°C, ample moisture will be in place for thunderstorm development. The low-level jet that develops Thursday evening will also be helping propagate elevated moisture levels northwards.
  • Instability: Significant instability is in place with MLCAPE values in excess of 2000 J/kg developing over much of th region. MUCAPE values continue above 2000 J/kg through the overnight period. CAPE also appears to be fairly "fat", bolstered by potent mid-level lapse rates over 8°C/km.
  • Shear: Ample speed and directional shear will be in place with 0-6km bulk shear values of 35-50kt and strongly veering profiles. Low-level wind profiles in eastern Saskatchewan & western Manitoba will favour discrete supercell thunderstorm development with storm motion to the east-southeast.
  • Trigger: Strong solar insolation coupled with an incipient thermal wave and associated boundaries should provide multiple foci for thunderstorm initiation.

In general, it’s expected that discrete supercell thunderstorms with primary threats of damaging hail, wind gusts in excess of 100 km/h and a non-zero tornado threat. These storms will likely be scattered and progress to the east-southeast. As the evening wears on and the low-level get strengthens, the scattered activity has a high probability of growing upscale and organizing into an MCS[2]. If an MCS develops and moves eastwards, then the primary threats will be heavy rain and damaging hail. There is growing confidence that the MCS will develop into a bow echo, which is a fast-moving storm that produces severe wind gusts. Should this occur, than much of southwestern Manitoba and the Red River Valley will see a very significant threat of damaging hail and severe winds.

Temperatures will remain quite warm on Thursday night with low temperatures throughout the Red River Valley near 20°C.

Friday will continue to be warm with mainly sunny skies once any overnight convection clears out of the region. Temperatures will rocket to the upper 20’s by midday and while the highest humidity will push off to the east, it will still remain a bit muggy with dewpoint values stabilizing near 15-17°C. Winds will shift to be out of the northwest at around 20km/h. Expect a low on Friday night near 15°C.

Winnipeg’s seasonal daytime high is currently 23°C while the seasonal overnight low is 10°C.

  1. In the summer, deep southerly flows over the Eastern Prairies tap into humidity from the Gulf of Mexico and pull it northwards across the Great Plains and into the Southern Prairies.  ↩
  2. Mesoscale Convective System: A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 km or more in horizontal scale in at least one direction.  ↩

A Couple More Cool Days Before We Heat Up

Scott Leave a comment

We’ll have a couple days of cool weather before an upper ridge builds in, bringing hot & humid weather to southern Manitoba in the second half of the week. The arrival of the heat and humidity is also expected to bring our first significant risk of severe thunderstorms this year.

A cool northerly flow will be in place over southern Manitoba on Monday
A cool northerly flow will be in place over southern Manitoba on Monday

This Week

Today will remain on the cool side as a surface high to our north-west pumps cool air into southern Manitoba. Some cloud cover is expected in southern Manitoba during the morning as an upper disturbance moves through, but skies should clear by the afternoon. Daytime highs will be in the upper teens with gusty north winds at 40 km/h gusting to 60 km/h.

Tuesday will remain cool as we remain under the influence of that surface high. Temperatures will once again be in the upper teens, although some areas in western Manitoba may reach the low twenties. Skies are expected to be mainly sunny and winds will be breezy from the north.

Warmer weather will begin to move into southern Manitoba on Wednesday as the surface high moves off to the east. A southerly flow will be in place over southern Manitoba, helping to bring warmer air into the region and push daytime highs into the mid twenties over the Red River Valley and the upper twenties over western Manitoba. There will likely be a risk of severe thunderstorms in eastern Saskatchewan on Wednesday and that may spill over into western Manitoba. Depending on how conditions develop, the thunderstorm risk may extend across all of southern Manitoba on Wednesday night as storms from Wednesday evening move east with time. A westerly steering flow and a strong southerly low-level jet would tend to favour easterly or south-easterly storm motions, which would help steer storms toward the Red River Valley during the overnight period. More details on Wednesday’s potential thunderstorm risk will be available as the week progresses.

Long Range

The long range forecast suggests a hot, but unsettled pattern, will be in place for southern Manitoba from late this week into the weekend. An upper ridge will be centred over southern Manitoba during this time period, but we are expected to remain at the top of this ridge, putting us along the storm track. The influx of warm, humid air due to the southerly flow in this ridge combined with the moderate to strong flow with the jet stream aloft should favour numerous thunderstorm chances during the Wednesday-Monday period. The nature of the thunderstorm threat remains quite unclear, but at least one or two severe events seems probable at this time. An upper trough is expected to approach either late this weekend or next week, which will push out this hot/humid air mass.