Currently have a broad upper low off the BC coast with a shortwave trough ejecting out of the southern end of it currently located just off the coast of Vancouver Island and down through WA/OR as indicated on W/V imagery below (first image). This trough is currently firing off the thunderstorms through southern AB/MT at the moment which is forecast to develop a large scale system overnight tonight for western SK, possibly a weak MCS. This trough forecast to push into the Prairie Provinces by tomorrow afternoon which will aid in overall ascent and instability. Second image below (second image) shows the 18Z NAM forecast of where the trough will be which is supported by the GEM/GFS /ECMWF solutions.

At the surface currently have a low located just NW of the elbow of ON with a backdoor boundary pushing through north central SK, northern AB and BC. This boundary is expected to drift south through the overnight which will likely serve as the focus for surface based convection as the trough pushes in.

Tomorrow afternoon this backdoor front along with the trough looks to setup a secondary wave through the Prairies which will help with surface convergence and likely some additional local effects through eastern SK. But the real good energetic air will be just south of the warm front through southeastern SK into southern MB where SBCAPE values are forecast to range from 2000-3000 j/kb, and he GEM is even going as high as 4000+ J/Kg for the Brandon, MB region. There will be some uncertainty with this though as the evolution of any overnight convection from the MCS can bring some lingering cloud which would reduce these numbers.

Second issue is 500 mb flow is forecast to be quite ranging from 15-30 kt, this will lead to any storms being quite slow moving and HP in nature, but at the same time vectors are perpendicular to the forcing so somewhat isolated updrafts look likely (Image below). Low level shear is also quite low but with surface winds out of the ENE and 850 winds from the ESE directional shear is quite good and this just may be enough as the high CAPE values will help with higher vertical velocities and thus able to enhance low level shear present to get some rotation updrafts. That being said tomorrow is case where there is low chance of tornadoes, but the better risk will be associated with the higher CAPE regions. Will have to monitor any ongoing convection through central SK through the day for any additional outflow boundaries, which will easily be able to initiate any storms in the warm sector with such high instability and eroding CAP through the mid-afternoon period. The synoptic situation appears as through storms would initiate in extreme south eastern SK/ND through the 2-4 pm CST and push into southwestern MB through the late afternoon and evening period. Thus there will likely be general thunderstorm risk in the purple region associated with the upper trough and the pink region highest threat for severe; with possible tornado risk in areas of highest CAPE This area includes Yorkton and Estevan, SK. Brandon, MB and south along Hwy 10. Regina region is also in the risk for possibly severe risk but has some uncertainty still as the overngiht convection could prevent suitable airmass recovery for tomorrow. NOTE: This general region could get pushed south and east depending on evolution of system in SK tonight.

Hot, humid airmass in place for southern Ontario over the next few days will bring a persistent risk of afternoon thunderstorms for the next few days. But this discussion I will focus on today just to keep things brief. Morning analysis below shows that the warm front is pushed into central/eastern ON and had allowed moisture latent airmass to surge into southern ON, which is further reinforced by current theta-e meso analysis. Note that this front is expected to stall out there for the next few days as well.

There is some high cloud and a few isolated showers to deal with this morning, which should gradually break up some through the morning hours which should lead to suitable heating through the day allowing for maximum destabilization through this afternoon. 06Z NAM is currently forecasting axis if 500-3000 J/Kg from the southern Muskokas to Windsorn by 2:00 pm this afternoon, but GEM is really underplaying the instability. Given the strong Theta-e riidge pushing in with the higher dew points, I think GEM may not be resolving CAPE well this i don't think instability will be an issue today however; the issue today will be the weak flow aloft and little CAP. I don’t think the lack of CAP will be much issue though since there are no real triggers except for the LB boundaries it will just be a matter of when the boundaries will decide to fire off. Flow aloft will be another cause for issue, with only roughly 15-30 kts of 500 mb flow, storms will have very little divergence and poor venting which will likely result into storms chocking off their own inflow and multiple outflow boundaries which can either enhance low level shear and aid in triggering more convection.

As briefly mentioned above main triggers for today will be mainly lake breeze fronts pushing inland, but will point out that the GEM is forecasting a little shortwave trough which could aid to reinforce the environment mainly for southern Ontario. Current indications are that convection could initiate as early as 2:00 pm due to the GEM short wave, but may be able to hold off until the 4-5 pm time frame. Thus the risk area will be the usual lake breeze convergence zone from Barrie to London, and narrow corridor from London to Windsor but lake modified air may push far enough inland here that storms may not be long lived. Storms should be able to sustain themselves long enough to push into the GTA regions, and Niagara is still kind of a question mark but at least a 30% chance there.

Little added note is that bulk shear is fairly low, but low level shear according to NAM bufkit profiles show a descent amount of sfc-850 low lever shear which could make for some good structure and a very small risk of a maybe a brief spin up, but nothing substantial in this department. As an example below I've shown the London forecast soundings and hodographs for 2, 5, and 8 pm which how graduall increas in low level shear. I only mention this risk because if CAPE values do get to forecast values, vertical velocities in updrafts may be enough to get good stretching within the column with suitable low level turning leading to a few brief spin ups.

Have a few minutes where I was able to look some things over this afternoon and write a quick update on storm potential for this afternoon in Saskatchewan and Manitoba. Current meso analysis shows stronger jet core of 40-50 kts pushing through WY/MT and water vapor imagery also showing an associated shortwave trough pushing through MT associated with this jet core. These two variables are expected to push into southwestern SK this afternoon and evening which will aid with the over storm initiation.

At the surface we have an occlusion from AB through SK with the warm front sitting well into ND. Models did struggle last night with how long overnight storms would last and to how far east they would progress. The squall line that pushed into southern MB this morning really put a halt on how far north that warm front would push thus hindering moisture return and instability to an extent (see first image below for current sfc analysis). But a peak at visibly satellite (second image, pink area shows convergence along the occlusion) shows decent clearing through central to southeastern SK and into ND which should allow for suitable airmass recovery, which is currently shown on SBCAPE meso analysis (last image at bottom). This showing a an area of about 1000 j/kg building into SK and area of 2000+ j/kg building into ND which should also begin to build in for the southeastern part of SK. As the upper level winds and shortwave begin to push into SK aiding overall ascent would expect surface storms to initiate roughly within the 3-6 pm CST timeframe and gradually push ENE eventually into MB in the evening. With the warm front sitting so far south I don’t think moisture will be suitable to allow for real low cloud bases but shear should be enough for some weak rotating updrafts. Greater risk for stronger supercells will be more toward the Estevan and Carnduff, SK region and even into the extreme southwest corner of MB. With elevated nature of these storms tornado risk is pretty small but could be moderately sized hail. Greatest risk I think will be in the area outlined in pink where some severe storms are possible this afternoon and evening.

It has been a pretty active couple of days in AB in terms of severe weather and is expected to be once again today and even into tomorrow possibly, but will focus on today. The reason for this severe weather in recent days is all due to large upper low that has been almost stationary off the west coast of WA and BC. This analysing the current water vapor image can see that this upper low now centered over the WA/OR border is pushing inland. At the base of this upper low is a strong shortwave trough which is pushing through northern NV, this shortwave is forecast to push into MT late this afternoon and evening which will aid with overall large scale ascent within the warm sector of the low. Associated with this upper low is a strong jet core at 500 mb out of the south southeast (see 2^nd image) which will move along and parallel to the Rockies which will also produce mesoscale regions of enhanced vorticity and lift which will also bring the BC interior and AB foothills into play today (as indicated in the 3^rd image). Furthermore 500 mb analysis of this afternoon also shows region of strong difluence located over the southern portion of AB.

At the surface is a rather complex situation this morning, image below indicates where morning front positions are with the warm that that has stalled some in eastern AB but radar this morning does indicate the presence of an outflow boundary that is slow pushing northward which should stall some point today near or just south of Calgary to around Oyen and there is current indication that the convection ongoing near Swift Current may be putting out an outflow boundary as well. These two boundaries could serve as initiation points later this afternoon, or could act to enhance the storm environment with added low level shear; this would depend on whether they mix out also.

  By this afternoon the warm front will push into southern AB with stationary front through the BC interior and a dryline extending through the U.S. where it intersects a cold front in MT. There are two area outlined on the map below the purple indicated where I believe there is the risk of some storms today possibly severe. The pink area indicates where I believe there is likely hood of severe storms with the risk of isolated tornadoes. Within the warm sector SBCAPE values are forecast to reach the 2000-3000 J/kg range which is agreed upon by the NAM/GEM, as well as the RAP/HRRR to an extent. With the southeast flow near the surface I suspect some drying out will take place to the southeast of the Medicine Hat area due to some down sloping form the Cypress Hills, these CAPES near here will decrease quite a bit due to the drying out. Along with the instability is sfc-500 mb bulk shear values in the 40-50 kts range with 25-30 kts in the sfc-850 mb layer with largely veered hodographs within the lowest 1-1.5 km. All parameters considered this leads me to believe that there will strong storms, with supercell structures within the pink outlined area. Expect storm to initiate along the foothills in AB and interior BC and in MT this afternoon with later initiation within the area outlined by Medicine Hate, Letbridge, and Brooks, where I believe most dangerous storms will be. Storms along AB foothills will likely follow a slightly east of north track following the 500 mb flow. As the 850 mb winds increas fromt the due east and northeast sfc winds expect strongly rotation storms to develop here, this also puts Calgary within an isolated tornado risk for this afternoon as well. There is some indication that the warm front in SK will light off this evening as the 850 low level jet strengthens. As storms progress NNE will likely congeal into massive line/MCS where some spinups are possible along or in the vicinity of the warm front. NOTE: Will have to monitor any outflow boundaries as mentioned above through today for additional initiation in the warm sector in SW SK and AB, or enhancement of storm environment.

Same low that brought severe storms to the Edmonton and south eastern portion of Alberta will push into Saskatchewan today. Will begin by looking at water vapour image from this morning which continued to show the broad upper low currently centered on the WA/OR borders. There is a little shortwave trough ejecting out of the base of this broad low shown in the circled area in the first image below. This will ride along the axis of strong 500 mb winds and is forecast to enter the southwestern part of Saskatchewan this afternoon as indicated by the second image. This shortwave in combination with strong upper level divergence and diffluence within the warm sector of the low will aid in overall ascent and destabilization of the arimass.

At the surface there is currently a broad area of low pressure along the AB/SK borders south of Lloyminster that is forecast to become more organized and strengthen some in the area between Kindersley and North Battleford, SK. From this low a warm front is forecast to extend east through Saskatoon, a cold front is forecast to extend south toward Swift Current and down into the U.S., and a occluded front/stationary front pushing back into AB. The ongoing convection near Swift Current may spit out an outflow boundary back to the south later today, thus this will be something to watch for. The focus for surface based convection will be along both the cold and warm fronts and area in between the two along and just north of the upper shortwave trough mentioned above. Profiles within the warm sector are highly veered with large cycle shaped forecast hodographs along with bulk shear values forecast to reach the 35-45 kt range. Forecast SBCAPE values are forecast to be within the 1000-1500 J/KG range by the GEM and NAM however the RAP is currently favoring the 500-1000 J/KG range, which seems to be the more reasonable number at the moment. But this will greatly depend on the amount of clearing through today. All factors combined, looks like storms could begin to fire as early as 21 UTC (2:00 pm local time), where initial modes will be a little messy at first, but as storms push ENE and get into better inflow associated with the strengthening 850 LLJ, I would expect supercells to develop. The area outlined in purple indicates general risk with the pink outline showing where I believe the better environment is for supercells and even a tornado risk. This are includes Saskatoon, Swift Current, Moose Jaw, and Regina, as well as areas along the AB/SK border from Lloydminster to Hwy 7. One thing to note is that some better convective models are not breaking much out in the way of organized convection, which is cause to believe there is a bust potential with this system. Things will have to be monitored through the day to see how things evolve, particularly if any outflow boundaries produce which could enhance the threat within the warm sector with any storm interaction. Will have updates on Twitter when possible.