Looks like three areas of concern for today, and those region are circled above green the weakest, yellow stronger storms, and red the area where the worst of the storms will be today. Starting in SW'rn ON, there is un upper level vorticity maxima currently near the Sault Ste. Marie region tracking southward. This upper disturbance along with the frontal boundary will make for a few thunderstorms this afternoon. CAPE values look high enough for some storms to reach sever limits with soundings supporting some strong straight line winds and LCL's look to be a little elevated.

Area from Kingston up to Quebec city looks pretty good with the main upper jet passing through the warm sector which should provide some extra kick to the system. Shear vectors are oriented as such that isolated updrafts will be supported and low level shear looks to be supportive of a few supercells. Hodographs are indicating though mostly splitting modes and thus not likely no real organized supercells will get going. CAPES are high enough though to provide a good hail risk and chance for some strong winds and likely see some severe storms through the Ottawa, Cornwall areas and down into Kingston.

The greatest risk for today is in NW'rn ON from Fort Francis across to the Lake Superior shore line. Here strong upper level jet and low level flow and moisture will provide enough fuel for strong thunderstorms. Some of which a on going through the MB area. All parameters here looks to support strong thunderstorms with the risk of some large hail, winds, and even an isolated tornado is possible. The greatest tornado threat is in the MN but regions right along the U.S. border (as outlined above) cannot rule out the risk of a brief tornado.

The above shows my forecast analysis for this afternoon showing the scenario for Saskatchewan. A potent upper trough currently rounding the Rockies along the Oregon/Idaho border region will eject into southeastern AB by this afternoon providing strong large scale ascent and rapid intensification of the surface low forecast to be located around the Mose Jaw area by 6 pm local time. From this location a triple point will be located as analyzed above and will be the focus point for maximum forcing for later this afternoon (green line indicates the 850 low level jet orientation). Current convection in AB will work its way into western SK through today which will bring a risk heavy downpours, hail and strong winds. Initiation looks little uncertain at the moment as models are struggling with current convection. Thus the area outlined in yellow is a general risk area where supercells are possible with large hail and strong winds. Shear vectors along the occlusion are perpendicular to the forcing thus leading to isolated rotating updrafts. Thus the NW portion of the areas outlined in yellow proves to have a substantial tornado threat for today, this area is approximately between Swift Current and Saskatoon. The area outlines in red and right at the tri[ple point (which isnt in the red area but should be) is where the stronger threat for tornadoes are for today but has a minimal window for it. The cold front will rapidly overtake the dryline and undercut most convection causing the 850 low level winds to veer around to a more westerly direction cutting down and the shear needed. However the area right near just north of the triple point will see an extend period of southeasterly low level winds and will be an environment conducive to longer lived supercells and enhanced risk of tornadoes. Looks like convection northwest of Mose Jaw will be underway by around 2-3 pm time frame and in southeatern SK by the 5-7 pm time frame and this is spported by tge RAP/HRRR/NAM and GEM with some differences in coverage and extent.

The same potent upper trough that was responsible for yesterdays severe convective weather in Manitoba is once again the focus for today in northwestern Ontario. Latest water vapor imagery shows strong vorticity center just south of Saskatchewan along the U.S. border in Montana. This will provide large scale ascent within the warm sector of the low.

The low is currently located near Charron Lake, MB just west of the elbow of Ontario. From here a warm front extends across northern Ontario currently in Pickle Lake and across to Kapuskasing and Timmins. The cold front is currently sitting right along the MB/ON borders from Charron Lake and extends down into MN along the ND and SD borders. As the low and wave progress ENE through today, the cold front as well as regions near the low centre will see thunderstorms develop throughout today and into the evening. The NAM/WRF surface forecast here shows the wave does not progress much during the day but does begin to surge ENE through the overnight period. Therefore there is a dual wave that develops overnight with the primary wave in ON and a secondary cold front in southern MB. With MLCAPES forecast to be between 2000 - 2500 J/KG in northwestern ON and between 400-600 J/KG in central MB there will be two primary areas for thunderstorms development. 1. The Interlake region in MB where heavy downpours and large hail are the main threat. 2. In northwestern ON where regions along the the cold front (from Fort Frances across to Thunder Bay and up to Big Trout Lake) where weakly veered hodographs and shear vectors parallel to the cold front will make for fast moving splitting cells with some supercells in the area. Also regions along the warm front will see some convection as well where hail and heavy downpours are the main threat. As the 850 mb low level jet strengthens this evening expect storms to increase in intensity and thus bringing in the threat of a few isolated tornadoes. The largest threat for tornadoes looks the be in the region outlined by Sandy Lake, south to Goose Lake, then east to Pipestone River Provincial Park. The peak tornado threat will be between 8 pm and 2 am local time. Storms that do initiate will progress NE at about 30 to 50 knots and continue through the overnight period, but gradually decrease in strength as they push NE.

There seems to be quite the excitement and buzz in the air as to what is in store weather wise for southern Manitoba tomorrow, and rightfully so. Latest water vapor imagery shows the potent upper trough sitting just on the western edge of Vancouver Island which will be the main focus for widespread large scale ascent over the northern U.S. Prairies/Canadian prairies tomorrow afternoon.

Starting aloft however for tomorrow, models (NAM-WRF/GEM/GFS) agree on a strong 250 mb jet nosing into the southeastern SK and southwestern MB through the afternoon/evening period and again at 500 mb same group of models indicating a strong jet axis into extreme southeaster SK and southwestern MB. Because of this scenario we end up with a deepening vorticity maxima aloft and enhanced large scale ascent across much of the prairies.

But this causes some issues now near the surface. With this rapidly deepening upper low, the surface low will occlude at a much faster pace thus leaving the possibility of having the warm sector pinched off before it even reaches the border. If this is the case then tomorrows severe weather potential goes virtually to 0. Current guidance however still indicates a warm front should extend from Winnipeg across to the ON/MN border just south of Thunder Bay. A cold front will extend from Winnipeg down through east central ND, into northwestern SD, and into northern CO. A trowal will then extend from Winnipeg up into north central SK around Prince Albert National park. The analysis was derived from the NAM/WRF 00Z surface forecast for Sunday June 10 (or the afternoon of June 9). Thus the southeastern corner of MB from Winnipeg to Kenora, ON and across the warm front boundary, a well as the portion of SK and MB which sit along the trowal are the focus areas for severe convective weather tomorrow afternoon. Note that both the GEM/GFS do have the triple point slightly north and west of the NAM/WRF, but given the rapid intensification of the upper low and vorticity center, I prefer the NAM/WRF solution here.

That being said, a quick look at the 500 mb chart above shows a ridge axis through eastern MB thus which may lead to some capping issues. Given 700 mb temps and CIN forecast, the cap will be breakable more the extreme southeastern portion of MB. Along the trowal however there is virtually no cap present, with 700 mb temperatures around the 3 to -1 degree C mark, thus there is a stronger potential for more vigorous convection with an even greater hail threat, but at the same time will make for a convective mess. Because of this there appears to be two regions of interest for strong tornadic thunderstorms tomorrow. A look at 850 mb flow and MLCAPE forecast will help reinforce the reasoning behind why this is. There are two main axis of strong low level flow indicated on the 850 mb forecast, the obvious axis through southeastern MB/northwester ON and the secondary axis through east central SK. The axis through SK appears to be a result of a secondary low spinning up along the trowal in response to strong cyclonic shear due to the 250+500 mb jets. In both areas forecast soundings indicate strongly veered hodographs thus rendering both the warm sector and areas along the trowal conducive to tornadoes. Thus two areas of focus for tomorrow where people should be aware and on the look out for severe weather: 1. Southern MB from Brandon across to northwestern ON along the Trans Canada and south along hwy 71. 2. From Portage la Prairie along hwy 16 northwest to Yorkton, SK and up to north-central SK to area east of Prince Albert National Park. Areas which I believe the most conducive to tornadoes are the Steinbach, MB area and regions just east of the Prince Albert National Park. Along with the tornadic threat is a large hail threat where greater than golf ball sized hail is possible for southeastern MB and up to golf ball sized hail possible for region in north central SK. Keep in mind however, these are regions I feel the worst could happen and that most of the people in MB and eastern SK need to be alert tomorrow since the entire region is prone to severe convective weather. That includes strong straightline winds, large hail, and tornadoes.

May 31, 2012

Today we blew off the risk in southeastern Texas as we would have to race the rapidly progressing gust front spit out by the MCS that plowed trough Kansas and Oklahoma last night. With shear parameters and the setup it was not worth chasing a linear mess and follow the front all the way to the Gulf. May 30th's chase turned out for the better as we were able to get on a rapidly intensifying supercell just northwest of Guthrie, TX. It popped up behind the main line and we suspect it initiated by the convergence along the outflow boundary from a large supercell to its southeast and the dryline. The inflow was nuts and had us driving through blinding dust storms as we tried to race ahead of it. Still unsure if it produced a tornado due to all the dust obscuring out view but it dropped some massive hail near Guthrie that we were able to play with after.

June 1, 2012 Forecast

Tomorrow looks to be marginal right now but if CAPE values can get up into the 3000 j/kg range we may be in business. Aloft the flow is marginal but is still on the lower end of what is suitable for severe thunderstorm development. The one down side is that we will once again be dealing with a northwest flow, but I'm not complaining since it has been producing for us this season. What I'm interested in as the 500 mb wind maxima shown here for tomorrow afternoon which is rounding the base of the main jet axis into the northeast portion of the Texas Panhandle. As this feature round the Rockies there should be some mesoscale stretching which could lead to enhanced vorticity and weak lee cyclogensis. 

Low level flow, particularly at the 850 mb level is pretty weak until about 00Z in through the northeast Panhandle region but by 03Z and around sunset the  low level flow should strengthen sufficiently to enhance low level shear. It is for this reason that the large CAPE will be needed, to be able to tap into the minimal shear initially close to initiation along stationary boundary between weak lee cyclone in eastern New Mexico and outflow from ridge sitting in southwestern MO. The resulting stationary boundary will extend from Wichita Fall, TX up to Amarillo then into northeastern NM will be the trigger for initiation as seen below. The CAPE maxima looks to establish itself in the vicinity of this boundary thus peaking my confidence that there should be supercell modes, this is further reinforced by veered hodographs in the vicinity of the boundary. Later in the evening as upper impulse strengthens and MCS should develop. The NAM/WRF and 4 km WRF precip models both indicate a precip maxima in the northeast portion for the Texas Panhandle with the 4 km WRF precip model keeping isolated supercells by 00Z with moderately rotating updrafts, as shown in the final image. Thus target for tomorrow Pampa, TX.