|Posted by Near Zero Probability Chasers on June 7, 2016 at 1:15 AM|
It's warm, humid and nice out in the Prairies! Well that also usually means that storm season is upon us. It looks like this year has been an early one for Saskatchewan and Manitoba with multiple reports of funnel clouds, landspouts and severe thunderstorm watches & warnings being issued. The first major threat for severe weather as advertised by us almost a week ago, will be this upcoming week. The main culprit will be this upper level trough set to eject from the west coast into the eastern Prairies. Usually, we see this pattern starting to set up in the end of June and into July. This is the earliest I have seen the Prairies get a "big setup". Below is the daily breakdown of what to expect.
P.S. - We focus on Saskatchewan and Manitoba since this will be the areas we will be chasing in. No detailed discussion will be written about Alberta's severe weather threat even though it does exist for the earlier part of this week.
Today and Tuesday
- Severe thunderstorms may errupt in Alberta along the foothills due to the extremely warm and unstable airmass. Here is the Prairie and Arctic Storm Prediction Center's (PASPC) forecast for both days:
DESPITE GENTLY FALLING HEIGHTS, WITH THE RIDGE NEARBY, IT WILL LIKELY
TAKE A) SYNOPTIC-SCALE LIFT FROM THE IMPULSE, B) CONVERGENCE NEAR THE
SURFACE TROUGH/LOW, AND/OR C) UPSLOPE EASTERLY FLOW TO INITIATE
CONVECTION. IF STORMS DO INITIATE, THEY WILL BE IN AN ENVIRONMENT OF
1000 TO 1500 J/KG MLCAPE AND 40 KNOTS OF BULK SHEAR, SUFFICIENT FOR
SUPERCELL DEVELOPMENT. HIGH BASES, AROUND 8 KFT AGL, WILL ENSURE THE
MAIN THREATS FROM THE STORMS WILL BE HAIL AS BIG AS GOLF BALLS AND
WIND GUSTS IN EXCESS OF 100 KM/H. STORMS ARE EXPECTED TO FORM
SOMEWHERE IN THE VICINITY OF EDSON TO SLAVE LAKE AND TRACK DUE EAST
OVER THE COURSE OF THE EVENING. NOCTURNAL STRENGTHENING OF THE
LOW-LEVEL JET IS EXPECTED TO OCCUR, AND A STRONG-TO-SEVERE MCS MAY
PERSIST INTO WESTERN SASKATCHEWAN OVERNIGHT.
FARTHER SOUTH ALONG THE TROUGH, INITIATION IS MORE QUESTIONABLE WITH
WEAKER FORCING ALOFT, ALTHOUGH MANY OF THE CAMS DEPICT INITIATION
AROUND 21Z. SHEAR WON'T BE AS STRONG AS FARTHER NORTH, SO IF STORMS
DO INITIATE, EXPECT MULTICELLS OR MARGINAL SUPERCELLS WITH HAIL AND
WIND UNTIL NOCTURNAL COOLING OCCURS.
ON TUESDAY AFTERNOON/EVENING, A ROUND OF SEVERE THUNDERSTORMS IS
LIKELY OVER THE SOUTHERN THIRD OF ALBERTA. A SOUTHWARD-DRIFTING LOW
PRESSURE SYSTEM WILL TAKE THE SHEAR, MOISTURE, AND CONVERGENCE ALONG
WITH IT. DEEP-LAYER SHEAR ON THE ORDER OF 40 KNOTS COBINED WITH
MLCAPE AROUND 1500 J/KG WILL PROMOTE HIGH-BASED SUPERCELLS WITH LARGE
HAIL AND DAMAGING WINDS. THE RISK OF SEVERE THUNDERSTORMS WILL BE
ENHANCED JUST NORTH AND EAST OF THE LOW/NEAR THE EFFECTIVE
FRONT/POSSIBLE OUTFLOW BOUNDARY LATE IN THE AFTERNOON, WHERE THE
SHEAR AND INSTABILITY WILL BE MAXIMIZED. CONVECTIVE EVOLUTION AND
THE LOCATION OF OUTFLOW BOUNDARIES FROM DAY 1 WILL PLAY A VITAL ROLE
IN FOCUSING THE AREA OF CONCERN." - PASPC (http://kamala.cod.edu/Canada/latest.focn45.CWWG.html)
Wednesday the threat shifts into Saskatchewan and Manitoba. Relatively high moisture (dew points) and surface heating should give way to moderate instability, especially near the Saskatchewan and Manitoba provincial border. Supercells (possibly high based) may develop somewhere near Regina and move southeast (similar to last Friday). Tornado threat is relatively LOW at this time due to the lagging of the Low, which should be further west (unless a faster model solution occurs). However, supercell threat is MODERATE due to relaltively high instability. Any storms that pop up during the afternoon and evening hours should have no problem becoming severe and supercellular.
Simulated radar for 4pm CDT
Thursday is the bigger day out of the week essentially because all the ingredients for tornadic supercells seem to be in place. Significant instability values in the upper 3000 to 4000J of Convective Available Potential Energy (CAPE) is forecast. Instability is the spark that makes storm explode as they form, this is the first thing to look at for thunderstorms and more specifically severe thunderstorms. We already know the forcing is there (first image above), so the trigger for the storms to form should not be an issue. The main difference with Thursday is that the Low will be near the instability, therefore mid to low level winds will support any storm that explodes and will make it rotate, thus creating supercells. If supercells do emerge, they should have no problem being long-lived supercells with lower cloud bases. For this reason, tornado threat is MODERATE with any storms that errupt and is sustainable in that environment. Supercell threat is HIGH due to the impressive kinematics and thermodynamics in place in southern Manitoba. Hard to say at this time where the storms will errupt. It could be anywhere in southern Manitoba at this time and even near the SK/MB border. If the Low can manage to get closer to the SK/MB border as the first image below depicts, then a higher tornado threat could arise.
Moisture content & positioning of the Low (two different models)
700MB Shear chart
Southern Manitoba could still see the threat of strong to severe thunderstorms as the Low slowly moves east. A bigger threat may be further south into North Dakota depending on how fast the Low moves east. Still a few discrepancies in models so won't go into too much details. Supercell threat is MODERATE, especially for the southeast corner of Manitoba and tornado threat is LOW due to lack of model input but could be higher as the day nears.
Saturday & Beyond
Low should move out the Prairies and give us fairly quiet weather. Some strong to severe thunderstorms will be possible further south into the Northern Plains, however the threat could easily shif north and impact southern Manitoba. Will keep you updated.
Keep updated to our facebook page where we will post regular updates as each individual event nears: https://www.facebook.com/NZPChasers/
Categories: Severe Weather Forcasts