Storm Threat: April 25-27.11

[Derecho]

Well folks, looks like next week parts of Southern Ontario may be in for a round or two of thunderstorms as a low pressure system originating from Texas makes a pass over the Great Lakes.

The greatest area of severe weather will be south of the Ohio Valley, but it does appear that a modest damaging wind and hail threat may exist over Southern Ontario especially Tuesday through Wednesday with the passage of the slow moving cold front. Dewpoints, instability, wind shear, and other parameters all look sufficient to support at least a strong threat in the form of a line of thunderstorms moving SW to NE or W to E.

We could also be seeing some pretty significant rainfall amounts through to Wednesday and possibly several areas of embedded thunder.

Hopefully I didn't just jinx the threat

[davefootball123]

Deffenitley looks like a heavy rain event for sure. The dynamics are deffenitley there for the potential of some strong storms in the period. Hopefully all pans out and hopefully the models get better every run

[Derecho]

For what it's worth, 21z SREF is in...

Significant tornado parameters for 4pm Tuesday... obviously take this with a grain of salt and it likely won't verify, but it sure is mighty interesting...

[davefootball123]

That is very interesting. I was taking a look at the latest GFS run. Dynamics are there for some possible strong thudnerstorms. Hopefully it all pans out. CAPE appears to be in between 500-1000j/kg with slightly above that in some areas. There looks to be plenty of bulk shear and a strong LLJ will be in place which is always good for nader development. Liftied indicies look to be in the -2 or below range. And to cap it all of surface temps look to be into the 70's with dewpoints into the 60's. Gotta keep watching this thing

[Derecho]

Originally Posted by davefootball123

That is very interesting. I was taking a look at the latest GFS run. Dynamics are there for some possible strong thudnerstorms. Hopefully it all pans out. CAPE appears to be in between 500-1000j/kg with slightly above that in some areas. There looks to be plenty of bulk shear and a strong LLJ will be in place which is always good for nader development. Liftied indicies look to be in the -2 or below range. And to cap it all of surface temps look to be into the 70's with dewpoints into the 60's. Gotta keep watching this thing

It's still climatologically early for southern Ontario so 500-1,000j/kg of any CAPE would be enough to support a severe threat with low topped storms. In fact, that is how much of 2011's severe events have been like across Michigan, northern Ohio an southern Ontario. Low CAPE environments.

I just noticed that tornadoes were confirmed on April 19 in northwestern Ohio just southwest of Pelee Island, Essex County, Ontario. Parameters were not the greatest in that region when those tornadoes occurred, so goes to show that right now we can still have a decent event without the June to August -like- instability. Now those confirmed tornadoes were not bigguns, just brief spin-ups embedded in the line of severe storms that moved from the Mississippi Valley northward to southern Ontario.

[davefootball123]

Yes deffenitley. The NAM also has a pretty good hold on this upcoming tuesday night risk, looking pretty good at the moment (crosses fingers). And on top of this it appears a second low may form over Oklahoma on Wednesday tracking through michigan and across lake huron on thursday bringing us another risk of thunderstorms. However this time the low appers to be stronger and negativley tilted.

[Derecho]

SPC has put us under a Slight Risk on the new Day 3 Outlook.

...LOWER GREAT LAKES/OH VALLEY REGION...
   AS A STRONG SHORT-WAVE TROUGH AND SURFACE WARM FRONT LIFT QUICKLY
   NEWD ACROSS THE REGION...EXPECT WIDESPREAD SHOWERS AND THUNDERSTORMS
   EARLY IN THE PERIOD...WHICH SHOULD CONTINUE/REDEVELOP THROUGH THE
   PERIOD.  NARROWING DOWN EXACT AREAS OF SEVERE WEATHER POTENTIAL
   REMAIN DIFFICULT AT THIS TIME WITH WIDESPREAD AREA OF AT LEAST
   MARGINAL INSTABILITY AND A BROAD AREA OF STRONG FLOW ALOFT/FAVORABLE
   SHEAR.  DETAILS SHOULD BECOME CLEARER IN LATER FORECASTS...BUT
   ATTM...WILL INCLUDE A LARGE PORTION OF THE LOWER GREAT LAKES REGION
   SWWD INTO THE OH VALLEY AREA...WHERE POTENTIAL FOR MULTIPLE EPISODES
   OF STRONG/OCCASIONALLY SEVERE STORMS APPEARS TO EXIST -- INCLUDING
   THREATS FOR HAIL...DAMAGING WINDS...AND A COUPLE OF TORNADOES.

[davefootball123]

I was just gonna post that lol

[davefootball123]

I was just checking the latest NAM model. Looks pretty good for tuesday. I also noticed that the NAM shows a crazy squall line in the mid south on thursday. And i mean crazy

[DarkSky]

EC predicting tstorms for St. Kitts !