Saturday, July 21, 2012

Modest Severe Threat on July 25, 26

A couple days ago, two areas of severe weather potential were outlooked by the Storm Prediction Center at very long range dates. Since then, the SPC has not put out outlooks with those dates being specifically delineated on the long range graphics. That said, let's take a look at where things stand now.

July 25 is looking OK at this point in time, with the GFS portraying a wide area of instability across the Plains into the Midwest. While I did mark high instability into the northern Plains, the highest instability will be located in the Central Plains and Midwest.
Some light to moderate shearing should be in place over the northern Plains if the latest GFS run holds up. I have a feeling that, due to the potentially scattered nature of this shearing, it looks like that some pulse cells may be more supported by high instability and little shear. However, in pockets of this shearing, a mesoscale convective system (MCS) could form thanks to elevated instability and fair shearing pockets.

As for July 26, there should be an increase in both strength and coverage of this light to moderate shear, which could reach past 40 knots (sfc-500mb) on this day. The high instability will most likely be displaced to the south as a cold front attempts to interrupt the party. It should be noted that some fair instability exists in Minnesota and Wisconsin on the order of 2000-3000 j/kg, but was not marked in favor of marking the higher instability over the Plains and Midwest, where 4000 j/kg+ of instability will exist. 
The battle ground of shear and instability appears to want to exist from the Midwest into the Upper Midwest, specifically from Iowa into Wisconsin and Minnesota. Some more pulse cells appear possible farther south into the Central Plains and Midwest, but there is potential for an MCS to fire in the circled area.



ERN WX said...

This is all I can post today, so I hope it is interesting. Mon./ Tues look like decent svr days for my area after a big bummer. Shear for Mon looks about 35kts ( suff for mltcls and weak sprcls), CAPE AOA 2000 j/kg, pwats 1.5+ in, and steep lapse rates greater than 7C, along with downdraft CAPE AOA 1000j/kg; are all supportive of dmgg wind gusts and large hail. The high yesterday did not even reach 70!!!!!!!!!!!!! Crazy after 100!!!!!!!!!!!!!!! Clouds do a lot to temp. SPC needs a slgt risk for Mon. for my area. Andrew, did you hear that Alaska is looking mild this winter and there may be a Newfoundland warm air regime????= -NAO+El Nino=lots of snow!!!!!!!!!!! That is if the Euro is right.

Anonymous said...

So, where is that 2012-2013 winter forecast map that was supposed to be out now, I would love to see it.
I saw a message a few yesterday that mentioned that it would be ready by 12pm today, but I don't see it yet, can't wait to see what your expecting for this year