On Aug 1, 9:13 am, danlj wrote:
On Jul 31, 9:52 am, nimbusgb wrote:

What is the soaring like in the US Midwest?

Are there significant weather, airspace or other factors that limit
the soaring in Minnessota, Illinois, Indiana and the central midwest?

Dear Ian,

There are fundamentally 3 different types of airmasses interacting to
create weather in the midwest. The proportion of time each influences
local soaring is different in the various areas, of course. (Caveat:
this is written from memory -- others, living in different regions,
may have different impressions of what's important or dominant.)

1: Continental Polar: The great soaring days in the midwest typically
are in the continental polar airmass that cyclically washes down from
the Canadian plains once or twice a week; if there's enough humidity
to create cu (about 40% of the time, I'd say), the bases are usually
at least 4k agl to 7k agl, rarely 9k -- the land is mostly about 1k
msl. The winds in this airmass are usually 20-25 kt just after the
front passes, and cus street up on the first day. Rarely there's
sustained winds of 30-40 kt with long streets. Long downwind flights
are possible if you have time and crew. Talk to Jim Hard.

Soon after 1 September each year, a semipermanent low tends to set up
over Hudson's Bay, causing cold fronts to sweep across the upper
Mississippi Valley every 2 or three days for 3-6 weeks. When this
happens, the air is unstable and the winds more than 20 kt behind each
front. These days are pretty challenging.

2: Pacific: The blue days in the northern Mississippi Valley are often
due to the Pacific airmass that has been adiabatically dried crossing
the Rocky Mountains. This airmass may dominate the northern tier of
states for 1-3 weeks when the polar jet crosses Canada without dipping
south, which happens 3 or 4 times a year. The top of the usable lift
is relatively high, but it's all blue; winds tend to be light. Our
Indian Summer occurs if this happens in September-October, and some
years brings weeks of warm, sunny conditions.

3 Gulf: The difficult days are dominated by the humid gulf airmass.
This brings lower bases, 2k to 4k agl, haze, southerly winds, and
challenging xc conditions. I live in Wisconsin; up here, the gulf
airmass shows up cyclically ahead of the intruding continental polar
airmass, so these days tend to have strong southerly winds and low
cloudbase. Further south, the gulf airmass dominates more, and the
winds are not so strong, and I think the bases are a little higher.
Afternoon popcorn thunderstorms are common.

4: Occlusions. Sometimes the cyclicic rhythm of frontal movement
slows down, and these airmasses simply slop around over each other,
creating occluded fronts, which, especially in the late fall (mostly
after soaring is long over), can create 2-3 weeks of continually
overcast weather. Traditionally these don't happen between the middle
of June and the middle of September.

Your Midwest soaring career will be most satisfying if you have a job
that allows you to skip off to the gliderport for 2-3 days after each
cold front comes through, and stay at work otherwise.

And a benefit of soaring around here is that nearly every bean field
or hayfield is fairly flat and landable...

DJ

Check out OLC for Caesar Creek Soaring Club. We have had some very
good soaring conditions this year including 8 days at Sports Class
Nationals.

Jim Price

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