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Chase forecast update for May 12-22
The long-range models continue to show mostly bad news for expeditioners
through at least the next 10 days, as a strong upper ridge continues
to build over the central US. Strong mid and upper level winds
should remain confined to the extreme northern US, near and mostly
north of the Canadian border. Both GFS and Euro models show a
small shortwave trough developing and trying to move in from the Pacific by
late next week (visible on the GFS prog below), but the Euro shows it getting decimated as it runs into the
ridge, long before it can affect the Plains.
Despite the stubborn ridge,
moisture is shown as slowly recovering across the center of the
country day by day, but it is questionable that a sufficiently deep
moisture layer (robust enough to avoid detrimental afternoon mixing)
will reach northward all the way to the good upper support. The
situation is similar to late May of 2006, when shallow surface
moisture layers 'mixed out' by late afternoon, becoming too dry to
support anything more than high-based storms.
If deep moisture can somehow make the long trek in the weak flow to
North Dakota/northern Minnesota, wind profiles are supportive of
severe weather around Friday/Saturday of next week if mature storms
can get established. It may be a worthy expedition day or two for those stuck on
fixed chase vacations or tours, but doubtful it will be enough to get
'on-call' expeditioners like me to pull the trigger on such a long trip.
My take on the current pattern is just to wait and make the most of
the downtime (saving money and vacation days; taking care of
day-to-day tasks usually neglected in the spring). Even if it ends
up being late June or not at all, waiting for good patterns to return
is always the better choice (in my opinion).
Despite the tornado/supercell threat across the Plains/Midwest being
close to zero for the next 2 weeks, some non-severe thunderstorm days
should be in the cards here and there, providing that moisture slowly
recovers enough to re-introduce daily instability. These conditions can provide
some nice low-key chase opportunities for lightning, cloud and storm
structure close to home, which of course I will be out for should they
occur at dates/times I'm off of work (it's doubtful I will use any
vacation days for these).
To sum things up, I don't see any sign of another Plains trip on the
horizon. Beyond the 'reasonable model horizon' of May 22, the
probabilities will remain at the standard 30%.
The following table plots the chance of a Plains weather expedition happening in a particular date range (Midwestern expedition days are not factored into this table):
|2012 Plains Storm Expeditions - Probabilities as of May 12|
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