Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sun May 08 2022
Valid 111200Z - 161200Z
...DISCUSSION...
The medium-range period appears likely to be characterized overall
by the eastward advance of a formerly quasi-stationary trough over
the West. Global models are in reasonable agreement through the
middle stages of the period, before more substantial differences in
solutions emerge late in the period.
On Day 4/Wednesday, the trough is progged to begin its initial
eastward advance, though is expected to remain over the
Intermountain West while ridging persists over the Plains and
Midwest. Some severe weather will be possible over the
north-central U.S., but likely elevated/north of a warm front for
the most part. Limited severe risk may also occur across western
portions of the central and southern Plains, as the onset of weak
height falls begins. However, confidence remains too low in either
of these areas to introduce a 15% area at this time.
Severe risk becomes more apparent Day 5/Thursday, across the
north-central CONUS. As the western U.S. trough shifts
northeastward across the central High Plains toward the northern
Plains into the afternoon, models indicate the feature acquiring
negative tilt with time -- supporting fairly substantial northern
Plains cyclogenesis. Models differ with strength of the upper
system, and as such, location of the surface low and associated warm
and cold frontal progression. Still, confidence is high enough to
include a broad 15% risk area to cover what appears at this time to
be the envelope of greatest risk. Given several days of low-level
moist advection beneath steep lapse rates aloft, and the increase in
deep-layer flow that will accompany the advance of the upper system,
potential for supercells -- and an all-hazards severe risk -- seems
a reasonable bet from afternoon into the overnight hours.
Some severe weather will likely continue Day 6/Friday, however the
upper system is forecast to shift northward into the Canadian
Prairie, with some weakening of the trailing front which should
stretch from the Upper Mississippi Valley into to Oklahoma/Texas.
Uncertainty regarding frontal strength/location, partially affected
by lingering convective effects/outflow, precludes any areal
highlights for Day 6 at this time.
Uncertainty increases for Day 7/Saturday, as models forecast that a
short-wave trough will rotate southeastward out of Canada and across
the Plains on the southern periphery of the initial low/trough still
shifting northward across the Prairie provinces. The
location/progression of this short-wave feature varies according to
different model solutions, and therefore similar variance exists
with surface boundary position. While some severe risk will likely
evolve within a broad zone that extends roughly along the
Mississippi Valley, too much uncertainty is evident to highlight a
risk area at this time.
Finally, model differences which increase through Day 7 into Day
8/Sunday, with predictability too low to allow a reasonable
assessment of convective potential.
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