SPC Apr 22, 2017 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0350 AM CDT Sat Apr 22 2017

Valid 251200Z - 301200Z

...DISCUSSION...
...Tuesday/Day 4...
The ECMWF and GFS solutions move an upper-level trough eastward into
the Great Plains on Tuesday/Day 4. Both solutions forecast a
corridor of moderate instability in the southern Plains by late
afternoon. A severe threat will be possible along parts of this
instability corridor in the southern Plains during the late
afternoon and evening. Will hold off on adding an area due to
spatial uncertainties.

...Wednesday/Day 5...
The ECMWF and GFS solutions move the upper-level trough into the mid
Mississippi Valley on Wednesday/Day 5 as a cold front advances
across the region. Ahead of the cold front, an axis of moderate
instability is forecast by both models suggesting a severe threat
will again be possible along parts of the instability corridor in
the late afternoon and evening. Again, spatial uncertainties
preclude adding an area at this time.

...Thursday/Day 6...
As with previous runs, the ECMWF ejects a lead shortwave trough
across the central Plains on Thursday/Day 6 while the GFS maintains
an upper-level trough further west in the Four Corners region. Both
solutions surge a moist high-quality airmass northward into the
southern Plains and develop a well-formed dryline by late afternoon.
In spite of the differences at 500 mb, both solutions move a
mid-level jet over the moist sector as a low-level jet strengthens
during the early evening. This setup suggests a higher-end severe
weather event will be possible in the southern and central Plains
during the late afternoon and evening with a potential for
tornadoes, large hail and wind damage.

...Friday/Day 7...
The ECMWF and GFS solutions continue to develop an upper-level
trough in the Four Corners region on Friday/Day 7 as a mid-level jet
ejects out of the base of the trough into the southern and central
Plains. The GFS maintains a high-quality moist sector over the
southern Plains Friday afternoon and evening while the ECMWF waits
until the overnight period to surge moisture northward across the
Southern Plains. Both of these solutions would be favorable for a
severe weather event in parts of the southern and central Plains
Friday or Friday night. A higher-end severe weather event will be
possible with supercells and a potential for tornadoes, large hail
and wind damage.

...Saturday/Day 8...
The ECMWF and GFS solutions move an upper-level trough across the
Four Corners region and southern Rockies on Saturday/Day 8 as
southwest mid-level flow remains over the central U.S. Both
solutions suggest a cold front will advance eastward across the mid
Mississippi Valley by late Saturday afternoon. A severe threat would
be possible along the front but uncertainty is substantial at this
range in the forecast period.

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