Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 270834
SWOD48
SPC AC 270833

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Tue Jun 27 2017

Valid 301200Z - 051200Z

...DISCUSSION...
On Fri/D4, an upper trough will be centered over the northern
Plains, with embedded shortwaves moving from the middle MS Valley
into the upper Great Lakes, with a weak surface low over Lower MI by
afternoon. A cold front will extend southwestward from this low,
with a moist air mass to the east. Indications are that substantial
rain and thunderstorms will be ongoing along this front, which lends
uncertainty to forecast instability levels. For example, the ECMWF
shows much less MUCAPE than the GFS, with minimal instability into
Lower MI where the most favorable shear will be. While a Slight risk
may eventually be issued, will defer to later outlooks given these
uncertainties.

Similar predictability issues exist for the next few days as the
upper trough gradually shifts eastward, affecting the Northeast on
Sat/D5.

In the D6-D7 time frame, a northwest flow regime is expected across
the Plains, and southerly surface winds will bring substantial
moisture back north across the central Plains and mid/lower MO
Valley. While some wind/hail threat would exist with this pattern,
predictability is low at this time.

..Jewell.. 06/27/2017



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