SPC Sep 18, 2017 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0321 AM CDT Mon Sep 18 2017

Valid 211200Z - 261200Z

...DISCUSSION...
Deep, meridionally oriented flow will exist across the central and
northern Great Plains throughout the extended forecast period as a
longwave trough remains nearly stationary over the Intermountain
West.  This flow regime will likely be accompanied by at least an
isolated severe risk in the central Plains from D5/Friday onward as
a warm, moist airmass (maintained by low-level southerly flow on the
western periphery of a stationary anticyclone) interacts with 1) a
nearly stationary front from Nebraska northward to the Dakotas and
2) a lee surface trough across the southern High Plains.  The
general areas of focus for deep convection should shift gradually
southward over time as a surface ridge migrates slowly southward in
the lee of the Rockies.  Uncertainty regarding specific placement of
these aforementioned surface boundaries and overall magnitude of
severe risk (especially beyond D5/Friday) preclude severe
probabilities for the extended period.

Read more

from SPC Forecast Products http://ift.tt/snHfri