Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 180834
SWOD48
SPC AC 180833

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0333 AM CDT TUE JUN 18 2013

VALID 211200Z - 261200Z

...DISCUSSION...
...NRN PLAINS TO THE UPPER GREAT LAKES...
A SEVERAL DAY PERIOD OF ORGANIZED SEVERE TSTMS MAY PERSIST INTO
EARLY NEXT WEEK. HOWEVER...SYNOPTIC/MESOSCALE PREDICTABILITY BREAKS
DOWN ON D3 AND LINGERS INTO THE MEDIUM-RANGE RENDERING LOW
CONFIDENCE FOR HIGHLIGHTING ANY INDIVIDUAL DAY WITH HIGH-END SEVERE
PROBABILITIES.

ON THE LARGE-SCALE...THERE IS BROAD CONSISTENCY AMONG ECMWF/GFS/CMC
DETERMINISTIC RUNS ALONG WITH ENSEMBLE MEANS THAT THE UPPER-LEVEL
TROUGH OVER THE NORTHWEST WILL EITHER DAMPEN OR EJECT NEWD INTO
S-CNTRL CANADA. IN THE WAKE OF THIS...A PRIMARILY ZONAL FLOW REGIME
SHOULD DEVELOP AROUND D6/SUN WITH A BELT OF MODERATE TO STRONG
MID-LEVEL WLYS PERSISTING ALONG THE NRN TIER OF STATES.
TIMING/EVOLUTION DIFFERENCES HAMPER THE HANDLING OF SHORTWAVE
IMPULSES AND HOW THEY MODULATE TSTM ACTIVITY ALONG THE LINGERING
PRESENCE OF A QUASI-STATIONARY FRONT. BUT WITH A STRONG TO EXTREMELY
UNSTABLE AIR MASS REMAINING S OF THE BOUNDARY OWING TO A PRONOUNCED
EML...DAILY BOUTS OF ORGANIZED MESOSCALE SEVERE EVENTS APPEAR
POSSIBLE.

..GRAMS.. 06/18/2013
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