Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS48 KWNS 200838
SWOD48
SPC AC 200837

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0337 AM CDT WED AUG 20 2014

VALID 231200Z - 281200Z

...DISCUSSION...
AN ACTIVE BUT MESSY PATTERN WILL PERSIST FOR PORTIONS OF THE
NORTHERN AND CENTRAL PLAINS INTO THE UPPER MIDWEST THROUGH MUCH OF
THE FORECAST PERIOD. ON DAY 4-5/SAT-SUN...THE SHORTWAVE UPPER TROUGH
OVER THE INTERMOUNTAIN WEST WILL BECOME NEGATIVELY TILTED AS A IT
PROGRESSES EWD ACROSS THE NORTHERN PLAINS. SEVERAL LEAD SHORTWAVE
IMPULSES WILL MIGRATE NEWD FROM THE SOUTHERN ROCKIES THROUGH THE
CENTRAL PLAINS/MID-MO VALLEY SATURDAY AFTERNOON...AIDING IN
THUNDERSTORM DEVELOPMENT OVER KS/NEB. ADDITIONAL STORMS WILL LIKELY
BE ONGOING IN A WARM ADVECTION REGIME OVER THE NORTHERN PLAINS AND
UPPER MIDWEST. AS THE WESTERN TROUGH APPROACHES THE AREA OVERNIGHT
SATURDAY...AN MCS MAY EVOLVE OVER THE DAKOTAS INTO NEB...AND WHILE
AT LEAST LOW-END SEVERE POTENTIAL IS POSSIBLE...CONFIDENCE IN A
HIGHER-END THREAT IS LOW DUE TO SEVERAL ROUNDS OF CONVECTION
EXPECTED ACROSS THIS SAME AREA EACH DAY BETWEEN DAY 1/WED INTO THE
WEEKEND.

BEYOND SUNDAY...MEDIUM RANGE GUIDANCE HAS TRENDED /OVER THE LAST
DAY/ TOWARD A MORE AMPLIFIED LONGWAVE TROUGH ACROSS THE WEST
TRACKING EWD THROUGH THE PLAINS AND SHUNTING THE UPPER RIDGE TO THE
EAST COAST. THIS IS A BIT OF CHANGE FROM PREVIOUS DAYS WHERE A
FLATTER RIDGE AND SUBTROPICAL HIGH WAS MAINTAINED ACROSS THE
SOUTHERN PLAINS INTO THE SOUTHEASTERN U.S. SO...WHILE A SEVERE
THREAT MAY SHIFT SOUTHWARD INTO PARTS OF THE CENTRAL AND SOUTHERN
PLAINS INTO THE MID-MS VALLEY AROUND DAY 7/8-TUE/WED...TRENDS WILL
NEED TO BE MONITORED FOR DAY TO DAY CONSISTENCY.

..LEITMAN.. 08/20/2014



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