Severe Storm Outlook Narrative (AC)
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000
ACUS48 KWNS 280900
SWOD48
SPC AC 280900

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT THU AUG 28 2014

VALID 311200Z - 051200Z

...DISCUSSION...
THE GFS AND ECMWF APPEAR TO BE IN FAIRLY GOOD AGREEMENT THROUGH
ROUGHLY DAY 6 /TUE 9-2/ WITH RESPECT TO THE EVOLUTION OF THE
LARGE-SCALE PATTERN.  BOTH MODELS DEPICT THE ADVANCE OF A FAIRLY
STRONG UPPER TROUGH INTO THE CENTRAL U.S. DAY 4 /SUN 8-31/...ALONG
WITH AN ASSOCIATED/SHARP COLD FRONTAL PROGRESSION.  ON DAY 5...THE
MAIN PUNCH OF SHORT-WAVE ENERGY WITHIN THE LARGER-SCALE TROUGH IS
PROGGED TO SHIFT QUICKLY NEWD ACROSS THE GREAT LAKES AND INTO/ACROSS
ONTARIO...LEAVING A MUCH-LESS-AMPLIFIED CYCLONIC FLOW FIELD IN ITS
WAKE.  BY DAY 6...A NEARLY ZONAL UPPER PATTERN IS FORECAST ACROSS
THE U.S. -- THOUGH A TROUGH SHIFTING SEWD OUT OF THE GULF OF AK/WRN
CANADA WILL BEGIN AFFECTING THE PAC NW LATE.  MODEL DIFFERENCES WITH
RESPECT TO THE HANDLING OF THIS TROUGH THROUGH BECOME INCREASINGLY
APPARENT DAY 7 AND BEYOND.

THE MOST SUBSTANTIAL SEVERE RISK THIS PERIOD REMAINS APPARENT DAY 4
FROM THE CENTRAL PLAINS NEWD TO THE UPPER MS VALLEY...AS THE UPPER
TROUGH SHIFTS INTO/ACROSS THIS AREA.  AS THE ASSOCIATED COLD FRONT
ADVANCES INTO A MOIST/DESTABILIZING AFTERNOON AIRMASS...VIGOROUS
THUNDERSTORM DEVELOPMENT IS EXPECTED TO OCCUR.  WITH A BELT OF 40 TO
50 KT SWLY FLOW PROGGED TO SPREAD ACROSS THE MID MO VALLEY VICINITY
THROUGH THE DAY ATOP LOW-LEVEL WARM-SECTOR SSELYS...SHEAR WILL
BECOME FAVORABLE FOR ROTATING STORMS.  AS A RESULT...A RISK FOR
LARGE HAIL AND LOCALLY DAMAGING WINDS -- AND POSSIBLY A FEW
TORNADOES -- SEEMS LIKELY TO MATERIALIZE...PARTICULARLY WITHIN A
ZONE FROM NRN KS NNEWD INTO MN/WRN WI DURING THE AFTERNOON AND EARLY
EVENING HOURS...AND THEN INTO IA/NWRN MO THROUGH THE EVENING HOURS.

WIDESPREAD CONVECTION IS FORECAST AT THE START OF DAY 5 ACROSS THE
MID AND UPPER MS VALLEY/UPPER GREAT LAKES AREA...AS THE STRONGEST
UVV SPREADS NEWD INTO ONTARIO WITH TIME.  WIDESPREAD
CLOUDS/PRECIPITATION AND THUS LIMITED DESTABILIZATION POTENTIAL
WOULD APPEAR TO BE A LIMITING FACTOR FOR SIGNIFICANT SEVERE WEATHER.
 BY DAY 6...A BELT OF FAST WLY FLOW ALOFT SHOULD RESIDE ACROSS THE
NRN HALF OF THE CONUS...BUT WITH A WEAKENING/INCREASINGLY W-E
ORIENTED FRONT EXTENDING ACROSS THE MIDWEST AND INTO THE
PLAINS...LOCATION AND DEGREE OF SEVERE POTENTIAL APPEAR TOO
UNCERTAIN TO WARRANT ANY AREAL HIGHLIGHTS ATTM.

..GOSS.. 08/28/2014



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