Severe Storm Outlook Narrative (AC)
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
000
ACUS02 KWNS 280522
SWODY2
SPC AC 280521

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1221 AM CDT SUN AUG 28 2016

VALID 291200Z - 301200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
VALLEY...

...SUMMARY...
A MARGINAL SEVERE THREAT WITH STRONG WIND GUSTS AND HAIL WILL BE
POSSIBLE MONDAY AFTERNOON ACROSS PARTS OF MINNESOTA...NORTHWEST
WISCONSIN AND WESTERN LAKE SUPERIOR.

...UPPER MS VALLEY...
WEST TO NORTHWEST MID-LEVEL FLOW IS FORECAST TO BECOME ESTABLISHED
ACROSS THE NRN TIER OF THE U.S. AS A SUBTLE SHORTWAVE TROUGH MOVES
ESEWD ACROSS THE UPPER MS VALLEY. AT THE SFC...A COLD FRONT IS
FORECAST TO ADVANCE SEWD ACROSS WRN AND NRN MN WITH A MOIST AIRMASS
/SFC DEWPOINTS OF 65 TO 70 F/ IN PLACE AHEAD OF THE FRONT. THIS MAY
RESULT IN A POCKET OF MODERATE INSTABILITY IN THE UPPER MS VALLEY BY
MONDAY AFTERNOON. THE NAM AND GFS MODELS SUGGEST THAT SCATTERED
THUNDERSTORMS WILL DEVELOP AHEAD OF THE FRONT AS LOW-LEVEL
CONVERGENCE BECOMES MAXIMIZED ACROSS CNTRL MN...NWRN WI AND WRN LAKE
SUPERIOR DURING THE MID TO LATE AFTERNOON.

NAM FORECAST SOUNDINGS FROM CNTRL MN NNEWD INTO THE ARROWHEAD OF MN
FOR 00Z/TUE SHOW MODERATE INSTABILITY WITH MLCAPE AT OR ABOVE 2000
J/KG...0-6 KM SHEAR OF 30 TO 35 KT AND STEEP LOW TO MID-LEVEL LAPSE
RATES. THIS WOULD BE SUFFICIENT FOR STORM ROTATION WITHIN THE
STRONGER UPDRAFTS MAKING HAIL POSSIBLE. A MARGINAL WIND DAMAGE
THREAT COULD ALSO OCCUR AS LOW-LEVEL LAPSE RATES STEEPEN DURING THE
AFTERNOON. THE NAM SOLUTION APPEARS TO BE THE MOST AGGRESSIVE
CONCERNING A SEVERE THREAT. THE GFS IS MOSTLY IN AGREEMENT WITH THE
NAM CONCERNING INSTABILITY AND CONVECTIVE COVERAGE BUT SHOWS
RELATIVELY WEAK DEEP-LAYER SHEAR. THE ECMWF APPEARS TO BE THE
OUTLIER KEEPING THE ENVIRONMENT INSUFFICIENT FOR STORM ORGANIZATION
WITH ONLY ISOLATED CONVECTIVE COVERAGE. THE GFS AND ECMWF SOLUTIONS
ADD UNCERTAINTY INTO THE FORECAST. FOR THAT REASON...WILL BE
CONSERVATIVE AND GO WITH A MARGINAL RISK. IF THE NAM SOLUTION ENDS
UP BEING CLOSER TO CORRECT...THEN A SLIGHT RISK AREA COULD BE NEEDED
IN LATER OUTLOOKS.

..BROYLES.. 08/28/2016

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.