DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 270453
SWODY2
SPC AC 270450

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1150 PM CDT THU SEP 26 2013

VALID 281200Z - 291200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
A POTENT SHORTWAVE TROUGH WILL EJECT RAPIDLY NEWD ACROSS THE NRN
PLAINS AND UPPER MS VALLEY DURING THE DAY...AND WILL BE LOCATED OVER
ONTARIO BY SUNDAY MORNING. AT THE SURFACE...A LOW WILL DEEPEN FROM
NRN MN INTO WRN ONTARIO...WITH A SHARP COLD FRONT EXTENDING SWD INTO
WI AND UPPER MI. FORCING WILL BE STRONG WITH THE FRONT BUT
INSTABILITY FOR THUNDERSTORMS WILL BE EXTREMELY LIMITED. TO THE
S...THE TAIL END OF THE COLD FRONT WILL MOVE SLOWLY ACROSS OK AND
INTO NWRN TX BY AFTERNOON...WHERE MORE SUBSTANTIAL MOISTURE AND
INSTABILITY WILL EXIST BUT WEAKER SHEAR.

ACROSS THE PACIFIC NW...A SIGNIFICANT STORM SYSTEM WILL BRING STRONG
WINDS AND HEAVY PRECIPITATION ALONG THE W SLOPES OF THE WA CASCADES
AND INTO COASTAL WA AND OREGON.

ELSEWHERE...AWAY FROM THE AFOREMENTIONED COLD FRONT...HIGH PRESSURE
WILL KEEP CONDITIONS DRY.

...WA...
A VERY STRONG TROUGH WILL ARRIVE MAINLY AFTER 00Z AND WILL BRING
STRONG WINDS AND A LONG DURATION OF HEAVY RAIN. FORECAST SOUNDINGS
INDICATE THAT EXTREME SHEAR PROFILES WILL MATERIALIZE...WITH
SUBSTANTIAL LOW LEVEL VEERING WITH HEIGHT/LOOPING LOW LEVEL
HODOGRAPHS ALONG WITH SPEED SHEAR ALOFT. STRONGLY
FORCED...LOW-TOPPED LINES OR SMALL BOWING SEGMENTS WILL BE POSSIBLE
ALONG COASTAL WA AND OREGON DURING THE LATE AFTERNOON/EVENING WHEN
THE MAIN FRONTAL FORCING ARRIVES AND COOLING BELOW 500 MB OCCURS.
WITH SUCH STRONG SHEAR...SOME OF THESE ELEMENTS COULD ENHANCE WIND
POTENTIAL AT THE SURFACE...ALTHOUGH LIGHTNING PRODUCTION COULD BE
LIMITED.

...UPPER MS VALLEY...
INSTABILITY AHEAD OF THE COLD FRONT WILL BE QUITE WEAK DUE TO POOR
LOW TO MIDLEVEL LAPSE RATES. IT IS DIFFICULT TO FIND ANY NAM
FORECAST SOUNDING WITH MORE THAN 15 J/KG MLCAPE OVER THE WARM
SECTOR...DESPITE BOUNDARY LAYER DEWPOINTS IN THE UPPER 50S/LOWER
60S. THEREFORE...WHILE WINDY CONDITIONS WILL OCCUR WITH THE COLD
FRONT PASSAGE...SEVERE THUNDERSTORMS ARE NOT EXPECTED.

...OK INTO NWRN TX...
MORE SUBSTANTIAL LOW LEVEL MOISTURE WILL EXIST ACROSS THE SRN PLAINS
WITH A PLUME OF UPPER 60S F DEWPOINTS AHEAD OF THE FRONT. WITH
HEIGHT RISES BEHIND THE EJECTING UPPER TROUGH...FORCING WILL BE WEAK
OVERALL...BUT HEATING NEAR THE FRONT COULD RESULT IN A REJUVENATION
OF STORM VIGOR. A FEW LOCALLY STRONG WIND GUSTS WOULD BE
LIKELY...BUT WITH THE FILLING SURFACE TROUGH AND WEAKENING SHEAR
WITH SRN EXTENT...SEVERE APPEARS UNLIKELY.

..JEWELL.. 09/27/2013

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