National Weather Service Weather Forecast Office

Severe Storm Outlook Narrative (ac)

033
ACUS02 KWNS 030548
SWODY2
SPC AC 030546

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT THU OCT 03 2013

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN NEB...IA...SRN
MN...WI...NWRN MO...ERN KS...NWRN OK...

...SYNOPSIS...
LATEST GUIDANCE FROM THE GFS AND ECMWF MODELS SUGGESTS A SLOWER
EVOLUTION TO THE UPPER TROUGH THAN COMPARED TO THE MORE AGGRESSIVE
NAM MODEL WHICH IS FARTHER E WITH THE COLD FRONT AND DEEPER WITH THE
UPPER LOW VALID AT 00Z. FOR THIS OUTLOOK...THE SLOWER SOLUTION IS
PREFERRED.

DURING THE DAY...LOW PRESSURE IS FORECAST TO DEEPEN OVER WRN KS AND
INTO CNTRL NEB...WITH A NEARLY STATIONARY BOUNDARY FROM FSD/SUX EWD
ACROSS NRN IA OR SRN MN AND INTO WRN WI. THIS BOUNDARY WILL BE
REINFORCED BY EPISODES OF RAIN AND STORMS THROUGHOUT THE
PERIOD...BUT MAY RETURN SLIGHTLY AS A WARM FRONT AHEAD OF THE
DEVELOPING LOW. SEVERE STORMS WILL BE POSSIBLE IN ASSOCIATION WITH
THIS FRONT WELL AHEAD OF THE MAIN SYSTEM.

BY LATE AFTERNOON...A STRONG COLD FRONT WILL EXTEND SWWD FROM THE
ERN NEB LOW...INTO CNTRL KS...NWRN OK AND THE TX PANHANDLE. A
RAPIDLY DEVELOPING SQUALL LINE IS EXPECTED...WITH THE MOST INTENSE
STORMS FROM ERN NEB INTO IA...AND PERHAPS SRN MN BY EVENING.

...ERN NEB...IA...SRN MN...WRN WI...
SCATTERED THUNDERSTORMS MAY BE ONGOING ALONG THE WARM FRONT EARLY
WITH A THREAT OF HAIL. DEPENDING ON HOW MUCH RAIN FALLS ALONG THE
FRONT...IT COULD MODULATE ITS LATITUDINAL LOCATION. HEATING WILL
OCCUR S OF THE FRONT...WITH MODERATE INSTABILITY DEVELOPING. AS THE
UPPER TROUGH NEARS...SHEAR PROFILES WILL INCREASE...WITH LARGE
LOOPING HODOGRAPHS NEAR THE WARM FRONT. THIS WILL CONDITIONALLY
FAVOR SUPERCELLS WITH LARGE HAIL AND A FEW TORNADOES. THE GFS AND
EURO BOTH HAVE STRONG CONVECTIVE SIGNALS ACROSS NRN IA...FAR SRN
MN...AND SWRN WI DURING THE AFTERNOON...SUGGESTING CLUSTERS OF
SEVERE STORMS ARE PROBABLE.

MEANWHILE TO THE SW...A LOW PRESSURE TROUGH WILL DEEPEN AHEAD OF A
STRONG COLD FRONT WITH SFC LOW CENTER ACROSS ERN NEB BY 21-00Z. GFS
SHOWS CLASSIC LOADED GUN TYPE SOUNDINGS OVER ERN NEB AHEAD OF THE
LOW...WITH STRONG CONVERGENCE AND DEEP MIXED LAYERS JUST W OF THE
FRONT AT PEAK HEATING. WITH LARGE HODOGRAPHS AND STRONG
FORCING...THE AREA FROM ERN NEB INTO CNTRL IA APPEARS TO HAVE THE
GREATEST THREAT OF TORNADIC SUPERCELLS. IF THE COLD AIR SURGES
QUICKER THAN FORECAST...A MORE LINEAR STRUCTURE COULD RESULT...BUT
WITH EMBEDDED ROTATION AND LEWPS CAPABLE OF SIGNIFICANT STRAIGHT
LINE WINDS.

A MODERATE RISK COULD BE ISSUED IN LATER OUTLOOKS AS PREDICTABILITY
OF THIS SYSTEM INCREASES.

...OK...ERN KS...WRN MO...
LAPSE RATE PROFILES WILL STEEPEN ACROSS THE REGION DUE TO HEATING
AND UPPER COOLING. STORMS ARE EXPECTED TO RAPIDLY FORM ALONG THE
COLD FRONT AND QUICKLY BECOME A SQUALL LINE. THE STRONG FORCING AS
WELL AS AMPLE DEEP LAYER SHEAR ORIENTED ALONG THE FRONT SHOULD
SUPPORT A LARGE LINEAR MCS CAPABLE OF LOCALLY DAMAGING WINDS AND
AREAS OF LARGE HAIL...ALTHOUGH THE HAIL THREAT SHOULD DECREASE ONCE
INDIVIDUAL STORM CELLS MERGE. THIS LINE SHOULD REMAIN SEVERE INTO
EVENING...BUT WILL LIKELY DECREASE IN INTENSITY OVERNIGHT AS THE
COLD FRONT UNDERCUTS THE MCS.

..JEWELL.. 10/03/2013