DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 140832
SWODY3
SPC AC 140830

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CST THU NOV 14 2013

VALID 161200Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
THE VIGOROUS SHORT WAVE IMPULSE EXPECTED TO DIG INTO THE PACIFIC
NORTHWEST BY LATE FRIDAY NIGHT APPEARS LIKELY TO REMAIN PROGRESSIVE
DURING THIS FORECAST PERIOD. CONSIDERABLE VARIABILITY EXISTS AMONG
THE MODELS CONCERNING THE SPEED OF THIS FEATURE INTO AND THROUGH THE
CENTRAL U.S...WITH THE GFS REMAINING SIGNIFICANTLY FASTER THAN THE
ECMWF EAST OF THE ROCKIES AND THROUGH THE CENTRAL PLAINS. THE
14/00Z OPERATIONAL ECMWF AND THE ECMWF ENSEMBLE MEAN HAVE TRENDED A
BIT FASTER...AND APPEAR IN RELATIVELY GOOD AGREEMENT WITH THE 14/03Z
NCEP SREF...WHICH IS FASTER THE 14/00Z OPERATIONAL NAM. IT
CURRENTLY SEEMS MOST PROBABLE THAT STRONG MID-LEVEL HEIGHT FALLS
ASSOCIATED WITH THE SHORT WAVE TROUGH WILL SHIFT EAST OF THE ROCKIES
INTO THE CENTRAL PLAINS SATURDAY NIGHT...SUPPORTING A DEEPENING
SURFACE CYCLONE ACROSS THE CENTRAL PLAINS THROUGH THE MID MISSOURI
VALLEY BY 12Z SUNDAY.

IN ADVANCE OF THE PRIMARY SHORT WAVE IMPULSE...AND ASSOCIATED
SURFACE CYCLONE...ANOTHER SIGNIFICANT SHORT WAVE IMPULSE AND
ASSOCIATED SURFACE FRONTAL WAVE ARE EXPECTED TO RAPIDLY PROGRESS
NORTHEAST OF THE CENTRAL PLAINS...INTO THE UPPER GREAT LAKES
REGION...DURING THE DAY SATURDAY...BEFORE CONTINUING NORTH
NORTHEASTWARD THROUGH NORTHERN/EASTERN ONTARIO. ALTHOUGH LOW-LEVEL
MOISTENING WILL ALREADY BE UNDERWAY IN ASSOCIATION WITH A DEVELOPING
RETURN FLOW ACROSS THE WESTERN GULF COAST...TOWARD THE UPPER
MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION...DEEPER BOUNDARY LAYER
MOISTURE RETURN WILL BE SLOWER TO OCCUR...AND MAY NOT BEGIN
INCREASING SUBSTANTIVELY ACROSS EASTERN PORTIONS OF THE CENTRAL
PLAINS/OZARK PLATEAU AND MIDDLE MISSISSIPPI VALLEY UNTIL SATURDAY
EVENING. DESTABILIZATION PROBABLY WILL BE SUFFICIENT TO SUPPORT
INCREASING THUNDERSTORM ACTIVITY EAST OF THE MID MISSOURI VALLEY
THROUGH THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION DURING
THE DAY SATURDAY...BUT ANY SEVERE THUNDERSTORM POTENTIAL STILL
APPEARS LIKELY TO AWAIT BETTER MOISTURE RETURN...AND MID-LEVEL
FORCING ASSOCIATED WITH THE STRONG UPSTREAM IMPULSE.

...LOWER CENTRAL PLAINS INTO UPPER MISSISSIPPI VALLEY...
MODELS ARE BECOMING MORE SUGGESTIVE OF INCREASING SEVERE STORM
POTENTIAL ACROSS THE CENTRAL U.S. DURING THE LATTER HALF OF THIS
FORECAST PERIOD. DUE TO CONSIDERABLE LINGERING UNCERTAINTIES...
ONLY SUB-SLIGHT RISK SEVERE PROBABILITIES ARE BEING INTRODUCED FOR
NOW...BUT THESE COULD BE INCREASED IN LATER OUTLOOKS FOR THIS TIME
PERIOD. THE AREAL DELINEATION OF THE 5 PERCENT SEVERE PROBABILITIES
WAS HEAVILY INFLUENCE BY THE AFOREMENTIONED ECMWF/ECMWF ENSEMBLE AND
NCEP SREF ENSEMBLE DEPICTION OF DEVELOPMENTS. INCREASING LOW-LEVEL
MOISTURE/CAPE AND VERTICAL SHEAR ALONG THE WESTERN EDGE OF THE
STRENGTHENING LOW-LEVEL JET /50-60+ KT AT 850 MB/ MAY PROVIDE THE
FOCUS FOR SEVERE STORM DEVELOPMENT...AS THE LEADING EDGE OF STRONGER
MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION SHIFTS INTO THE PLAINS.
THIS COULD BE AS EARLY AS LATE SATURDAY EVENING...BEFORE POTENTIAL
INCREASES AND SLOWLY DEVELOPS EASTWARD OVERNIGHT. THE ENVIRONMENT
MAY BECOME CONDUCIVE TO THE DEVELOPMENT OF SUPERCELLS...AND THE
EVOLUTION OF A SQUALL LINE.

..KERR.. 11/14/2013

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