SWODY3
SPC AC 180649
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0149 AM CDT SUN SEP 18 2011
VALID 201200Z - 211200Z
...SYNOPSIS...
MODELS INDICATE THE UPPER FLOW PATTERN WILL AMPLIFY ON TUESDAY AS AN
UPPER LOW DEVELOPS OVER THE UPPER MS VALLEY. AT THE SURFACE... AN
OCCLUDED LOW WILL MOVE SLOWLY EWD ACROSS MN...WITH A COLD FRONT
ARCING SWD FROM THE LOW AND PROGRESSING EWD/SEWD FROM THE WRN GREAT
LAKES AND MIDDLE MS VALLEY INTO THE SRN HIGH PLAINS.
...WI AREA...
LARGE SCALE ASCENT ASSOCIATED WITH THE UPPER LOW COUPLED WITH LOW
LEVEL CONVERGENCE ALONG THE ADVANCING FRONT WILL PROVIDE SUPPORT FOR
CONVECTION TO SPREAD EWD DURING THE PERIOD. MOISTURE RETURN INTO
PARTS OF THE UPPER MIDWEST IN THE WAKE OF THE PREVIOUS COLD FRONTAL
PASSAGE IS EXPECTED TO BE QUITE LIMITED...WITH MODELS INDICATING A
NARROW BAND OF SURFACE DEW POINTS IN THE 50S AHEAD OF THE PRIMARY
COLD FRONT. A PLUME OF STEEPER MID LEVEL LAPSE RATES IS FORECAST TO
SPREAD EWD/NEWD FROM THE CENTRAL PLAINS TOWARD THE UPPER MS
VALLEY...AND THIS WILL AID IN DEVELOPING AN AXIS OF MARGINAL
INSTABILITY WITH SBCAPE OF 250-500 J/KG IMMEDIATELY AHEAD OF THE
COLD FRONT.
THERE IS POTENTIAL FOR LOW-TOPPED STORMS /INCLUDING LINE SEGMENTS/
TO DEVELOP ALONG/AHEAD OF THE COLD FRONT FROM PARTS OF UPPER MI INTO
WI DURING THE AFTERNOON...WITH ACTIVITY SPREADING EWD THROUGH THE
EVENING HOURS. THERE IS UNCERTAINTY IN THE SWD EXTENT OF CONVECTIVE
DEVELOPMENT ALONG THE FRONT...WITH SOME GUIDANCE INDICATING STORMS
FORMING AS FAR SOUTH AS ERN IA/NWRN IL. STRONG LOW/MID LEVEL WINDS
ARE FORECAST TO VEER WITH HEIGHT WHICH WILL ENHANCE STORM
ORGANIZATION AND INTENSITY. STRONGER CELLS MAY BE CAPABLE OF
PRODUCING STRONG WIND GUSTS...ESPECIALLY DURING THE AFTERNOON AND
EVENING...BUT OVERALL SEVERE THREAT IS EXPECTED TO BE LIMITED BY
WEAK INSTABILITY.
..WEISS.. 09/18/2011
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment