SWODY1
SPC AC 271956
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT TUE MAR 27 2012
VALID 272000Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF MIDDLE MS VALLEY...
...20Z OUTLOOK UPDATE...MIDDLE MS VALLEY...
LATEST WATER VAPOR IMAGERY INDICATES THAT THE CENTER OF THE COMPACT
BUT VIGOROUS UPPER MIDWEST CLOSED LOW IS STILL LIFTING
NORTHEASTWARD...NOW ACROSS NORTHWEST ONTARIO. MODERATELY STRONG
FLOW ON ITS SOUTHERN AND EASTERN PERIPHERY HAS ADVECTED WARM
ELEVATED MIXED LAYER AIR ACROSS THE MID/LOWER MISSOURI VALLEY AREA
INTO THE UPPER MIDWEST...AND THIS CONTINUES TO CAP RELATIVELY WEAK
TO MODEST WARM SECTOR MOISTURE RETURN. DEEPER LAYER MOISTENING
APPEARS TO BE CONFINED TO A NARROW PRE-FRONTAL CORRIDOR EXTENDING
OUT OF THE CENTRAL PLAINS THROUGH NORTHERN MISSOURI INTO EASTERN
IOWA. AS LOW-LEVEL FLOW GRADUALLY VEERS TO AN INCREASINGLY WESTERLY
COMPONENT...THIS WILL TEND TO SHIFT MORE RAPIDLY EASTWARD ACROSS
NORTHERN ILLINOIS...THAN SOUTHWARD TOWARD THE I-70 CORRIDOR OF
MISSOURI LATE THIS AFTERNOON AND EVENING.
INITIATION OF STORM DEVELOPMENT REMAINS A BIT UNCLEAR...BUT LATEST
RUC GUIDANCE SEEMS TO POINT TO THE QUAD CITIES AREA AROUND 23-00Z
...AND EAST NORTHEAST OF KANSAS CITY INTO THE KIRKSVILLE AREA NOT
LONG THEREAFTER. AT LEAST WEAK MID-LEVEL HEIGHT FALLS AS FAR SOUTH
AS NORTHERN MISSOURI AND CENTRAL ILLINOIS ARE EXPECTED BY THAT
TIME...IN ASSOCIATION WITH A GRADUAL EASTWARD TURN OF THE MID-LEVEL
LOW AND TRAILING SHORT WAVE TROUGH ACROSS THE UPPER MIDWEST. THIS
PROBABLY WILL CONTRIBUTE TO SUFFICIENT WEAKENING OF INHIBITION TO
ALLOW AT LEAST SCATTERED STORM DEVELOPMENT IN THE PRESENCE OF MIXED
LAYER CAPE ON THE ORDER OF 1000-2000 J/KG AND 40-50 KT WESTERLY DEEP
LAYER MEAN FLOW AND SHEAR. IN ADDITION TO THE RISK FOR A COUPLE OF
SUPERCELLS...THIS ENVIRONMENT WILL BE CONDUCIVE TO THE EVOLUTION OF
ONE OR TWO SMALL ORGANIZED STORM CLUSTERS CAPABLE OF PRODUCING
DAMAGING WIND GUSTS AND SOME HAIL.
TORNADIC POTENTIAL IS MORE UNCERTAIN. FORECAST SOUNDINGS CONTINUE
TO INDICATE THAT THE LOW-LEVEL HODOGRAPHS WILL BE LARGE AND
CLOCKWISE CURVED...BUT VERTICAL SHEAR FROM MID-LEVELS ON UP IS
LIKELY TO REMAIN RATHER WEAK. AND...PERHAPS MORE IMPORTANTLY...THE
LOW-LEVEL THERMODYNAMIC STRUCTURE...WITH LINGERING LAYERS OF
POTENTIALLY SIZABLE TEMPERATURE-DEW POINT SPREADS...APPEARS MORE
QUESTIONABLE FOR SUSTAINED NEAR SURFACE STRONG ROTATION.
..KERR.. 03/27/2012
.PREV DISCUSSION... /ISSUED 1124 AM CDT TUE MAR 27 2012/
...SYNOPSIS...
INTENSE UPPER LOW CURRENTLY MOVING NEWD OVER NRN MN IS FORECAST TO
CONTINUE INTO ONTARIO AND PROGRESS EWD TONIGHT JUST NORTH OF THE
UPPER GREAT LAKES...AS AN UPSTREAM TROUGH OVER THE ERN PACIFIC
APPROACHES THE PACIFIC NW COAST. THIS WILL RESULT IN THE PRIMARY
WESTERLY FLOW ALOFT EXTENDING FROM THE PACIFIC COAST AND ACROSS THE
NRN HALF OF THE CONUS...WITH WEAK WINDS ALOFT ACROSS MUCH OF THE SRN
US. AT THE SURFACE...A LOW OVER EXTREME NWRN MN WILL TRANSLATE
ACROSS THE NRN MN BORDER TODAY BEFORE MOVING INTO ONTARIO TONIGHT.
A COLD FRONT ARCING SWD/SWWD FROM THE LOW WILL PROGRESS INTO WI/ERN
IA/NWRN MO/SRN KS AND THE TX PANHANDLE BY THIS EVENING...REACHING A
SERN LOWER MI/CENTRAL IL/NRN OK LINE BY LATER TONIGHT.
...MIDDLE MS VALLEY REGION...
SATELLITE DATA INDICATE A RELATIVELY NARROW AXIS OF MOISTURE IS
PRESENT FROM THE SRN PLAINS ACROSS ERN KS/NWRN MO INTO CENTRAL/ERN
IA AND WRN WI WITH PW VALUES OF 0.75-1.0 INCH. THIS CORRESPONDS TO
AN AXIS OF 55-60F SURFACE DEW POINTS EXTENDING NNEWD INTO CENTRAL IA
IMMEDIATELY AHEAD OF THE COLD FRONT. A BAND OF ELEVATED STORMS HAS
BEEN OCCURRING WITHIN THE MOIST AXIS FROM NERN KS INTO NRN MO/SRN
IA...AND SATELLITE/RADAR/LIGHTNING TRENDS INDICATE THE STORMS HAVE
BEEN SLOWLY WEAKENING.
12Z UPPER AIR DATA SHOW AN ELEVATED MIXED LAYER PLUME HAS SPREAD
NEWD FROM THE PLAINS INTO THE MIDDLE MS VALLEY ON THE SRN EDGE OF
THE STRONGER SWLY MID LEVEL WINDS. MODEL GUIDANCE INDICATES THE EML
WILL PERSIST THROUGH THE AFTERNOON AND EVENING WHICH WILL LIKELY
LIMIT THE DEVELOPMENT OF SURFACE-BASED STORMS IN THE WARM SECTOR
THROUGH MUCH OF THE DIURNAL HEATING CYCLE.
THE PRIMARY FOCUS FOR POTENTIAL CONVECTIVE DEVELOPMENT WILL BE ALONG
THE COLD FRONT LATER THIS AFTERNOON AND EVENING...WITH NWP GUIDANCE
VARYING SOMEWHAT IN THE TIMING...LOCATION AND COVERAGE OF DEEP
CONVECTION. THE MOST LIKELY REGION FOR INITIAL CONVECTIVE
DEVELOPMENT IS EXPECTED OVER PARTS OF EXTREME EASTERN IA/NWRN IL
INTO NRN MO...WHERE MODEL/ENSEMBLE CONSENSUS IS THE HIGHEST. THIS
ALSO IS WITHIN A REGION OF STRONGER VERTICAL SHEAR JUST TO THE SOUTH
OF A STRONG 500 MB JET STREAK...WHICH WILL ENHANCE POTENTIAL FOR
SEVERE STORMS INCLUDING A FEW SUPERCELLS. FORECAST SOUNDINGS ALSO
SHOW FAVORABLE LOW LEVEL SHEAR/CLOCKWISE HODOGRAPHS SUGGESTING
THREAT FOR A TORNADO OR TWO TO DEVELOP WITH ANY PERSISTENT
SUPERCELLS THAT ARE ABLE TO DEVELOP. THE SEVERE THREAT IS EXPECTED
TO CONTINUE AFTER DARK FOR SEVERAL HOURS BEFORE STORMS GRADUALLY
DIMINISH AFTER 06Z.
...KS/OK...
CONVERGENCE ALONG THE COLD FRONT WILL GRADUALLY WEAKEN WITH SWWD
EXTENT...AND THE PERSISTENT CAPPING INVERSION IS EXPECTED TO LIMIT
STORM COVERAGE OVER PARTS OF KS INTO OK. HOWEVER...CONTINUED
DESTABILIZATION DURING THE DIURNAL HEATING PERIOD WILL RESULT IN
CAPE OF 1500-2000 J/KG LATER THIS AFTERNOON AND EVENING. AND
DESPITE WEAKER WINDS ALOFT...VEERING PROFILES WITH HEIGHT WILL
RESULT IN DEEP LAYER SHEAR OF AROUND 30 KT WHICH MAY PROMOTE A
ORGANIZED MULTICELL STORM STRUCTURES FOR ANY SUSTAINED UPDRAFTS THAT
DEVELOP. ISOLATED STRONGER STORMS MAY BE CAPABLE OF PRODUCING LARGE
HAIL AND STRONG WIND GUSTS VERY LATE THIS AFTERNOON AND EVENING.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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