Severe Storm Outlook Narrative (AC)
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
ACUS01 KWNS 042001
SWODY1
SPC AC 041959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0159 PM CST WED MAR 04 2015

VALID 042000Z - 051200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
ISOLATED THUNDERSTORMS MAY OCCUR FROM THE SOUTHERN GREAT PLAINS TO
THE LOWER MISSISSIPPI VALLEY REGION.

...DISCUSSION...
FORECAST RATIONALE REMAINS LARGELY UNCHANGED FROM PREVIOUS
DISCUSSION. AMDAR DATA NEAR NEW ORLEANS AND HOUSTON CONTINUE TO
SAMPLE THE WARM LAYER NEAR 700 MB WHICH SHOULD RESULT IN ONLY
SHALLOW CONVECTION/SHOWERS AHEAD OF THE SOUTHWARD-SINKING FRONT OVER
THE LOWER MISSISSIPPI VALLEY. PROSPECTS FOR A SUSTAINED TORNADO OR
DAMAGING WIND RISK HERE REMAIN LOW.

FARTHER WEST...POST-FRONTAL ELEVATED CONVECTION IS EXPECTED TO
INCREASE THIS EVENING OVER THE RIO GRANDE IN TEXAS TO THE EDWARDS
PLATEAU. STEEPER MID-LEVEL LAPSE RATES AS SAMPLED BY 12Z DEL RIO
RAOB ALONG WITH FAVORABLY ROBUST CLOUD-BEARING SHEAR COULD YIELD
SMALL HAIL DESPITE MEAGER MUCAPE.

..GRAMS.. 03/04/2015

.PREV DISCUSSION... /ISSUED 1029 AM CST WED MAR 04 2015/

...SYNOPTIC SETUP...
SPLIT FLOW OF RECENT DAYS WILL GIVE WAY TO A BROAD BUT MORE
PROGRESSIVE POSITIVE-TILT TROUGH AS SRN STREAM LOW NOW OVER SONORA
IS RAPIDLY ABSORBED WITHIN STRENGTHENING SWLY FLOW AHEAD OF
AMPLIFYING NRN STREAM. REMNANT OF SONORAN LOW SHOULD REACH THE SRN
HI PLNS THIS EVE...AND THE OZARKS EARLY THU...AS SEVERAL MUCH WEAKER
IMPULSES SHEAR NEWD IN STRENGTHENING FLOW ACROSS THE SRN PLNS/LWR MS
VLY.

AT THE SFC...STRONG COLD FRONT ASSOCIATED WITH LEAD NRN STREAM
DISTURBANCE...MARKING THE ARRIVAL OF YET ANOTHER ARCTIC AIR
MASS...WILL ADVANCE STEADILY SE THROUGH THE PERIOD...REACHING A N GA
TO S TX LINE THIS EVE...AND THE N CNTRL GULF OF MEXICO EARLY THU.
THE BOUNDARY INCREASINGLY WILL UNDERCUT MID-LVL WARM CONVEYOR BELT
ASSOCIATED WITH THE SONORAN SYSTEM AND...WITH TIME...ALSO THE
LOW-LVL MOIST PLUME ORIGINATING OVER THE WRN GULF.

...S/ERN TX TO LWR MS VLY TODAY/TNGT...
BANDS OF CONVECTION LIKELY WILL PERSIST AND POSSIBLY INCREASE IN
COVERAGE THROUGH THE PERIOD FROM PARTS OF TX NEWD INTO THE TN VLY...
IN WAKE OF AFOREMENTIONED COLD FRONT CROSSING THE S CNTRL STATES.
SOME OF THIS ACTIVITY...ESPECIALLY WELL BEHIND THE FRONT...MAY YIELD
SPORADIC THUNDER AS UNDERCUTTING COLD AIR CONTINUES TO DEEPEN AND AS
LARGE SCALE ASCENT SOMEWHAT STRENGTHENS WITH THE GLANCING INFLUENCE
OF DEAMPLIFYING SRN STREAM TROUGH. THE MAIN FACTORS LIMITING MORE
WIDESPREAD/STRONGER DEVELOPMENT INCLUDE /1/ WEAK MID-LVL LAPSE RATES
/REFLECTING POSITIVE-TILT OF LARGE-SCALE TROUGH/...AND /2/ MODEST
LARGE-SCALE FORCING FOR ASCENT.

A BIT FARTHER SE...SOME POTENTIAL WILL EXIST FOR THE DEVELOPMENT OF
A CONVECTIVE BAND ALONG THE IMMEDIATE SFC FRONT OVER SRN/ERN
TX...LA...AND MS. IN ADDITION...A SEPARATE BROKEN BAND OF
SHOWERS/POSSIBLE STORMS MAY FORM ALONG WEAK CONFLUENCE AXIS AHEAD OF
THE FRONT OVER PARTS OF LA/MS/AL...WITH THE LATTER DEVELOPMENT
DEPENDENT UPON THE PRESENCE OF APPRECIABLE DAYTIME HEATING IN THE
WARM SECTOR.

AS WITH THE POST-FRONTAL ENVIRONMENT...HOWEVER...BOTH MID-LVL LAPSE
RATES AND FORCING FOR ASCENT WILL BE WEAK. IN PARTICULAR...700 MB
WARM LAYER SAMPLED BY THE 12Z LA AND MS RAOBS LIKELY WILL REMAIN IN
PLACE TODAY...LIMITING UPDRAFT DEPTH AND INTENSITY. AND...STEADY
ADVANCE OF ARCTIC BOUNDARY WILL UNDERCUT STORMS ALONG IT. WHILE
PARTS OF SE TX...LA...AND MS AHEAD OF THE FRONT WILL HAVE TO BE
CLOSELY MONITORED FOR THE POSSIBILITY OF RELATIVELY SHALLOW
CONVECTION/SHOWERS ASSUMING SOME DEGREE OF LOW-LVL ROTATION GIVEN
MOIST LOW-LVL ENVIRONMENT AND MODERATELY-SHEARED NEAR-SFC
FLOW...PROSPECTS FOR A SUSTAINED TORNADO OR DMGG WIND THREAT ATTM
APPEAR LOW.

...SRN RCKYS AND VICINITY THIS AFTN...
LARGELY UNIMPEDED SFC HEATING...TERRAIN UPLIFT...AND ASCENT AHEAD OF
AND BENEATH EJECTING SRN STREAM TROUGH SHOULD SUPPORT WDLY SCTD AFTN
CONVECTION OVER PARTS OF NM AND PERHAPS ADJACENT SECTIONS OF ERN
AZ/FAR SRN CO. THIS ACTIVITY MAY SUFFICIENTLY DEEPEN TO YIELD
SPORADIC LIGHTNING IN AREAS W AND SW OF SHALLOW ARCTIC SURGE OVER
THE SRN HI PLNS.




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.