Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 242002
SWODY1
SPC AC 242000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SUN MAY 24 2015

VALID 242000Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER SERN CO...SWRN KS INTO THE
OK/TX PANHANDLES...

...THERE IS A SLGT RISK OF SVR TSTMS FROM LA INTO ERN IA AND IL...

...THERE IS A MRGL RISK OF SVR TSTMS OVER MUCH OF THE PLAINS AND
MID/LWR MS VALLEY...

...SUMMARY...
SEVERE THUNDERSTORMS ARE POSSIBLE TODAY ACROSS THE SOUTHEASTERN
PLAINS AND OZARK PLATEAU INTO PORTIONS OF THE MIDDLE AND LOWER
MISSISSIPPI VALLEY.  OTHER STRONG TO SEVERE STORMS ARE POSSIBLE FROM
SOUTHEAST COLORADO INTO SOUTHWESTERN KANSAS AND OKLAHOMA.

...LOWER TO MIDDLE MS VALLEY NWD INTO MUCH OF IL...
A LARGE AREA OF HIGH PW AND DEEP SLY FLOW ARE IN PLACE WITH GRADUAL
DESTABILIZATION DUE TO HEATING AND MOISTURE ADVECTION WELL NWD INTO
IL. LAPSE RATES ALOFT AND LIFTED INDICES ARE WEAK...HOWEVER...A
BRIEF/WEAK TORNADO IS POSSIBLE DUE TO THE FAVORABLE LOW-LEVEL JET AS
NOTED ON AREA VWPS. HAVE EXTENDED LOW TORNADO PROBABILITIES NWD INTO
IA AND IL DUE TO FAVORABLE LOW-LEVEL SHEAR NEAR THE BROADER WARM
FRONT AND HEATING.

...SERN CO...SWRN KS...OK/TX PANHANDLES...
STRONG HEATING PERSISTS ACROSS THE REGION BENEATH A MIDLEVEL THERMAL
TROUGH. THE RESULT IS STEEPENING LAPSE RATE PROFILES AND INCREASING
INSTABILITY. INDEED...STORMS ARE INCREASING IN COVERAGE ACROSS MUCH
OF ERN CO...WITH OTHER TOWERING CU FORMING ALONG THE TX/NM STATE
LINE. SHEAR PROFILES ARE BEST ACROSS THE SLIGHT RISK AREA FROM SERN
CO INTO SWRN KS AND THE LOW-LEVEL JET IS ALSO FORECAST TO INCREASE
THIS EVENING. AS CELLS FORM OVER SERN CO AND CONTINUE EWD...SOME
COULD EVENTUALLY CONTAIN A TORNADO THREAT IN ADDITION TO HAIL.
THEREFORE HAVE INCREASED SEVERE PROBABILITIES INTO SWRN KS.

FOR AREA INTO THE TX S PLAINS...HAIL LOOKS TO BE THE MAIN THREAT IF
STORMS CAN FORM...BUT THERE IS A LOT OF DRY AIR ALOFT AS SEEN ON WV.
THUS HAVE EXTENDED THE MARGINAL RISK A BIT FARTHER S BASED ON THIS
CONDITIONAL THREAT. SEE FORTHCOMING MCD 742.

..JEWELL.. 05/24/2015

.PREV DISCUSSION... /ISSUED 1132 AM CDT SUN MAY 24 2015/

...SYNOPSIS...
A LARGE/COMPLEX UPPER TROUGH -- COMPRISED OF NUMEROUS SMALLER-SCALE
FEATURES EMBEDDED WITHIN BROADER CYCLONIC FLOW -- WILL CONTINUE
MOVING OUT OF THE ROCKIES AND INTO THE PLAINS TODAY.  ONE OF THE
MORE SUBSTANTIAL OF THESE SMALLER-SCALE FEATURES IS MOVING ENEWD
ACROSS TX ATTM...AND IS SUPPORTING AN EXPANSIVE AREA OF ONGOING
CLOUDS/PRECIPITATION -- AND EMBEDDED MESOSCALE CONVECTIVE
CIRCULATIONS -- CROSSING ERN PORTIONS OF THE SRN PLAINS AND ADJACENT
MO/AR/LA ATTM.

AT THE SURFACE...A BROAD/ILL-DEFINED AREA OF GENERAL LOW PRESSURE IS
EVIDENT ACROSS THE ROCKIES AND PLAINS.  THE WRN EXTENT OF THE MAIN
CONVECTIVE/SEVERE RISK AREA TODAY WILL BE DELINEATED BY AN
EWD-MIXING DRYLINE NOW OVER W TX...AND FOCUSED AREALLY/LOCALLY BY
NUMEROUS MESOSCALE/CONVECTIVE BOUNDARIES AND CIRCULATIONS FROM THE
CENTRAL/SRN PLAINS INTO THE MID/LOWER MO VALLEY.

...MO/AR/LA/WRN MS VICINITY...
A COMPLEX SCENARIO EXISTS ATTM NEAR AND W OF THE MID AND LOWER MS
VALLEY REGION...WITH A BAND OF SHOWERS AND THUNDERSTORMS EXTENDING
FROM IA SSWWD TO E TX/WRN LA.  THREE EMBEDDED/NNEWD-MOVING MESOSCALE
CIRCULATIONS ARE EVIDENT -- ONE OVER ERN IA...ONE CROSSING SERN
KS/SWRN MO...AND A THIRD OVER NERN TX...EACH WITH ARCS OF CONVECTION
TRAILING SWD TO THE NEXT CIRCULATION CENTER IN THE SERIES.

SEVERE RISK TODAY WILL EXIST ALONG AND AHEAD OF THIS CONVECTION --
PRIMARILY WITH INTENSIFICATION OF THE ONGOING BANDS OF STORMS BUT
ALSO WITH ANY ISOLATED CELLS DEVELOPING AHEAD OF THE LINE.  CLOUD
COVER ACROSS LARGE PORTIONS OF THE AREA WILL LIMIT HEATING...WHICH
SHOULD TEMPER STORM INTENSITY TO SOME DEGREE.  HOWEVER...MODERATE TO
STRONG FLOW ALOFT -- THOUGH LARGELY SLY/UNIDIRECTIONAL -- WILL
SUPPORT ORGANIZED UPDRAFTS.  IN ADDITION...BACKED/SELY SURFACE WINDS
-- PARTICULARLY INVOF THE MESOSCALE CIRCULATIONS -- WILL SUPPORT
LOW-LEVEL MESOVORTICES WITHIN THE CONVECTIVE BANDS AND POTENTIAL FOR
LOW-LEVEL MESOCYCLONES WITH ANY ISOLATED CELLULAR DEVELOPMENT.  THUS
-- A FEW TORNADOES APPEAR LIKELY AS STORMS SPREAD EWD/NEWD ACROSS
THE SLIGHT RISK AREA...ALONG WITH LOCALLY DAMAGING WINDS AND
POSSIBLY MARGINAL HAIL.  THE PRIMARY RISK SHOULD REMAIN GENERALLY
ALONG AND W OF THE MS VALLEY THROUGH THIS EVENING...WITH SOME
WEAKENING OF STORMS AND ATTENDANT SEVERE RISK AS WIDESPREAD
CONVECTION SPREADS E OF THE MS VALLEY OVERNIGHT.

...ERN CO SEWD INTO NWRN TX/SWRN OK...
AFTERNOON THUNDERSTORM DEVELOPMENT IS FORECAST FROM THE CENTRAL HIGH
PLAINS SEWD ACROSS THE TX/OK PANHANDLES AND INTO SWRN OK/WRN N
TX...AS STEEP MID-LEVEL LAPSE RATES ATOP AN AMPLY MOIST BOUNDARY
LAYER COMBINE WITH DIURNAL HEATING TO RESULT IN MODERATE INSTABILITY
/1000 TO 2000 J/KG MIXED-LAYER CAPE/.

WITH 30 TO 35 KT MID-LEVEL WLYS EXPECTED ACROSS THIS AREA ATOP
LOW-LEVEL SELYS ON THE COOL SIDE OF A WEAK/REMNANT OUTFLOW LYING
NW-SE ACROSS THIS AREA...SHEAR SUPPORTIVE OF UPDRAFT ROTATION
SUGGESTS THAT ANY DEVELOPING STORMS WILL LIKELY BECOME SUPERCELLS --
WITH ATTENDANT RISK FOR LARGE HAIL AND LOCALLY DAMAGING
WINDS...ALONG WITH POTENTIAL FOR A COUPLE OF TORNADOES.  ONE
QUESTION ATTM REVOLVES AROUND THE NUMBER OF STORMS WHICH WILL
DEVELOP OVER THE WRN N TX/SWRN OK REGION IN THE WAKE OF A PRONOUNCED
VORT MAX CROSSING TX...BUT EXPECT AT LEAST ISOLATED STORMS TO
DEVELOP -- COMMENSURATE WITH SLIGHT RISK ACROSS THIS AREA.



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