Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 282009
SWODY1
SPC AC 282007

DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0307 PM CDT THU APR 28 2016

VALID 282000Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TX PANHANDLE INTO SRN
OK...NRN AND CNTRL TX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM SERN OH/WV ACROSS THE WRN
VIRGINIAS INTO NC...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS MUCH OF THE SRN
PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS MUCH OF THE SERN
STATES...

CORRECTED FOR GRAPHIC IN WV

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS ARE FORECAST THIS AFTERNOON OVER
PARTS OF SOUTHWEST VIRGINIA/NORTH CAROLINA...AND LATER TODAY THROUGH
EARLY FRIDAY OVER THE SOUTHERN PLAINS. STRONG TO ISOLATED SEVERE
STORMS ALSO MAY OCCUR OVER THE CENTRAL GULF COAST REGION...CENTRAL
AND EAST TEXAS...AND PARTS OF THE SOUTHEAST.

...I-35 CORRIDOR CNTRL INTO NRN TX THIS EVENING/OVERNIGHT...
A CONDITIONAL SLIGHT RISK FOR HAIL HAS BEEN ADDED TO PORTIONS OF
CNTRL AND NRN TX.

SURFACE ANALYSIS SHOWS RICH BOUNDARY LAYER MOISTURE SURGING NWWD
INTO CNTRL TX WITH STRONG HEATING AND DEWPOINTS RISING TO NEAR 70 F.
AS THE LOW LEVEL JET INCREASES THIS EVENING...SO WILL LIFT VIA WARM
ADVECTION. NUMEROUS MODELS ARE NOW SHOWING ISOLATED TO SCATTERED
STORMS DEVELOPING ACROSS CNTRL TX...AND PERSISTING OVERNIGHT MOVING
NNEWD UP THE I-35 CORRIDOR. STRONG INSTABILITY AND LAPSE RATES AS
WELL AS VEERING WINDS IN THE LOW-LEVELS WILL FAVOR SUPERCELLS WITH
ANY STORMS THAT DEVELOP. LARGE HAIL WILL BE THE PRIMARY THREAT WITH
ANY CELLS THAT CAN DEVELOP IN THIS RELATIVELY WEAKLY FORCED REGIME.

...TX PANHANDLE AND S PLAINS...
RAPID WWD MOISTURE ADVECTION PERSISTS WITH MID 50S F DEWPOINTS INTO
CDS AND AN EXPANDING CU FIELD. STRONGLY BACKED AND INCREASING WIND
FIELDS LATE AFTERNOON THROUGH EVENING WILL CLEARLY SUPPORT
SUPERCELLS CAPABLE OF VERY LARGE DAMAGING HAIL...AND PERHAPS A
TORNADO OR TWO. THE THREAT WILL PERSIST INTO WRN OK OVERNIGHT AS THE
LOW LEVEL JET CONTINUES TO DESTABILIZE THE REGION VIA ADVECTION.

...SRN LA...
STRONG INSTABILITY IS IN PLACE WITH CELLS DEVELOPING ALONG AN
OUTFLOW BOUNDARY ACROSS SERN LA. THESE CELLS MAY CONTINUE TO
GRADUALLY PROPAGATE WWD WITH MAINLY A MARGINAL HAIL OR WIND THREAT.

...ERN IN/SRN OH...
A FEW STRONGER CELLS ARE FORMING ALONG A WARM FRONT...WITH ROTATION
NOTED AT TIMES AS INSTABILITY INCREASES AND 0-1 SRH APPROACHES 100
M2/S2. AS SUCH...HAVE EXPANDED MARGINAL RISK INTO THIS AREA. FOR
MORE INFORMATION SEE MCD 482.

..JEWELL.. 04/28/2016

.PREV DISCUSSION... /ISSUED 1132 AM CDT THU APR 28 2016/

...SYNOPTIC SETUP...
POSITIVE-TILT LWR CO VLY LOW/TROUGH WILL PROGRESS E INTO NM BY 12Z
FRI...ASSUMING A SOMEWHAT NEGATIVE TILT AS ASSOCIATED JET STREAK NOW
ALONG THE SRN CA CST SWEEPS SE INTO NRN CHIHUAHUA. AT THE SAME
TIME...EXPECT IA UPR IMPULSE TO CONTINUE SHEARING EWD IN CONFLUENT
FLOW ACROSS THE LWR GRT LKS/NORTHEAST.

AT THE SFC...LEE LOW WILL BECOME BETTER ORGANIZED LATER TODAY
THROUGH TNGT OVER THE SRN HI PLNS...LIKELY BECOMING CENTERED OVER
THE SRN TX PANHANDLE BY THE END OF THE PERIOD. AS FRONTOGENESIS
STRENGTHENS TO ITS E...EXPECT A WNW-ESE FRONTAL ZONE TO BECOME
ESTABLISHED ACROSS N CNTRL TX BY THE END OF THE PERIOD. AT THE SAME
TIME...ELONGATED AREA OF LOW PRESSURE EXTENDING FROM IA INTO SRN OH
SHOULD REFORM/CONSOLIDATE SE INTO WRN NC LATER TODAY...ALONG SWRN
FRINGE OF COLD AIR DAMMING REGIME OVER THE MID-ATLANTIC. LINGERING
FRONTAL ZONE NOW EXTENDING SW ACROSS PARTS OF THE OH-TN AND LWR MS
VLYS SHOULD FURTHER WEAKEN AS NEW FRONTAL ZONE BECOMES ESTABLISHED
ACROSS TX.

...MID-OH VLY ESE INTO NC THIS AFTN/EVE...
VORT LOBE ROUNDING SE QUADRANT OF IA UPR LOW WILL OVERSPREAD ERN
KY/WV/WRN VA-NC AREA TODAY...FURTHER DESTABILIZING REGION OF STRONG
SFC HEATING S OF WEAK FRONT OVER THE OH VLY/APPALACHIANS...AND S OF
COLD-AIR DAMMING BNDRY FARTHER E. HOWEVER...OBSERVED SOUNDINGS
SUGGEST THAT MID-LVL LAPSE RATES WILL NOT BE PARTICULARLY
STEEP...POSSIBLY AS A RESULT OF WIDESPREAD UPSTREAM CONVECTION OVER
THE PAST TWO DAYS. NEVERTHELESS...COUPLED WITH 30-40 KT
UNIDIRECTIONAL WLY 700-500 MB FLOW...DESTABILIZATION SHOULD BE
SUFFICIENT FOR SUSTAINED MULTICELLS AND WEAK SUPERCELLS AS MLCAPE
INCREASES TO 1500-2000 J/KG...ESPECIALLY OVER AND E OF THE MTNS.
SOME OF THE STORMS WILL BE CAPABLE OF SVR HAIL AND LOCALLY DMGG WIND
AS THEY ORGANIZE INTO SMALL...ESE-MOVING CLUSTERS.

...CNTRL/ERN GULF CST THIS AFTN...
PERSISTENT MCS SHOULD REMAIN QSTNRY OVER THE CNTRL GULF CST INTO THE
AFTN AS WEAK WAA/MOISTURE TRANSPORT CONTINUE IN MODERATE/DEEP WLY
FLOW. OUTFLOW MERGERS AND PRECIP LOADING MAY YIELD AN OCCASIONAL
STRONG WIND GUST OR PERHAPS A BRIEF TORNADO /REF MCD 481/ BEFORE THE
CONVECTIVE SYSTEM WEAKENS WITH ONSET OF INCREASED UPR RIDGING LATER
TODAY. A FEW STRONG STORMS ALSO COULD FORM ON PERIPHERY OF THE MCS
ANVIL CANOPY OVER PARTS OF LA-MS-AL-GA-FL THROUGH THE AFTN.

...SRN PLNS LATE TODAY THROUGH TNGT...
SCTD TSTMS EXPECTED TO FORM THIS AFTN THROUGH TNGT...BEGINNING OVER
W TX AND THE TX PANHANDLE...AND SPREADING E/SE THROUGH EARLY
FRI...AS LOW-LVL MOISTURE ACCELERATES NWWD AHEAD OF APPROACHING UPR
TROUGH. ALTHOUGH MID/UPR-LVL FORCING FOR ASCENT INITIALLY WILL BE
WEAK...UPR DIVERGENCE WILL STRENGTHEN WITH TIME...ESPECIALLY LATE
TNGT AS LEAD PORTION OF UPR SYSTEM REACHES CNTRL NM.

SFC HEATING OF CONFLUENT SELY LOW-LVL FLOW SHOULD INITIATE STORMS BY
LATE AFTN ALONG DRYLINE/LEE TROUGH...AS SFC DEWPOINTS RISE INTO THE
TO MID/UPR 50S F. DEEP...VERTICALLY-VEERING WIND PROFILES...WITH
25-30 KT SSELY 850 MB FLOW VEERING TO 50 KT SWLY AT 500 MB WILL
PROMOTE SUPERCELLS...WITH A CONDITIONAL RISK FOR LARGE HAIL.
AND...ALTHOUGH CLOUD BASES INITIALLY MAY BE RELATIVELY
HIGH...CONTRIBUTING TO A POTENTIAL FOR APPRECIABLE STORM OUTFLOW...A
NON-ZERO RISK WILL EXIST FOR TORNADOES...ESPECIALLY WITH ANY MORE
DISCRETE CELLS INITIATING AFTER DARK AS LLJ STRENGTHENS AND FURTHER
MOISTENS.

STORM COVERAGE SHOULD CONTINUE TO INCREASE LATE TNGT THROUGH EARLY
FRI ACROSS WRN AND NRN TX...WITH ADDITIONAL ELEVATED ACTIVITY LIKELY
NWD INTO OK AS WAA/MOISTURE TRANSPORT FURTHER STRENGTHEN. ALL SVR
THREATS COULD ACCOMPANY THE TX STORMS...WITH SVR HAIL POSSIBLE NWD
INTO OK.

...SE TX THIS AFTN THROUGH TNGT...
A CONDITIONAL SVR RISK WILL EXIST THIS AFTN AND EVE WITH STORMS THAT
FORM INVOF DEVELOPING WARM FRONTAL ZONE ACROSS CNTRL AND E TX TODAY
INTO TNGT. ALTHOUGH UNCERTAINTY REMAINS REGARDING MOST LIKELY
LOCATION AND EXTENT OF SUCH DEVELOPMENT...WIND PROFILES AND DEGREE
OF BUOYANCY /SBCAPE AOA 3000 J PER KG/ WILL BE FAVORABLE FOR
SUPERCELLS WITH LARGE HAIL/LOCALLY DMGG WIND AND POSSIBLY A TORNADO.

$$


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