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 232000
SWODY1
SPC AC 231958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT WED JUL 23 2014

VALID 232000Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN WA INTO THE NORTHERN
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF OK/AR/TX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM PA/NY INTO NEW ENGLAND...

...SUMMARY...
SEVERE STORMS WITH MAINLY LARGE HAIL ARE LIKELY FROM PARTS OF
WASHINGTON EASTWARD INTO THE NORTHERN GREAT PLAINS THIS AFTERNOON
INTO TONIGHT.  STORMS WITH LOCALLY SEVERE WINDS WILL OCCUR THROUGH
THE EVENING FROM EASTERN NEW YORK INTO NEW ENGLAND. ADDITIONAL
SEVERE STORMS PRODUCING STRONG AND POTENTIALLY DAMAGING WINDS ARE
EXPECTED ACROSS PARTS OF ARKANSAS AND SOUTHEAST OKLAHOMA INTO NORTH
TEXAS.

...NORTHERN ROCKIES...

THE PREVIOUS FORECAST IS GENERALLY ON TRACK. ONLY MINOR CHANGES WERE
MADE TO THE WESTERN EDGE OF THE SIG HAIL AREA. LATEST RAP FORECAST
SOUNDINGS AND HI-RES HRRR SUGGESTS BETTER SIG HAIL THREAT WILL EXIST
TO THE EAST FROM NEAR HVR EWD INTO NE MT.

...SE OK...NRN/CNTRL AR INTO N TX...

THE SLIGHT RISK AREA HAS BEEN EXPANDED TO ENCOMPASS ONGOING SEVERE
STORM CLUSTERS FROM NE AR INTO ERN OK...AND TO INCLUDE THE DFW
METROPLEX. SEVERAL 60+ MPH GUSTS HAVE ALREADY BEEN REPORTED WITH
ONGOING CONVECTION...AND THREAT SHOULD INCREASE AND BECOME BETTER
ORGANIZED AS LINE/BOWING SEGMENT PROPAGATES GENERALLY S/SW INTO
GREATER INSTABILITY. A 30 PERCENT WIND AREA HAS BEEN INCLUDED WHERE
MIDLEVEL LAPSE RATES ARE APPROACHING 8 DEG C/KM AND EFFECTIVE BULK
SHEAR VALUES HAVE INCREASED TO NEAR 30 KT ACROSS PARTS OF SE OK/SW
AR. HERE...STRONG DOWNDRAFTS WILL HAVE A BETTER CHANCE OF PRODUCING
POTENTIALLY WIDESPREAD STRONG/DAMAGING WINDS. HI-RES GUIDANCE SHOWS
A STRONG LINE/BOWING SEGMENT PERSISTING INTO NORTH TEXAS THIS
EVENING BEFORE WEAKENING AFTER ABOUT 01-02Z NEAR/JUST SOUTH OF THE
METROPLEX. FOR MORE DETAILS REF MCD 1444.

THE WESTERN EXTENT OF THE SEVERE THREAT IS A LITTLE MORE UNCERTAIN
AS SOME GUIDANCE SUGGESTS ADDITIONAL STORMS MAY DEVELOP INTO SW OK
LATE THIS AFTERNOON/EARLY EVENING. EFFECTIVE SHEAR AND SFC DEWPOINTS
/WHILE ADEQUATE/ DIMINISH WITH WESTWARD EXTENT HOWEVER. AS
SUCH...THE 5 PERCENT AREA HAS BEEN EXPANDED SLIGHTLY WESTWARD TO
ACCOUNT FOR AT LEAST A SMALL POTENTIAL FOR ISOLATED STRONG/SEVERE
STORMS INTO THIS EVENING.

...NEW ENGLAND...

NO CHANGES NEEDED.

..LEITMAN.. 07/23/2014

.PREV DISCUSSION... /ISSUED 1128 AM CDT WED JUL 23 2014/

...NORTHERN ROCKIES INTO HIGH PLAINS...
A RATHER STRONG UPPER TROUGH IS DIGGING INTO THE PACIFIC NORTHWEST
REGION.  INCREASING LARGE SCALE FORCING AND DESTABILIZATION WILL
HELP TO INITIATE SCATTERED THUNDERSTORMS OVER THE MOUNTAINS OF
EASTERN WA/ORE INTO ID AND WESTERN MT LATE THIS AFTERNOON AND
EVENING.  STRENGTHENING WINDS ALOFT AND STEEP LAPSE RATES WILL
PROMOTE THE RISK OF STRONG/SEVERE STORMS CAPABLE OF HAIL AND
DAMAGING WINDS.  DURING THE EVENING...STORMS ARE EXPECTED TO DEVELOP
EASTWARD INTO THE PLAINS OF CENTRAL/EASTERN MT WHERE STRONGER LOW
LEVEL WINDS AND MODERATE CAPE VALUES WILL RESULT IN A GREATER RISK
OF SUPERCELL STORM STRUCTURES.  THESE MAY BE CAPABLE OF VERY LARGE
HAIL OR ISOLATED TORNADOES...MAINLY AFTER DARK.

12Z MODEL SOLUTIONS ARE LESS BULLISH ON EVOLUTION OF STORMS INTO THE
DAKOTAS LATE TONIGHT...SO HAVE REDUCED SEVERE PROBABILITIES IN THIS
REGION.  CONSENSUS OF MODELS ALSO SUGGESTS THAT INITIATION OF STORMS
OVER EASTERN WY INTO WESTERN SD WILL BE VERY ISOLATED THIS AFTERNOON
AND EVENING...SO HAVE REDUCED SEVERE PROBS IN THIS AREA AS WELL.

...ARKLATEX...
A REMNANT CLUSTER OF THUNDERSTORMS IS TRACKING SOUTHEASTWARD OVER
SOUTHEAST KS.  MEANWHILE SCATTERED ACCAS/HIGH-BASED STORMS ARE
FORMING OVER CENTRAL AR.  IT SEEMS LIKELY THAT SOME COMBINATION OF
THESE TWO CLUSTERS OF CONVECTION WILL SPREAD SOUTH-SOUTHWESTWARD
INTO EASTERN OK AND WESTERN AR THIS AFTERNOON.  DEWPOINTS IN THE MID
70S AND STRONG HEATING WILL LEAD TO EXTREME INSTABILITY...ALONG WITH
30+ KNOTS OF EFFECTIVE SHEAR.  MORE RECENT MODEL SOLUTIONS SHOW
REMARKABLE AGREEMENT THAT A BOWING STRUCTURE MAY FORM IN THIS REGION
AND POSE A RISK OF DAMAGING WINDS THIS AFTERNOON AND EVENING.
STORMS MAY MOVE INTO NORTHEAST TX BEFORE WEAKENING AFTER DARK.

...NEW ENGLAND...
A BAND OF THUNDERSTORMS IS SLOWING INCREASING ALONG/AHEAD OF A COLD
FRONT EXTENDING FROM LAKE ERIE INTO EASTERN QUEBEC.  STRONG HEATING
AHEAD OF THE FRONT AND AMPLE LOW LEVEL MOISTURE WILL YIELD AFTERNOON
MLCAPE VALUES OF 1500-2000 J/KG.  12Z OBSERVED AND MODEL FORECAST
SOUNDINGS SUGGEST THAT WINDS ALOFT WILL NOT BE PARTICULARLY
STRONG...AND THAT MID LEVEL LAPSE RATES WILL BE ONLY MARGINALLY
STEEP TODAY.  THIS SUGGESTS THAT WHILE CONVECTIVE COVERAGE MAY BE
RATHER HIGH...ITS UNCLEAR HOW MANY STORMS WILL BECOME SEVERE.
NEVERTHELESS...HAVE MAINTAINED THE SLIGHT RISK AREA ACROSS THE
REGION TODAY.




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